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The eutectoid Ti–Cu alloy has the advantages of high strength and hardness. However, the pearlite eutectoid structures with coupled α + Ti2Cu lamellae result in low plasticity. In this study, a Zr alloying method is proposed to suppress the formation of lamellar pearlite and promote a bainite-like morphology. Increasing the Zr content can transform the α lamellae into rod-like laths and the Ti2Cu lamellae into dispersed particles, thereby reducing their embrittlement effect. The α laths are further refined to about 0.27 and 0.37 μm with 30% and 50% Zr addition, resulting in strong grain boundary strengthening effects. As a result, the mechanical properties are enhanced after Zr alloying. The best combination of compressive yield strength, maximum strength, and plasticity is achieved with 30% Zr addition, which is about 1040 MPa, 2505 MPa, and 33%, respectively. The results in this study can offer valuable insights into microstructure optimization and performance enhancement in active eutectoid Ti–Cu systems.

In this study, the effects of sintering temperatures and pressures on densification, crystalline phases, microstructural characterization and mechanical properties of mechanical alloyed equimolar CoCrFeNiMo HEA were investigated. The alloy was composed of major BCC and minor FCC solid solutions coexisting after 40 h of milling. Increasing milling time caused to increase in lattice strain and a decrease in crystallite size. Furthermore, sintering temperature and pressure resulted in the decomposition of the BCC metastable phase and the formation of intermetallic phases and the FCC phase. Herein, increasing sintering temperature and pressure led to decrease lattice strain and increase crystallite size. Moreover, sintering temperature and pressure caused to formation of new intermetallic phases in HEA2 and HEA3. Results revealed that increasing sintering temperatures and pressures of equimolar CoCrFeNiMo end up with a reduction of large pore, enhancement of density value from 7.53 ± 0.02 to 8.78 ± 0.005 g/cm3, hardness from 3.915 to 8.316 GPa, and increment of wear rate from 21.8 × 10−7 to 57.6 × 10−7 mm3/Nm. [ABSTRACT FROM AUTHOR]

The main motivation for this study was to improve implant materials. The influence of silver and gold on the structure and mechanical properties of Mg–Nd–Zr alloy was studied. In the work, quantitative and qualitative evaluation of the structural components of magnesium alloy with noble metal additives was performed. The research methods used were investigation of the mechanical properties and observation of micro– and macrostructures. The results showed that modification of magnesium alloy with Ag and Au contributes to the formation of spherical intermetallics of smaller size groups, which become additional centers of crystallization and grind the cast structure. The best composition from additional alloying with silver and gold was determined. Their positive effect on the strength and ductility properties of the metal was established. Preclinical and clinical testing was performed and the prospects for noble metal modification of bioabsorbable magnesium alloy for implant production usage were shown. [ABSTRACT FROM AUTHOR]

Herein, a novel method is proposed to prepare the multimaterial composite component for aerospace applications using the current sintering. Two representative high‐temperature structural materials, the new potential intermetallic NiAl and the widely used Ni‐based superalloy K4202, have been employed to achieve the target. As shown by the results, a clean interface with almost no defects is successfully obtained in NiAl/K4202 alloy. Nevertheless, the existence of a continuous Cr(Mo) phase along the region leads to an insufficient bonding ability. To optimize the interfacial microstructure, a Ni foil is employed as the interlayer. The results indicate that the interlayer can hinder the intense diffusion of elements and prevent the abnormal growth of Cr(Mo) phases, which result in a considerable improvement of interfacial properties. [ABSTRACT FROM AUTHOR]

In this work, the approach to improve the mechanical properties of a biodegradable Mg-Nd-Zr alloy through modification with noble metals (Ag and Au) was proposed. The separate and combined influence of silver and gold on the macro- and microstructure of the alloy was studied. A qualitative and quantitative assessment of the structural components of the alloy was carried out. It was shown that when modifying the melt, noble metals form the complex intermetallic phases which served as additional crystallization centers. It has been established that adding 0.05 to 0.1 wt.% of noble metals to Mg-based alloy increase the volume fraction of intermetallic compounds by ~1.5 times, shifting them towards smaller size groups with the simultaneous formation of spherical intermetallic compounds. The latter are located in the center of the grain proving them to be the additional nucleation sites. It was shown that complex modification (0.1% Ag + 0.1% Au) of a Mg-based alloy refined its structural components by ~1.5 times, increasing the strength by ~20%, and ductility by ~2 times due to the formation of the intermetallic compounds. The proposed technology for modifying cast biodegradable Mg-based alloys is feasible to be used for the manufacture of implants for osteosynthesis. [ABSTRACT FROM AUTHOR]

Sn-Mg alloys are potential Pb-free solder options. However, their mechanical strength and interfacial characteristics with electronic substrates remain barely understood. This study focuses on the interfacial heat transfer aspects, microstructure, and tensile strength of a Sn-2.1wt.%Mg alloy. Samples with various thermal histories were produced using a directional solidification apparatus. In these experiments, a Sn-2.1wt.%Mg alloy was solidified on Cu and Ni substrates, which are of interest in the electronics industry. Mathematical modeling was then employed, allowing for the determination of the overall and interfacial heat transfer coefficients (hov, and hi, respectively). The results show that the Ni substrate exhibits higher interfacial thermal conductance with the Sn-2.1wt.%Mg alloy compared to the Cu substrate, as indicated by the higher hi profiles. This fact occurs mainly due to their metallurgical interaction, resulting in a stronger bond with the presence of Sn-Ni-rich intermetallics at the interface. Finally, experimental equations based on the Hall–Petch relationship are proposed to describe how the refinement of the fibrous spacing of the Mg2Sn interphase (λG) and an increase in hi enhance both yield and ultimate tensile strengths. [ABSTRACT FROM AUTHOR]

