Direct formation of peritectic phase but no primary phase appearance within Ni_83.25Zr_16.75 peritectic alloy during free fall

Ni_83.25Zr_16.75 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.