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In this paper, a series of Cu-3.2Ni-0.6Co-xSi-0.2Cr-0.15 Mg (x = 0.62, 0.75, 0.92 and 1.09) (wt.%) alloys were fabricated and subjected to multi-step thermo-mechanical treatment (TMT), and the microstructure and properties of the alloys were investigated in detailed. The results showed that the alloys achieved the combination of high strengths and high conductivity, i.e. yield strengths of 809–913 MPa, tensile strengths of 849–951 MPa, and electrical conductivity of 33.4–42.0 %IACS. The good properties were due to nanoscale δ-(Ni,Co) 2 Si and Cr 3 Si precipitates, high-density dislocations, and even deformation twins. More importantly, it is found that the Ni, Co and Cr solute atoms decreased but the Si solute atoms increased with the Si contents in the alloys according to the principle of conservation of mass. For deformation, this change aggravated dislocation annihilation, reduced twinning propensity, and thus weakened the work-hardening effect. For precipitation, this change promoted the coarsening of nanoscale precipitates and the depletion of solute atoms, and thus weakened the precipitation-strengthening effect but benefited the electrical conductivity. • Cu–Ni–Co–Si–Cr–Mg alloys after TMT achieved high strengths and high conductivity. • High performance was due to dislocations, δ-(Ni,Co) 2 Si and Cr 3 Si precipitates. • Principle of conservation of mass provided important microstructural information. [ABSTRACT FROM AUTHOR]

The evolution of microstructures and properties of the hot rolled cobalt (Co) during the isothermal annealing at different temperature was investigated. Recrystallization only occurred in hexagonal closed-packed (HCP) Co below martensitic transformation temperature (400 °C), the proportion of face-centered cubic (FCC) Co decreased dramatically and the Co sample became an HCP-Co single-phase with increasing annealing time due to the diffusive phase transformation promoted by high angle boundaries (HABs). For samples annealed at 400 °C, recrystallization occurred in both of HCP-Co and FCC-Co. The proportion of FCC-Co reached the highest value of 50% in sample annealed at 400 °C for 4 h, and the average grain size was less than 2.5 μm even after 12 h annealing due to the formation of special boundaries, annealing twins and the alternate permutation of nano FCC-Co lamellae and HCP-Co lamellae. The recrystallization mechanism was analyzed by the Johnson-Mehl-Avrami-Kolmogorov model and modified Arrhenius relationship. The nucleation and grain growth through the migration of HABs promoted the FCC→HCP diffusive phase transformation below martensitic transformation temperature. At temperature above martensitic transformation temperature, recrystallization kinetics of HCP-Co and migration of HABs was hindered by reverse martensitic transformation. • A new phase transformation mechanism in pure Co was theorized and HCP single-phase Co was obtained. • The trend and mechanism of proportion of retained FCC-Co during annealing above martensitic transformation temperature was analyzed. • Two special orientation relationship were observed and analyzed. • The interaction between phase transformation and recrystallization was analyzed. [ABSTRACT FROM AUTHOR]

In this paper, Yttria-stabilized zirconia reinforced tungsten alloys (W-YSZ) were prepared by liquid phase method combined with powder metallurgy technology, aiming at optimizing the powder quality and improving the properties of tungsten alloy. In the process of hydrothermal synthesis, ZrO 2 with various crystal structures can be prepared by controlling the ratio of ZrO 2 to Y 2 O 3. When the doping mass ratio of ZrO 2 and Y 2 O 3 is 4:1, ZrO 2 can be stabilized to form cubic phase structure. ZrO 2 and excessively doped Y 2 O 3 in the composite powders can refine the particle size of tungsten particles and reduce the degree of agglomeration. Compared with SPS sintered samples, the size of the samples sintered by vertical melting is coarser, but because of the low sintering temperature of SPS, the density is lower, while the density and hardness of the samples sintered by vertical melting are higher. After sintering at high temperature, the zirconia did not undergo crystal transformation, but remained cubic phase. The (110) of W and (002) of YSZ have a semi-coherent relationship, and the mismatch rate is 12% according to calculation, with good interface bonding and no obvious cracks. Due to the doping of YSZ particles, the strength and toughness of the tungsten alloy are enhanced by the combined effect of dispersion strengthening and fine grain strengthening. • ZrO 2 with different crystal structure was prepared by hydrothermal method. • Excessive doping of Y 2 O 3 can not only stabilize zirconia, but also refine the grain. • W-YSZ alloy prepared by liquid phase method has fine particles and uniform distribution. • The addition of YSZ particles increases the strength and toughness of the tungsten alloy. • W (110) and YSZ (002) have a semi-coherent relationship. [ABSTRACT FROM AUTHOR]

In this paper, Yttria-stabilized zirconia reinforced tungsten alloys (W-YSZ) were prepared by liquid phase method combined with powder metallurgy technology, aiming at optimizing the powder quality and improving the properties of tungsten alloy. In the process of hydrothermal synthesis, ZrO 2 with various crystal structures can be prepared by controlling the ratio of ZrO 2 to Y 2 O 3. When the doping mass ratio of ZrO 2 and Y 2 O 3 is 4:1, ZrO 2 can be stabilized to form cubic phase structure. ZrO 2 and excessively doped Y 2 O 3 in the composite powders can refine the particle size of tungsten particles and reduce the degree of agglomeration. Compared with SPS sintered samples, the size of the samples sintered by vertical melting is coarser, but because of the low sintering temperature of SPS, the density is lower, while the density and hardness of the samples sintered by vertical melting are higher. After sintering at high temperature, the zirconia did not undergo crystal transformation, but remained cubic phase. The (110) of W and (002) of YSZ have a semi-coherent relationship, and the mismatch rate is 12% according to calculation, with good interface bonding and no obvious cracks. Due to the doping of YSZ particles, the strength and toughness of the tungsten alloy are enhanced by the combined effect of dispersion strengthening and fine grain strengthening. • ZrO 2 with different crystal structure was prepared by hydrothermal method. • Excessive doping of Y 2 O 3 can not only stabilize zirconia, but also refine the grain. • W-YSZ alloy prepared by liquid phase method has fine particles and uniform distribution. • The addition of YSZ particles increases the strength and toughness of the tungsten alloy. • W (110) and YSZ (002) have a semi-coherent relationship. [ABSTRACT FROM AUTHOR]

