The effects of heat treatment on the microstructure and mechanical property of laser melting deposition γ-TiAl intermetallic alloys

摘要

Ti-47Al-2.5V-1Cr and Ti-40Al-2Cr (at.%) intermetallic alloys was fabricated by the laser melting deposition (LMD) manufacturing process. The microstructure was characterized by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The room-temperature (RT) tensile properties and Vickers hardness of the as-deposited and heat-treated specimens were evaluated on longitudinal directions. Results shows that full density columnar grain with fully lamellar (FL) microstructure consisted of y-TiAl and α_2-Ti_3Al was formed in the as-deposited γ-TiAl samples. The room-temperature tensile strength of the as-deposited Ti-47Al-2.5V-1Cr alloy is up to approximately 650MPa in the longitudinal direction and 600MPa for the as-deposited Ti-40Al-2Cr alloy, while the tensile elongation is approximately 0.6% at most. Different microstructure types were obtained in the Ti-47Al-2.5V-1Cr and Ti-40Al-2Cr alloy after heat treatment. The stress-strain curve and the tensile fracture sub-surface indicate that the fracture manner of the as-deposited and heat-treated specimens was inter-granular manner.