Direct formation of peritectic phase but no primary phase appearance within Ni(83.25)Zr(16.75) peritectic alloy during free fall

Ni(83.25)Zr(16.75) peritectic alloy was containerlessly solidified in a drop tube. When the droplet diameter exceeds a critical value (D(crit)), Ni(7)Zr(2) phase primarily solidifies, followed by the peritectic reaction of Ni(7)Zr(2) + L → Ni(5)Zr. Once the droplet diameter is smaller than the critical value (D(crit)), peritectic phase Ni(5)Zr directly solidifies from the undercooled melt by completely suppressing the nucleation and growth of Ni(7)Zr(2) phase, which is ascribed to high undercooling and cooling rate. Additionally, peritectic phase Ni(5)Zr grows equiaxially in the sample solidified in a DSC at a cooling rate of 0.167 K/s.