Abstract: The microstructure transition, shape memory effect, machinability and mechanical property of the CuAlMnZn alloy with and without Te have been studied using X-ray diffraction analysis, chips observation and scanning electron microscopy (SEM), tensile strength test and differential scanning calorimeter (DSC), and semi-quantitative shape memory effect (SME) test. The particles with richer Te dispersedly distributed in grain interior and boundary with size of 2–5μm. After the addition of Te, the CuAlMnZnTe alloy machinability has been effectively increased to approach that of BZn15–24–1.5 and its shape memory property remains the same as the one of CuAlMnZn alloy. The CuAlMnZn shape memory alloys with and without Te both have good ductility as annealed at 700°C for 15min. [Copyright &y& Elsevier]

Abstract: The fabrication conditions of Cu–Al–Ni–Mn alloy powder by mechanical alloying and powder metallurgy have been systematically studied. The mechanically alloyed powder (MAed powder) was fabricated at a speed between 100rpm and 300rpm for various milling times with and without process control agent (PCA). With an increasing of milling time, the size of crystallite grain decreases. Only the Cu diffraction pattern appear as the rotation speed is up to 300rpm for 25h. The elemental powders with PCA agglomerate slightly, but the degree of alloying is lower than that without PCA. The shape memory recovery of the quenched sample hot-extruded at extrusion rate of 50:1 is measured to be 100% recovered in 250°C oil bath for 40s after deformed to 4.0%. After aging at 120°C for 10 days, the shape memory recovery of the alloy remains 98%. [Copyright &y& Elsevier]

A novel Cu-Cr-Yb alloy was designed and processed by thermo-mechanical treatment. The microstructure, mechanical and electrical properties were investigated in detail. The results showed that the Cu-Cr-Yb alloy had a higher strength, a better softening resistance and a considerably high electrical conductivity than the Cu-Cr alloy. After 80% cold rolling followed by aging at 500 °C, the peak-aged Cu-Cr-Yb alloy had a Vickers hardness of 160 ± 1 HV, a tensile strength of 465 MPa, an elongation of 21.1% and an electrical conductivity of 89.5 %IACS, respectively. After a long-time aging at 500 °C, the nano-scale Cr-rich precipitates with FCC structure in the Cu-Cr-Yb alloy hardly coarsened. Thermodynamics analysis showed that the Cr-rich precipitates were inclined to nucleate with FCC structure, and the addition of Yb hindered the nucleation of the Cr-rich precipitates. • Cu-Cr-Yb alloy had better comprehensive properties than Cu-Cr alloy. • Nano-scale Cr-rich precipitates in Cu-Cr-Yb alloy hardly coarsened. • Yb hindered the nucleation of the Cr-rich precipitates. [ABSTRACT FROM AUTHOR]

The interfacial morphologies play a crucial role in mechanical properties of laminated/bimetal composite. This study investigates the effects of heat treatments on the interfacial characteristics, mechanical properties and fracture behaviour of a 2205 duplex stainless steel/AH36 carbon steel bimetal composite with varying interface situations fabricated by the hot-rolling and subsequent heat treatments. The bimetal composite was annealed from 850 °C to 1150 °C in steps of 100 °C with soaking 1 h. Heterogeneities of grain size and element concentration exist in the microstructural evolution of bonding zone adjacent to interface after annealing treatments, which were observed by the optical microscope and scanning electron microscope (SEM) coupled with the energy dispersive X-ray spectroscopy (EDS). It was found that the diffusion transition zone of Cr and Fe alloy elements between component 2205 and AH36 steel layers present an increasing trend with the rise of annealing temperature. The results of conventional, shear and compact tensile test indicate that the tensile strength of 2205/AH36 bimetal composite gradually decreases but the fracture elongation increases with the rising annealing temperature, the thicker alloy element diffusion zone results in the stronger interfacial shear strength and better ductility of bimetal composite, but the thick and strong interface has less positive effect than the mechanical properties of bimetal composite itself on preventing the fatigue crack growth across the interface. [ABSTRACT FROM AUTHOR]

A novel Cu-1.01%Ni-0.28%Si-0.14%Co-0.45%Cr (mass percent) alloy with high strength and high conductivity was fabricated. Microstructure, mechanical and electrical properties of the alloy after multi-stage thermo-mechanical treatment were investigated in detail. The alloy has excellent comprehensive properties, with a tensile strength of 810 MPa, yield strength of 777 MPa, elongation of 3.4%, and electrical conductivity of 57.5%IACS (International Annealing Copper Standard). Three kinds of precipitates, (Cr,Co) 2 Si, (Ni,Co) 2 Si and Cr, form during aging treatment. Addition of Co element promotes the precipitation of Cr, Ni and Si solute elements from the matrix, while inhibits the growth of the (Cr,Co) 2 Si. The high strength of the alloy treated by multi-stage thermo-mechanical process is attributed to the dispersion strengthening, sub-structure strengthening, and work-hardening. The multi-aging process and addition of Co effectively improve the electrical conductivity of the studied alloy. The high strength and high conductivity of studied alloy make it as a potential candidate for lead frame materials in electrical and electronics industry. [ABSTRACT FROM AUTHOR]

