Effects of cold work on material properties for high temperature fastener materials

该项目将涉及广泛的材料性能评估，包括蠕变、应力松弛、低应变率拉伸试验、氧化、总疲劳寿命、疲劳裂纹扩展阻力和缺口应力断裂试验。先进的材料表征技术将包括EBSD和分析的透射电子显微镜和扫描电子显微镜。总体而言，该方案将有助于确定冷加工材料的使用范围，并为具体应用合理选择冷加工或非冷加工材料。预计要探索的冷加工材料领域将包括考虑相稳定性、环境敏感性、裂纹起始寿命、缺口脆性、裂纹扩展速率和应力松弛速率--所有这些都是在高温下进行的。结果将与基本微观结构特征相关联，以便在整个方案中详细描述。对冷加工材料在高温下的行为还没有很好的了解，该项目将有助于从根本上理解这一主题，以及对其用作紧固件的问题给予一些具体关注。

This project will involve extensive material property evaluation including creep, stress relaxation, slow strain rate tensile tests, oxidation, total fatigue life, fatigue crack growth resistance and notched stress rupture tests. Advanced material characterisation techniques will include EBSD and analytical TEM and SEM. Overall the programme will contribute to defining an operating envelope for the cold worked material and to rationalise the choice of cold-worked or non-cold worked material for specific applications. Areas to be explored for cold worked material are expected to include a consideration of phase stability, environmental susceptibility, crack initiation life, notch- brittleness, crack growth rates and stress relaxation rates- all at elevated temperatures. Results will be correlated with underlying microstructural features to be characterised in detail throughout the programme. The behaviour of cold- worked materials at high temperatures is not well understood and the project will contribute to fundamental understanding of this topic, together with some specific attention to issues focused on their use as fasteners.