摘要:
对真空冶炼铸造Ti-6Al-4V钛合金 (简称ZTC4) 表面α污染层的组织、氧氢含量及纳米硬度趋势进行了研究, 分析了α污染层对铸造钛合金拉伸性能的影响。结果表明, α污染层为粗大的片状结构, 最大深度为0.28 mm;与心部区域相比, 氧元素含量增加了1.64倍, 氢元素减少了1倍, 0硬度值增加了0.94倍, α污染层对ZTC4的拉伸性能影响显著, 与不含α污染层试样相比, 屈服强度、抗拉强度、延伸率和断面收缩分别降低了14.2%、12.5%、20%和35%, 这是由于氧等原子固溶在试样表面形成脆而硬的α污染层, 在拉伸载荷作用下α层不易变形形成多源断裂, 在材料最薄弱区域形成宏观断裂源并向基体快速扩展, 最后形成脆性解理断裂。
Abstract:
The microstructure,oxygen and hydrogen content,nano hardness trend of α-contaminant layer on the surface of Ti-6Al-4V titanium alloy by vacuum smelting（ZTC4 for abbreviation）were investigated,and the effects of α-contaminant layer on the tensile properties of ZTC4 titanium alloy were also analyzed.The results show that α-contaminant layer has a thick lamellar structure with the maximum thickness of 0.28 mm.Compared with the those of the heart zones of ZTC4 alloy,the oxygen content and average hardness of the α-contaminant layer respectively increases by 1.64 and 0.94 times while its hydrogen content decreases by 1 time.The α-contaminant layer has a significant effect on the tensile properties of ZTC4,and the yield strength,tensile strength,elongation and section shrinkage of ZTC4 respectively decreases by 14.2%,12.5%,20% and 35% in comparison with those of the alloy without α-contaminant layer.The hard and brittle α-contaminant layer is formed on the surface of the alloy by dissolving oxygen atoms,which is difficult for deformation under the tensile load,and then the macroscopic fracture sources are formed in the weakest zones of alloy and quickly expand to the matrix resulting in brittle cleavage fractures in the alloy finally.
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