300M钢锻件中的凹坑缺陷及其形成机理

对300M钢制锻件中的凹坑缺陷进行了观察与分析，并对凹坑缺陷的形成机理进行了分析与研究，结果表明，锻件中的凹坑缺陷是在锻造过程中产生的，它是在锻件裂纹延性开裂与扩展时，伴随锻造裂纹的产生，扩展以及微裂纹与空洞形成，连通，圆钝与氧化而形成的。     

Portevin-Le Chatelier effect in Al-Zn-Mg-Cu-Zr aluminum alloy

Portevin-Le Chatelier (PLC) effect in a severely cold-rolled Al-Zn-Mg-Cu-Zr aluminum alloy (AA7055 type) plate before and after annealing was investigated. The results show that the sample annealed at 300 °C undergoes PLC effect, whereas the PLC effect is not observed in the deformed sample or the samples annealed at 110 °C or 200 °C. The main precipitates in the sample annealed at 300 °C are the coarsened η phases, while a mixture of small η' phases and η phases dominates in the sample annealed at 200 °C. In the deformed sample and sample annealed at 110 °C, GP zone are the main precipitates. The different flow behaviors are ascribed to the type of precipitates as well as the dislocation density differences.     

300M钢锻件中的裂纹扩展机理

对300M钢制筒锻件中的裂纹缺陷进行了观察与分析，并对裂纹扩展的机理进行了研究。结果表明，钢制锻件中裂纹是以微孔聚集型延性开裂并扩展，裂纹断面及其附近的凹坑别是伴随着锻造裂纹的产生以及微裂纹和空洞的形成、连通、圆钝、氧化而形成。