In the aircraft industry, the high-strength aluminum alloys AA7075 and AA2024 are extensively used for the manufacture of structural parts like stringers and skins, respectively. Additive manufacturing (AM) of the AA7075-T6 aluminum alloy via friction stir deposition to build continuously multilayered parts on a substrate of AA2024-T4 aluminum has not been attempted so far. Accordingly, the present work aimed to explore the applicability of building multilayers of AA7075-T6 alloy on a substrate sheet of AA2024-T4 alloy via the additive friction stir deposition (AFSD) technique and to optimize the deposition process parameters. The experiments were conducted over a wide range of feed rates (1–5 mm/min) and rotation speeds (200–1000 rpm). The axial deposition force and the thermal cycle were recorded. The heat input to achieve the AFSD was calculated. The AA7075 AFSD products were evaluated visually on the macroscale. The microstructures were also investigated utilizing an optical microscope and scanning electron microscope (SEM) equipped with an advanced EDS technique. As well as the presence phases, the mechanical performance of the deposited materials in terms of hardness and compressive strength was also examined. The results showed that the efficiency of the deposition process was closely related to the amount of heat generated, which was governed by the feeding rate, the rotational speed, and the downward force. AA7075 defect-free continuously multilayered parts were produced without any discontinuity defects at the interface with the substrate at deposition conditions of 1, 2, 3, and 4 mm/min and a constant 400 rpm consumable rod rotation speed (CRRS). The additively deposited AA7075-T6 layers exhibited a refined grain structure and uniformly distributed fragment precipitates compared to the base material (BM). The gain size decreased from 25 µm ± 4 for the AA7075-T6 BM to 1.75 µm ± 0.41 and 3.75 µm ± 0.78 for the AFSD materials fabricated at 1 and 4 mm/min deposition feeding rates, respectively, at 400 rpm/min. Among the feeding rates used, the 3 mm/min and 400 rpm rod rotation speed produced an AA7075 deposited part possessing the highest average hardness of 165 HV ± 5 and a compressive strength of 1320 MPa. [ABSTRACT FROM AUTHOR]

The application of the electromagnetic casting (EMC) to aluminum alloys is capable of producing structures, hardly obtainable by the conventional methods of casting due to the constant stirring of the crystallizing alloy and high cooling rate (∼103 K/s). For the first time we study EMC high purity binary Al-0.5Fe and Al-2.5Fe (wt.%) alloys in the as-cast state as well as after equal-channel angular pressing (ECAP) and cold rolling (CR). We demonstrate that EMC process leads to formation of metastable Al2Fe-alike intermetallic phase which does not decompose by further straining and annealing. Combined deformation by ECAP and CR results in the formation of ultrafine grained structure in which providing the increase in ultimate tensile strength up to 200 MPa in Al-0.5Fe and up to 340 MPa in Al-2.5Fe. Electrical conductivity level of Al-0.5Fe alloy increases up to 58.5% IACS, while the conductivity of Al-2.5Fe alloy decreases to 47.9% IACS. Both alloys demonstrate thermal stability of microstructure, mechanical and electrical properties under annealing up to 230 °C for 1h. These effects are discussed in terms of as-cast and strain-induced microstructures.

Here, two multi-principal element alloys (MEPAs): CoCrFeNi and CoCrFeNiGd0.05 are fabricated by high-energy ball milling and spark plasma sintering. The effect of Gd on microstructure and mechanical properties of the CoCrFeNi MPEA is investigated. The addition of Gd to the CoCrFeNi base alloy leads to precipitation of a GdNi5-type phase with hexagonal structure (HS) and minor amounts of a Gd-rich oxide phase from the FCC matrix. Compared to the CoCrFeNi base alloy, the grain size of CoCrFeNiGd0.05 is smaller, and the tensile yield strength of CoCrFeNiGd0.05 significantly increases from 546 MPa to 859 MPa, along with minor sacrifices in plasticity where the elongation only slightly decreases from 20.8% to 19.4%. The enhanced strength of Gd-containing MPEA is mainly attributed to grain boundary strengthening from the ultrafine-grained microstructure and the precipitation strengthening contributed by the HS phase. Transmission electron microscopy (TEM) results demonstrate that the GdNi5-type intermetallic phase is coherent with the FCC matrix and shows the following orientation relationship: {111¯}FCC//{2¯119¯}HS. The high plasticity of the composite-structured CoCrFeNiGd0.05 alloy is attributed to the homogenous distribution of the ultrafine HS phase and the coherent HS-FCC interface facilitating dislocation slipping.

The effects of solution and aging heat treatment on microstructural evolution and room temperature tensile properties for as-forged Ni–45Ti–5Al–2Nb–1Mo alloy were investigated through scanning electron microscopy (SEM), transmission electron microscopy (TEM) and tensile tests. The results show that the microstructure of solution-treated alloy comprises NiTi matrix, Ti2Ni and (Nb,Ti)SS phases. After aging treatment at 700 °C for 6 and 100 h, the distribution of Ti2Ni and (Nb,Ti)SS precipitates increases in uniformity. No new type of precipitate is observed in the specimen aged at 700 °C. After aging at 800 °C for 100 h, numerous nanosized Ni2TiAl phases are precipitated within the grains. Solution and aging treatments improve the tensile properties at room temperature. Tensile strength and ductility are improved after solution treatment at 1100 °C plus aging treatment at 800 °C for 6 h or 700 °C for 100 h. With aging time prolonging to 100 h at 800 °C, the precipitation of fine Ni2TiAl particles leads to the improvement in tensile strength and deterioration of elongation. [ABSTRACT FROM AUTHOR]

Laminated Mg-intermetallic composites were successfully fabricated by reaction synthesis in vacuum using 1 mm thick magnesium sheets and 0.25 mm thick copper foils. The final microstructure consisted of alternating layers of a hypoeutectic alloy containing crystals of CuMg2 and eutectic mixture of CuMg2 and solid solution of copper in magnesium and unreacted magnesium. The mechanical properties and fracture behavior of the fabricated composites were examined under different loading directions through compression, three-point bending and impact tests. The results indicated that the composites exhibited anisotropic features. The specimens compressed in the parallel direction failed by cracking along the layers of intermetallics and buckling of magnesium layers. The specimens compressed in the perpendicular direction failed by transverse cracking in the intermetallic layers and fallowing catastrophic cracking inclined about 45° to the interface of both intermetallic and magnesium layers. The flexural strength of the composites was higher in perpendicular than in parallel direction. When the load parallel to the layers was applied, the failure occurred by cleavage mode showing limited plastic deformation. When the load perpendicular to the layers was applied, the failure occurred by transverse cracking of the intermetallic layers and gradual cracking of the Mg layers. The Charpy-tested samples showed the same fracture behavior as the bend-tested specimens, which indicated that the same mechanisms operated at both high impact rate and low bending-test rate.

