新型铌基高温合金热处理组织性能研究

Research of heat treatment on the microstructure and mechanical properties of a Nb-base superalloy

摘要:

摘 要：研究了热处理对一种HRS定向凝固技术制备Nb/Nb5Si3原位复合材料组织和性能的影响。采用扫描电子显微镜（SEM）、X射线衍射（XRD）和电子探针（EPMA）等分析手段对热处理过程中组织演变进行了分析：铸态合金主要由Nbss、γ-(Nb,Ti)5Si3、β-(Nb,Ti)5Si3以及初生碳化物组成；热处理后，铸态组织中部分β-(Nb,Ti)5Si3向α-(Nb,Ti)5Si3转变以及二次碳化物析出，同时硅化物相逐渐溶解或破碎成小块并发生球化；1150℃时效可促进(Nb,Ti)5Si3向(Ti,Nb)5Si3转变。热处理后，合金压缩以及室温拉伸强度提高，而1000℃拉伸强度变化不明显；温度对断裂方式有明显影响，低温下为脆性解理断裂，高温下为韧性断裂。

Abstract:

The effect of heat treatment on the microstructure and mechanical properties of an Nbss/Nb5Si3 in situ composites prepared by HRS method was investigated. The microstructure evolution of samples during heat treatment process were analysed by SEM、XRD and EPMA: the result showesd that the as-cast alloy consisted of Nbss、γ-Nb5Si3 、β-Nb5Si3 and primary carbide phase; after heat treatment, the β-(Nb,Ti)5Si3 phase was transformed to α-(Nb,Ti)5Si3 phase and the secondary carbide was precipitated. Meanwhile, the silicide phase gradually dissolved or broken into small pieces, with the morphology changing from the needle into granules. The transformation (Nb,Ti)5Si3 →(Ti,Nb)5Si3 occurred when aging at 1150℃.The compressive strength and room temperature tensile strength of heat-treatment specimens were improved, while the tensile strength of as-cast and heat-treated samples at 1000℃ was at same level. The temperature has a great influence on the fracture mode, cleavage fracture at low temperature and ductile fracture at high temperature.