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This article presents the results of research on a new combined process involving multi-cycle wire-drawing and subsequent cryogenic cooling after each deformation stage. For theoretical research, modeling in the Deform software was performed. The analysis of temperature fields and the martensitic component in all models showed that for both considered thicknesses, the most effective option is a low deformation velocity and the conduct of a process without heating. The least effective option is to use an increased thickness of the workpiece at an increased deformation velocity and the conduct of a process without of heating to ambient temperature, which acts as a local cooling of the axial zone of the workpiece with an increase in the workpiece thickness. An analysis of laboratory studies on this combined process revealed that in the absence of intermediate heating of a wire between deformation cycles, 100% martensite is formed in the structure. However, if intermediate heating to 20 °C between deformation cycles is carried out, a gradient distribution of martensite can be obtained. And, since the wire has a circular cross-section, in all cases, martensite is distributed symmetrically about the center of the workpiece. [ABSTRACT FROM AUTHOR]

One of the promising and little-studied methods for obtaining an ultrafine-grained structure and enhanced mechanical properties is the so-called cryogenic deformation - deformation at temperatures below 120K. It is assumed that low deformation temperatures suppress recovery processes, thus contributing to the accumulation of an extremely high dislocation density and increase internal stresses, as well as activate deformation twinning, which together will accelerate grain refinement. In this regard, in this work, we studied the drawing of steel wire under cryogenic cooling in liquid nitrogen. The results of the laboratory experiment show that the application of cryogenic deformation treatment after wire drawing improves mechanical properties compared to conventional wire drawing. In this case, after two cycles of deformation, the relative contraction after stretching decreases by 8 %, the ultimate strength increases by 40 %, and the conditional yield strength by 26 %. The results show that the deformation conditions during cryogenic drawing are an additional factor for the realization of structural resources of steel wire physical and mechanical properties optimizing. [ABSTRACT FROM AUTHOR]

New technology is presented in the work for copper wire processing. This technology consists of deforming wire in a rotating equal-channel stepped die and subsequent drawing. The die rotates around the axis of the wire and creates stress due to equal-channel angular broaching and twisting within the die. Results of a laboratory experiment show that after deformation an ultrafine grained graded microstructure with a high content of high-angle grain boundaries is obtained. Tensile strength of deformed copper wire in comparison with undeformed wire increases from 302 to 635 MPa, and yield strength increases from 196 to 406 MPa. [ABSTRACT FROM AUTHOR]

Strength and electrical conductivity (EC) are key properties for heat-resistant Al-Zr-based alloy wires used as overhead transmission lines. Developing high-strength conductors with EC over 61.0% IACS has been a long-standing issue for heat-resistant Al conductive wires. In this work, a new design idea involving the coupling design of deformation and ageing was innovatively proposed to produce ultra-heat-resistant Al-0.2Zr-0.06Sc wires. The desired combination of high strength (195 ± 2 MPa) and good EC (61.2% IACS) was successfully achieved without annealing treatment. The strength residual rate of cold-drawn Al-0.2Zr-0.06Sc wire is as high as 94.0% after heat exposure of 280°C/1 h. [ABSTRACT FROM AUTHOR]

In this work, wire arc additive manufactured (WAAM-ed) Inconel 617- and 625-wmo grade alloys are characterized in detail for the type and distribution of precipitates in as-built and heat-treated conditions. The analyses are carried out near (~1 mm) and away (~10 mm) from the substrate along the build direction to investigate the effect of the substrate on the nature of precipitate formation. For each analysis location, morphological and chemical information of at least 400 precipitate features was identified and classified using stoichiometric analysis of SEM-EDS data combined with feature analytics. Carbides and carbonitrides are present in both Inconel 600 series alloys but Laves phase precipitates are identified only in the case of Inconel 625 wmo alloy. It is observed that the nature of precipitates size distribution is not altered significantly when compared between the two analysed locations for a particular grade. Furthermore, Laves phase precipitates closer to the substrate (1 mm) are richer in iron because of the effect of mild steel substrate on precipitation characteristics in Inconel 625 alloy. Our novel characterization approach will pave the way for comparing the microstructures of additively manufactured samples printed using different process parameters and variations. [ABSTRACT FROM AUTHOR]

A novel arc additive manufacturing process using cable-type welding wire (CWW) and ER1070 Al wire was used for the first time to successfully fabricate Alx-Co-Cr-Ni (x = 0–29) high entropy alloy with a variation in Al concentration along the building direction. Microstructure and mechanical properties of the in-situ prepared Alx-Co-Cr-Ni compositionally graded high-entropy alloys were investigated. Results indicate that a continuous transition from a single-phase FCC to FCC + B2 dual-phase was achieved, benefiting from the special structure of the CWW and repeating thermal cycles during deposition. With the increase in Al content, microstructure changed from columnar grains to dendrites, and Al-Ni rich B2 phase precipitated in the inter-dendritic region. A lamellar eutectic microstructure was observed in the interface of Al-19 HEA and Al-29 HEA. The mechanical properties of the alloy showed a gradient significant change with increase in Al concentration, with (i) microhardness increasing from 170 to 450 HV (ii) yield strength increasing from 257 to 640 MPa (iii) change in fracture mode from ductile (Al-0) to brittle (Al-29) due to excess B2 phase precipitation. From microstructure-properties relationship, the significant enhancement in mechanical properties along the build direction is identified to be due to solid solution strengthening and second phase strengthening brought forth by the presence of compositionally gradient Al. [ABSTRACT FROM AUTHOR]

Ceramic materials are widely used in national defense, military industry, information technology and other fields, are a typical hard and brittle material. Microstructure and mechanical properties not only affect the overall performance of ceramic parts, but also affect their machining performance. The diamond wire sawing technology has the characteristics of high machining efficiency, small crack damage, low cutting loss, and green environmental protection, and is widely used in the cutting of hard and brittle materials. Therefore, exploring the influence of ceramic microstructure on diamond wire sawing has theoretical significance and practical value. This article first prepares high-performance alumina ceramics with different grain sizes to provide preliminary material preparation for diamond wire sawing; Then, characterization experiments such as microstructure, mechanical properties, fracture and indentation morphology, and indentation depth were conducted to provide technical methods for in-depth research on material removal in diamond wire sawing; Finally, the removal form, chips, roughness, and removal rate of diamond wire sawing were studied to obtain the influence of different microstructures of alumina ceramics on diamond wire sawing, providing a certain theoretical and technical basis for efficient machining of high-performance ceramics by diamond wire saw. [ABSTRACT FROM AUTHOR]

