The structure and thermal parameters of ordered Cu65Fe10Pd25 ternary alloy

Abstract

Structural and thermal parameters have been studied in Cu65Fe10Pd25 alloy during order–disorder (O–D) transformation using differential scanning calorimetry (DSC) and high temperature X-ray diffraction (HTXRD). The results reveal that the Cu65Fe10Pd25 alloy undergoes an O–D transformation at Tc=797K. The alloy shows L12 type ordering below Tc and has disordered face centered cubic (fcc) structure above Tc. The lattice parameter shows a positive deviation from Vegard’s rule which may be related to the weakening of interatomic forces by the addition of Fe. The integrated intensity data obtained from the diffraction experiments was utilized to determine the coefficient of thermal expansion (α(T)), mean square amplitude of vibration (u2¯(T)) and Debye temperatures (ΘD) during the O–D transformation. The abrupt change in the value of lattice parameter and coefficient of thermal expansion at Tc shows that the nature of O–D transition is first order. These results have been discussed by comparing them to those for Cu3Pd alloy.