The microstructure evolution of Cu-15Ni-8Sn-0.8Nb alloy during prior cold deformation by rotary swaging (RS) and subsequent aging treatment was investigated. Electron back scattered diffraction (EBSD) results indicated that the deformed microstructure mainly consisted of refined and elongated grains. Discontinuous precipitates appeared at previous grain boundaries (PGBs) and shear bands after deformation of 45 pct reduction. Transmission electron microscope (TEM) studies revealed that the transformation kinetics of both DO 22 ordered phases and discontinuous precipitates were significantly accelerated by prior deformation, and the transformation from DO 22 to L1 2 ordering was suppressed to a certain degree. The maximum yield strength of the specimens with 45 pct reduction reached to about 1230 MPa after aging treatment, but the corresponding ductility was poor due to the rapid growth of discontinuous precipitates. [ABSTRACT FROM AUTHOR]

Aging is an important step in improving the comprehensive properties of Cu-3.5Ti alloy. However, both prolonged holding times and high heat treatment temperatures lead to significant oxidation and substantial energy consumption. The effects of heat treatment (HT) and electropulsing treatment (EPT) on the microstructure and mechanical properties of the solid solution Cu-3.5Ti alloy were comparatively examined in this study. The findings demonstrated that EPT quickly completed the processes of spinodal decomposition and short-range ordered to long-range ordered phase transformation, thereby fully precipitating fine and diffusive β′-Cu 4 Ti phase, which greatly enhanced the precipitation strengthening effects. In addition to enhancing the strength of the alloy, EPT significantly reduced the peak aging time (to just 1/12 of that of HT) and greatly increased the plasticity (elongation to failure rose by 47 % compared to HT). The main reason for the rapid completion of the spinodal decomposition and the full precipitation process by the EPT was the additional free energy provided by the electropulsing, which significantly accelerated the Ti atomic diffusion and lowered the nucleation barrier of the β′-Cu 4 Ti phase. EPT is a toughening heat treatment process for metallic materials, which offers the advantages of high efficiency, low energy consumption, and low cost. • Compared with HT, the Cu-3.5Ti alloy after EPT exhibits superior mechanical and electrical properties. • EPT provides additional free energy for accelerating spinodal decomposition. • EPT reduced the thermodynamic energy barrier of nucleation, forming more and finer dispersive β′-Cu 4 Ti phase. • EPT is a new toughening heat treatment process for metallic materials, with high efficiency and low energy consumption. [ABSTRACT FROM AUTHOR]

The properties of materials are intricately dependent on their chemical composition, and microstructures. Achieving a precise modulation in the composition and microstructure of materials to enhance properties significantly is a huge challenge. In this work, we uncovered the effects of nickel and silicon composition on the precipitates, dislocations, and properties of Cu–Ni–Si alloys. The results show that the volume fraction of precipitates increased from 0.84 % to 4.80 % with the increase of Ni and Si contents. The average diameter of the precipitates increased from 6.20 nm to 20.21 nm, and the dislocation density increased from 2.16 × 1013 m−2 to 4.08 × 1015 m−2 concerning the Ni and Si contents. In addition, the dislocation type changes from half-edge dislocation and half-screw dislocation to screw dislocation. The modified WHWA (Williamson Hall-Warren Averbach) method was proved to be the most accurate way of calculating dislocation density. As anisotropy was present in the alloy, adding a dislocation contrast factor and removing some lower-intensity diffraction peaks could further correct the obtained results and reduce the calculation error. Furthermore, the above analysis and findings were employed to design a Cu-3.21Ni-0.66Si alloy with a high yield strength (814 MPa), high ultimate tensile strength (970 MPa), and comparable electrical conductivity of 42.4 % IACS. This work offers a meaningful way to develop precipitation-strengthening alloys. [Display omitted] [ABSTRACT FROM AUTHOR]

A multi-core through steel wire reinforced brass composite rod was fabricated using a solid-liquid continuous casting and composite technique. Microstructure evolution, interface, mechanical properties, and deformation behavior of the composite rod during the room temperature tensile process were studied. The results showed that the steel wires in the composite rod were distributed in a regular hexagonal shape, forming a brass/steel interface with good metallurgical bonding. After annealing at 700 °C for 1h, the tensile strength of the composite rod was 376 MPa, and the elongation to failure was 46.3 %, whose tensile strength was 21 % higher than that of the brass cladding single steel wire composite rod with the same steel percentage. During uniform tensile deformation, each steel wire in the composite rod experienced a consistent and uniform tensile stress. When the tensile deformation became unstable, the central steel wire experienced the highest level of tensile stress, initially leading to the occurrence of necking and fracture. As the tensile strain increased, the brass grains underwent twisting and rotation. In addition, the steel grains were elongated along the tension direction, and the number of low-angle boundaries increased. The straight brass/steel interface was transformed into a wavy pattern with a good bonding interface, indicating that the composite rod exhibited excellent synergetic deformation capability. The mixing laws based on hybrid effects have good applicability to multi-core through steel wire reinforced brass composite rod, with a strength error of less than 7 %. • A multi-core through steel wire reinforced brass composite rod was fabricated by using a solid-liquid continuous casting and composite technique • After annealing at 700 °C for 1h, the tensile strength of the composite rod was 376 MPa, it was 21 % higher than that of the brass cladding single steel wire composite rod with the same steel percentage. • The mixing laws based on hybrid effects have good applicability to multi-core through steel wire reinforced brass composite rod [ABSTRACT FROM AUTHOR]

