粉末冶金医用超细晶β型Ti28Nb2Zr8Sn合金的显微组织与力学性能

Microstructure and Mechanical Property of Biomedical Ultrafine-grained β-type Ti28Nb2Zr8Sn Bulk Alloys Fabricated by Power Metallurgy

摘要:

为了进一步对比不同成分医用b型钛合金的显微组织和力学性能,本文采用机械球磨 放电等离子烧结的方法制备出高强度低模量的超细晶β型Ti28Nb2Zr8Sn合金。XRD和SEM测试表明,60h球磨后的终态合金粉末经放电等离子烧结后,获得的超细晶块体合金为完全的bcc结构；TEM分析表明,超细晶块体合金中bcc b-Ti的晶粒为等轴状,其尺寸约为500-1000nm,远小于铸造法制备同类合金几十微米的晶粒尺寸；力学性能测试表明,随升温速率增大或保温时间减少,超细晶块体合金的压缩强度逐渐增大,弹性模量逐渐减少。在烧结温度为900℃、升温速率为150℃/min且保温时间为0min的烧结条件下,得到的超细晶块体合金晶粒最细小,其压缩强度达到最大(2675MPa),对应的断裂应变也最大(0.54),且其弹性模量也最低(31.6GPa)；同时,该合金试样的加工硬化指数0.073远高于Ti6Al4V合金,这说明其加工硬化和塑性变形能力远远优于Ti-6Al-4V合金,故能够承受更大的载荷和经历更大的变形,可作为一种优异的生物医用金属材料的候选材料。

Abstract:

In order to further comparatively investigate microstructure and mechanical property of biomedical β-type titanium alloys with different compositions, ultrafine-grained β-type Ti28Nb2Zr8Sn bulk alloys with high strength and low elastic modulus were fabricated by mechanical alloying and spark plasma sintering in this work. XRD and SEM examinations indicate that the fabricated ultrafine-grained bulk alloys are fully bcc β-Ti structure by spark plasma sintering of 60h-milled alloy powders. Further TEM analysis proves that the grains of bcc β-Ti are equiaxed and their sizes are approximately 500-1000nm in the fabricated ultrafine-grained bulk alloys, which is far smaller than several micron-sized grains of similar titanium alloys prepared by casting method. In addition, mechanical property tests show that compressive strength increases and elastic modulus decreases gradually for the fabricated ultrafine-grained bulk alloys with the increased heating rate and decreased holding time. Under sintering temperature of 900℃, the heating rate of 150℃/min and no holding, the fabricated ultrafine-grained bulk alloy has the smallest grain size of bcc β-Ti,and thus the largest ultimate strength of 2675MPa, and the highest fracture strain of 0.54 along with lowest elastic modulus of 31.6GPa. Meanwhile, its work-hardening exponent 0.073 is far higher than that of Ti6Al4V alloy, indicating its excellent work-hardening ability and plastic deformation ability. This suggests that the fabricated ultrafine-grained bulk alloy can withstand high load and large deformation, and consequently can be an excellent candidate metallic material used as biomedical applications.