Effect of thermal exposure on microstructure and tensile properties of laser deposited Ti60A alloy

摘要

A near a high-temperature titanium alloy Ti60A (Ti5.54A13.38Sn3.34Zr0.37Mo0.46Si) was fabricated by laser melting deposition (LMD) manufacturing process. Room-temperature tensile properties before and after 600 ℃/100 h thermal exposure were evaluated. Microstructural changes and tensile fracture characteristics were examined by OM, SEM and TEM equipped with EDX. Results indicate that a lamellae coarsening and the precipitation of incoherent silicides and coherent Ti_3Al in the alloys after thermal exposure cause the degradation of tensile properties. The silicides are confirmed to be hexagonal quasi-S_2 type (TiZr_(0.3))_6Si_3, with α=0.71 nm and c=0.37 nm by electron diffraction analysis. Compared to wrought Ti60A alloy with coarse Widmanstatten microstructure, laser deposited Ti60A alloy with fine basket-weave microstructure exhibits slightly higher strength and ductility after thermal exposure. The effect of thermal exposure on tensile properties related to the precipitation of Ti_3Al and silicides is discussed.