A novel polycrystalline Ni 3 Al-based intermetallic alloy was prepared using the vacuum induction melting process. Subsequently, the alloy was subjected to the solution-treatment underwent two different aging processes: 870 °C for 24 h in air cooling, referred to as AT 1, and 1060 °C for 4 h in air cooling followed by 870 °C for 24 h in air cooling, referred to as AT 2. The effects of different aging processes on the microstructure and mechanical properties of the polycrystalline Ni 3 Al-based intermetallic alloys were analyzed. Results indicated the cubicity of the primary γ′ phase within the dendritic γ+γ′ structure of the AT 2 sample was significantly enhanced, yielding the best overall mechanical properties for the alloy. The percentage elongation increased from less than 3 % for the AT 1 sample to about 4.5 %, highlighting a notable enhancement in room temperature tensile plasticity. The creep rupture time at 1100 °C/30 MPa reached 113 h. The α-Cr particles in the As-cast and solid solution alloy gradually transformed into Cr 23 C 6 during the aging process, exhibiting the orientation relationships of (020) Cr23C6 ||(010) γ' and [103] Cr23C6 ||[103] γ'. High-temperature aging treatments resulted in Cr 23 C 6 particles that provided enhanced precipitation strengthening effects, thereby improving the creep rupture performance of the Ni 3 Al-based intermetallic alloys. Following high-temperature aging, a four-layer interface structure formed around the blocky γ′ matrix phase, which altered the alloy's fracture mechanism from a brittle intergranular fracture to a ductile transgranular fracture. • The orientation relationship of (020) Cr23C6.||(010) γ' and [103] Cr23C6 ||[103] γ' between the precipitates Cr 23 C 6 and γ′-matrix • A four-layer interface structure formed around the blocky matrix γ′ phase after high-temperature aging process. • The unique interface structure causes the fracture mechanism of the alloy to transition from brittle transgranular fracture to ductile intergranular fracture. [ABSTRACT FROM AUTHOR]

The present work reports the direct production of a high-entropy (HE) intermetallic CoNi0.3Fe0.3Cr0.15Al material with a B2 structure from mechanically activated elemental powder mixtures. Fast and efficient combustion synthesis (CS), spark plasma sintering (SPS), and reactive SPS (RSPS) methods were used to synthesize the HE powders and bulks. The formation of the main B2 phase along with some amounts of secondary BCC and FCC phases are reported, and L12 intermetallic (CS scheme) and BCC based on Cr (CS + SPS and RSPS schemes at 1000 °C) were observed in all samples. The interaction between the components during heating to 1600 °C of the mechanically activated mixtures and CS powders has been studied. It has been shown that the formation of the CoNi0.3Fe0.3Cr0.15Al phase occurs at 1370 °C through the formation of intermediate intermetallic phases (Al9Me2, AlCo, AlNi3) and their solid solutions, which coincidences well with thermodynamic calculations and solubility diagrams. Compression tests at room and elevated temperatures showed that the alloy obtained by the RSPS method has enhanced mechanical properties (σp = 2.79 GPa, σ0.2 = 1.82 GPa, ε = 11.5% at 400 °C) that surpass many known alloys in this system. High mechanical properties at elevated temperatures are provided by the B2 ordered phase due to the presence of impurity atoms and defects in the lattice. [ABSTRACT FROM AUTHOR]

The advanced heterogeneous laminated composites were successfully fabricated by vacuum hot pressing using Ni and Al foils by in situ solid-state reaction synthesis. The effects of holding time and temperature on the microstructure and phase distribution were analyzed using scanning electron microscopy. Based on the optimized processing parameters, the microstructure and phase transformation, and the relationship between the microstructure and the corresponding mechanical properties were discussed in detail. To clarify the mechanical response of the laminated structure, the deformation microstructure and fracture characteristics were studied by scanning electron microscopy and electron backscatter diffraction. The results indicated that the evolution of the interfacial phases in the laminated composite occurred via the sequence: NiAl3, Ni2Al3, NiAl, and Ni3Al. An interface between the Ni and Ni3Al layers without cracks and voids formed due to the uniform pressure applied during hot pressing. The laminated composites hot pressed under 620 °C/5 MPa/1 h + 1150 °C/10 MPa/2 h exhibited the best ultimate tensile strength of 965 MPa and an elongation of 22.6% at room temperature. Extending the holding time during the second stage of the reaction synthesis decreased the thickness of the Ni3Al layer. This decreased the tensile strength of the laminated composite at 1000 °C but improved the tensile strength at room temperature. Moreover, the layer–thickness relationship of the laminated structure and the matching pattern were important factors affecting the strength and elongation of the laminated composites. The reinforcement form of the materials was not limited to a lamellar structure but could be combined with different forms of reinforcement to achieve continuous reinforcement over a wide range of temperatures. [ABSTRACT FROM AUTHOR]

The application of the electromagnetic casting (EMC) to aluminum alloys is capable of producing structures, hardly obtainable by the conventional methods of casting due to the constant stirring of the crystallizing alloy and high cooling rate (~10³ K/s). For the first time we study EMC high purity binary Al-0.5Fe and Al-2.5Fe (wt.%) alloys in the as-cast state as well as after equal-channel angular pressing (ECAP) and cold rolling (CR). We demonstrate that EMC process leads to formation of metastable Al2Fe-alike intermetallic phase which does not decompose by further straining and annealing. Combined deformation by ECAP and CR results in the formation of ultrafine grained structure in which providing the increase in ultimate tensile strength up to 200 MPa in Al-0.5Fe and up to 340 MPa in Al-2.5Fe. Electrical conductivity level of Al-0.5Fe alloy increases up to 58.5% IACS, while the conductivity of Al-2.5Fe alloy decreases to 47.9% IACS. Both alloys demonstrate thermal stability of microstructure, mechanical and electrical properties under annealing up to 230 °C for 1h. These effects are discussed in terms of as-cast and strain-induced microstructures. [ABSTRACT FROM AUTHOR]

