Research On Properties Of B Modified Ti-6Al-4V Alloy Synthesized By SPS

Spark plasma sintering (SPS) is a new rapid sintering technique developing in recentyears. Due to its fast heating rate, short sintering time and low sintering temperaturesproperties, it has a great potential in praparing high-performace new material. In this paper,a B modified Ti-6Al-4V alloy was prepared by a spark plasma sintering process. Theinfluence of B content of the mixed powder and sintering temperature as well as heattreatment process on the B modified Ti-6Al-4V alloy’s microstructure and mechanicalproperties was investigated.Four typical sintering stages are divided according to the shrinkage features of thecompact and microstructure evolution in the SPS process. The characteristic for these fourstages are particles activation and rearrangement, connection of particles, growth ofsintering neck, and bulk deformation, respectively. The fine grain product will be producedwhen these four stages are carried on in order.Ti-6Al-4V and B powders were mixed, and then the mixed powders were poured intographite molds for SPS sintering. A total of three different mixture powders (B powdercontents were0.05,0.1, and0.2wt.%) and four sintered temperature points (850,950,1050,and1150℃) were used.The microstructure of B modified Ti-6Al-4V alloy is refinedremarkable, when sintering temperature reached950℃by adding B element. The density,hardness and tensile strength of the material increasd as the B contents increasing, however,the elongation of the material initially increase and then decrease with increasing sinteringtemperature and B contents. The B modified Ti-6Al-4V alloy was prepared through SPSprocess with the high density of99.7%, the hardness of31.2HRC, the tensile strength of975MPa and the elongation of18.9%when the B content reached0.1wt%. As the heat-treattemperature increased, the hardness and tensile strength of the material increased, and theelongation of the material decrease. Compared to the commercial forged TC4alloy, theprotection coefficient of B modified Ti-6Al-4V alloy remarkably increased.The fracture mode of B modified Ti-6Al-4V alloy prepared by SPS method is mainly ductile fracture. The microstructure of fracture showed three typical fracture modes: brokenTiB whiskers, TiB whiskers separated from Ti substrate interface and ductile fracture of Tialloy. As the sintering and heat treatment temperature rised, the ratio of broken TiBwhiskers in alloy fracture increased; the ratio of ductile fracture of Ti alloy is decliningresult in reduced alloy’s plastic.