In this paper, a novel Cu-0.60Cr-0.20Nb-0.05Si-0.02Ca-0.02Ce (CCNSCC, wt.%) alloy is designed. By comparing the differences in the properties and microstructure with the Cu-0.60Cr-0.20Nb (CCN, wt.%) alloy under the same process, the effects of trace Si, Ca, and Ce elements on the CCNSCC alloy are disclosed. After undergoing cold rolling by 80% and aging at 450 °C for 60 min, the CCNSCC alloy exhibits a tensile strength of 524 MPa and a softening temperature of 600 °C. These values represent an increase of 104 MPa and 90 °C respectively compared with the CCN alloy. After a multi-stage combined thermo-mechanical treatment including preaging at 400 °C for 30 min, the tensile strength and electrical conductivity of the CCNSCC alloy reach 618 MPa and 75.2%IACS respectively. Microstructure analysis shows the existence of rod-like and polygonal Cr 8 Nb 3 Si particles, as well as globular, ellipsoidal, and crescent-shaped (Ca,Ce)Cu 5 particles. During the process of aging, the precipitation of the Cr phase occurs at the phase boundaries of Cr 8 Nb 3 Si particles. Additionally, significant quantities of fine Cr particles at the nanoscale surround the Cr 8 Nb 3 Si particles, exerting a beneficial influence on the strength and electrical conductivity of the CCNSCC alloy. Besides, the CCNSCC alloy has finer Cr particle size and lower volume fraction of recrystallized grains after aging in comparison to the CCN alloy. This indicates that the addition of trace Si, Ca, and Ce elements significantly inhibits the growth of Cr particles and occurrence of recrystallization. Plenty of dislocations are observed in different states of the CCNSCC alloy, and their interaction with the Cr precipitates is the primary factor contributing to the excellent mechanical properties of the CCNSCC alloy. The findings of this study provide valuable insights for improving the properties and microstructure of Cu–Cr–Nb alloys. • A novel Cu-0.60Cr-0.20Nb-0.05Si-0.02Ca-0.02Ce (wt.%) with excellent comprehensive properties is designed. • Cr particles and (Ca,Ce)Cu 5 particles precipitate at the boundaries of nanoscale Cr 8 Nb 3 Si particles during aging. • The addition of trace Si, Ca, and Ce significantly inhibits the growth of Cr particles and occurrence of recrystallization. [ABSTRACT FROM AUTHOR]

The homogenization heat treatment is a key procedure to controlling the second phase, enhancing composition uniformity and workability of as-cast Cu–15Ni–8Sn alloy. Nonetheless, high annealing temperature and long holding time result in high energy consumption, high costs and severe oxidation. The effects of electropulsing treatment (EPT) and conventional homogenization treatment (CHT) on the microstructure and mechanical properties of Cu–15Ni–8Sn alloy by downward continuous casting were studied. The results showed that with increase of pulse current density, the treatment temperature of the alloy increased continuously. Subsequently, γ-(Cu, Ni) 3 Sn phase and lamellar (α+γ) phase underwent progressive spheroidizaiton and dissolution. Compared with CHT, EPT contributes to significant reductions in both treatment temperature (about 100 °C) and treatment time (1/34 of the CHT), the tensile strength decreased from 437 Mpa (as-cast alloy) to 380 MPa, while the elongation increased dramatically from 9.2 % to 41.6 %. Compared with being treated by CHT, the alloy treated by EPT performed excellent comprehensive mechanical properties. The extra free energy provided by EPT diminishes the thermodynamic energy barrier of γ phase dissolution and significantly accelerates atomic diffusion, which mainly contribute to rapid homogenization of Cu–15Ni–8Sn alloy by EPT at lower temperature. EPT can work as a novel homogenization heat treatment process for metallic materials, boasting advantages such as high efficiency, low energy consumption and low costs. [ABSTRACT FROM AUTHOR]

A Cu-0.48Cr-0.20Nb-0.27Zn (wt.%) alloy with excellent comprehensive performance is designed and prepared by adding Zn element and combining it with a novel combined thermo-mechanical treatment. A high-temperature short-time treatment is introduced to the traditional thermo-mechanical treatment. Results show that the hardness, tensile strength, yield strength, elongation, and electrical conductivity of Cu-Cr-Nb-Zn alloy reach 180HV, 580 MPa, 535 MPa, 7.6%, and 80.2%IACS, respectively. Compared with conventional thermo-mechanical treatment, the alloy after the new process has increased by 15HV, 35 MPa, 40 MPa, 1.3%, and 2.0%IACS, respectively. Submicron grains and nanoscale twins emerge following high-temperature short-time treatment (850 °C/5min), and the grains undergo substantial refinement. Besides, this process promotes the precipitation of solid solution Cr atoms, thereby significantly improving the electrical conductivity of the alloy. Two distinct crystal structures (C14 and C15) of Cr 2 Nb with diameters ranging from 80 to 200 nm are observed. The alloy's strength is greatly increased in the following aging process, which precipitates a significant quantity of nanoscale Cr phase. All of the above results have certain reference significance for the optimization design of Cu-Cr-Nb alloy composition as well as performance improvement. • A novel Cu-0.48Cr-0.20Nb-0.27Zn with good comprehensive properties was designed. • High-temperature short-time treatment refines the grains by recrystallization. • Nanoscale Cr 2 Nb particles with two different crystal structures can effectively pin dislocations. [ABSTRACT FROM AUTHOR]

A Heusler Fe 2 TiSi-phase strengthened 12Mn maraging steel Fe–12Mn–5Co–1Ti–1Mo–1Si was extensively studied using various experimental (EBSD, TEM and uniaxial tensile) techniques. The results indicate that the fine and dispersed Fe 2 TiSi particles, precipitating within the martensite, were the primary strengthening phase when aged at 450 °C regardless of whether the alloy is cold rolled or solid-solution treated. Furthermore, a soft reverted austenite nano-layer was observed at the lath interface, imparting significant toughness to the martensite matrix. By carefully optimizing the aging process parameters, the 12Mn alloy achieved a high tensile strength of ∼1700 MPa with a moderate elongation of ∼7% at break. When aged at 400 °C, unexpected precipitation of α-Mn particles within the martensite structure was observed, displacing the Fe 2 TiSi phase as the dominant strengthening phase. Simultaneously, elemental Mn segregation was found to occur at the lath interface, instead of the formation of reverted austenite. This Mn segregation layer was identified as the main factor contributing to brittle fracture behavior. These findings illustrate that synergistic improvement of strength and plasticity can be realized via an optimal combination of precipitation strengthening and interfacial layer toughening mechanisms. [ABSTRACT FROM AUTHOR]