Sn-Mg alloys are potential Pb-free solder options. However, their mechanical strength and interfacial characteristics with electronic substrates remain barely understood. This study focuses on the interfacial heat transfer aspects, microstructure, and tensile strength of a Sn-2.1wt.%Mg alloy. Samples with various thermal histories were produced using a directional solidification apparatus. In these experiments, a Sn-2.1wt.%Mg alloy was solidified on Cu and Ni substrates, which are of interest in the electronics industry. Mathematical modeling was then employed, allowing for the determination of the overall and interfacial heat transfer coefficients (hov, and hi, respectively). The results show that the Ni substrate exhibits higher interfacial thermal conductance with the Sn-2.1wt.%Mg alloy compared to the Cu substrate, as indicated by the higher hi profiles. This fact occurs mainly due to their metallurgical interaction, resulting in a stronger bond with the presence of Sn-Ni-rich intermetallics at the interface. Finally, experimental equations based on the Hall–Petch relationship are proposed to describe how the refinement of the fibrous spacing of the Mg2Sn interphase (λG) and an increase in hi enhance both yield and ultimate tensile strengths.

In this study, we analysed the effect of Fe, Mn, or Fe and Mn additions (5 or 10 at%) on the structure, mechanical properties, deformation behaviour, including microstructure evolution, and oxidation resistance of a lightweight (density of 3.92 g/cm3) intermetallic Al 55 Cr 23 Ti 22 complex concentrated alloy (CCA) with a L1 2 + C11 b structure. The additions of Fe, Mn, or Fe and Mn (at the expense of Cr) retained the density below 4 g/cm3 and resulted in forming a D8 a phase (Th 6 Mn 23 -prototype; cF120; Fm-3m) in all the alloys, except for the Al 55 Cr 18 Ti 22 Mn 5 alloy. The D8 a phase nucleated with a different morphology within or adjacent to the C11 b phase, and adopted an orientation relationship of (110) C11b || (4 ‾ 4 ‾ 0) D8a , [3 3 ‾ 1] C11b || [ 1 ‾ 1 1 ‾ ] D8a , which provided coherent C11 b /D8 a interfaces. Alloying with Mn or Fe and Mn had either neutral or negative effect on the mechanical properties, while the Fe additions boosted the strength along with some decrease in the compressive plasticity at room temperature. Specifically, the Al 55 Cr 13 Ti 22 Fe 10 alloy showed a yield strength of 250 MPa at 1000°С, which was 60 % higher compared to the Al 55 Cr 23 Ti 22 alloy. During plastic deformation, all the alloys demonstrated pronounced strain hardening at T ≤ 800 °C and steady state flow at 1000 °C. Post-deformation observation of the microstructure of the Al 55 Cr 13 Ti 22 Fe 10 alloy showed the inhomogeneous distribution of the strain-induced defects between the L1 2 matrix and (C11 b + D8 a) regions at 800 °C and partial recrystallisation of these phases at 1000 °C. All the alloys exhibited complex oxidation behaviour with multistage oxidation kinetics. The addition of 5 at% of Fe or Mn was beneficial for the oxidation resistance, while the further increase in their contents intensified the mass gain after a certain time. The latter effect was more pronounced in the Al 55 Cr 13 Ti 22 Mn 10 alloy than in the Al 55 Cr 13 Ti 22 Fe 10 alloy, because of forming a loose Al 2 O 3 oxide layer. All the alloys investigated exhibited a superior synergy of 1000°C-specific yield strength and compressive plasticity at room temperature, as well as a lower mass gain after 100 h at 1000 °C, compared to both lightweight and the most oxidation-resistant refractory CCAs. • Effect of Fe, Mn, or Fe and Mn additions on the Al 55 Cr 23 Ti 22 CCA were studied. • The alloying resulted in the precipitation of D8 a phase with coherent interfaces. • Fe increased the strength at 22–1000 °C, while Mn or Fe and Mn had neutral effects. • Addition of 5 at% of Fe or Mn reduced the mass gain at 1000 °C. • All the alloys were stronger and more oxidation-resistant at 1000 °C than other CCAs. [ABSTRACT FROM AUTHOR]

Metallic material concepts associated with the sustainable and efficient use of resources are currently the subject of intensive research. Al addition to steel offers advantages in view of lightweight, durability, and efficient use of high-Fe scrap from the Al industry. In the present work, Al was added to Fe-12Cr-(9,12)Ni-3Mn-0.3C-xAl (x = 0.1–6) (wt.%) stainless steels to assess its influence on microstructure and mechanical properties. According to density measurements based on Archimedes' principle, densities were between 7.70 and 7.08 g/cm3. High-energy X-ray diffraction estimations of the lattice parameter indicated that nearly 31% of density reduction was caused by the lattice expansion associated with Al addition. Depending on Al concentration, austenitic and duplex matrix microstructures were obtained at room temperature. In the presence of up to 3 wt.% Al, the microstructure remained austenitic. At the same time, strength and hardness were slightly enhanced. Al addition in higher quantities resulted in the formation of duplex matrix microstructures with enhanced yield strength but reduced ductility compared to the austenitic alloys. Due to the ready formation of B2-(Ni,Fe)Al intermetallics in the ferrite phase of the present alloy system, the increase in strength due to the presence of ferrite was more pronounced compared to standard duplex stainless steels. The occurrence of B2 intermetallics was implied by dilatometry measurements and confirmed by electron microscopy examinations and high-energy X-ray diffraction measurements. [ABSTRACT FROM AUTHOR]

Laminated Mg-intermetallic composites were successfully fabricated by reaction synthesis in vacuum using 1 mm thick magnesium sheets and 0.25 mm thick copper foils. The final microstructure consisted of alternating layers of a hypoeutectic alloy containing crystals of CuMg2 and eutectic mixture of CuMg2 and solid solution of copper in magnesium and unreacted magnesium. The mechanical properties and fracture behavior of the fabricated composites were examined under different loading directions through compression, three-point bending and impact tests. The results indicated that the composites exhibited anisotropic features. The specimens compressed in the parallel direction failed by cracking along the layers of intermetallics and buckling of magnesium layers. The specimens compressed in the perpendicular direction failed by transverse cracking in the intermetallic layers and fallowing catastrophic cracking inclined about 45° to the interface of both intermetallic and magnesium layers. The flexural strength of the composites was higher in perpendicular than in parallel direction. When the load parallel to the layers was applied, the failure occurred by cleavage mode showing limited plastic deformation. When the load perpendicular to the layers was applied, the failure occurred by transverse cracking of the intermetallic layers and gradual cracking of the Mg layers. The Charpy-tested samples showed the same fracture behavior as the bend-tested specimens, which indicated that the same mechanisms operated at both high impact rate and low bending-test rate. [ABSTRACT FROM AUTHOR]

