选区激光和电子束熔化成形纯钨的组织、性能及裂纹形成机理研究

Study on microstructure, properties and crack formation mechanism of pure tungsten fabricated by selective laser and electron beam melting

摘要:

采用选区激光熔化(SLM)和选区电子束熔化(SEBM)技术成形纯钨,对比研究了两种成形方法对纯钨的宏/微观组织和力学性能的影响,利用SEM和EBSD等表征技术,分析了裂纹萌生位置及形成机制。研究结果表明,通过调控纯钨打印过程的工艺参数,可有效地减少 SLM和SEBM成形样品内部的裂纹。SLM和SEBM打印态纯钨的致密度和硬度与输入样品的能量密度呈正比例关系。与SLM相比,SEBM成形时样品内部的温度梯度更低,热应力累积更少,成形后样品中的裂纹更少。SLM打印态样品的内部裂纹多存在于搭接区域,SLM和SEBM制备过程中产生的裂纹均具有沿晶界分布的特征,而且裂纹多萌生于大角度晶界。

Abstract:

Selective Laser Melting (SLM) and Selective Electron Beam Melting (SEBM) were used to fabricate pure tungsten. The microstructure and mechanical properties of pure tungsten were compared under different process parameters. The crack initiation location and formation mechanism were analyzed by SEM and EBSD. The results show that the crack generation of pure tungsten printing process can be effectively reduced by adjusting the process parameters in SLM and SEBM process. The relative density and hardness of pure tungsten samples are proportional to the energy density input by SLM and SEBM. Compared with SLM, SEBMed pure tungsten has lower temperature gradient, less thermal stress accumulation and fewer cracks. There were many cracks in SLMed samples, and that mostly existed in the lap areas. Cracks in SLMed and SEBMed samples were distributed along grain boundaries, most of which were initiated at high-angle grain boundaries.