电子束选区熔化成形纯钨的显微组织与晶体取向研究

采用增材制造技术中的电子束选区熔化成形方法制备了高致密度纯钨试件,分析了电子束选区熔化成形纯钨的传热过程和显微组织特点,重点研究了在几种热传导的共同作用下,纯钨的显微组织特点和晶体的取向分布。结果表明,电子束选区熔化纯钨的显微组织为以外延生长的方式形成的柱状晶。在样品内部,沿成形方向向下为最主要的热传导方向,温度梯度最大,柱状晶生长方向与热流方向相反,形成完全竖直生长的柱状晶；在样品外侧面,沿成形方向向下的热传导和向侧面粉床的热传导共同作用,使得热传导的方向与成形方向出现一定偏差,因此柱状晶组织与成形方向呈30-45_⁰夹角。同时,电子束选区熔化成形纯钨沿着成形方向,形成[111]和[100]方向的择优取向。

Research on Microstructure and Crystal Orientation of pure tungsten Fabricated by Selective Electron Beam Melting

Pure tungsten specimens were prepared by additive manufacturing of selective electron beam melting(SEBM). The heat transfer process during SEBM and microstructure characteristics of pure tungsten were analyzed. The results show that the microstructure is columnar crystal grown in the form of epitaxial growth. In the inner side of the sample, the heat conduction along the building direction of the sample is dominant. The columnar crystal growth direction is opposite to the heat flow direction, forming a cylindrical crystal with complete vertical growth; In the outer side of the sample, the heat conduction are the joint action of conduction along the building direction and conduction to the powder bed. This makes the direction of the heat conduction deviate from the building direction, so the columnar crystal is 30-45_⁰ angle with the building direction. Furthermore, the preferred orientation of [111] and [100] is formed along the building direction in the SEBM pure tungsten.