放电等离子烧结预合金粉末法制备生物医用近β钛合金的组织演变和力学性能

Microstructural evolution and mechanical properties of a biomedical β-Ti alloy produced by spark plasma sintering its prealloyed powder

摘要:

本研究利用放电等离子烧结(SPS)预合金粉末的方法,成功制备出生物医用的近β钛合金Ti-25Nb-3Zr-3Mo-2Sn (wt %)。 近β钛合金的预合金粉末利用等离子旋转电极法制备,粉末的凝固组织主要是由β相主导的不发达的树枝晶组成,同时存在少量的β相单晶组织粉末球。1000℃/5min/50MPa条件下的SPS可以完全致密化近β钛合金的预合金粉末,并且消除原始的凝固偏析结构。β单相区固溶处理后,合金组织由β相和α″相组成,合金的拉伸强度达到815MPa,延伸率达到14%,同时具备62GPa较低的弹性模量。进一步500℃时效处理,合金组织中产生大量的纳米针状α相,使得合金的拉伸强度达到1015MPa,同时具备较好的延伸率和中等的弹性模量。然而,应当避免过低的时效处理温度,防止脆性ω相的析出。

Abstract:

In this study, a biomedical β-Ti alloy Ti?25Nb?3Zr?3Mo?2Sn (wt. %) was fabricated via spark plasma sintering (SPS) its prealloyed powder. The prealloyed powder was produced by a plasma rotating electrode process. The majority of the powder particles had a microstructure composed of β-phase predominant dendrites, while a small fraction of the powder particles had a single crystal microstructure. SPS with a condition of 1000℃/5min/50MPa could just completely densify this β-Ti alloy powder and remove its prior dendritic segregation. After solution treatment, the consolidated alloy had a microstructure consisting of α″ + β phases, and exhibited a good tensile strength of 815 MPa and an optimal elongation of 14%, as well as a low elastic modulus of only 62 GPa. Aging at 500 ℃ brought about high number density of pure nanosized α needles, which renders this alloy a superior tensile strength up to 1015 MPa along with elongation and elastic modulus both acceptable. However, excessively low aging temperature should be avoided, due to the sharp embrittlement induced by nanoscale ω-phase precipitates.