A new strategy for the preparation of Cu–Fe alloy with excellent comprehensive performance is proposed. This strategy combines the construction of dual-scale polymetallic second phases with the addition of trace solid-solution atoms. A series of Cu–2Fe-0.3Cr-0.2Si-xMg (x = 0.1, 0.3, 0.5) alloys are designed and prepared through multi-stage thermo-mechanical treatment. Among the reported Cu–Fe alloys with low Fe content (Fe content less than 3 wt%), the designed Cu–2Fe-0.3Cr-0.2Si-0.3 Mg alloy has the highest product of the tensile strength times the electrical conductivity (PSC). The tensile strength and PSC of the Cu–2Fe-0.3Cr-0.2Si-0.3 Mg alloy are 698 MPa and 43.9 GPa∙%IACS, respectively. The dual-scale polymetallic second phase has been successfully constructed. The submicron-scale Fe 8 CrSi phase triggers the generation of substructures, such as geometrically necessary dislocation boundaries in lamellar structures and random dislocation boundaries in cell shapes. The high-density low angle grain boundaries (LAGBs) of substructure evolution enhances the substructure strengthening of the alloy. The main strengthening phase in precipitation strengthening is the nanoscale Fe 11 CrSi 4 phase. An appropriate amount of Mg reduces the ultimate solid solubility of Fe atoms in Cu alloys, promotes the formation of a dual-scale second phase and refines the grain size of the alloy. Therefore, the comprehensive performance of the design alloy is significantly improved. [ABSTRACT FROM AUTHOR]

The effect of the multi-stage thermo-mechanical treatment on the microstructure and properties of a Cu–2Fe-0.5Ti alloy (wt.%) was investigated. After repeated thermos-mechanical treatment, the alloy has the yield strength, tensile strength, elongation, electrical conductivity and softening temperature of 521 MPa, 554 MPa, 5.9%, 70.4 %IACS and 550 °C, respectively. The nano-scale Fe 2 Ti and γ-Fe precipitates, accompanying with some submicron-scale primary Fe 2 Ti phase, are found in the aged alloy. The orientation relationship between the nano-scale Fe 2 Ti precipitate and the Cu matrix is Fe 2 Ti [ 1 ‾ 2 1 ‾ 6]//Cu [0 1 ‾ 1] (with a small deviation) and Fe 2 Ti (02 2 ‾ 1 ‾)//Cu (200), while that between the nano-scale γ-Fe precipitate and the Cu matrix is γ-Fe [110]//Cu [110] and γ-Fe (111)//Cu (111), respectively. The precipitation of Fe 2 Ti and γ-Fe phase contributes to the improvement of the electrical conductivity and mechanical properties of the alloy. The strengthening mechanisms of the designed alloy is mainly grain boundary strengthening, dislocation strengthening and precipitation strengthening. • A novel CuFeTi alloy was designed and the alloy has good comprehensive properties. • The orientation relationship between the precipitates and the Cu matrix were investigated in detail. • The core strengthening mechanisms of the CuFeTi alloy was analyzed. [ABSTRACT FROM AUTHOR]

In order to shorten the production process of Cu-Fe alloy and improve the microstructure homogeneity and properties and properties, Cu-10 wt%Fe alloy billet was prepared by double-melt mixed casting process and then cold rolled. Microstructure and mechanical property evolutions of the alloy and its deformation behaviours were investigated. The results showed that the alloy billet had dispersed spherical Fe phase particles and dendritic Fe phases. The alloy billet had excellent plasticity, and the cumulative cold rolling reduction without intermediate annealing reached 98%. When the reduction was 30%, numerous dislocations produced in the Cu matrix and the Cu matrix near the Fe phase underwent local crystal rotation, and the Fe phase particles deformed slightly. When the reduction exceeded 90%, dynamical recrystallization of the Cu matrix happened, fine grains with average diameter of ~300 nm formed, and the dendritic Fe phases were evenly distributed along the rolling direction, which mainly contributed to achieve large-reduction of cold rolling. When the reduction was 98%, the tensile strength and hardness increased from 340 MPa and 87 HV of the as-cast alloy to 543 MPa and 164 HV, respectively, and the elongation and electrical conductivity was reduced to 3.0% and 13.5%IACS. A process of double-melt mixed casting → cold rolling can work as a novel high-efficiency and compact method to produce Cu-Fe alloy sheet. • Cu-10 wt%Fe alloy billet was produced by double melt mixed casting and then cold rolled. • Microstructure evolution and deformation behaviour of Cu-10 wt%Fe alloy during cold rolling was revealed. • Cu-10 wt%Fe alloy billet had excellent plasticity, and the cumulative cold rolling reduction reached 98%. • Most of the Cu matrix was refined into nanocrystalline grains with the reduction exceeded 90%. [ABSTRACT FROM AUTHOR]

There is microstructural heterogeneity in titanium alloy deposited by high-energy-density beam additive manufacturing (AM) technologies in an as-built condition that leads to anisotropy of mechanical properties, especially poor ductility. To resolve this problem, use of an alternating thermal cycle strategy during plasma arc AM has been studied. The results show that the equivalent thermal balance is maintained in the process, preventing the coarsening microstructure from growing along a single direction. As a result of the change of the maximum temperature gradient, the close-packed plane growth of the α phase deviated from the preferred orientation direction; i.e., the α phase deviated from the growth of {0002} and {10 1 ¯ 0} planes in the vertical direction but {10 2 ¯ 0} and {10 1 ¯ 0} planes in the horizontal direction. The grain size and the width of lamellar α are refined, specially the layer band region. The horizontal as-built mechanical properties are higher than those of the forging standards, with elongation of 11.6 ± 0.2%, and 28 ± 1.8% reduction of area. Meanwhile, the average vertical tensile properties were also commensurate with the forging strength, thus anisotropy and heterogeneity of the microstructure and mechanical properties are effectively weakened without post heat treatment. [ABSTRACT FROM AUTHOR]