This paper presents new technology for stainless steel wire processing. This technology consists of using cryogenic cooling immediately after the wire leaves the drawing die. Results of a laboratory experiment show that use of cryogenic processing after wire drawing improves mechanical properties compared with traditional drawing. Metallographic analysis proves that deformation conditions during cryogenic drawing are an additional factor for realization of structural resources to optimize steel wire physical and mechanical properties. [ABSTRACT FROM AUTHOR]

Purpose: Wire arc additive manufacturing (WAAM) is one of the most researched and fastest-growing AM technique because of its capability to produce larger components with medium complexity. In recent times, the use of WAAM process has been increased because of its ability to produce complex components economically when compared with other AM techniques. The purpose of this study is to investigate the capabilities of wire arc additive manufacturing (WAAM), which has emerged as a recognized method for fabricating larger components with complex geometries. Design/methodology/approach: This paper provides a review of process parameters for optimizing and analyzing mechanical properties, hardness, microstructure and corrosion behavior achieved through various WAAM-based techniques. Findings: Limited analysis exists regarding the mechanical properties of various orientations of Inconel 625 alloy. Moreover, there is a lack of studies concerning the corrosion behavior of Inconel 625 alloy fabricated using WAAM. Originality/value: The review identifies that the formation of intermetallic phases reduces the desirability of mechanical properties and corrosion resistance of WAAM-fabricated Inconel 625 alloy. Additionally, the study reported notable results obtained by various research studies and the improvements to be achieved in the future. [ABSTRACT FROM AUTHOR]

To receive a high-quality welding structure of high-strength S700MC steel for applications in the automotive industry, newly developed electrode wires with increased silicon and manganese content were used. The strength and structural tests of the obtained joints were performed. In the weld, we identified the beneficial oxides strengthening the joint structure and unfavorable MnS inclusions. The non-metallic inclusions were formed inside the weld. Their arrangement, morphology, and chemical composition is described. A view on the high-temperature mechanisms of the formations included during the welding process with new electrode wires is presented. It was found that the dominant mechanism of the inclusion formation and the temperature of the welding process impact the content and varied morphology of inclusions, thus determining the exploitation time of the welded joints obtained. The obtained MAG joints made S700MC steel, due to the formation mainly of oxide inclusions and a relatively small amount of MnS phase, were characterized by a high value of yield and tensile strength, which makes them a promising solution for the automotive industry, especially against the background of connections from the discussed steel grade presented in the literature. [ABSTRACT FROM AUTHOR]

Ag-Sn-In-Ni-Te alloy ingots were produced through a heating–cooling combined mold continuous casting technique; they were then drawn into wires. However, during the drawing process, the alloy wires tended to harden, making further diameter reduction challenging. To overcome this, heat treatment was necessary to soften the previously drawn wires. The study investigated how variations in heat treatment temperature and holding time affected the microstructure, microhardness and corrosion resistance of the alloy wires. The results indicate that the alloy wires subjected to heat treatment at 700 °C for 2 h not only exhibited a uniform microstructure distribution, but also demonstrated low microhardness and excellent corrosion resistance. [ABSTRACT FROM AUTHOR]

In this study, the welding performance of three filler wires, ER4043, ER5356, and the newly developed FMg0.6, were systematically investigated in the gas metal arc welding of high-strength AA6011-T6 plates. An extensive analysis of the microstructural evolution, mechanical properties, fatigue resistance, and corrosion behavior of different weldments was conducted. The ER4043 and FMg0.6 joints exhibited finer grain sizes in the fusion zone (FZ) than the ER5356 joint. The as-welded ER5356 and FMg0.6 joints exhibited higher hardness and tensile strength values than the ER4043 joint. The FMg0.6 joint demonstrated the highest mechanical strength among all of the joints with superior fatigue resistance under both the as-welded and post-weld heat treatment (PWHT) conditions. In the as-welded state, the ER5356 joint exhibited the lowest corrosion resistance, attributed to the precipitation of β-Al2Mg3 at the grain boundaries. The FMg0.6 joint, characterized by a high-volume fraction of eutectic Mg2Si in the as-welded state, exhibited a higher corrosion rate than that of the ER4043 joint. However, the PWHT effectively improved the corrosion resistance of the FMg0.6 joint. Given its excellent tensile properties, superior fatigue properties, and satisfactory corrosion resistance, particularly with PWHT, the newly developed FMg0.6 filler has emerged as a promising candidate for welding high-strength 6xxx alloys. [ABSTRACT FROM AUTHOR]

This study evaluates the feasibility of producing high-strength low-alloy (HSLA) steel using advanced wire-fed laser additive manufacturing (LAM-W) and wire arc additive manufacturing (WAAM) technologies. Optimized parameters were independently developed for each heat source, utilizing a self-designed HSLA steel wire as the feedstock. Microstructural features and mechanical properties of the fabricated steels were characterized and compared, taking into account differences in heat input and cooling rates. LAM-W samples exhibited a finer columnar grain microstructure, while both LAM-W- and WAAM-produced steels predominantly showed lower bainite and granular bainite microstructures. LAM-W demonstrated higher strength and hardness, lower ductility, and comparable low-temperature toughness compared to WAAM. Both processes demonstrated an excellent balance between strength and ductility, with absorbed energy exceeding 100 J at −40 °C. The study confirms the feasibility of producing high-strength and tough HSLA steel parts using LAM-W and WAAM technologies, and compares the advantages and disadvantages of each method. These findings assist in selecting the most suitable wire-fed AM process for HSLA steel fabrication at high deposition rates. [ABSTRACT FROM AUTHOR]

Defect-free thin-walled samples were built using wire arc additive manufacturing (WAAM) combined with the "coldArc" deposition technique by feeding a Ti-6Al-4V welding wire and using two deposition strategies, namely with and without the welding torch weaving. The microstructures formed in these samples were examined in relation to mechanical characteristics. The arc torch weaving at 1 Hz allowed us to interfere with the epitaxial growth of the β-Ti columnar grains and, thus, obtain them a lower aspect ratio. Upon cooling, the α/α′+β structure was formed inside the former β-Ti grains, and this structure proved to be more uniform as compared to that of the samples built without the weaving. The subtransus quenching of the samples in water did not have any effect on the structure and properties of samples built with the arc torch weaving, whereas a more uniform grain structure was formed in the sample built without weaving. Quenching resulted also in a reduction in the relative elongation by 30% in both cases. [ABSTRACT FROM AUTHOR]

