(1. 福州大学 材料科学与工程学院，福州 350002；
2．浙江大学 材料科学与工程系， 杭州 310027)
摘 要: 采用透射电镜动态拉伸、 原位观察研究了低层错能合金H68黄铜断裂的微观过程。 结果发现： 黄铜薄膜试样拉伸时， 裂尖首先发射位错， 平衡时形成无位错区和反塞积位错群； 裂尖前方较厚区域可以发生孪生变形，形成形变孪晶， 微裂纹在孪晶中形核、 扩展， 导致裂纹呈Z字形扩展； 裂尖无位错区也可能形成微孪晶， 微裂纹在微孪晶中形核，使裂纹呈不连续扩展； 微裂纹也可以从主裂纹顶端连续形核、 扩展。
关键字: 断裂； 无位错区； 形变孪晶； 黄铜
fracture of H68 brass
（1. School of Materials Science and Engineering,
Fuzhou University, Fuzhou 350002, China;
2. Department of Materials Science and Engineering,
Zhejian University, Hangzhou 310027, China）
Abstract:The micro process of crack initiation and propagation in H68 brass with low stock fault energy was observed by in situ tensile test in TEM. The results show that many dislocations are emitted from a loaded crack tip and move forward. A dislocation free zone(DFZ) is formed between crack tip and the inversely pile-up dislocations when the dislocation emission and motion reach equilibrium. Mechanical twin forms in the thicker area ahead of crack, and then the micro-crack initiates and propagates in the mechanical twin, which result in a zig-zag crack propagation. The micro-twin forms in the DFZ and the micro-crack initiates in the micro-twin, resulting in the crack propagation discontinuously. Sometimes the micro-crack propagates from a blunted crack tip continuously.
Key words: fracture; dislocation free zone; mechanical twin; brass
