Synergistic improvement of strength and ductility is challenging in the engineering applications of titanium matrix composites (TMCs). Herein, we fabricated the TC4 composites reinforced with grain boundary micron-TiC and intragranular nano-Ti 2 Cu using spark plasma sintering (SPS) and hot rolling (HR) to achieve a good balance between strength and ductility. An interfacial reaction between Ti and C forms the grain boundary TiC, and the vast majority of intragranular nano-Ti 2 Cu precipitates to accommodate the severe lattice distortion caused by the solid solution of Cu in β-Ti phase. Benefiting from Ti 2 Cu nanoprecipitates and their ability to effectively suppress dislocation motion , precipitation strengthening, and dislocation strengthening are the main factors, in addition to grain refinement strengthening due to deformation processing , that contribute to the realization of the superior yield strength (YS) of 1360 MPa and ultimate tensile strength (UTS) of 1504 MPa in composites than TC4 matrix (YS = 986 MPa, UTS = 1160 MPa). Meanwhile, the interfacial strain-delocalization effect of TiC/Ti 2 Cu with Ti matrix, the shear-lag effect of TiC, and the sustained strain-hardening effect provided by TiC/Ti 2 Cu empower the composites with an outstanding ductility (fracture elongation of 8.4 %). This study highlights the untapped potential for improving the mechanical properties of Ti matrix composites.
Zhaoyang Zheng,Dong Han,Tianyu Zhang,An Du,Ruina Ma,Yongzhe Fan,Xue Zhao,Xiaoming Cao
The Co-depletion zone in WC–Co brazed joints is the main zone of joint failure, so it is crucial to explore novel processes to inhibit the Co-depletion zone and enhance the joint shear strength. In this study, a composite process of pre-plating Cu on the WC–Co surface + brazing was designed. Co-depletion zone reduces from 6 μm to 1 μm due to the Cu plating. Meanwhile, the formation of a plating fusion zone in the filler layer transforms TiCo with a thickness of 2.5 μm into a small number of TiCo particles. Moreover, the high concentration of Cu atoms in the vicinity of the WC particles at the interface changes the Co-segregation layer in the WC into a Cu-rich layer. The concentration of Cu in the filler layer leading to precipitation of TiCu and Ti 2 Cu particles. Ti 2 Cu particles encapsulated by ductile Ag–Cu–In ternary eutectic contribute to inhibit the cracks propagation. The shear strength of the joints was enhanced by 51.3 % to 295 MPa. The composite process of pre-plating on the base material surface + brazing has positive significance in inhibiting the excessive diffusion of elements from the base materials to the filler layer.
危险品化学品经营许可证（带存储）