Recent technological breakthroughs have had a significant impact on wire arc additive manufacturing (WAAM) technology in the metal manufacturing industry. Current and tool speed are the essential factors influencing the bead quality in WAAM, and experiments were conducted to optimize these parameters. Central composite design was applied for the deposition of beads, and their responses (bead width, height, depth of penetration and surface roughness) were measured using the coordinate measuring machine and 3D profilometer. Analysis of variance was applied to check the validity of the actual and predicted models. In this research, the morphology, microstructure, microhardness and wear behavior of the aluminum alloy ER-4043 were examined. Specimens were deposited using robotic gas metal arc welding (GMAW), using a 1.2 mm wire diameter, a constant current of 250 A and varying tool speed from 7 to 11 mm/s. [ABSTRACT FROM AUTHOR]

This study investigates the relationship between the microstructure and the mechanical properties and the residual stresses of thermomechanically rolled, butt‐welded S1100MC ultra high‐strength steel plates. Matching metal‐cored filler wires are used for metal active gas welding of the plates in horizontal and vertical‐up positions. The effect of the heat input on the microstructures of both the weld metal (WM) and the heat‐affected zone (HAZ) is studied in detail. The microstructure of the WM consists of different types of ferrite, but the microstructure of the HAZ predominantly consists of fresh martensite at the top and bottom areas. Structure and size of the prior austenite grain boundaries are dependent on the welding positions and affect the impact toughness of the welds. HAZ of the weld produced in vertical‐up position is under intensive tensile residual stresses next to the fusion line. Even with matching filler wires, the strength of the welds is insufficient, and fracture of the weld metal occurs because the extended cooling time leads to the formation of acicular ferrite instead of martensite. [ABSTRACT FROM AUTHOR]

The dimensional accuracy and microstructure affect the service performance of parts fabricated by wire arc additive manufacturing (WAAM). Regulating the geometry and microstructure of such parts presents a challenge. The coupling method of an artificial neural network and finite element (FE) is proposed in this research for this purpose. Back-propagating neural networks (BPNN) based on optimization algorithms were established to predict the bead width (BW) and height (BH) of the deposited layers. Then, the bead geometry was modeled based on the predicted dimension, and 3D FE heat transfer simulation was performed to investigate the evolution of temperature and microstructure. The results showed that the errors in BW and BH were less than 6%, and the beetle antenna search BPNN model had the highest prediction accuracy compared to the other models. The simulated melt pool error was less than 5% with the experimental results. The decrease in the ratio of the temperature gradient and solidification rate induced the transition of solidified grains from cellular crystals to columnar dendrites and then to equiaxed dendrites. Accelerating the cooling rate increased the primary dendrite arm spacing and δ-ferrite content. These results indicate that the coupling model provides a pathway for regulating the dimensions and microstructures of manufactured parts. [ABSTRACT FROM AUTHOR]

Aluminum–magnesium (Al–Mg) alloys, known for their lightweight properties, are extensively utilized and crucial in the advancement of wire and arc additive manufacturing (WAAM) for direct high-quality printing—a focal point in additive manufacturing research. This study employed 1.2 mm ER5356 welding wire as the raw material to fabricate two sets of 30-layer thin-walled structures. These sets were manufactured using two distinct welding modes, speed-twin pulse (STP) and twin pulse (TP). Comparative evaluations of the surface quality, microstructures, and mechanical properties of the two sets of samples indicated that both the STP and TP modes were suitable for the WAAM of Al–Mg alloys. Analyses of grain growth in the melt pools of both sample sets revealed a non-preferential grain orientation, with a mixed arrangement of equiaxed and columnar grains. The STP mode notably achieved a refined surface finish, a reduced grain size, and a slight increase in tensile strength compared to the TP mode. From the comparison of the tensile data at the bottom, middle, and top of the two groups of samples, the additive manufacturing process in the STP mode was more stable. [ABSTRACT FROM AUTHOR]

The microstructure, texture, and dislocation configuration of cold‐drawn pearlitic steel wires were investigated by scanning electron microscopy (SEM), electron backscattering diffraction (EBSD), and transmission electron microscopy (TEM). In addition, Fe/Fe3C interface structure at the atomic level was clearly observed and analyzed by high‐resolution TEM (HRTEM), and the microscopic deformation mechanism of cementite lamellae at different drawing strains is revealed. The results show that pearlite lamellae turn to the drawing direction to form ferrite <110> fiber texture, and the cementite and ferrite lamellae are simultaneously thinned with the increase of drawing strain. During the cold drawing process, shear‐bands(S‐bands) are formed in the cementite lamellae; the dislocation of ferrite transits from single slip to multi‐slip stage, and the dislocation density increases. After drawing, the lattice structures of cementite and ferrite phases show the evolution from single‐crystal to polycrystal, and the cementite lamellae are divided into a multilayer structure: central relative large‐size cementite crystal and outside relative small‐size cementite crystal layer; the dissolution of cementite lamellae in some regions results in the lattice expansion of ferrite phase and the occurrence of neck‐down regions in the cementite lamellae. [ABSTRACT FROM AUTHOR]

It is common to use heat treatment process to control the microstructure of additive manufacturing parts and improve the mechanical properties. However, there are few reports about the control of microstructure properties of WAAM hybrid inter-layer hammering fabricated parts by heat treatment. In this study, the effect of annealing on microstructure and mechanical properties of inter-layer hammering hybrid wire arc additively manufactured aluminum alloy was studied. The ratio variation of fine grain (FG) and coarse grain (CG) regions, grain size and dislocations were analyzed, and the strength-plasticity mechanism was revealed. The results shown that with the increase of annealing temperature, the ratio of FG and CG region changed from 4:1–1:5, grain growth and recrystallization happened in FG and CG regions, respectively, dislocations mostly retained in FG region and released in CG region. With the introduction of annealing and the increase of annealing temperature, the strength of hybrid manufactured samples gradually weakened while the plasticity first improved and then reduced. The best tensile properties of ultimate tensile stress 366 MPa and elongation 29.2% were achieved at 180 °C annealing. Compared with as-deposited sample, the synergistic enhancement of strength and plasticity in annealed samples is owing to dislocation strengthening, grain refinement, and heterogeneous structural strengthening. Compared with hammered sample, the strength retained and significant improved in plasticity of annealed sample, owing to dislocation released, grain refinement and heterogeneous structural. • The variation ratios of FG and CG regions were studied. • Superior strength-ductility was achieved with annealing treatment. • The effect of annealing on strengthening mechanism was revealed. [ABSTRACT FROM AUTHOR]

