HR3C奥氏体耐热钢晶界蠕变损伤的电子背散射衍射分析

Electron Backscattered Diffraction Investigation of Grain Boundary Creep Damage Features of HR3C Austenitic Heat-resistant Steel

摘要:

对不同条件下的HR3C奥氏体耐热钢蠕变试样进行性能测试和微观结构观察，研究奥氏体耐热不锈钢蠕变沿晶破坏行为和损伤特征。电子背散射衍射（EBSD）分析结果表明，不同蠕变速度下材料的晶粒尺寸基本不变，未产生择优取向，但高蠕变速度条件下部分孪晶界演变成一般晶界，而低蠕变速度下原始孪晶结构基本保持不变。EBSD分析结果清楚地反映了微观蠕变应变的不均匀性。沿晶微裂纹和蠕变空洞的产生和扩展是最显著的损伤特征，这些损伤现象与不同蠕变速度下的蠕变机制及晶界性质密切相关。

Abstract:

In order to investigate the intergranular fracture characteristics of HR3C austenitic heat-resistant steel at various creed rates， several techniques are employed to test the properties and observe the microstructure evolution. The quantitative electron backscatter diffraction （EBSD） analysis results show that creep strain has little effect on the grain size， and grains do not exhibit a preferred orientation or no obvious texture after crept at different creep rates. The lowest proportion of low Σ CSL grain boundaries at 150 MPa implies that the primary twin structures is preserved at a low creep rate， while some twin structures are evolved into general grain boundaries at a high creep rate. The EBSD analysis methods well describe the creep micro-strain distribution， which shows that the creep strain is inhomogeneous between grains and strain occurs mostly close to grain boundaries and induces grain boundary migration. The generation and propagation of intergranular microcracks and creep voids are the most significant damage characteristics. These damage phenomena are closely related to the creep rates and the character of the grain boundaries.