The aim of this investigation is to study the effect of time and temperature on the solid-state diffusion welding of commercial aluminum alloy 2xxx series with a pure copper at 425°C, 475°C, 500°C, and 525°C during holding times from 15 min to 240 min. The main characterization techniques were optical microscopy, scanning electron microscopy, energy dispersive spectrometry, nanoindentation, microhardness measurements, and x-ray diffraction. Results showed that increasing the temperature and the holding time had an effect on the apparition of the intermetallics at the Al alloy/Cu interface. Five intermetallic phases namely Al2Cu, AlCu, Al3Cu4, Al2Cu3, and Al4Cu9 were identified at the interface. The mechanical properties of the welded joint Al/Cu alloy varied also with the time and temperature. The nanoindentation measurements showed that the highest values of hardness were recorded in AlCu and Al3Cu4 phases. The welding success of these dissimilar metals can be used for battery cables or to form heat exchanger plates for vehicles. [ABSTRACT FROM AUTHOR]

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Enhanced understanding of NbSi2 alloys allows to better control properties and performance. This challenge involves establishing the relationship between processing conditions and the features of the ordered structure of the silicide. Further correlation with mechanical properties remains a challenge. In this study, the dependency between processing conditions and properties of NbSi2 processed by solid-state diffusion was investigated. Pack cementation was used to process NbSi2 with different Si availability conditions (5-20wt.%) at 1000 and 1150 °C. Experimental results showed that hypo-stoichiometric NbSi2 compounds (atomic Si/Nb ratio below 2.0) formed and that lattice distortion increases with reduced Si availability during processing. The measured Young's modulus (331.69-303.9 GPa) and hardness (13.27-11.13 GPa) on NbSi2 decrease with increasing lattice distortion. Discussion reveals that lattice distortion has contributions from point defects density and the chemical bond of Nb and Si atoms. [ABSTRACT FROM AUTHOR]

Advancement in modern manufacturing processes is allowing researchers to develop new alloy configurations for different applications to reduce weight and increase efficiency. Many alloy combinations are produced that randomly generate different phases of intermetallic compounds (IMCs) in the structure during manufacturing which show unique mechanical and chemical properties. But, the fundamental knowledge of different IMCs is scattered across the material research domain. Thus, in this review, the crystal structures of IMCs are thoroughly discussed which are having structural and functional applications. Furthermore, the issues associated with the dissimilar Fe‐Al, Fe‐Ni, and Ni‐Al systems via modern manufacturing processes such as arc additive manufacturing have been discussed. Moreover, detailed knowledge of ferro‐nickel, nickel‐aluminides, and ferro‐aluminides formed at the interface during the dissimilar deposition in modern manufacturing is provided. Currently, a few transition metal IMCs and some Heusler alloys, are the most promising and are used in applications. The addition of a third alloying element provides the broadening effect on the phase domain of a specific IMC. Furthermore, it has been observed that modern manufacturing processes such as additive manufacturing and others are new and advanced manufacturing technologies used for dissimilar metal deposition, which can control the IMCs in a more favorable direction. [ABSTRACT FROM AUTHOR]

To offer a response to the increasing interest on high-temperature shape memory alloys, mainly driven by the aeronautic and aerospace industries, the design and characterization of Cu-Al-Ni shape memory alloys with high transformation temperatures, between 373 K and 473 K, are approached. The present alloy design is based on the transformation from cubic β3 austenite to the monoclinic β'3 martensite, which offers the advantage of exhibiting not only higher transformation temperatures but also a thermal hysteresis of about 12 K, much smaller than the orthorhombic γ'3 martensite historically considered for this alloy system. The influence of the alloy concentration and the thermal treatments, on the martensitic transformation temperatures is systematically analyzed and a quantitative and predictive equation is proposed. The influence of the stress on the transformation was also studied under two experimental conditions: at constant stress as a function of temperature (shape memory effect) and at constant temperature as a function of the stress (superelastic effect). A double stress-induced transformation from β3 to β'3 and α'3 with an outstanding reversible and reproducible 24% superelastic strain is also reported. The experimental results allows also determine the Clausius-Clapeyron diagrams for this series of alloys, as a fundamental tool for further design of sensing and actuating devices based on these high-temperature shape memory alloys.

This work investigated the interaction between in situ grain refiner and ultrasonic treatment (UT) and its influence on the mechanical properties of Mg–Sm–Al magnesium alloy. The grain size is reduced with the increasing of Al content, which is attributed to the enhancement of heterogeneous nucleation by Al2Sm particles. The ultrasonic melt treatment also refines grains via increasing the number of nucleation sites by ultrasonic cavitation. There is a maximum grain refinement efficiency on a certain solidification circumstance. The alloying method (generation the in situ grain refiner) and UT have a positive interaction, which increases the number of potential nucleation particles in melt, while the number of activated nucleation particles is decided by solidification condition. The increase of Al content and UT improve both yield strength and ultimate tensile strength due to grain refinement strengthening and the second phase strengthening. The UT significantly improves the elongation of each alloy with an increasing range of up to 312%. The de-agglomeration of second particles and increased diversity of grain orientation respond to such improvement.

The tensile properties at elevated temperatures (780, 800 and 820 ℃) for the laminated CuAl10Fe3Mn2-intermetallics composites have been investigated. The bronze-intermetallics laminated composites were transformation superplastic at 800 ℃. When the initial strain-rate was 0.7 × 10-3 s-1 fracture elongation of 455% was achieved. An excursion through the transformation range α→β and back β→α resulted in a finite, irreversible strain increment on each thermal cycle. These strains were accumulated without fracture of intermetallic layers. A small amount of cavities were formed during superplastic deformation of aluminum bronze which were nucleated at the iron-rich particles and grew along the force axis. At 780 and 820 ℃, the expected superplastic behavior of laminated composites was not realized because α and β phase grains were too coarse to allow deformation by grain-boundary sliding through microstructural superplasticity and cracking in the intermetallic layers began.

