To overcome the tradeoff between strength and ductility of materials and obtain titanium matrix composites with excellent mechanical properties, in this study, the in situ-synthesized TiC particles and Ti-Al-V-Mo-Cr (Ti1400) alloy-reinforced Ti6Al4V (TC4) matrix composites ((Ti1400 + TiC)/TC4) were fabricated by low-energy ball milling and spark plasma sintering. The inhomogeneous distribution of TiC particles and Ti1400 alloy, as well as the compositional and structural transition zone, were characterized. The TiC/TC4 composite displayed a significantly higher yield strength and tensile strength compared to the TC4 alloy. However, the total elongation of the TiC/TC4 composite was only 57% of that in the TC4 alloy. In contrast, the (Ti1400 + TiC)/TC4 composites exhibited noticeably higher total elongation than the TiC/TC4 composite. Furthermore, the tensile strength of the composite increased with the increase in Ti1400 alloy content. The increase in strength can be attributed to solid solution strengthening and fine grain strengthening. The compositional and structural transition zone, formed by element diffusion, provided a better interface combination between the reinforcements and TC4 matrix. In the transition zone and Ti1400 region, a large number of α/β interfaces can effectively alleviate the stress concentration, and the increase in the β phase can bear more plastic deformation, which is conducive to improving the elongation of the composite. As a result, the (Ti1400 + TiC)/TC4 composites exhibited simultaneous improvements in strength and ductility.

One of the long-standing challenges in the field of titanium matrix composites is achieving the synergistic optimization of high strength and excellent ductility. When pursuing high strength characteristics in materials, it is often difficult to consider their ductility. Therefore, this study prepared a Ti1400 alloy and in situ synthesized TiC-reinforced (TiC + Ti1400)/TC4 composites using low-energy ball milling and spark plasma sintering technology, followed by hot rolling, to obtain titanium matrix composites with excellent mechanical properties. The Ti1400 alloy bonded well with the matrix, forming uniformly distributed Ti1400 regions within the matrix, and TiC particles were discontinuously distributed around the TiC-lean regions, forming a three-dimensional network structure. The (TiC + Ti1400)/TC4 composites effectively enhanced their yield strength to 1524 MPa by using 3 wt.% of Ti1400 alloy while preserving an impressive elongation of 9%. When the Ti1400 alloy content reaches 20 wt.%, the overall mechanical properties of the composites decrease. A small amount of Ti1400 does not reduce the strength of the composite. On the contrary, it can undergo stress-induced phase transformation during plastic deformation, thereby coordinating deformation, which not only provides higher strain hardening and increases tensile strength but also benefits ductility.

When ceramic particles are incoherent with copper matrices, or when large coherent strains exist due to the differences between their crystal structure and lattice parameters in traditional dispersion-strengthened copper alloys, the strengthening effect of dispersoids at high temperatures is reduced. In the present work, a Cu-0.48Al-3.5Yb₂O₃ alloy was fabricated by mechanical alloying and spark plasma sintering. The investigation results prove that completely coherent inert ceramic particle YbAlO₃ without coherent strains is introduced into the copper matrix. The microstructural evolution and thermal stability of the alloy after annealing at high temperatures are investigated and discussed, and it is found that the alloys exposed at 600~800 °C for 3 h exhibit excellent thermal stability and exceptional structural stability. The exceptional resistance to grain growth in the alloy can be attributed to the Zener pinning effect provided by the fine dispersion of YbAlO₃ particles. High-density geometrically necessary dislocation (GND) is retained in the alloy even after annealing at 800 °C for 3 h, as is the presence of parallel GND rows because they do not easily react with opposite rows to annihilate the dislocation. At the same time, dispersed YbAlO₃ acts as a strong obstacle to moving the GND. The present work proves that the structural stability of copper can be significantly improved by introducing completely coherent dispersed particles.