Role of intermediate phases on microstructures, wear and corrosion resistance in new-developed (α plus β) titanium alloy

A new (alpha + beta) Ti alloy has been designed and prepared in this work, and the results show that three intermediate phases will be transformed including alpha '' martensite, O ' and omega. Upon continuous heating, the alpha '' martensite decomposes gradually and disappears before alpha precipitation. The omega and O ' domains are generated continuously upon aging, and such two intermediate phases co-exist when alpha phase nucleation occurs. It has been proved that the omega and O ' domains play a direct role in promoting alpha phase formation. Through the omega and O ' domains assisting alpha nucleation mechanism, a uniform distribution of fine alpha precipitates can be obtained after aging. Under the treatment of pre-aging at 300 degrees C plus aging at 600 degrees C, the alpha phase having smallest size and largest number density is obtained, resulting in highest wear resistance and corrosion resistance. For this sample, its average friction coefficient and wear ratio are 0.174 and 3.75x10(-4) mm(3)/(N<middle dot>m), respectively. During friction tests, the mixture of abrasive wear, adhesive wear and oxidation wear should be activated. Due to the formation of passivation films on the alloy surface, this alloy has exhibited better anti-corrosion properties than Ti-6Al-4 V alloy, and its corrosion current density in 3.5 wt% NaCl solution can be reduced to 1.79x10(-8) A<middle dot>cm(-2). Compared with the samples under duplex aging treatments, the direct aged sample also presents outstanding anti-corrosion properties.