As a type of ultra-high strength steel, AerMet100 steel is used in the aerospace and military industries. Due to the fact that AerMet100 steel is difficult to machine, people have been exploring the process of additive manufacturing to fabricate AerMet100 steel. In this study, AerMet100 steel was produced using an in situ rolling hybrid with wire arc additive manufacturing. Microstructure, tensile properties, and fracture toughness of as-deposited and heat-treated AerMet100 steel were evaluated in different directions. The results reveal that the manufacturing process leads to grain fragmentation and obvious microstructural refinement of the AerMet100 steel, and weakens the anisotropy of the mechanical properties. After heat treatment, the microstructure of the AerMet100 steel is mainly composed of lath martensite and reversed austenite. Alloy carbides are precipitated within the martensitic matrix, and a high density of dislocations is the primary strengthening mechanism. The existence of film-like austenite among the martensite matrix enhances the toughness of AerMet100 steel, which coordinates stress distribution and restrains crack propagation, resulting in an excellent balance between strength and toughness. The AerMet100 steel with in situ rolling is isotropy and achieves the following values: an average ultimate strength of 1747.7 ± 16.3 MPa, yield strength of 1615 ± 40.6 MPa, elongation of 8.3 ± 0.2% in deposition direction, and corresponding values in the building direction are 1821.3 ± 22.1 MPa, 1624 ± 84.5 MPa, and 7.6 ± 1.7%, and the KIC value up to 70.6 MPa/m0.5. [ABSTRACT FROM AUTHOR]

In the conditions of an energy crisis, an important issue is the increase in energy efficiency and productivity of welding and hardfacing processes. The article substantiates the perspective of using exothermic additives introduced into core filler for flux-cored wire arc welding processes as a relatively cheap additional heat source, reducing energy consumption when melting filler materials, and increasing the deposition rate. The mixture design (MD) was selected as the design method to optimize the average values of current and voltage, as well as arc stability parameters depending on core filler composition. This article studies the influence of the introduction of exothermic addition (EA), as well as the ratios CuO/C and CuO/Al on arc stability for the FCAW S process. Parameters characterizing arc stability were determined using an oscillograph, and from the obtained oscillograms, an analysis was conducted on arc voltage and welding current signals during flux-cored arc welding. It was determined that various methods can be used to evaluate arc stability, which can be divided into two groups: graphical (current and voltage cyclograms, box plots with frequency histograms, ellipse parameters plotted on current, and voltage cyclograms) and statistical (standard variation and coefficients of variation for welding current and arc voltage). In this paper, a comprehensive evaluation of arc stability depending on the composition of the cored wire filler was carried out. It was determined that the most stable current parameters were observed for the flux-cored wire electrode with an average exothermic addition content at the level of EA = 26.5–28.58 wt.% and a high carbon content (low values of CuO/C = 3.75). Conversely, the lowest values of arc stability (CV(U) and Std(U)) were observed during hardfacing with a flux-cored wire electrode with a high CuO/Al ratio ≥ 4.5 and a content of exothermic addition in the core filler below the average EA < 29 wt.%. Mathematical models of mean values, standard deviation, coefficient of variation for welding current, and arc voltage were developed. The results indicated that the response surface prediction models had good accuracy and prediction ability. The developed mathematical models showed that the ratio of oxidizing agent to reducing agent in the composition of exothermic addition (CuO/Al) had the greatest influence on the welding current and arc voltage characteristics under investigation. The percentage of exothermic mixture in the core filler (EA) only affected the average welding current (Iaw) and the average arc voltage (Uaw). The graphite content expressed through the CuO/C ratio had a significant impact on welding current parameters as well as the coefficient of variation of arc voltage (CV(U)). Two welding parameters were selected for optimization: the mean welding current (Iaw) and the standard deviation of arc voltage (Std(U)). The best arc stability when using exothermic addition CuO-Al in the core filler was observed at CuO/Al = 3.6–3.9, CuO/C = 3.5–4.26, and at an average EA content of 29–38 wt.%. The significant influence of the CuO/Al and CuO/C ratios on arc voltage parameters can also be explained by their impact on the elemental composition of the welding arc (copper, cupric oxide (CuO), and Al2O3). The more complete this reaction, the higher the amount of easily vaporized copper (Cu) in the arc plasma, enhancing arc stability. The influence of core filler composition on the microstructure of deposited metal of the Fe-Cr-Cu-Ti alloy system was investigated. [ABSTRACT FROM AUTHOR]

Traditionally, structural wire is characterized by a homogeneous microstructure, where the average grain size in different parts of the wire is uniform. According to the classical Hall–Petch relationship, a homogeneous polycrystalline metal can be strengthened by decreasing the average grain size since an increase in the volume fraction of grain boundaries will further impede the motion of dislocations. However, a decrease in the grain size inevitably leads to a decrease in the ductility and deformability of the material due to limited dislocation mobility. Putting a gradient microstructure into the wire has promising potential for overcoming the compromise between strength and ductility. This is proposed a new combined technology in this paper in order to obtain a gradient microstructure. This technology consists of deforming the wire in a rotating equal-channel step die and subsequent traditional drawing. Deformation of copper wire with a diameter of 6.5 mm to a diameter of 5.0 mm was carried out in three passes at room temperature. As a result of such processing, a gradient microstructure with a surface nanostructured layer (grain size ~400 nm) with a gradual increase in grain size towards the center of the wire was obtained. As a result, the microhardness in the surface zone was 1150 MPa, 770 Mpa in the neutral zone, and 685 MPa in the central zone of the wire. Such a symmetrical spread of microhardness, observed over the entire cross-section of the rod, is a direct confirmation of the presence of a gradient microstructure in deformed materials. The strength characteristics of the wire were doubled: the tensile strength increased from 335 MPa to 675 MPa, and the yield strength from 230 MPa to 445 MPa. At the same time, the relative elongation decreased from 20% to 16%, and the relative contraction from 28% to 23%. Despite the fact that the ductility of copper is decreased after cyclic deformation, its values remain at a fairly high level. The validity of all results is confirmed by numerous experiments using a complex of traditional and modern research methods, which include optical, scanning, and transmission microscopy; determination of mechanical properties under tension; and measurement of hardness and electrical resistance. These methods allow reliable interpretation of the fine microstructure of the wire and provide information on its strength, plastic, and electrical properties.

