Microstructure And Properties Of Ti-30Mo Based Composites

The β-type Ti-30Mo alloy has a broad application prospect in offshore engineering due to its excellent corrosion resistance.But this greatly limits the wide application ofβ-type titanium alloys attributed to its low Young’s modulus and insufficient strength.The addition of second-phase particles and alloying elements to titanium alloys is an effective method to regulate the microstructure and improve the properties of titanium alloys.In this paper,a series of Ti-30Mo-x TiC（x=0,0.5,2.5,5 wt.%）composites were prepared by adding nano-TiC particles with Tipowder as the titanium source and a series of Ti-30Mo-0.5TiC-y Zr（y=0,4,8,12 wt.%）composites were prepared by adding ultra-fine Zr powder with TiH₂powder as the titanium source.wt.%)composites were prepared.The effects of TiC and Zr additions on the microstructure and mechanical properties of Ti-30Mo based composites were systematically analyzed.The main conclusions are as follows.（1）In Ti-30Mo-x TiC composites,C elements diffuse from TiC particles to the matrix region at the interface with a large solid solution,and this atomics diffusion promotes sintering densification.Compared with Ti-30Mo,the composites with TiC addition have higher density;meanwhile,there exists[1 11]（01 1）β-Ti_（bcc）|[011]（11 1）TiC_（fcc）interfacial relationship between TiC andβ-Timatrix lattice,which is a semi-coherent interface.（2）With the increase of TiC content,the microhardness and Young’s modulus of the composite matrix can be improved.Due to the synergistic effect of densification and semi-coherent interface strengthening,the mechanical properties of the composite have been improved,but with the increase of TiC aggregation,the tensile strength and elongation will be reduced.Ti-30Mo-0.5TiC composite has excellent performance combination.The matrix microhardness,tensile strength,elongation and Young’s modulus are 294 HV_0.3,820 MPa,6.5%and 112 GPa,respectively.（3）The preparation of titanium alloy from TiH₂powder can effectively promote the densification process of Ti-30Mo alloy,which is conducive to obtain titanium matrix composites with excellent mechanical properties.For Ti-30Mo-0.5TiC-y Zr,when the addition amount of Zr is less than 8 wt.%,the composite has high relative density（>98%）,but when the addition amount of Zr is 12 wt.%,the relative density decreases significantly.With the increase of Zr content,Theβphase lattice constant will increase and the aggregation of carbide will increase,resulting in the decrease of tensile strength of the composite,but its hardness will increase.（4）In the high temperature tensile test at 600℃,the fracture modes of both Ti-30Mo-0.5TiC and Ti-30Mo-0.5TiC-4Zr composites were dominated by ductile fracture rupture,in which Ti-30Mo-0.5TiC composites still had high mechanical properties with tensile strength and elongation of 472 MPa and 12.8%,respectively.There are 46 figures,8 tables and 96 references...