A novel mechanical stirring-assisted double-melt in-situ reaction casting process was developed to prepare Cu-1TiB2 (wt

Synergistic effects of a novel Cu51Hf14 inoculant and Zr element on the microstructure, mechanical and damping properties of Cu-Al-Mn shape memory alloy were investigated. The results showed that grains of the alloy could be significantly refined due to the heterogeneous nucleation of Cu51Hf14 and the pinning effect of AlCu2Zr particles on grain boundaries (GBs), the martensite lath was also greatly refined. Mechanical properties were improved obviously, the alloy with the smallest grain size showed the highest tensile strength and elongation. This attributed to grain refinement, increasing difficulty of grain coordination deformation, decreasing mobility of martensite variants and the pinning effect of AlCu2Zr on dislocation. The compound refining alloys possessed high room-temperature damping owing to the increased interface density and the uncoordinated deformation of AlCu2Zr and Cu-Al-Mn matrix. While its high-temperature damping was lower than that of the inoculated alloy because of the decreasing martensite content caused by the increasing GB influence zone and the precipitation of AlCu2Zr.

The effect of cryogenic rolling and intermediate aging on the microstructure and properties of the Cu-10Fe-1Nb composites were investigated. After aging for 1800 min, the microhardness, tensile strength and elongation of the Cu-10Fe-1Nb samples reached 158 HV, 623 MPa and 22%, respectively. The microstructure results showed that the fibrous Fe-rich phases and the matrix of the Cu-10Fe-1Nb samples were refined significantly after cryogenic rolling. It could be attributed to the increasing shear strain between the Fe-rich phases and matrix with dislocation density of the matrix, which inhibited the dynamic recovery recrystallization of the matrix. The intermediate aging promoted the dissolved Fe to precipitate obviously, and these precipitates effectively impeded the recrystallization of the matrix during the subsequent aging process. The improvement of mechanical properties was mainly attributed to the Orowan strengthening, refinement strengthening and work hardening resulted from the numerous precipitates, fine grains and high-density dislocation in the matrix, respectively.

Copper matrix composites (CMCs) offer promising applications by combining the functional characteristics of copper with composite phases. With the rapid advancement in aerospace, microelectronics, and intelligent terminal engineering, the demand for CMCs with superior mechanical and electrical properties has become increasingly critical. This paper reviews the design principles, preparation methods, microstructures and properties of some typical CMCs. The existing form of composite phases in the Cu matrix and their effects on microstructure evolution and comprehensive properties are summarised. Key underlying mechanisms governing these enhancements are discussed. The results provide a systematic understanding of the relationship between reinforcement phases and properties, offering insights for the future development of CMCs aimed to achieve much better comprehensive properties. The paper concludes by outlining the development trends and future outlook for the application of CMCs.

In order to improve the comprehensive properties of the Cu-11.9Al-2.5Mn shape memory alloy(SMA),multilayer graphene(MLG)carried by Cu51Zr14 inoculant particles was incorporated and dispersed into this alloy through preparing the preform of the cold-pressed MLG-Cu51Zr14 composite powders.In the resultant novel MLG/Cu-Al-Mn composites,MLG in fragmented or flocculent form has a good bonding with the Cu-Al-Mn matrix.MLG can prevent the coarsening of grains of the Cu-Al-Mn SMA and cause thermal mismatch dislocations near the MLG/Cu-Al-Mn interfaces.The damping and mechanical properties of the MLG/Cu-Al-Mn composites are significantly improved.When the content of MLG reaches 0.2 wt.％,the highest room temperature damping of 0.0558,tensile strength of 801.5 MPa,elongation of 10.8％,and hardness of HV 308 can be obtained.On the basis of in-depth observation of microstructures,combined with the theory of internal friction and strengthening and toughening theories of metals,the relevant mechanisms are discussed.

Pre-aging treatment was demonstrated to significantly enhance the mechanical properties of Cu-10Fe-1Nb (wt. %) composites. Specifically, after rolling and aging at 400 degrees C for 8 h, the microhardness, tensile strength, and elongation of the pre-aged samples reached 163 HV, 559 MPa, and 11.2%, respectively. The refinement of Ferich phases in pre-aged samples was primarily attributed to the increased shear strain between the Fe-rich phases and the matrix, which was driven by the precipitation-strengthening effect induced by pre-aging. Additionally, the matrix of the pre-aged samples suffered significant refinement as dynamic recovery and recrystallization of the matrix were suppressed during the rolling process, forming a high-density dislocation structure that greatly enhances the work-hardening effect. The main contribution to strength improvement in the Cu-10Fe-1Nb composites was identified as precipitation strengthening, refinement strengthening, and work hardening. Moreover, compared with the sample without pre-aging treatment, the refinement strengthening and work hardening effects of pre-aged samples exhibited substantial improvements, with increment of 49 MPa and 21 MPa, respectively.

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 degrees C, respectively. The nano-scale Fe2Ti and & gamma;-Fe precipitates, accompanying with some submicron-scale primary Fe2Ti phase, are found in the aged alloy. The orientation relationship between the nano-scale Fe2Ti precipitate and the Cu matrix is Fe2Ti [1 21 6]//Cu [01 1] (with a small deviation) and Fe2Ti (02 21)//Cu (200), while that between the nano-scale & gamma;-Fe precipitate and the Cu matrix is & gamma;-Fe [110]//Cu [110] and & gamma;-Fe (111)//Cu (111), respectively. The precipitation of Fe2Ti and & gamma;-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.

