采用电场凝固技术在自制电场定向凝固装置上进行电场单晶生长，研究了直流电场对一种镍基单晶高温合金室温拉伸性能和高温持久性能的影响. 结果表明，随着电流密度增大，合金的室温屈服强度明显提高，但抗拉强度无明显改善，且塑性降低；在980 ℃和221 MPa条件下, 高温持久时间显著延长，持久塑性得到改善. 利用扫描电镜和电子探针对该合金的凝固组织、合金成分分布和断口形貌进行了分析.结果表明，直流电场引起枝晶间距及γ’相尺寸减小、成分偏析减轻,共晶和亚晶界减少. 直流电场作用导致的γ’相尺寸减小及成分偏析减轻导致的γ/γ’错配度变化, 对合金的屈服强度和高温持久性能的提高有贡献.
The tensile properties at room temperature and stress-rupture properties at high temperature of a kind of Ni-based single crystal superalloy grown under a DC field were measured. The results show that the yield strength at room temperature is increased and the stress-rupture life and ductility at 980 ℃ and 221 MPa are improved, whereas the ultimate tensile strength at room temperature varies unnotedly and the ductility at room temperature is reduced. SEM observation and EMPA analysis showed that the prime dendrite arm spacing (PDAS), size of γ’ particles, alloying element segregation, eutectic and the sub-grain boundaries are reduced with the increase of the current. It is considered that the improvement of yield strength and stress-rupture properties arise from the refining of γ’particles and the change of γ/γ’misfits caused by reduction of microsegregation of alloying elements. Furthermore, the enhancement of the stress-rupture properties is also related to the reductions in the PDAS, eutectic and sub-grain boundaries under the action of the electric field.
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