Ultra-thick offshore steel, known for its high strength, high toughness, and corrosion resistance, is commonly used in marine platforms and ship components. However, when offshore steel is in service for an extended period under conditions of high pressure, extreme cold, and high-frequency impact loads, the weld joints are prone to fatigue failure or even fractures. Addressing these issues, this study designed a narrow-gap laser wire filling welding process and successfully welded a 100-mm new type of ultra-thick offshore steel. Using finite element simulation, EBSD testing, SEM analysis, and impact experiments, this study investigates the weld's microstructure, impact toughness, and fracture mechanisms. The research found that at −80 °C, the welded joint exhibited good impact toughness (>80 J), with the impact absorption energy on the surface of the weld being 217.7 J, similar to that of the base material (225.3 J), and the fracture mechanism was primarily a ductile fracture. The impact absorption energy in the core of the weld was 103.7 J, with the fracture mechanism mainly being a brittle fracture. The EBSD results indicated that due to the influence of the welding thermal cycle and the cooling effect of the narrow-gap process, the grains gradually coarsened from the surface of the welded plate to the core of the weld, which was the main reason for the decreased impact toughness at the joint core. This study demonstrates the feasibility of using narrow-gap laser wire filling welding for 100-mm new type ultra-thick offshore steel and provides a new approach for the joining of ultra-thick steel plates. [ABSTRACT FROM AUTHOR]

The possibility of using wire arc additive manufacturing to obtain multilayer blanks from steels 30CrMgSi and 307Lsi by their simultaneous supply in different ratios is studied. The microstructure obtained in the samples following wire arc additive manufacturing is shown. In general, a defect-free structure is formed. [ABSTRACT FROM AUTHOR]

The 70/30 copper–nickel alloy is used mainly in critical parts with more demanding conditions in marine settings. There is a need for innovative methods that offer fast production and cost-effectiveness in order to supplement current copper–nickel alloy manufacturing processes. In this study, we employ wire arc additive manufacturing (WAAM) to fabricate the 70/30 copper–nickel alloy. The as-built microstructure is characterized by columnar grains with prominent dendrites and chemical segregation in the inter-dendritic area. The aspect ratio of the columnar grain increases with increasing travel speed (TS) at the same wire feed speed (WFS). This is in contrast with the equiaxed grain structure, with a more random orientation, of the conventional sample. The sample built with a WFS of 8 m/min, TS of 1000 mm/min, and a track distance of 3.85 mm exhibits superior corrosion properties in the 3.5 wt% NaCl solution when compared with the conventional sample, as evidenced by a higher film resistance and breakdown potential, along with a lower passive current density of the WAAM sample. The corrosion morphology reveals the critical roles played by the nickel element that is unevenly distributed between the dendrite core and inter-dendritic area. [ABSTRACT FROM AUTHOR]

The surface of the hot forging die is prone to failure due to severe high heat and cyclical load during service. The remanufacturing of a forging die by wire and arc additive manufacturing technology could greatly improve the performance of the die and prolong its service life. In this paper, the remanufactured zone of the die was divided into three additive deposition layers with gradient mechanical properties based on temperature and stress analysis, namely, the transition layer, intermediate layer and strengthen layer, according to the thermal and stress conditions. A wire and arc additive manufacturing experiment with gradient material was conducted on 5CrNiMo hot forging die steel. The microstructure and mechanical properties of the gradient additive layer were characterized and analyzed. The results indicated that the microstructure of the gradient additive layer presents a transformation process of bainite-to-martensite from bottom to top. The hardness and strength of the transition layer, intermediate layer and strengthen layer exhibit a rational gradient increasing trend, while the impact toughness shows a decreasing trend. The wear loss and cumulative friction dissipated energy of the strengthen layer are considerably lower than those of the other layers. The mechanical properties of the gradient additive layer are shown as a gradient increase in hardness, strength, and wear resistance at high temperature, which is conducive to enhancing the overall pressure bearing capacity and preventing the failure of plastic deformation on the surface of the remanufactured hot forging die. [ABSTRACT FROM AUTHOR]

In addition to cold drawing, the process of annealing is also essential in the preparation of Mg-4.7 wt%Gd (G4.7) alloy wires. The effect of annealing treatment on the recrystallized microstructure and texture of cold-drawn G4.7 wires was investigated. The results demonstrate that the uniformity and regularity of the recrystallized grains, as well as the annealing texture, impact the follow-up cold drawing performance. When the as-drawn G4.7 wires were annealed at 375 °C, the recrystallized grains were refined, accompanied by uniformity and regularity. Accordingly, the G4.7 wire had a good subsequent drawing deformability, with a maximum accumulative true strain (ATS) of 144%. Additionally, the evolution of the microstructure was consistent with the evolution of the texture. While annealing at a lower temperature (325 °C), the {0002} basal texture of the G4.7 wire was weak, forming the main texture component <10 1 ¯ 0>//DD (the drawing direction). With the increase in temperature, the basal texture was gradually strengthened and the texture component transformed from <10 1 ¯ 0>//DD to a recrystallized texture based on <11 2 ¯ 0>//DD. Even under high-temperature annealing, the G4.7 wire was still affected by the cold-drawn deformation texture and could not fully recover to the as-extruded texture, thus causing a decrease in the subsequent drawing performance. [ABSTRACT FROM AUTHOR]

TiAl alloys with different Al atomic compositions, i.e. Ti45Al, Ti48Al, and Ti51Al, were produced via double-wire arc-based additive manufacturing by altering the aluminum wire feed rate. The microstructure and mechanical performance of deposited parts were researched. By changing the aluminum composition from 45 at% to 51 at%, the microstructure in the uniform area transforms from equiaxed α2/γ lamellar and near-lamellar colonies to dual-phase structures and near-lamellar colonies, the volume fraction of α2 phase decreases from 46.5% to 12.4%, and the total microhardness decreases from 411 to 356 HV. As the aluminum composition increases, the compressive strength presents an increasing trend first and then a decreasing trend, and the compressive ratio presents an increasing trend. The maximum compressive strength and compressive ratio in the vertical and horizontal orientations are 1822.5 MPa, 1732.5 MPa, 19.9%, and 20.2%, respectively. [ABSTRACT FROM AUTHOR]

