High-temperature mechanical performance of directed energy deposited Ti6242S alloy

Ti6242S is a near-α titanium alloy that is expected to be used in engineering below 500 °C. The high-temperature mechanical performance including the high-temperature tensile property and the high-temperature high-cycle fatigue property is well investigated by directed energy deposition using a laser beam (DED-LB) in the paper. It is confirmed that the high-temperature tensile mechanical property can highly satisfy the forging standard for heat treated DED-LB Ti6242S. And the heat-treated DED-LB Ti6242S is of reliable high-temperature high-cycle fatigue limit relying on an analysis on the coefficient of variation of the fatigue life. It is presented that the high-temperature high-cycle fatigue life of DED-LB Ti6242S alloy is highly related to the pore position and its size. Thus a new parameter is proposed to build a relationship with the high-temperature high-cycle fatigue life. Moreover, the fatigue deformation mechanism depends strongly on the α and α′ colony orientations that vary frequently and intricately in accordance with the fine microstructure morphology, leading to a reduced crack expansion rate for DED-LB Ti6242S.