电子束选区熔化技术对钛合金组织和力学性能的影响

Effect of Electron Beam Selective Melting on the Microstructure and Mechanical Properties of Ti Alloy

利用光学显微镜、扫描电镜和力学万能试验机研究了ELITA7金属粉末在电子束选区熔化快速成形件的显微组织和力学性能。结果表明:真空度3.0×10-2～5.0×10-2Pa、工作电流2.0～3.0mA,Z字型扫描路线可以有效提高烧结件的致密度、室温强度和延伸率。烧结件的相对密度可达97%,抗拉强度740MPa,延伸率8%,接近锻件的性能。致密度高的原因是电子束高的能量利用率在烧结过程中产生瞬时液相,同时真空下粉末的表面得到净化,提高了烧结活性;而快速的冷凝过程有助于产生细小的晶粒。同时致密度的提高以及晶粒的细化均有助于烧结件力学性能的提高。

The microstructure and mechanical property of forming parts by electron beam selective melting （EBSM） for ELI Ti-5Al-2.5Sn metal powder were investigated by means of optical microstructure and SEM, and universal mechanical testing machine. The results indicate that the density, the elongation and the room temperature strength of the forming parts are improved effectively according to zigzag scanning way with a vacuum of 3.0×10-2～5.0×10-2 Pa and a current of 2.0 to 3.0 mA,. The relative density, the tensile strength and the elongation are 97%, 740 MPa and 8%, respectively, close to the properties of forging parts, due to the transit liquid phase from the electron beam high energy utilization during sintering. Meanwhile, the cleaned surfaces of powders in vacuum improve the sintering actively. A rapid condensation process makes forming fine grains easy, while the increase of density and the refinement of grains are helpful to improve the mechanical properties of parts.