Herein, the favorable influence of sandwich‐stacked Sn/SAC305/Sn multilayers on the micromechanical and electrical properties of the Cu‐Sn/SAC305/Sn‐Cu solder joints over Cu‐SAC305‐Cu joints is reported. Solder joint interface is characterized through X‐ray diffraction spectroscopy, scanning electron microscopy, transmission electron microscopy, scanning tunneling microscopy (STM), and nanoindentation studies. The use of Sn multilayers facilitates the formation of more homogeneously distributed intermetallic compounds (IMCs) with smaller crystallite sizes and higher dislocation densities at the joint interface. Nanoindentation test results manifest that the hardness, modulus, and resistance to plastic deformation of the joint interface for the samples prepared with Sn multilayer are 3.26 GPa, 123.3 GPa, and 1.5 × 109, respectively, much higher and improved than 0.32 GPa, 41.82 GPa, and 5.28 × 105 in turn, found for samples prepared without using Sn multilayers. STM results confirm a much better electron transfer capacity of the solder joint interface that consists of Sn multilayers compared with solder joints produced without incorporation of Sn multilayer. Wherein, Sn multilayer containing solder joint found less prone to be affected by the humid atmosphere compared with nonlayered solder joint, in which, the former is found to be 48% less sensitive toward humidity (85% Rh) than later. [ABSTRACT FROM AUTHOR]

The possibility of producing by electron beam melting the ingots of titanium aluminide of Ti–Al system, additionally alloyed by refractory elements, namely niobium, chromium and molybdenum, was studied. A procedure of adding the refractory elements was developed, and technological modes were calculated, which allow optimizing the alloying element evaporation during melting. Test melting of Ti–28Al–7Nb–2Mo–2Cr intermetallic alloy was conducted in UE-121 electron beam unit. An ingot of 200 mm diameter was produced and its quality, structure and mechanical properties were studied. Ref. 11, Tabl. 2, Fig. 5. [ABSTRACT FROM AUTHOR]

Ti–22Al–25Nb intermetallic alloy is the latest generation of lightweight aerospace material with superior high-temperature performance. In the present study, a novel hybrid 3D-printing technique, point-forging and laser-deposition (PF-LD), was adopted for demonstrating its possibility in the preparation of near-net-shaping Ti–22Al–25Nb component. We innovatively exploited the top ductile B2/β-phase-zone as a natural protective layer, successfully preparing Ti–22Al–25Nb intermetallic parts with relatively larger build-height without initiating any macro-micro cracks. Three groups of control trials were further performed to ascertain the effect of initial laser parameters on microstructural characteristic and mechanical performance. Among three deposition strategies, the sample with intermediate laser scanning rate reached the best combination of ultimate tensile strength (UTS: ∼ 1280.7 MPa) and elongation after failure (EL: ∼ 5.7 %), while superior tensile strength (UTS: ∼ 1314.8 MPa) could be also achieved at the expense of tensile ductility (EL: ∼ 2.4 %). This study not only reveals a new idea to low-temperature forming Ti–22Al–25Nb alloy, but also provides an insight into the relationship between PF-LD processing parameters and mechanical performance. • PF-LD is a novel hybrid 3D-printing technique which introduces point-forging into the process of conventional laser-deposition. • Ti 2 AlNb intermetallic sample with relatively-larger build height was successfully prepared by hybrid PF-LD technique. • The influence mechanism of initial laser parameters on microstructural evolution and mechanical properties was discussed. [ABSTRACT FROM AUTHOR]

The roles of Al 11 Sm 3 and Al 2 Sm phases on microstructure evolution, mechanical properties and corrosion behavior of the Mg-5Sm-xAl system was investigated. The results showed that adding Al to Mg–5Sm binary alloy brought two Al–Sm phases, Al 11 Sm 3 and Al 2 Sm, which had two distinct roles regarding the microstructure evolution, mechanical properties and corrosion behavior of the Mg-Sm-Al alloy. Al 11 Sm 3 produced a strong galvanic couple with the Mg matrix, and significantly accelerated the corrosion. The Al 2 Sm particles promoted heterogeneous nucleation and refined the grains, which increased the tensile strength and ductility. Both types of Al–Sm particles provided strengthening effect for the alloy. With higher Al contents, Al 2 Sm formed an Al oxide protective surface layer and increased corrosion resistance. [Display omitted] [ABSTRACT FROM AUTHOR]

Ni3Al-based alloys have drawn much attention as candidates for high-temperature structural materials due to their excellent comprehensive properties. The microstructure and corresponding mechanical properties of Ni3Al-based alloys are known to be susceptible to heat treatment. Thus, a significant step is to employ various heat treatments to derive the desirable mechanical properties of the alloys. This paper briefly summarizes the recent advances in the microstructure evolution that occurs during the heat treatment of Ni3Al-based alloys. Aside from γ′ phase and γ phase, the precipitations of β phase, α-Cr precipitates, and carbides are also found in Ni3Al-based alloys with the addition of various alloying elements. The evolution in morphology, size, and volume fraction of various types of secondary phases during heat treatment are reviewed, involving γ′ phase, β phase, α-Cr precipitate, and carbides. The kinetics of the growth of precipitates are also analyzed. Furthermore, the influences of heat treatment on the mechanical properties of Ni3Al-based alloys are discussed. [ABSTRACT FROM AUTHOR]

Long-length bimetallic conductors with a copper core and a shell from an aluminum alloy up to 2.4 mm in diameter with enhanced strength are obtained by swaging. The effect of the swaging strain on the structure, phase composition and mechanical properties of the bimetallic conductors is studied. [ABSTRACT FROM AUTHOR]

