Si对Ti-46Al-5Hf-0.6B合金凝固组织的影响

The Effect of Si Addition on the Ti-46AL-5Hf-0.6B Alloy Solidification Structure

为研究Si对Ti-46Al-5Hf-0.6B(原子百分比)合金铸态组织的影响,将名义成分为Ti-46Al-5Hf-0.6B-xSi(x=0,0.5%,1.5%,3%)合金用电弧熔炼法在氩气保护下制成纽扣锭.合金宏观和微观组织的特征采用OM、SEM、XRD技术进行分析.结果表明:Si在合金中形成Ti5Si3相,Ti5Si3相的数量和形态随Si含量的增加而变化.当Si的原子数等于0.5%、1.5%、3.0%时,合金凝固组织分别为近片层的粗大柱状晶、细化的柱状晶和以块状和条状Ti5Si3为初生相的等轴组织.Ti5Si3为脆性相,Si的原子数应小于1.5%.

To investigate the effect of Si addition on the solidification structure,the alloys with nominal compositions of Ti-46Al-5Hf-0.6BxSi（x=0,0.5%,1.5%,3%）are arc-melted into small ingots in an argon atmosphere.The characteristics of macro and micro structures are studied using OM,SEM and XRD techniques.The results show that Si addition forms Ti5Si3 phase in the alloy.When Si=0.5,1.5 and 3.0,the solidification structure is near lamellar with coarse columnar dendrite morphology,fine columnar dendrite and equiaxed dendrite with blocky and strip Ti5Si3 phase distributing on the matrix,respectively.Because of the brittleness of Ti5Si3 phase,the amount of Si addition should be less than 1.5%.