【摘要】 以Ti-6Al-3Mo-1.5Zr-0.3Si钛合金加工过程中的组织异常和开裂为基础,研究了α+β型钛合金在形变过程中裂纹的萌生及其扩展规律。通过对于合金中出现的"剪切带"设计有效的压缩实验,分析了该类型组织在后续变形过程中的演化过程,讨论了精锻变形、低速率压缩在α+β型钛合金的裂纹萌生及其扩展的演变机理。结果表明:锻造过程中裂纹从材料表面形核并以双滑移机制扩展,低速率压缩时裂纹从剪切带内开始萌生并以再生形核机制扩展;对比研究说明"剪切带"和"剧变区"有着本质区别,"剧变区"对材料的力学性能未造成直接影响,而"剪切带"却是裂纹萌生之处,或是已形成裂纹的尖端塑性区。更多还原

【Abstract】 Crack initiation and propagation behavior and mechanism of Ti-6Al-3Mo-1. 5Zr-0. 3Si titanium alloy in the process of deformation were studied. The compression experiments of the alloy specimen with shear band which had been formed during forging were carried out. The evolution of α + β structure in the compression deformation was examined. The different crack initiation and extension mechanism were observed under the different deformation conditions of forging and compression. The results show that the crack is initiated from alloy specimen surface and propagates by double slip mechanism in the process of forging,and the crack is nucleated in the shear band and propagates by re-nucleation mechanism for compression deformation. It is found that the shear band and severe deformation band formed during plastic deformation are different. The severe deformation band has little influence on the mechanical properties of the alloy,and the shear band is crack tip plastic zone,promoting crack initiation.更多还原