Ta对镍基单晶合金铸态组织和偏析的影响

Effect of Ta on As-cast Microstructure and Segregation of Ni-base Single Crystal Superalloy

利用螺旋选晶法制备了不同Ta含量的镍基单晶合金,研究了Ta对镍基单晶合金铸态组织和偏析的影响。结果表明:镍基单晶铸态组织主要由枝晶组成,枝晶间的γ'较大,枝晶干的γ'较小;Ta对枝晶有较大影响,随着Ta含量的提高,枝晶间距减小,并且逐渐出现三次枝晶臂;Ta提高了Mo的偏析系数,促进了Mo在枝晶间的偏析;Ta改变了γ'的形貌,Ta含量较低时,γ'为圆形,Ta含量提高时,γ'向方形转变,同时合金的错配度增大。

The Ni-base superalloys with different Ta contents were prepared by using screw selecting crystal method, its as-cast microstructure and elements segregation of the alloys were investigated. The results show that the as-casting microstructure consists of dendrites, the γ′ in inter-dendrite is larger and that in dendrite is smaller. The dendrite distance is effected by Ta content, with the increase of Ta, the dendrite distance decreases, Mo segregation in inter-dendrite zone and the segregation coefficient increases. The morphology and size of γ′ phase is effected by the addition of Ta, with the increase of Ta content, the γ′ changes from ellipse to squareness, in the meantime the mismatch degree of the alloy increases.