研究了一种新型镍基合金在750℃下长期时效1500 h过程中的组织变化及其对750℃高温拉伸性能的影响.利用扫描电子显微镜对合金长期时效过程中的显微组织和高温拉伸断口进行了观察分析.结果表明:GH4586B合金在时效过程中晶界和晶内均有碳化物析出,晶界析出碳化物的形貌呈弥散的颗粒状,并随时效时间的延长有逐步转变为连续链状的趋势,同时合金内未见有害拓扑密堆(TCP)相析出;合金在750℃高温下拉伸.随着时效时间的延长合金的强度和塑性在500 h时表现为峰值,且随着时效时间的延长略有降低,这与晶界析出碳化物的形貌、分布、数量直接相关;通过750℃高温拉伸断口的形貌分析,合金断裂均具有塑性断裂特征.
The relationship between high-temperature tensile properties and microstructure of a new Ni-base alloy used in spacecrafts after long-term aging at temperature of 750 ℃ was investigated. The microstructure and tensile fracture were analyzed by means of SEM and TEM. The resuhs indicate that TCP phase,a harmful phase to Ni-base alloy,is not observed in the aged alloy. The granular carbides are precipitated at both grain boundary and grain interior of the aged alloy. The granular carbides of M23 C6 containing Cr precipitated at grain boundary is transformed gradually to continuous-chain distribution with the increasing of aging time. The morphology of M_(23)C_6 at grain boundaries influences the high-temperature tensile properties of the aged alloy. The optimum combination of tensile strength and ductility at 750℃ is obtained for the alloy aged at 750 ℃ for 500 h,and the decrease of the properties is observed with increasing aging time. The high-temperature tensile fracture presents some ductility fracture features.
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