Microstructure and mechanical properties of laser melting deposited γ-TiAl intermetallic alloys

摘要

Ti-47Al-2.5V-1Cr intermetallic alloy was fabricated by the laser melting deposition (LMD) manufacturing process. The microstructure was characterized by OM, SEM, TEM and XRD. The tensile properties and Vickers microhardness were evaluated on both longitudinal and transverse directions. Results showed that full density directionally solidified (DS) columnar grain with fully lamellar (FL) microstructure consisted of γ-TiAl and α_2-Ti_3Al lamellae was formed in the as-laser deposited samples along the longitudinal direction due to the high thermal gradient. The room-temperature tensile strength of the as-deposited alloy is up to approximately 650 MPa in the longitudinal direction and 600 MPa in the transverse direction, while the tensile elongation on both directions is approximately 0.6%. The tensile fracture surfaces are different for the longitudinal and transverse directions, indicating that the room-temperature tensile properties were affected by the DS microstructure.