High Temperature Mechanical Properties and Microstructure of TC4 Titanium Alloy Prepared by Selective Laser Melting

In this paper,the mechanical properties and microstructure of TC4 titanium alloy,prepared by selective laser melting（SLM）,at room temperature（RT） to 550 ℃ were studied by universal tensile testing machine,optical microscopy,scanning electron microscopy,and transmission electron microscopy.The results show that the TC4 alloy produced by SLM consists of acicular α' martensite with a large number of grain boundaries,and the dislocation movement is limited to the interior of martensite during plastic deformation.Therefore,the experimental alloy has a high strength,with a tensile strength of 1 265 and 834 MPa at RT and 500 ℃ respectively,which is better than that of the TC4 alloy separately by solid solution aging treatment and anneal treatment.However,when it is deformed at temperatures above 500 ℃,martensite gradually transforms into equilibrium α phase,and the morphology changes from acicular to lamellar structure.The decrease in the number of grain boundaries leads to a decrease in deformation resistance,so the tensile strength decreases rapidly to 562 MPa at 550 ℃.