Abstract Cu-0.47Cr-0.16 Nb (wt%) alloys were designed and prepared, and the microstructures of the Cu-Cr-Nb alloy were investigated using transmission electron microscopy and three-dimension atom probe tomography technique. After homogenizing at 950 °C for 4 h, cold rolling by 80% reduction, then aging at 450 °C for 30 min, the micro-hardness, electrical conductivity, tensile strength, yield strength and elongation of the alloy were up to 150 HV, 89.1%IACS, 453 MPa, 443 MPa and 11.4%, respectively. The tensile strength / elongation of the alloy approached 399 MPa / 22.9% as test at 200 ℃, 334 MPa / 14.8% for 300 ℃, and 282 MPa / 12.3% for 400 ℃, respectively. The Cr 2 Nb phase with an average size of 700 nm and Nb phase with an average size of 500 nm formed during the solidification process, while the nano-scale Cr-rich phases precipitated from the solid solution during the aging process. The sizes of Cr 2 Nb and Cr-rich phases were close to each other during aging. These precipitates located in the grain and sub-grain boundary could effectively pin the movement of boundary, resulting in a high strength of the alloy at the elevated temperature. The addition of Nb can promote the precipitation of Cr from the solid solution during aging, thus both strength and electrical conductivity of the alloy were improved. [ABSTRACT FROM AUTHOR]

Abstract The Cu–4.5Ni–1.2Co–1.0Si–0.15Mg alloy with super-high strength and high electrical conductivity was designed, and a two-step thermo-mechanical treatment was applied to improve the mechanical and electrical properties of the alloy. The microstructure and properties of the alloy were investigated by transmission electron microscope observation, tensile test, hardness and electrical conductivity measurements. The results show that the final alloy treated by two-step thermo-mechanical process has a hardness of 329 HV, a yield strength of 1086 MPa, an elongation of 3.6%, and an electrical conductivity of 30.1%IACS, respectively. The nanoscale β-Ni 3 Si and δ-(Co,Ni) 2 Si precipitates form during the thermo-mechanical process, and the addition of the Co could promote the precipitation of δ-(Co,Ni) 2 Si particles. The orientation relationship (OR) between Cu matrix and the precipitates is: (022) Cu //(011) β //(010) δ and [100] Cu //[100] β //[001] δ. Comparing with the directly aging treatment and one step thermo-mechanical treatment, precipitates that form during the two-step thermo-mechanical process are much smaller and distributed more densely, resulting in the better comprehensive properties of the alloy. [ABSTRACT FROM AUTHOR]

Effect of Mn content and annealing temperature on the microstructure of a classic G-phase strengthened Fe–20Cr–3Ni–3Si–1Ti ferritic steel was extensively examined using advanced electron microscopy techniques (SEM, EBSD and TEM) and theoretical predictions (thermodynamic calculation). Firstly, a ternary precipitating phase named τ (Fe 7 TiSi 2) which is isotypic to the structure of α-Mn (I -43m), existing at high-temperature (∼1050 °C), was discovered for the first time. Secondly, the ferrite matrix was observed to decompose into the mixture of the martensite, austenite and σ-phase at the mid-temperature region (700–850 °C). Thirdly, the nano-sized G-phase was discovered at both the intragranular sites and the grain boundaries after aging at 550 °C, behaving a strong over-aging resistance with the increased Mn content. Finally, phase stabilities of the detected τ, σ, G, ferrite, martensite and austenite phases with different Mn content were discussed under different annealing temperatures. These findings pave a new pathway to design the microstructure of G-phase steel via optimal annealing strategies. [ABSTRACT FROM AUTHOR]

High strength and high electrically conductivity Cu-Ni-Si alloys are important candidate materials for extending the life of currently used elastic-conductor materials. Phase transformation behaviors and properties of a synthesized Cu-6.0Ni-1.0Si-0.5Al-0.15Mg-0.1Cr alloy were investigated systematically. After homogenized for 4 h at 940 °C, hot rolled by 80% at 850 °C, solution treated for 6 h at 970 °C, cold rolled by 50%, and annealed for 60 min at 450 °C, the studied alloy approached physical properties of 1097.5 MPa in tensile strength and 26.4%IACS in electrical conductivity. Transmission electron microscope observations showed that four precipitation phases including δ-Ni 2 Si, β-Ni 3 Si, β-NiAl, and γ′-Ni 3 Al were formed in the studied alloy, which was subjected to different annealing temperatures. A detailed diagram for isothermal decompositions has been established. The high strength of the studied alloy was primarily attributed to the Orowan precipitation strengthening, and secondary attributed to the solid solution strengthening, the Hall-Petch type grain boundary strengthening, and the work hardening. Multi-precipitation phases of Ni 2 Si, γ′-Ni 3 Al, β-Ni 3 Si played significantly into the strengthening effects, and the low electron diffraction influence of Mg and Cr contributed to both solution strengthening and maintaining a high electrical conductivity. Multi-phase precipitation strengthening and using trace amount alloying elements for solution strengthening will be a new strategy to develop high strength and high electrical conductivity copper alloys. [ABSTRACT FROM AUTHOR]

