Effect of Trace Boron Addition on Microstructure and Properties of as-Cast Ti-6Al-4V Alloy

摘要:

通过添加0.1wt%Ｂ对铸态Ti-6Al-4V合金组织和性能影响研究表明：微量B添加在合金中形成TiB相，TiB相位于原始β晶界处。微量的B添加使得原始β晶粒和α集束都得到了明显的细化，获得的铸态组织更加均匀。微量的B添加同时提高了铸态合金的强度和塑性，并改变了合金的拉伸断裂机制。由微空洞在α集束交界处聚集、长大及裂纹形成扩展改变为TiB相与基体合金的变形不协调造成微裂纹的形成和扩展。

Abstract:

The effects of 0.1wt% boron addition on microstructures and properties of as-cast Ti-6Al-4V alloy were studied. The results show that TiB phase forms in the original β grain boundaries of Ti-6Al-4V alloy due to 0.1% boron addition. Compared with boron-free Ti-6Al-4V alloy, boron added alloy is refined with uniform β grains. In addition, boron addition results in an improved strength, ductility and a changed fracture mechanism. The fracture mechanism of Ti-6Al-4V alloy is as follows: dislocation slip and pile up in the alpha colonies results in stress concentration and then voids growing until cracks forming. However, the fracture of the boron added Ti-6Al-4V alloy is as follows: a stress concentration occurs around the TiB phase and then micro-voids are formed. TiB phase breaks and is separated with the matrix and then cracks nucleate.