Wires of a Cu--3.8 wt% Zr alloy were produced by conform extrusion followed by wire drawing up to 0.2mm in diameter (S wire), or by conform extrusion and subsequent annealing during wire drawing up to 0.2mm (IA wire). The effects of microstructure on the strength and electrical conductivity of the S and IA wires were investigated. The severely drawn S and IA wires had a mixed microstructure consisting of a Cu parent phase with fine grains, fibrous eutectics elongated along the drawing direction, and granular eutectics. The 0.2% proof stress (·0.2) and tensile strength (·u) of the S and IA wires increased monotonically with increasing drawing ratio (©). The S wire with © = 7.8 exhibited large values of ·0.2 = 1080MPa and ·u = 1320 MPa. The S and IA wires having the mixed microstructure are strengthened primarily by high density of dislocations and grain refinement in the Cu phase and by the presence of fibrous and granular eutectics. The electrical conductivity (E) of the S wire increased in the early stage of wire drawing and then began to decrease, dropping to 42% IACS at © = 7.8. The increase in E is caused by refining of the eutectics, which was formed during casting, toward the granular or fibrous form. The E value of the IA wire after annealing was high, 72%IACS, and then decreased as © increased. Values of E of the S and IA wires with the mixed microstructure was estimated by applying rules of mixtures. The estimated values of E are in agreement with the measured values of E. It is shown that the presence of the fibrous and granular eutectics significantly increases the electrical conductivity. [ABSTRACT FROM AUTHOR]

This work studies evolution of copper microstructure during a combined deformation process. The essence of this process is in deformation of copper wire in a rotating equal-channel stepped matrix with subsequent drawing. Deformed wire is examined using transmission electron microscopy and EBSD analysis. After three cycles of deformation, an ultrafine-grained gradient microstructure with a high component of high-angle grain boundaries is obtained. [ABSTRACT FROM AUTHOR]

In the present study, the effects of varying heating and cooling rates during the solution treatment process on the microstructure and properties of AA7050 alloy wires were investigated using tensile tests, metallographic microscopy, electron backscattered diffraction, and transmission electron microscopy. It was found that the recrystallized grain size of the alloy, subjected to method of rapid heating, exhibited a smaller and more uniform distribution in comparison to method of slow heating. The low density of η′ strengthening phases after the artificial aging treatment was formed using air cooling method. Meanwhile, by using the water quenching method sufficient solute atoms and more nucleation sites were provided resulting in a large number of η′ strengthening phases being formed. In addition, the alloy processed using the water quenching method displayed higher strength than that treated using the air cooling method for the T6 and T73 states. Furthermore, coarse precipitates formed and less clusters were observed in the matrix, while high density nanoscale clusters and no continuous precipitation are formed when using the water quenching method. [ABSTRACT FROM AUTHOR]

In this study, the hot deformation behavior and deformation mechanism of Cu-18 wt.%Nb composite wire was studied based on the development of constitutive equations and hot processing maps. The constitutive equation of Cu-18 wt.%Nb composites was established based on the hyperbolic sinusoidal Arrhenius-type model, and the hot processing maps were developed using the principles of the dynamic materials model (DMM). In a view of microstructure refinement and work ability improvement, the optimum processing should be selected in the temperature range of 650–730 °C and the strain rate range of 0.001-0.1 s−1. [ABSTRACT FROM AUTHOR]

Wire arc additive manufacturing is an emerging technology in advance fabrication. It has become a very promising alternative to high value large metal components in many manufacturing industries. Even though it has high deposition rate and high metal utilization rates, coarse grains and anisotropy are the major drawbacks of this process. In this work, a study was done to investigate how to overcome these challenges. In this study, during the deposition of SS308L, Al2O3 particles are added in the middle of deposition. Analysis of the microstructure, hardness and related radiography tests are performed on the WAAM in-situ specimens and WAAMed specimens. An improvement in the grain size and hardness was observed with in the in-situ specimens when compared with WAAMed specimens. [ABSTRACT FROM AUTHOR]

Copper-clad aluminum wires have a high risk of electrical fire, and welding marks are easily affected by factors such as high temperature and fire water in the actual fire. To accurately identify the overcurrent fault, an electrical fault simulator was used in this study to simulate the overcurrent fault condition of a copper-clad aluminum at a current of 52.5–105 A. Then the microstructure characteristics such as metallographic structure, welding hole elements, and so on under different treatment methods were also analyzed using the metallographic microscope and SEM/EDS. The results of the study are summarized as follows: (1) under the method of natural cooling, the metallographic structure of the welding mark were mainly columnar crystals and dendritic crystals with a few holes in it. And we found that the maximum particle size and average particle size have a quadratic function relationship with the current value; (2) under the water-cooling method, the welding mark was mainly columnar crystals with a large number of holes in them. At a current of 75 A, the welding mark holes consisted of Al and Cu elements, while at the rest of the current value, they consisted of Al, Cu, and O elements; (3) when the temperature was raised to 450 °C, the welding trace has different elements at different currents. At the temperature of 650 °C, a large number of equiaxed crystals appeared in the welding trace, with a few holes in which at a current at 105 A only. Our study has provided a basis for the investigation of electrical fire accidents and the technical identification of the causes. [ABSTRACT FROM AUTHOR]

Mechanical and thermal processing of wire-arc additively deposited stainless steel is investigated with the purpose of improving its microstructure, surface morphology, formability, and stress response. Microscopy helps identifying the processing conditions that permit full recrystallization of the as-built columnar microstructure. Combination with strain loading paths, topography and fractography in tensile tests show that mechanical processing consisting of 20 % thickness reduction followed by annealing at 1100 °C under 4 h eliminates anisotropy and increases the fracture forming limits by 30 %. The work is a step forward to consolidate the hybridization of wire-arc additive manufacturing with metal forming as an alternative to conventional manufacturing. [ABSTRACT FROM AUTHOR]