A new dual-scale (submicron and nanoscale) FeCrSi ternary second-phase has been successfully constructed in designed Cu-2.5Fe-0.3Cr-0.2Si alloy. The synergistic addition of Cr and Si promotes the transformation of the submicron Fe phase morphology from "square" to "flower" shape in as-cast alloys. The orientation relationship between nanoscale FeCrSi phase and Cu matrix is: [ 011 ] Cu / / [ 0 1 ‾ 1 ] Fe 11 CrSi 4 and the misorientation angle between the (200) of the Cu matrix and the (022) of the Fe 11 CrSi 4 phase is about 4°. After three-stage thermomechanical treatment, the tensile strength and electrical conductivity of the alloy are 435 MPa and 70.52 %IACS, respectively. According to the calculated results, precipitation strengthening and substructure strengthening play an important role in the strengthening of Cu–Fe–Cr–Si alloys. With the addition of Cr and Si, the precipitation of the second phase in the alloy is promoted, which also leads to the improvement of the electrical conductivity and mechanical properties of the alloy. [ABSTRACT FROM AUTHOR]

The compressive properties of sintered tungsten alloys with different m -ZrO 2 weight percentage (0, 0.5, 1.0%) were tested at room temperature and high temperature, and the hot deformation behaviors of the three metals were investigated under different temperature (1300–1600 °C) and strain rate (0.005–1 s−1). The room temperature strengthening model of zirconia particle reinforced tungsten alloy was established, and the hot deformation activation energy and constitutive equation of the three metals were calculated. Characterized by field emission scanning electron microscopy (FE-SEM) and the electron back scattering diffraction (EBSD) technique, the results show that zirconia doping can significantly refine the tungsten grain size, improve sintering densities, and uniformly disperse in the boundaries and inside of tungsten grain. The room temperature compression results show that the ultimate compressive strength and strain-to-failure of W-1.0 m -ZrO 2 increase by 51.94% and 96.69%, respectively compared with pure tungsten. The main contribution to the room temperature strength of tungsten alloys is the fine grain strengthening caused by zirconia doping, about 60% for W-1.0 m -ZrO 2 ，while the strengthening of the secondary phase particles accounts only for about 5%. High-temperature compression results show that zirconia doping increases the dislocation density of the alloy and significantly improve the ultimate compressive strength under high-temperature compression, but the influence of zirconia content on the strength will be weakened at high temperature. The doping of zirconia reduces the hot deformation activation of tungsten alloys and improves the hot processing behavior of tungsten alloy. [ABSTRACT FROM AUTHOR]

WMoNbTaV refractory high-entropy alloy (RHEA) is facing the contradiction between strength and plasticity at room temperature, which greatly restricts its processing, forming and subsequent engineering applications. In the present work, WMoNbTaV and WMoNbTaV with 1 mass% additions of m-ZrO 2 (WMoNbTaV-1ZrO 2) RHEAs were successfully prepared by ball milling and spark plasma sintering technologies. The grain refinement of the one phase body-centered cubic alloy by presence of m-ZrO 2 is determined by microstructural analyses to be 31.5%. The yield strength, ultimate strength and fracture strain of WMoNbTaV-1ZrO 2 are 2171.1 MPa, 2461.4 MPa and 12.7% respectively, which are surprisingly increased by 69.0%, 62.5% and 32.3%, in comparison with that of WMoNbTaV without m-ZrO 2 , respectively. More importantly, they are remarkably superior to the same alloy prepared by the vacuum arc-melting method. A model is presented to study the strengthening mechanism of WMoNbTaV-1ZrO 2 , and the theoretical calculation shows that the extraordinary high strength is mainly due to the inherent strength in the multi-principal element WMoNbTaV alloy and grain boundary strengthening caused by the addition of m-ZrO 2 particles. • WMoNbTaV alloy with nano-ZrO 2 particles was fabricated by ball milling and SPS method. • Dispersed nano-ZrO 2 improved yield strength, ultimate strength and fracture strain of WMoNbTaV alloy. • Ultimate strength and fracture strain of WMoNbTaV-1ZrO 2 are 2461.4 MPa and 12.7%, respectively. • Nano-ZrO 2 pinning dislocations and refining grains causes changes in mechanical properties. [ABSTRACT FROM AUTHOR]

The orientation dependence of deformation microstructure has been investigated in uniaxial deformed body-centered cubic molybdenum by electron backscatter diffraction and transmission electron microscopy. It has been found that the dislocation boundaries in both tensile and compressed molybdenum, similar to that in face-centered cubic metals, can be classified into three types: dislocation cells (Type 2), and extended planar boundaries parallel to (Type 1) or not parallel to (Type 3) a {110} trace. Furthermore, it shows a reciprocal relationship between body-centered cubic metals and face-centered cubic metals on the orientation dependence of the deformation microstructure. Type 3 grains have stress axes direction which is near the [110] corner in the unit triangle for BCC metals, whereas Type 3 grains have stress axes direction which is near the [111] corner for FCC metals. The analysis of Schmid factors shows that the dislocation structure depends on the slip systems. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the creep behaviors of two Al2O3 particle reinforced copper composites were investigated using nanoindentation creep testing method. It has been shown that stress exponent determined by nanoindentation creep is much larger than that determined by traditional uniaxial tensile/compressive creep. A low externally applied loading results in a large scattering of the stress exponent due to limited grains joining the creep deformation and thus the different strain rates resulted from different grain orientations to the applied stress. The stress exponent of the composites increases with the externally applied loading for both composites, and the composite with higher reinforcement concentration shows larger stress exponents. [Copyright &y& Elsevier]

Abstract: Spray formed T15 high speed steel (HSS) billets were deposited using a state-of-the-art twin-atomiser spray forming facility. The effects of post thermo-mechanical processing (hot isostatic pressing and hot forging) and heat treatment on the microstructure and mechanical properties were investigated. As-deposited billet has a density over 99.3% of the theoretical value and no measurable macro-segregation was observed. The microstructure consists of the equiaxed grains with mean size of ∼18μm and MC- and M6C-type carbides non-uniformly distributed inside the grains and along the grain boundaries. After optimal thermo-mechanical processing and heat treatment, the microstructure was composed of equiaxed fine tempered martensites, and refined M6C and MC spherical carbides particles uniformly distributed along the grain boundaries and inside the grains. The hardness reached HRC68 after thermo-mechanical processing, and the corresponding impact toughness and bending strength reached 27J/cm2 and 4600MPa respectively. Although HIP cannot increase the bending strength significantly, it can effectively improve the impact toughness through refining and globurizing carbides. [Copyright &y& Elsevier]

