Mar-M247高温合金涡轮叶片微结构及拉伸性能

Microstructure and Tensile Properties of Mar-M247 Superalloy Turbine Blades

摘要:

以Mar-M247镍基高温合金涡轮叶片为研究对象，在25~980 ℃范围内开展拉伸测试，分析了合金的微观组织、拉伸性能及断裂机制。结果表明：合金的微观组织主要为γ相、花状γ′相、γ/γ′共晶组织和碳化物相；合金强度随温度升高呈现先增大后减小的趋势。低温断裂呈现穿晶为主，沿晶为辅的混合模式，裂纹优先在碳化物/基体界面萌生；当温度升至980 ℃时，断裂机制转变为微孔聚集型韧性断裂，断后伸长率提升至6.4%。变形机制分析表明，低温区（<400 ℃）以层错剪切主导，形成Lomer-Cottrell（L-C）位错锁；中温区（400~760 ℃）存在Portevin-Le Chatelier（PLC）效应并伴随中温脆性特征；当温度超过760 ℃时，基体通道变宽和层错能增加促使变形机制转变为反相畴界（APB）剪切与Orowan绕过协同作用，导致变形抗力显著下降。

Abstract:

The Mar-M247 nickel-based superalloy turbine blade was investigated by tensile tests conducted from room temperature to 980 ℃. The microstructure, tensile properties, and fracture mechanisms of the alloy were analyzed. Results indicate that the alloy's microstructure primarily consists of γ phase, flower-like γ′ phase, γ/γ′ eutectic structure, and carbide phases. The alloy strength initially increases and then decreases with increasing temperatures. At low temperatures, fracture exhibits a mixed mode dominated by transgranular fracture with intergranular fracture as a secondary component, where cracks preferentially initiate at carbide/matrix interfaces. When the temperature reaches 980 ℃, the fracture mechanism transitions to microvoid coalescence-induced ductile fracture, accompanied by an increase in elongation to 6.4%. Deformation mechanism analysis reveals that stacking fault shearing dominates in the low-temperature region (<400 ℃), forming Lomer-Cottrell (L-C) dislocation locks. The intermediate temperature range (400–760 ℃) displays Portevin-Le Chatelier (PLC) effects coupled with intermediate-temperature brittleness. Above 760 ℃, widening matrix channels and increased stacking fault energy promote a synergistic interaction between antiphase boundary (APB) shearing and Orowan bypassing mechanisms, leading to a significant decrease in deformation resistance.