热处理对SPS烧结Ti-24Nb-4Zr-8Sn合金显微组织和力学性能的影响

Effects of heat treatment on microstructure and mechanical properties of Ti-24Nb-4Zr-8Sn alloy by spark plasma sintering

利用放电等离子烧结技术制备生物医用Ti-24Nb-4Zr-8Sn合金,研究固溶时效处理对合金显微组织和力学性能(强度、塑韧性及弹性模量)的影响。结果表明:合金经850℃固溶处理后主要由β相、少量初生α相及淬火马氏体α″相组成;在450℃时效处理后,合金基体β相内析出大量细小无规则的针状次生α相,随着时效时间从4 h延长到48 h,次生α相趋于定向析出,含量和尺寸逐渐增大;与烧结态相比,固溶时效处理后合金抗压强度和弹性模量增大,而塑韧性呈先提高后降低趋势;经优化后固溶时效处理制度为(850℃,1.5 h,WQ)+(450℃,4 h,FC),此时合金抗压强度、屈强比和弹性模量分别为1701 MPa、0.69 GPa和42.8 GPa。

Biomedical Ti-24Nb-4Zr-8Sn alloys were prepared by spark plasma sintering. The effects of solution-aging heat treatments on the microstructure and mechanical properties （strength, ductility and elastic modulus） of the alloys were investigated. The results show that the alloys are composed of metastable β phase, little primary a phase and α martensite after solution treatment at 850℃. After aging at 450℃, much short, fine and disordered needle a phases precipitated within primary β grains. With the aging time increases from 4 h to 48 h, the content and grain size of secondary a phase grows up which precipitates directionally from fl matrix. Compared with the as-sintered, the compressive strength and elasticity modulus of the alloys increase after solution and aging heat treatment, while the ductility of the alloys increases at first and then decreases. After the suitable heat treatment of （850℃, 1.5 h, WQ）＋（450℃, 4 h, FC）, the compressive strength, yield ratio, elasticity modulus are 1701 MPa, 0.69 GPa and 42.8 GPa, respectively.