The effect of Si on the microstructure and properties of Cu–10Fe alloy was systematically studied in this paper. By adding 0.4 wt% Si to Cu–10Fe alloy, the mechanical properties, electric conductivity, thermal conductivity, saturation magnetization and electromagnetic interference shielding effectiveness are significantly improved. After 90% cold rolling and 450 °C/32 h heat treatment, the electrical conductivity, thermal conductivity, tensile strength, elongation and electromagnetic interference shielding effectiveness of Cu–10Fe-0.4Si alloy are 68.02 %IACS, 304 W/(m·K), 521 MPa, 29.6% and 107.4 dB, respectively. Microstructure observation shown that FCC FeSi phases formed in two different sizes and the precipitation of the Fe atoms was promoted in Cu–10Fe-0.4Si alloy, which lead to the simultaneously improvement of conductivity, strength and magnetic properties. This high-strength, high-conductivity and magnetic Cu–Fe alloy has great application potential in electromagnetic shielding and other fields. [ABSTRACT FROM AUTHOR]

Modern electronics components require copper alloys to have higher strength and ductility for processing and forming. Cu–Ti alloys exhibit excellent mechanical properties while their plasticity is limited. In this work, high ductility Cu–Ti alloys were fabricated and investigated systematically, results indicated that the samples' strength and plasticity can be improved by adding high Ti and Cr content. The crystal relationship between the β′-Cu 4 Ti and Cu is that: [100] Cu //[011] β'-Cu4Ti , (020) Cu //(2 1 ‾ 1) β'-Cu4Ti. Further increase aging time, metastable β′-Cu 4 Ti particles started cellular reaction to be β-Cu 3 Ti phase, which were detected at the grain boundary. The crystal relationship between the β-Cu 3 Ti and Cu is that: [100] Cu //[011] β-Cu3Ti , (220) Cu //(400) β-Cu3Ti. The hardness, yield strength, elongation of the CuTiCrMg alloy after aging at 450°C for 30 min are 394 HV, 1057 MPa, and 1.6%, respectively. While, those of the CuTiCrMg–Fe alloy are 370 HV, 1160 MPa, and 10%, respectively. The precipitation strengthening is the primary strengthening mechanism. These findings are of great significance for developing Cu–Ti alloys with high strength and high plasticity. • Additions of Al, Fe, and Zr increase CuTiCrMg alloys' strength and high plasticity. • The CuTiCrMg–Fe alloys showed a high yield strength of and high plasticity. • The addition of Fe improved the studied CuTiCrMg–Fe alloy's high-temperature properties. • The precipitation strengthening contributes the most hardening effects in CuTiCrMg alloys. [ABSTRACT FROM AUTHOR]

A Cu–Ti–Cr–Mg–Si alloy with the super-high strength and high electrical conductivity was designed, and the effects of multi-stage thermomechanical treatment on the microstructure and properties of the alloy were investigated. The alloy treated by the multi-stage thermomechanical treatment had a yield strength of 1072 MPa, tensile strength of 1144 MPa, elongation of 6.1% and electrical conductivity of 24.1 %IACS. During the thermomechanical treatment, the nanoscale β′–Cu 4 Ti particles, Cr precipitates and submicro-particles that mainly consisted of Cu, Ti, Cr and Si elements formed, leading to the high strength of the alloy. β′–Cu 4 Ti phase with body-centered tetragonal structure had a classic orientation relationship with copper matrix: [001] Cu //[001] β' and [3-10] Cu //[100] β'. The super-high strength of the designed alloy was mainly attributed to the precipitation strengthening, sub-structure strengthening, solid solution strengthening and work hardening. Electrical conductivity increased during aging due to the decomposition of supersaturated solid solution. Compared with direct aging treatment, multi-stage thermomechanical treatment with the stepped temperature-reduction further improved the mechanical and electrical properties of the alloy. • The Cu–Ti–Cr–Mg–Si alloy had both high strength and good electrical conductivity. • Nanoscale β′–Cu 4 Ti particles and Cr precipitates as well as particles mainly consisted of Cu, Ti, Si and Cr formed. • The stepped reduced temperature played an important role during multi-stage thermomechanical treatment. [ABSTRACT FROM AUTHOR]

As a high strength wearproof alloy, Cu–15Ni–8Sn alloy structures were fabricated by selective laser melting (SLM), while they possessed poor mechanical properties due to the absence of precipitated phase, and thus they are on the halfway to industrial application. SLM-processed Cu–15Ni–8Sn alloy subjected to heat treatments is studied to further improve the performance. Microstructure evolutions and mechanical properties variations were investigated, and the strengthening mechanisms are discussed. SLM-processed matrix is a supersaturated solid solution with fine grains, leading to important yield strength contributions from solid solution strengthening. The incremental strength for heat-treated samples aged at 400 °C is mainly due to the DO 22 ordering and the spinodal decomposition. The precipitation strengthening increased from 1.4% to above 70% after heat-treatment. Among the three aging methods, directly aging (DA) samples showed highest strength than the other two methods. The directly aged samples exhibit fine grains and high dislocation density, resulting in high grain boundary strengthening and dislocation strengthening. Moreover, direct aging treatment is an economical and environment-friendly way to improve mechanical properties of SLM-processed precipitation-hardened alloy, which is a high strength conductive elastic material. [ABSTRACT FROM AUTHOR]