The mechanical performance of as-cast and hot extruded Mg-4Si-4Ni-xCa alloys was studied. In the as-cast microstructures, the dendritic primary Mg2Si particles, eutectic α-Mg + Mg2Si constituent, blocky χ-phase (Mg8Ni7Si5 intermetallic), and α-Mg phase were observed. Moreover, the needle-shaped CaMgSi intermetallic at high Ca additions was detected. The modification effect of Ca was discussed based on the size refinement and morphological enhancement of Mg2Si phase. Accordingly, the tensile properties of the as-cast alloys were enhanced by Ca addition no more than 1 wt.%. However, large additions (3 wt.%) resulted in the deterioration of strength and ductility due to the appearance of the needle-shaped CaMgSi intermetallic. Compared to the cast ingots, the wrought alloys (obtained by hot extrusion) showed superior mechanical performance with much larger work-hardening exponents and tensile toughness values. For instance, the tensile toughness of the extruded alloy with 1 wt.% Ca was determined as 78.65 MJ/m3, which is much higher than the value of 9.32 MJ/m3 for the as-cast 0 wt.% Ca alloy. As the best combination of tensile properties, the ultimate tensile strength and the total elongation of the extruded alloy with 1 wt.% Ca were 348.4 MPa and 16.6%, respectively. [ABSTRACT FROM AUTHOR]

The tensile properties at elevated temperatures (780, 800 and 820 ℃) for the laminated CuAl10Fe3Mn2-intermetallics composites have been investigated. The bronze-intermetallics laminated composites were transformation superplastic at 800 ℃. When the initial strain-rate was 0.7 × 10-3 s-1 fracture elongation of 455% was achieved. An excursion through the transformation range α → β and back β → α resulted in a finite, irreversible strain increment on each thermal cycle. These strains were accumulated without fracture of intermetallic layers. A small amount of cavities were formed during superplastic deformation of aluminum bronze which were nucleated at the iron-rich particles and grew along the force axis. At 780 and 820 ℃, the expected superplastic behavior of laminated composites was not realized because α and β phase grains were too coarse to allow deformation by grain-boundary sliding through microstructural superplasticity and cracking in the intermetallic layers began. [ABSTRACT FROM AUTHOR]

The use of aluminum and copper materials increases due to their excellent electrical and thermal characteristics. The growth and the type of intermetallic compounds were varied with the various conditions in fusion welding. The present study focuses on the joining of aluminum to copper by friction welding to characterize the intermetallic layer in the interface. Heat treatment was applied for the welds using a constant temperature of 300 °C for the duration of 6 h, 12 h and 24 h. The growth of the intermetallics and their characteristics were examined by microscopic and energy-dispersive X-ray spectroscopy studies. The interdiffusion, growth rate and thickness of the intermetallic compounds were evaluated according to the heating time. The tensile strength and resistance of the welds gradually reduced with increasing the thickness of the intermetallic compounds. The fracture morphology of the welds was investigated by scanning electron microscopy on both sides of the welds. [ABSTRACT FROM AUTHOR]

Vehicle body structures are increasingly utilising multi-materials designs with advanced high strength steels (AHSS) and aluminium alloys. A robust process for joining aluminium alloys to AHSS based on resistance spot welding (RSW) is essential to widespread application of such bi-metallic structures in fuel-efficient vehicles. In this study, ultrasonic plus RSW was applied to join AA6022 to Zn-coated dual-phase steel DP980. During solid-state ultrasonic spot welding, an interface structure comprising multilayer, Al–Zn and Zn–Fe intermetallics formed due to alloying of aluminium with steel coating. Such structure was subsequently melted into the aluminium nugget, and new Al–Fe intermetallics formed during RSW. Ultrasonic plus resistance spot-welded joints had superior fracture energy than direct resistance spot-welded joints. [ABSTRACT FROM AUTHOR]

The influence of the addition of 2.3 at.-% Y and of 0.8 at.-% Zr + 0.2 at.-% Y on the properties of TiAl43Nb4Mo1B0.1 (TNM-B1) titanium aluminide alloy is investigated. Energy-dispersive X-ray spectroscopy analysis shows that the Y content of the β, γ, and α2 phases is low, and nearly all of the Y is in the Al2Y phase. The Zr content in the alloy phases is the same as that in alloy. Tensile tests show that Y addition decreases tensile strength and elongation, but only minor effects on these properties are observed after the addition of Zr and Y. It is shown that the addition of Y leads to a decrease in the heat resistance of TiAl43Nb4Mo1B0.1 alloy at 900°C. [ABSTRACT FROM AUTHOR]

Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Rare Metal Materials & Engineering is the property of Northwest Institute for Nonferrous Metal Research and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The deformation behaviour of single crystals of an Mg 85 Zn 6 Y 9 alloy with an 18R-LPSO structure was experimentally and numerically investigated using a micro-tensile testing method and a crystal plasticity finite element method, respectively. The deformation microstructure was characterised using optical and electron microscopy. The experimental results indicated that kink band was formed in the specimens depending on the initial crystal orientation relative to the loading direction. The kink banding was accompanied with remarkable ductility of over 50% nominal strain. The deformation behaviour observed was successfully reproduced in a crystal plasticity finite element analysis. The numerical results indicated that the kink band was formed by the accumulation of basal slip, which was enhanced by the geometrical softening owing to the lattice rotation. The growth of a kink band, which was reasonably explained by the changes in Schmid factor for a basal slip system due to lattice rotation, suppressed the localised failure at low strain. This resulted in the observed extended ductility, even in the LPSO structure with strong plastic anisotropy. Image 1 • Ductility of LPSO single crystals strongly depends on loading direction. • Remarkable ductility of LPSO crystals was achieved where a kink band was formed. • Numerical analysis reproduced deformation behaviour of a LPSO single crystal. • Changes in Schmid factor by lattice rotation lead to the remarkable ductility. [ABSTRACT FROM AUTHOR]

