Phase Transformation of Biomedical Metastable β Titanium Alloy during Aging
A kind of metastable β type Ti-30Nb-13Zr-0.5Fe (wt.%) alloy for biomedical application was newly designed and developed. In order to exam the phase transformation during aging and its effects on the mechanical properties, the alloy was β solubilized and aged at 350°C-550°C for 4 hours. The microstructures were observed by OM and TEM, and the phase structures were identified by XRD. The tensile tests were performed with various aged microstructures. The results show that a lot of ω phase precipitates during aging at 350°C, leading to the increase of strength and elastic modulus and drastic decrease of plasticity. Aging at 450°C, dot α phase uniformly precipitates from metastable β phase. The good combination of high strength 、high plasticity and low elastic modulus was obtained under this aging condition. With increasing aging temperature and aging time α precipitations coarsen and precipitation free zones (PFZ) along prior β grain boundaries form, which are the main reasons to lower the strength and plasticity.
Zhong Wei Gu, Yafang Han, Fu Sheng Pan, Xitao Wang, Duan Weng and Shaoxiong Zhou
A. H. Guo et al., "Phase Transformation of Biomedical Metastable β Titanium Alloy during Aging", Materials Science Forum, Vols. 610-613, pp. 1168-1173, 2009