Most of industrial hot deformation processes are performed in variable conditions where the strain rate and/or deformation temperature are not constant. In this work, hot compression tests in both constant and varying strain rate conditions were performed on 304L austenitic stainless steel using a Gleeble 3800 machine. The variations in microstructure and flow stress during and after the transient deformation stage are carefully analysed. It is clearly shown that, following the abrupt increase of strain rate, both the flow stress and substructural changes are subjected to a transient period over strains of ~0.2, before reaching states similar to those developed through constant strain rate conditions at the new strain rate. When the strain rate was rapidly decreased, the flow stress transient stage extended over a lower strain interval than the substructure transient period. It is shown that local misorientation distributions are good indicators of the deformation microstructure of low SFE materials as they capture small variations in deformation structures which cannot be analysed from stress-strain curves alone.

大多数工业热变形过程是在应变率和/或变形温度不恒定的可变条件下执行的。在这项工作中，使用Gleeble 3800机器对304L奥氏体不锈钢在恒定应变率和变化应变率条件下进行了热压缩测试。仔细分析了瞬态变形阶段期间和之后的微观结构和流动应力变化。清楚地表明，在应变率突然增加之后，流变应力和子结构的变化都在〜0.2的应变下经历了一个过渡时期，然后达到了与在新应变率下通过恒定应变率条件发展的状态相似的状态。 。当应变率迅速降低时，流动应力过渡阶段在比子结构过渡阶段低的应变间隔内延伸。结果表明，局部取向不良分布是低SFE材料变形微观结构的良好指标，因为它们捕获了变形结构中的细微变化，而这些变化不能仅通过应力-应变曲线来分析。