High temperature deformation behaviour and microstructure were investigated in cast in-situ TiAl matrix composite reinforced with carbide particles. Samples of the in-situ composite were prepared by vacuum induction melting followed by centrifugal casting of Ti-44.6Al-7.9Nb-3.6C-0.7Mo-0.1B (at.%) alloy. Compression, tensile and creep tests were carried out up to a temperature of 950 °C in air. The initial microstructure of the test specimens consists of coarse primary Ti 2 AlC particles and the matrix composed mainly of γ(TiAl) with small amount of retained α 2 (Ti 3 Al) lamellae and fine secondary P-Ti 3 AlC and H-Ti 2 AlC precipitates. During compressive deformation, the work hardening of the composite results from an increment of dislocation density and formation of deformation twins in the matrix. The work softening is caused mainly by dynamic recovery (DRV) and dynamic recrystallization (DRX) of the matrix and to a less extent by fracture of some coarse Ti 2 AlC particles. The composite shows brittle tensile behaviour below 850 °C. The brittle-ductile transition temperature (BDTT) is determined to be between 850 and 900 °C at a strain rate of 1 × 10−4 s−1. The creep deformation curves exhibit a primary creep stage, which is directly followed by the tertiary creep at temperatures ranging from 760 to 900 °C and applied stresses from 120 to 300 MPa. The coarse primary and fine secondary carbide particles act as effective obstacles to dislocation motion. The kinetics of creep deformation is controlled by diffusion assisted climb of dislocations at strains corresponding to minimum creep rates. • Coarse and fine carbide particles are effective obstacles to dislocation motion. • Tensile deformation and fracture depend strongly on BDTT. • Increase of dislocation density and formation of twins leads to work hardening. • Dynamic recovery, recrystallization and carbide fragmentation lead to work softening. • Kinetics of creep deformation is controlled by dislocation climb at low strains. [ABSTRACT FROM AUTHOR]

Hypereutectic Al–13.5Si alloy containing 1.47% of copper and 1.30% of magnesium was designed as a potential material for internal combustion engine pistons. The optical microscopy and scanning electron microscopy (SEM) revealed the fine dendrites of α-Al phase and significantly dispersed eutectics in as-cast specimens. Several intermetallic phases were observed indicating different crystallization velocities and alloy composition nonuniformities. The tensile testing and hardness measurements performed at room temperature have shown an excellent tensile strength and hardness of as-cast specimens, but low elongation due to a complex multiphase structure. The mechanical examinations at 250 °C and 300 °C have presented a decrease in tensile strength and an increase in elongation, while hardness was slightly changed. The fractographic analysis has shown the features of the brittle as well as ductile fracture. The areas of dimples and areas containing particles with smooth surfaces were detected. Electrochemical methods, Tafel linear polarization, cyclic voltammetry, chronoamperometric measurement and impedance spectroscopy were employed to determine the corrosion behavior of as-cast specimens in 0.5 M NaCl solution. The resistant oxide layer formed on the surface was not entirely consistent due to the appearance of intermetallic phases. SEM examinations of corroded samples did not discover severe pits on their surfaces. [ABSTRACT FROM AUTHOR]

The iron aluminides discussed here are Fe–Al-based alloys, in which the matrix consists of the disordered bcc (Fe,Al) solid solution (A2) or the ordered intermetallic phases FeAl (B2) and Fe3Al (D03). These alloys possess outstanding corrosion resistance and high wear resistance and are lightweight materials relative to steels and nickel-based superalloys. These materials are evoking new interest for industrial applications because they are an economic alternative to other materials, and substantial progress in strengthening these alloys at high temperatures has recently been achieved by applying new alloy concepts. Research on iron aluminides started more than a century ago and has led to many fundamental findings. This article summarizes the current knowledge of this field in continuation of previous reviews. [ABSTRACT FROM AUTHOR]

Hypereutectic Al-Fe alloys are extremely brittle owing to the formation of coarse Fe-rich intermetallics in the Al matrix. In this study, a Ce-rich rare-earth (RE) mixture was introduced to modify an Al-5Fe binary alloy, and the crystallization, microstructure, and mechanical properties of the alloy were investigated. The experimental results indicated that the RE addition decreased the temperature of the primary Al 3 Fe phase, enhanced the temperature of the eutectic transformation, and disturbed the normal crystallization process of eutectic α-Al crystals by decreasing the intrinsic growth along the preferential close-packed (111) Al plane and promoting the growths depending on the sub-closed (200) Al plane. Furthermore, RE addition refined the primary Al 3 Fe phases and formed Al-Ce eutectics in the as-cast state of the alloy. Fine nodules and rods of the Al 4 Ce and AlCe phases containing La elements were produced through homogeneous annealing via the decomposition of the Al-Ce eutectics and precipitation of REs from the RE-enriched area. Rolling further broke up the coarser primary Al 3 Fe phases into short rods and particles and caused the Al-Ce and Al-Fe phases to become uniformly distributed in the Al matrix. A mixed cleavage and dimple fracture was produced by RE modification, annealing, and rolling. The optimized amount of added RE mixture for improving the microstructure and mechanical properties of the alloy was 0.9 wt%. • RE addition decreased the primary temperature of Al 3 Fe phase. • RE addition inhibited intrinsic growth of eutectic α-Al along (111) plane. • RE addition promoted the growth of eutectic α-Al along sub-closed (200) plane. • RE addition refined primary Al 3 Fe phases and formed Al-Ce eutectics. • 0.9 wt% RE was optimized for improving microstructure and mechanical properties. [ABSTRACT FROM AUTHOR]

Ni 3 Al-based alloy joints were fabricated by transient liquid phase (TLP) bonding with Ni/Ti composite interlayer. The typical interfacial microstructure of the bonded joint was primarily composed of three zones: isothermal solidification zone, athermal solidification zone and base metal. Various reaction products were observed in the bonded joint, including γ′-Ni 3 (Al, Ti), TiNi 3 , Cr-Mo-Fe rich precipitates and β-Ti. The TiNi 3 phase in the athermal solidification zone was gradually reduced and eventually vanished by increasing the bonding parameters. The maximum room temperature shear strength of 828 MPa was obtained when the joint was bonded at 1220 °C for 60 min, while it was 625 MPa and 533 MPa at 650 °C and 800 °C, respectively. Cracks propagated primarily along the Ni 3 Al base metal and partially at the bonding interface when the joint was bonded at 1220 °C for 60 min, indicating the shear strength of the joint was almost equal to that of the base metal. • TLP bonding of Ni 3 Al-based alloy with Ni/Ti composite interlayer was achieved. • Ni 3 Al-based alloy joints had excellent room and high temperature strength. • Correlation between the joint microstructure and properties was established. [ABSTRACT FROM AUTHOR]