The mass production of metallic components requires high agility in the working process conditioned by the necessity of building details of different shapes and sizes. Changing the size of the components theoretically influences the thermal dissipation capability of the same, which could lead to a change in their structure and mechanical properties. This is particularly important when aluminum alloys are concerned. For this reason, two Al5356 single-track specimens were built using the same technological conditions of layer deposition by varying only their geometrical size. In all cases, the specimens were wire and arc additively manufactured (WAAM) using a process based on gas metal arc welding (GMAW) in the cold arc pulse mode (CAP). The structure of both specimens was studied and defects along their surfaces were detected in the form of micro-pores and micro-cracks. A high concentration of undissolved Mg particles was also detected, along with some standalone Si particles. Uniformity in the build-up process was achieved, which led to the formation of nearly identical structures in the specimens. Subsequently, the resultant mechanical properties were also highly comparable. This indicates that the geometry-related variation in thermal conditions has an insignificant influence on the component's structure and properties. [ABSTRACT FROM AUTHOR]

In this work, the interaction of an additively produced Ti-4Al-3V titanium alloy with a nickel superalloy tool and the features of the stir zone formation during friction stir processing have been studied. The stop-action technique was used to produce the samples to be studied using optical and scanning electron microscopy methods, as well as microhardness measurements. As a result, it was revealed that the tool, when moving, forms a pre-deformed area in front of it, which is characterized by a fine-grained structure. The presence of an interface layer between the workpiece material and primary fragmentation by the tool was revealed. It was demonstrated that the transfer of titanium alloy material occurs periodically following the ratio of feeding speed to tool rotation rate. Metal flow around the tool can occur in both laminar and vortex modes, as indicated by the tool material stirred into the transfer layer and used as a marker. [ABSTRACT FROM AUTHOR]

Wire arc additive manufacturing is an emerging technology in advance fabrication. It has become a very promising alternative to high value large metal components in many manufacturing industries. Even though it has high deposition rate and high metal utilization rates, coarse grains and anisotropy are the major drawbacks of this process. In this work, a study was done to investigate how to overcome these challenges. In this study, during the deposition of SS308L, Al2O3 particles are added in the middle of deposition. Analysis of the microstructure, hardness and related radiography tests are performed on the WAAM in-situ specimens and WAAMed specimens. An improvement in the grain size and hardness was observed with in the in-situ specimens when compared with WAAMed specimens. [ABSTRACT FROM AUTHOR]

Wire arc additive manufacturing (WAAM) is an approach to develop unique and sophisticated design products in comparison to other traditional techniques. In the present study, the components of Cu-Si alloy have been developed using WAAM with a robotic gas metal arc welding technique. In this process, the current and voltage varied from 70 to 110 A and 17 to 19 V, respectively. The effect of process parameters on the microstructure, hardness, and wear behavior of components have been studied in details. The results show that the surface roughness of the components reduced with the increase in current and voltage. The microstructure of the uppermost surface of WAAM components shows columnar followed by dendritic with equiaxed morphology. The process parameter also affects the mechanical and wear resistance properties of WAAM components. The results show that the microhardness (from 100.03 to 160.03 HV) and wear resistance of the Cu-Si alloy component increase with the increases in current and voltage. [ABSTRACT FROM AUTHOR]

This article presents the results of research on a new combined process involving multi-cycle wire-drawing and subsequent cryogenic cooling after each deformation stage. For theoretical research, modeling in the Deform software was performed. The analysis of temperature fields and the martensitic component in all models showed that for both considered thicknesses, the most effective option is a low deformation velocity and the conduct of a process without heating. The least effective option is to use an increased thickness of the workpiece at an increased deformation velocity and the conduct of a process without of heating to ambient temperature, which acts as a local cooling of the axial zone of the workpiece with an increase in the workpiece thickness. An analysis of laboratory studies on this combined process revealed that in the absence of intermediate heating of a wire between deformation cycles, 100% martensite is formed in the structure. However, if intermediate heating to 20 °C between deformation cycles is carried out, a gradient distribution of martensite can be obtained. And, since the wire has a circular cross-section, in all cases, martensite is distributed symmetrically about the center of the workpiece.

The influence of tensile stress on the interface structure of functionally gradient materials is studied in a stainless steel-copper composite fabricated using a wire-feed electron beam technology. A distinct boundary is observed between the two materials, with the two-phase transition regions formed on both sides of the interface. The mechanical tests demonstrate an important role of the interface orientation during the plastic deformation development under uniaxial tensile loading. In the case of the longitudinal and diagonal interfaces, copper and steel simultaneously undergo plastic deformation. The fracture surface also reveals the presence of heterogeneous regions. In the orthogonal interface, necking and subsequent rupture occur in milder copper. However, its mechanical properties are found to be better compared to those of the additively grown copper. [ABSTRACT FROM AUTHOR]

Wire arc additive manufacturing (WAAM) is a class of arc-based metal additive manufacturing (AM) under the category of direct energy deposition. As compared to other metal-based AM techniques, WAAM is capable of fabricating medium-to-large sized part (having low level of design complexity) with near fully-dense structure. Ease of near-net shaping with high material utilization rate has made the process economic in various industrial applications staring from prototype to customized product fabrication. Quality of the built part is strongly affected by the feedstock wire composition, welding parameters and deposition strategy. Due to complicated thermal history, WAAMed part suffers from considerable anisotropy in microstructure as well as mechanical properties. The present work attempts to fabricate a 3D slab by layer-wise deposition of molten SS308L-T1 feedstock wire through CMT + MIG based WAAM process. Initially, a few pilot experiments (by depositing single track bead-on-plate welds and stacked weld specimens) are performed to determine values of the appropriate process parameters for WAAM of SS308L part. The appropriate setting of parameters which includes current, voltage, gas flow rate, nozzle-to-plate distance, start/end current percentage, degree of overlap and deposition strategy (applicable for stacked specimens), etc. are obtained based on visual inspection of the built quality and measurable features of bead geometry. Finally, a 3D wall is successfully fabricated having approximate dimension 150 × 25 × 30 mm3. The microstructure evolution and mechanical property characterization of the as built part are carried out. It is experienced that microstructure and mechanical property of WAAMed SS308L are location-dependent. The as built microstructure contains δ ferrite (skeletal, vermicular and lathy morphologies) which is deposited at grain boundaries of γ austenite. The middle zone of the fabricated slab appears to be relatively softer than top and bottom zones; middle zone corresponds to the lowest tensile strength along horizontal direction (~ 541 MPa) but the highest fracture strain (elongation percent ~ 38%). The average tensile strength along horizontal direction is obtained as ~ 548 MPa. Fractographic results of failed tensile specimens evidence ductile fracture mode characterized by dimples along with the presence of second-phase spherical particles. The average microhardness of the as built SS308L obtained is 171 HV0.1. [ABSTRACT FROM AUTHOR]

