Joint effect of Mo and Cr on microstructure and properties of Ti–Al–Mo–Cr–B alloys

Abstract

Innovative Ti–3Al-xMo-yCr-0.1B (x = 4, 2, 4; y = 2, 4, 4, wt.%) alloys were developed via powder metallurgy by varying the contents of Mo and Cr. The aim is to reduce costs and attain outstanding performance by introducing relatively affordable alloying materials. The results display that all alloys feature lamellar microstructure, including α, β and TiCr2 phases. The appropriate combination of alloying elements can greatly increase the relative density value of the alloy to 99.34% (e. g. Ti–3Al–4Mo–4Cr-0.1B). The strength of these alloys is greatly improved (>1028 MPa) due to solid solution strengthening and αs/β interface strengthening. Ti–3Al–4Mo–2Cr-0.1B alloy shows the optimum properties combination with the tensile strength and ductility of 1080 MPa and 5.4%. The wear test results show that the wear resistance of the three alloys is much better than that of pure titanium. Ti–3Al–4Mo–4Cr-0.1B has the best wear resistance which could be the outcome of solid solution strengthening and higher density. Meanwhile, Ti–3Al–4Mo–4Cr-0.1B possesses the highest corrosion resistance with the Ecorr and Icorr of −0.15 V and 0.039 μA/cm2, which is attributed to the presence of more β phase and highest density. This work offers a good idea for creating low-cost titanium alloys with great strength and high density and provides the possibility to apply titanium alloys extensively.