固溶温度对定向凝固高温合金DZ22的组织和性能的影响

 随着固溶温度的提高,显微组织发生明显的变化,共晶Υ′相和初生的粗大Υ′相不断回溶,重新析出更多更细的Υ′相。与此同时,晶界状态也逐渐变成“细线”状。元素的枝晶偏析减小,中、高温的纵向持久寿命增加。但是,中温横向持久寿命显著降低。在试验中测定了DZ22合金的初熔温度为1230～1240°C,并进行了提高初熔温度的试验。文中讨论了确定定向凝固合金回溶温度的原则,根据试验结果,认为DZ22台金选用1200～1210°C为宜。

INFLUENCE OF SOLUTION TEMPERATURE ON MICROSTRUCTURE AND PROPERTIES OF DIRECTIONALLY SOLIDIFIED SUPERALLOY DZ22

Effects of solution temperature on the microstructure and stressrtipture properties of directionally solidified superalloy DZ22 were investigated. The results show that the microstructure changed markedly with increasing solution temperature, i. e. eutectic Y' phases and primary coarse Y' phases are redissolved continuously into- matrix, Ended at 1250-1260℃, and more and finer r' phases are reprecipitated afterwards. The grain boundary morphology changed gradually to"line"form. The dendritic segregation of elements decreased. With increasing solution temperature the longitudinal stress-rupture life at high-and intermediate temperature were enhanced, but the transverse stress-rupture life at intermediate temperature decreased significantly. It is considered that this is associated with the change of grain boundary condition due to exceedingly high solution temperature. The incipient melting temperature of DZ22 alloy was measured to be 1230-1240℃, and may be increased by homogenization at 1150℃. In this paper the principle of determining solution temperature of DS alloys was discussed. It was suggested that the solution temperature of alloys DZ22 selected at 1200-1210℃ is appropriate.