Ti-6Al-4V合金铸件拉伸性能差异原因分析

Tensile Property Difference of Ti-6Al-4V Alloy Castings

目的研究Ti-6Al-4V合金两种不同结构铸件产品之间,拉伸性能存在着较大差异的原因。方法分别对同批次母合金浇注的两种熔模精密铸件进行化学成分分析、金相组织检查和拉伸试棒宏微观断口形貌观察。方法分析发现,肋板和支承座铸件两者化学成分没有明显差异,断口表面未见明显冶金缺陷。金相组织检查表明:肋板的原始β晶粒尺寸和晶粒内部的α片层间距均,小于支承座的原始β晶粒尺寸和晶粒内部α片层间距。结论分析结果表明,拉伸性能数据存在差异主要与其晶粒度和晶内片层间距差异有关,该组织差异主要由铸造工艺中不同的冷却速度引起的。通过改变取样位置,试样的拉伸强度可获得明显提高。

The paper aims to research causes for tensile property difference in two Ti-6Al-4V titanium castings prepared by the same batch of parent alloy ingot. Two investment castings of the same batch were taken to carry out chemical component analysis, metallurgical structure examination and micro fracture surface observation of tensile test bar. Chemical components of lib and supporting holder had no apparent difference. There was no apparent metallurgical defect on the fracture surface. The metallurgical structure examination showed that the β grain size and the α lamellar spacing in grain of the lib was uniform, and was less than that of the supporting holder. Difference of tensile property is mainly because that the grain size and lamellar spacing in grain is different. This difference is mainly caused by the cooling speed in different casting technologies. Changing the sampling position might improve the tensile property obviously.