Microstructure And Properties Of TiB_W/Ti-6Al-4V Composite Prepared By Spark Plasma Sintering

Titanium-based composites have a wide range of applications in aerospace,medical devices and other fields due to their high specific strength,high hardness and good biocompatibility.The particle-reinforced titanium-based composites prepared by in-situ autogenous technology have good interface state;the melting method for preparing titanium-based composites are easy to introduce other impurities,and the composites prepared by Self-propagating High-temperature Synthesis are not dense.As a novel powder sintering method,SPS has a fast heating rate and a short sintering time.It can be raised to the temperature required for in-situ reaction in a short time,and can inhibit the particle size of in-situ synthesis and the grain size of the base alloy.The obtained composite material has high density and good comprehensive performance.Therefore,the use of SPS combined with in-situ autogenous technology can provide a new idea for the preparation of high performance particle reinforced titanium matrix composites.Currently,the research on the microstructure and properties of SPS in-situ TiB/Ti-6Al-4V composites is still rare.In this paper,micron-sized Ti-6Al-4V powder was mixed with nano-scale TiB₂powder by ball milling,and TiB/Ti-6Al-4V composite was prepared in situ by SPS sintering process.The effects of TiB₂ addition on its microstructure and comprehensive mechanical properties were studied.The TiB/Ti-6Al-4V composites were heat treated to observe the changes of microstructure and mechanical properties at different quenching and aging temperatures,and the friction and wear properties and wear mechanism of TiB/Ti-6Al-4V composites were discussed.The following experimental results were obtained:The effect of TiB₂ content on the structure and properties of TiB particulate reinforced Ti-6Al-4V composites was investigated.The results show that the microstructure of Ti-6Al-4V powder is Wechsler structure when TiB₂ is not added.When TiB₂ is added,the matrix structure is approximately equiaxed,TiB₂ reacts with the matrix Ti to form a rod-like and whisker-like TiB reinforcing phase,and TiB is distributed along the boundary of the original Ti-6Al-4V particles.As the amount of Ti B2 added increases,the strength of the composite increases gradually,and the engineering strain increases first and then decreases.When the addition amount of Ti B2 is 3wt%,the composite has good comprehensive performance,and the yield strength and compressive strength are1259 MPa and 1782 MPa,respectively,which are 43.1% and 25.9% higher than that of the base alloy.At the same time,the engineering strain was 24.5%,which was only slightly lower than the 26.5% of the base alloy.As the amount of Ti B2 added increases,the weight loss of the composite material decreases gradually.The microstructures and mechanical properties of Ti B/Ti-6Al-4V at different quenching and aging temperatures were studied.The results show that as the quenching temperature increases from 900 °C to 1050 °C,the martensite content in the matrix of the composite increases and the hardness of the material increases.The strength of the composite increases first and then decreases.The engineering strain of the composite material decreases with the increase of quenching temperature.During the aging process,martensite transforms into diffuse distribution α phase and β phase.As the aging temperature increases from 500 °C to 650 °C,the strength of the composite material decreases.The engineering strain increases first and then decreases,reaching a maximum value of 21.8 % at 550 °C.When the aging temperature is 550 ° C,the yield strength of the composite is 1465 MPa,which is 16.4% higher than that of the sintered composite,while maintaining the engineering strain of 21.8%.The friction and wear properties of Ti B/Ti-6Al-4V composites under different loads are studied.The results show that the weight loss of the composite material decreases with the increase of the load.When the load is 40 N,the wear weight loss of heat treated composites is 2.5mg,which is 45.7% lower than that of sintered composites.The wear mechanism of the composites is mainly abrasive wear and oxidation wear,accompanied by a small amount of adhesion wear.