The Cu-10Fe-based composites with different Nb content were fabricated by vacuum mold casting. The effect of Nb content on the solidification behavior and microstructure was investigated systematically and the optimal composition was determined as Cu-10Fe-1.0 Nb (wt%). The as-cast samples were rolled by 90% reduction at room and then aged at 250 celcius for different time. The properties results showed that, after aging for 1800 min, microhardness, tensile strength and elongation of the Cu-10Fe-1.0 Nb samples reached 145 HV, 553 MPa and 21.5%, respectively. The microstructure results showed that the primary Fe-rich phases in the Cu-10Fe-1.0 Nb samples were significantly refined due to the heterogeneous nucleation induced by Fe2Nb phases, and then led to the refinement of the matrix. The enhanced mechanical properties could be attributed to the Orowan strengthening, refinement strengthening and work hardening resulted from the numerous submicron-/nano-sized Fe particles, fine sub-grains and high-density dislocation in the matrix formed during thermo-mechanical treatment.

In this study, Cu-2.7Ti-0.2Fe (CT-0.2Fe) and Cu-2.7Ti–1Fe (CT-1Fe) alloys were fabricated and underwent multi-stage thermomechanical treatment, and the microstructure and properties evolution of the alloys during aging were investigated. After aging for 60 h at 350 °C, the CT-0.2Fe and CT-1Fe alloys exhibited the yield strength of 1068/935 MPa, tensile strength of 1127/1057 MPa, elongation of 2.54%/2.21%, and electrical conductivity of 20.3/26.4 %IACS, respectively. The relatively higher electrical conductivity of CT-1Fe was primarily attributed to the formation of numerous TiFe particles. Typical modulated structure and β′-Cu4Ti precipitates formed during direct aging in both alloys. However, in the CT-1Fe alloy, the growth of β′-Cu4Ti precipitates was suppressed. During multi-stage thermomechanical treatment, the interaction of the dislocations and precipitates was enhanced, retarding the softening effects of the alloy at the elevated temperatures. The calculation results showed that work hardening and precipitation strengthening significantly contributed to enhancing the mechanical properties of the alloys.

The investigation of the Al–Ag–Zr system is crucial for the development of heat-resistant Al alloys, which are essential for applications in high-temperature environments. In this work, we first determined the isothermal sections of the Al–Ag–Zr system at 500 and 600 °C using equilibrium alloys. Simultaneously, the τ 3 (Al 6 AgZr 6 ) phase was identified by transmission electron microscopy (TEM). In addition, the three-phase equilibrium of τ 3 + AgZr + (Ag) instead of Al 3 Zr 4 + AgZr + (Ag) was confirmed at 500 and 600 °C. The formation enthalpies of the end-members and ternary compounds in the Al–Ag–Zr system were calculated via first-principles calculations. Based on the experimental and computational results, a thermodynamic database of the Al–Ag–Zr system was established using the CALPHAD (calculation of phase diagrams) method. The hardness of τ 1 (Al 2.68 Ag 0.32 Zr) and τ 2 (Al 1.84 Ag 0.16 Zr) were determined to be 3.82 and 10.20 GPa, respectively, using nanoindentation. The introduction of the τ 2 phase in the design of Al alloys can considerably increase the mechanical properties of the alloys.

Cu-10Fe composites were produced by the vacuum suction casting and traditional vacuum mold casting, respectively. The evolution of microstructure and properties of the composites during cold rolling and aging processes was analyzed. Compared with the traditional mold-casted Cu-Fe composites, the suction-casted Cu-Fe composite had better mechanical properties, with microhardness, tensile strength and elongation of 146 HV, 526 MPa and 23.7%, respectively. The softening temperature of the suction-casted Cu-Fe composite was 520 degrees C, which was 220 degrees C higher than that of traditional mold-casted Cu-Fe composite. The good performance of the suction-casted Cu-Fe composite was mainly attributed to the refinement of the Cu matrix and the formation of the multi-scale alpha-Fe particles caused by the effect of solute trapping during vacuum suction casting. The yield strength of the composites was mainly attributed to the contribution of Orowan strengthening, refinement strengthening and dislocations strengthening, which count for 31.1%, 25.8% and 24.1%, respectively.

Grains of a Cu-Al-Ni shape memory alloy (SMA) were significantly refined by using the combined refining effect of Cu51Zr14 inoculant and Ti element. With the decrease of grain size, the damping capacity remarkably increased, and the Martensitic transformation (MT) temperatures shifted to low temperature side. Correlated mechanisms have been discussed.

A novel Mg/TiNiCu composite was successfully fabricated from porous TiNiCu shape memory alloy (SMA) and pure Mg via non-pressure infiltration process with the aim of developing a new kind of high damping material with excellent mechanical properties. In order to restrain the formation of undesired Mg2Cu phase, the methods of short-time infiltration and rapid consolidation were adopted. Resultant material had homogenously distributed and 3D interconnected Mg particles in the TiNiCu matrix. Compared with porous TiNiCu SMA, in addition to the notable increase of storage modulus the damping property of Mg/TiNiCu composite was also obviously improved, which could be attributed to the superposition effect of multiple damping sources. (C) 2018 Elsevier B.V. All rights reserved.