Mingyang Li

1. Cu-Ta alloys hold substantial application potential in armor materials, liquid rocket engines, offshore systems, and navigation control devices due to their outstanding mechanical properties, th...

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.

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.