Influence of Al content on martensitic transformation behavior in Zr50Cu50−xAlx

Abstract

Influence of Al content on martensitic transformation temperature in ZrCu phase was investigated by differential scanning calorimetry for a series of Zr50Cu50−xAlx alloys. The crystallographic structure of the martensite was predominantly a monoclinic Cm, which is a superstructure of B19′. Microstructural observations revealed that a higher Al content above 6mol% led to a pronounced formation of Zr2Cu and τ5 phases forming complex eutectic microstructures. The electron probe microanalysis indicated that the Al atoms in ZrCu phase substitute the Cu atoms up to 6mol% and the excess Al atoms exist mainly in the τ5 phase. The increasing Al content from 0 to 6mol% induced a decrease in the martensitic transformation start temperature, Ms, from 446K to 311K, and in the reverse martensitic transformation start temperature, As, from 537K to 468K. But Ms remained almost constant when the Al content is over 6mol%. Thus, the substitution of the Cu atoms by the Al atoms in ZrCu phase led to the decrease in Ms and As.