生长速率对NiAl-43V(Dy)合金定向凝固组织的影响

用高温梯度定向凝固液态金属冷却技术(LMC,GL=310 K/cm)制备NiAl-43V-x Dy(质量分数x=0,0.05%)过共晶合金,研究定向凝固生长速率对两种成分合金固液界面形态和稳态区组织演变影响,同时对比研究微量Dy对NiAl-43V合金定向凝固组织的影响。结果表明:在6~150μm/s内两种合金固、液界面均为胞枝共存界面;两种合金凝固组织均由初生V相和共晶组织(片层V相+NiAl相)组成,随生长速率增大,合金凝固组织中枝晶析出增多,枝晶体积分数增大,共晶组织和枝晶得到细化。在NiAl-43V合金中加入质量分数为0.05%的Dy使Gibbs-Thompson系数减小,在相同生长速率下,微量Dy可使共晶层间距减小,溶质原子重新分配,枝晶尖端过冷度降低,枝晶体积分数减小,枝晶间溶质原子浓度增加使一次枝晶间距增大;微量Dy可抑制初生枝晶生长。

Effect of growth rate on microstructure of directionally solidified NiAl-43V(Dy)alloy

A high temperature gradient directional solidification liquid metal cooling technology(LMC,GL=310 K/cm)was used to prepare NiAl-43 V-x Dy(mass fraction x=0,0.05%)hypereutectic alloy,and the effect of the directional solidification growth rate on the morphology of the solid-liquid interface and the microstructure evolution in the steady-state zone of two-component alloy was studied.The effect of the addition of trace Dy on the directional solidification structure of the NiAl-43 V alloy was also studied.The results show that in 6-150μm/s,the solid-liquid interface morphology of two-component alloys is cell-branched coexisting interface.The solidification structure of two alloys is composed of the primary V phase and the eutectic structure(lamellae V phase+NiAl phase).With the continuous increase of growth rate,the precipitation of dendrites in the alloy solidification structure increases,the number of dendrite integration increases,and the eutectic structure and dendrites are refined.Addition of a mass fraction of 0.05%Dy to NiAl-43 V alloy reduces the Gibbs-Thompson coefficient.At the same growth rate,a small amount of Dy can reduce the interlayer spacing,redistribute solute atoms,and dendrite tips the degree of subcooling decreases,the integral number of dendrites decreases,and the concentration of solute atoms between dendrites increases to increase the primary dendrite spacing.The trace Dy elements can inhibit the growth of primary dendrites.