An investigation of the effect of aging treatment on the mechanical properties of Ti-Ta-Zr-Nb alloy

The objective of this study is to find the effects of aging treatments on the microstructural and mechanical properties of the TTZN alloy (Ti-38.3Ta-22Zr-8.1 Nb), which possesses many desirable material attributes for biomedical applications, including high elastic strain and high mechanical strength. To this end, the TTZN alloy was aged at 300 oC under five various aging times, such as 15 min, 3h, 6h, 12h, and 24h. While the solution-treated TTZN has been called TTZN-1, the TTZN subjected to aging treatments at the referred aging times has been designated TTZN-2, TTZN-3, TTZN-4, TTZN-5, and TTZN-6, respectively. Compression and micro-hardness test results revealed that both the compressive yield strength and micro-hardness of TTZN increase with the increase of aging time. The compressive yield strength of TTZN-1 and TTZN-6 specimens was measured to be 948 MPa and 1315 MPa, respectively. Additionally, the micro-hardness of TTZN-1 was measured to be 310 HV; however the micro-hardness of TTZN-6 was measured to be 457 HV. Depending on the results, obtained from micro-scratch tests, it was concluded that increasing aging time leads to an increase in the micro-scratch hardness of TTZN as well as a decrease in its volume loss and specific wear rates. While the volume losses, measured for the TTZN-1 and TTZN-6, were 250x10-6 mm3 and 11.51x10-6 mm3, respectively, the specific wear resistance of TTZN-1 and TTZN-6 was 50.14x10-3 mm3/N.m and 2.3x10-3 mm3/N.m, respectively. Furthermore, the scratch hardness of TTZN-1 was 2.54 GPa whereas the scratch hardness of TTZN-6 was meausured to be 6.25 GPa. SEM examinations revealed that the aging treatments carried out on the TTZN alloy specimens do not influence the wear type, but they lead the distances between deformation bands formed near micro scratches to be less. By obtaining the number of deformation bands in per unit length from SEM images, the distances between deformation bands for TTZN-1 and TTZN-6 were calculated to be ~0.08 and ~0.43, respectively. As a result, the mechanical properties of TTZN have been significantly improved via conducting the aging treatments, making the TTZN alloy more appealing for biomedical applications.