电子束物理气相沉积TiAl基合金薄板的物相及显微分析

Phase Composition and Microanalysis of TiAl-Based Alloys Sheet by Electron Beam-Physical Vapor Deposition

采用电子束物理气相沉积(EB-PVD)技术,成功制备了尺寸为150mm×100mm的TiAl基合金薄板,并利用光学显微镜(OM)、扫描电子显微镜(SEM)和X射线衍射(XRD)等测试手段,对真空退火或热压前后试样的显微形貌、物相组成等进行了分析。结果表明,蒸镀态TiAl基合金薄板由γ相、α2相和τ相组成,成分呈梯度变化,内部自然分层,显微组织结构为柱状晶;经1000℃,16h的真空退火处理后,柱状晶和τ相消失,α2相含量显著减少,成分趋于均匀化;而经1250℃,1h的真空热压处理后,材料致密度得到明显提高。TiAl基合金薄板经真空退火或热压处理前后,断裂方式由沿晶断裂转变为解理断裂和沿晶断裂的混合断裂方式。

TiAl-based alloys sheet of 150 mm ×100 mm in size were successfully fabricated by electron beam-physical vapor deposition （EB-PVD） process. The phase composition and microscopic morphology were analyzed by optical microscope （OM）, scanning electron microscope （SEM） and X-ray diffractometer （XRD） for the as-deposited, as-annealed or as-pressed samples, respectively. The results show that the as-deposited sample of TiAl-based alloys sheet is composed of у, α2 andτ phases with a gradient component change, leading to the spontaneous delamination. The microstructure of as-deposited sheet is of columnar crystals. The columnar crystals and τ phase disappeared, and the a2 phase decreased greatly after vacuum annealing treatment at 1000 ℃ for 16 h, and the component tended to be uniform. After vacuum hot pressing treatment at 1250 ℃ for 1 h, the relative density of samples is increased obviously. Compared with the as-deposited samples, the fractographs of as-annealed or as-pressed samples were intergranular fracture and cleavage fracture. diverted from the intergranular fracture to the mixed manner of intergranular fracture and cleavage fracture.