以国产蒸汽发生器传热管用GH690合金为研究对象,通过评价其断裂韧性及拉伸特性,结合光学显微镜、扫描电镜和透射电镜分析,研究了合金由室温-623K的力学性能.研究结果表明,室温下GH690合金低的层错能,易生成形变孪晶,使得合金在孪生的协调下塑性变形能力提高,同时孪晶促进裂纹扩展转向,使合金在断裂过程中吸收更多的能量,维持合金高的断裂韧性.随着温度的升高,合金的层错能增加,导致形变孪晶生成困难,合金应力集中程度加剧,裂纹从而平直扩展,合金的断裂韧性降低.由于合金的室温层错能较低,合金在拉伸时能够通过孪生协调变形,同时生成的孪晶阻碍了位错的滑移而提高了合金的强度和塑性.随着形变温度的升高,合金通过孪生协调变形的能力降低,导至合金的变形机制由孪生转变为滑移,滑移产生的加工硬化效应小于孪生,故合金的强度和延伸率随之降低.
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