Duplex stainless steels (DSSs) are widely used due to their corrosion resistance. Austenite and ferrite determine the excellent properties. Ferrite provides strength and good corrosion resistance, while austenite provides toughness and weldability. During our research, samples were produced with ER 2209 duplex steel wire using wire arc additive manufacturing (WAAM). Two different 17 V and 19 V arc voltages were used during the production. Two shielding gases were used for each voltage: M12-ArC-2.5 and M12-ArHeC-20/2. The research aimed to determine the ferrite ratio as a function of the welding parameters. The ferrite (or austenite) content must be between 30% and 70% for duplex stainless steel welds, according to the ISO 17781 standard. Based on our research, it can be stated that the austenite ratio increases as the voltage increases, thus failing to fulfill the standard's requirements. The helium content reduced the ferrite ratio even when the 17 V voltage was used due to the gas's higher ionization potential. During the metallographic examination, our welded samples met the standard requirements for the austenite content for 17 V arc voltage and M12-ArC-2.5 shielding gas. The ferrite content in the entire sample cross-section fell between 30-42% during feritscope and image analysis measurements. These welding parameters can be recommended for industrial applications. [ABSTRACT FROM AUTHOR]

This study investigates the mechanical properties of exceptionally high-strength steel produced by wire and arc additive manufacturing (WAAM), using the 304 stainless steel wire and the low carbon wire (LCS). The study found that annealing treatment can enhance the steel's mechanical properties. The microstructure in the LCS layer changed from ferrite to bainite and then to a mixture of austenite, pearlite, and bainite with increasing annealing temperature. In contrast, the SS layer retained its martensitic structure, albeit with altered lath sizes. The annealing treatment also improved the orientation of the grains in the steel. The optimal annealing temperature observed for the steel was 900 ℃, which resulted in a maximum tensile strength of 1176 MPa along the Y direction and 1255 MPa along the Z direction. Despite the superior mechanical properties, the LCS layer still exhibited failure during tensile testing due to its lower hardness. The study suggests that annealing treatment can be a useful technique for enhancing the mechanical properties of high-strength steel in WAAM applications. [ABSTRACT FROM AUTHOR]

This study introduced continuous multi-pass friction stir processing (FSP) as post-processing on ER2319 alloy thin-walled components fabricated by wire-arc additive manufacturing (WAAM). The continuous multi-pass FSP was found to be effective in eliminating pores, with significant grain refinement and an increase in large misorientation angles. Meanwhile, the net-like precipitates were broken into particles, further improving the microstructure uniformity. Owing to these improvements, the average tensile strength and elongation both increased. However, due to the strong mechanical stirring and the frictional heat cycle generated, the precipitates partially overaged and grains grown, while grains recovery and dynamic recrystallization (DRX) occurred, which caused the average hardness to drop in the zone of continuous multi-pass FSP-treated. • Introducing continuous multi-pass FSP to enhance WAAM-fabricated Al-Cu alloy. • Continuous multi-pass FSP improved anisotropy of mechanical property. • The hardness in the zone of multi-pass FSP-treated decreased due to the DRX. • The hardness decreased more where FSPed earlier under the frictional thermal cycles. [ABSTRACT FROM AUTHOR]

Wire and arc additive manufacturing (WAAM) is the predominant technique to process Nickel-based superalloys due to its low cost and high flexibility. This article discusses the microstructural features and corrosion resistance of two Inconel 625 parts manufactured using the WAAM technique. Using the WAAM process, two single-walled Inconel 625(IN625) components were produced additively for inter-pass layer temperatures (IPT) of 200 °C and 300 °C. The grain size changed with a change in IPTs, according to an investigation using electron backscatter diffraction (EBSD). The preferred grain orientation changed from the texture {001} < 001> to {001} < 101> as the IPT increased. Potentiodynamic polarization was used to evaluate the corrosion behavior. The corrosion rate of the IPT 300 °C sample is 0.007255 mmpy, while the corrosion rate of the IPT 200 °C sample is 0.01315 mmpy. Tafel's extrapolation technique calculated the corrosion current density and corrosion current potential. The scanning electron microscope (SEM) explored the corroded area, and the energy-dispersive X-ray spectroscope examined the elemental composition. [ABSTRACT FROM AUTHOR]

This work investigated the Microstructure and corrosion behavior of wire arc additive manufactured Ti-6Al-xV (x = 0, 2, 4 mass%) alloys with varying vanadium content. It was found that Ti-6Al with pure ¡ phase showed irregular plate-like grains, which was distinct from the grains obtained in α + β alloys. Vanadium additions in the Ti-6Al-xV alloys promoted the formation of martensitic phase. The width of lamellae decreased and the size of prior β grains, the β phase content increased with the increase of Vanadium content. Electrochemical results suggested that Ti-6Al alloy possessed higher corrosion resistance than Ti-6Al-4V. The difference in corrosion behavior could be attributed to grain size and orientation and phase distribution. [ABSTRACT FROM AUTHOR]

In this study, the effect of heat treatment parameters on the optimized performance of Ni-rich nickel–titanium wires (NiTi/Nitinol) were investigated that were intended for application as actuators across various industries. In this instance, the maximum recovery strain and actuation angle achievable by a nitinol wire were employed as indicators of optimal performance. Nitinol wires were heat treated at different temperatures, 400–500 °C, and times, 30–120 min, to study the effects of these heat treatment parameters on the actuation performance and properties of the nitinol wires. Assessment covered changes in density, hardness, phase transition temperatures, microstructure, and alloy composition resulting from these heat treatments. DSC analysis revealed a decrease in the austenite transformation temperature, which transitioned from 42.8 °C to 24.39 °C with an increase in heat treatment temperature from 400 °C to 500 °C and was attributed to the formation of Ni4Ti3 precipitates. Increasing the heat treatment time led to an increase in the austenite transformation temperature. A negative correlation between the hardness of the heat-treated samples and the heat treatment temperature was found. This trend can be attributed to the formation and growth of Ni4Ti3 precipitates, which in turn affect the matrix properties. A novel approach involving image analysis was utilized as a simple yet robust analysis method for measurement of recovery strain for the wires as they underwent actuation. It was found that increasing heat treatment temperature from 400 °C to 500 °C above 30 min raised recovery strain from 0.001 to 0.01, thereby maximizing the shape memory effect. [ABSTRACT FROM AUTHOR]