燃气轮机用GH4720Li合金组织与性能关联性

摘要：基于光学显微镜、场发射电镜组织分析及系列力学性能测试，研究了固溶处理对燃气轮机用GH4720Li合金组织特征的影响，分析了组织特征与力学性能的关联性。结果表明：随着固溶温度的升高和固溶时间的增加，合金一次γ′相回溶，平均晶粒尺寸增加，当固溶温度高于1160℃，晶粒尺寸增大明显。GH4720Li合金的力学性能变化规律如下：经亚固溶处理后，室温拉伸强度和屈服强度呈现出相似规律，并在1130℃附近出现峰值；经过固溶处理后，拉伸强度和屈服强度均明显降低。在亚固溶处理区间，随着固溶温度的增加，持久寿命逐渐增加；经过固溶处理后，合金的持久寿命明显提高，而持久塑性呈现出与持久寿命相反的趋势。结合燃气轮机的服役工况，燃气轮机用GH4720Li合金的合理固溶处理应为过固溶处理，可获得组织性能的较佳匹配。

Correlation between microstructure characteristics and mechanical properties of GH4720Li alloy for gas turbine applications

Based on microstructure observation by optical microscope (OM), field emission scanning electron microscope (FESEM) and series mechanical property tests, the relationship between the microstructure characteristics and mechanical property of Ni based alloy GH4720Li for gas turbine applications under different as solution heat treatments was systematically investigated. The results show that the volume fraction of primary γ′ decreases and the average grain size increases with the increasing of solution temperature and the duration time. Especially, the grain size increases rapidly when the solution temperature over 1160℃. Under different as solution treatments, the mechanical properties of GH4720Li alloy vary as follows. The tensile and yield strengths follow the same role with the increasing of as subsolution treated temperature, and both reach the peak value at the treated temperature of about 1130℃. When as solution treated temperature is over 1160℃, the tensile and yield strengths decrease to a great extent. During the as subsolution treated temperature zone, the stress rupture life of GH4720Li alloy increases with the increasing of the solution treated temperature, and the stress rupture life of this alloy will increase to a great extent when as over solution treated. Based on the real service conditions, the optimal solution treatment processing for gas turbine applications for this alloy should be over aging or as over solution treatments in order to obtain the optimal match for microstructure and mechanical properties of this alloy.