Direct formation of peritectic phase but no primary phase appearance within Ni83.25Zr16.75 peritectic alloy during free fall

Ni83.25Zr16.75 peritectic alloy was containerlessly solidified in a drop tube. When the droplet diameter exceeds a critical value (D-crit), Ni7Zr2 phase primarily solidifies, followed by the peritectic reaction of Ni7Zr2 + L -> Ni5Zr. Once the droplet diameter is smaller than the critical value (D-crit), peritectic phase Ni5Zr directly solidifies from the undercooled melt by completely suppressing the nucleation and growth of Ni7Zr2 phase, which is ascribed to high undercooling and cooling rate. Additionally, peritectic phase Ni5Zr grows equiaxially in the sample solidified in a DSC at a cooling rate of 0.167 K/s.