添加微量B元素对铸造TC4钛合金显微组织和力学性能的影响

Effect of Boron Addition on Microstructure and Mechanical Properties of as-Cast TC4

为细化铸造TC4钛合金的晶粒,改善合金的力学性能,在合金中加入了少量B元素。结果表明:随着B含量逐步增加至0.06%(质量分数,下同),ZTC4钛合金晶粒尺寸从添加B之前的4.5 mm细化至0.36 mm,硼化物的主要分布也随之由晶粒内部分布转变为晶界处分布。当B含量为0.03%时,ZTC4钛材料具有最高的延伸率,但当B含量超过0.06%时,ZTC4钛材料拉伸时接近脆性断裂。导致ZTC4-0.06B材料几乎脆断的原因可能是B含量过多导致B化物分布由主要在晶粒内部转向晶界处。从晶粒细化效果和材料力学性能综合考量,铸造TC4钛合金中B的最佳添加量为0.02%～0.04%。

Small amount of boron was added in order to refine the grain and increase mechanical properties of TC4 alloy. The results show that the grain size of as cast TC4 is reduced from 4 500 to 360 μm with an addition of 0.06 wt% boron and the distribution of boride transforms from inner grain to grain boundary as well. When the boron is about 0. 03 wt%, the elongation is the highest. Whereas the titanium alloy shows brittleness as the boron is above 0. 06wt%. This may be caused by the boride precipitates mainly in the grain boundary. The proper content of boron is about 0. 02 -0.04 wt% , considering the grain refinement and mechanical properties.