The effect of low temperature annealing on the structure of Gd5Si2Ge2 alloy

Heat treatments at 150 and 400 deg C for different times were employed on the powdered and bulk Gd5Si2Ge2 alloy. The phase composition and transformations were characterized by X-ray powder diffraction (XRD) and differential scanning calorimetry (DSC). The powdered Gd5Si2Ge2 samples, which were heat-treated at 150 deg C for 2h and at 400 deg C for 0.5h, change from Gd5Si2Ge2-type structure to Gd5Si2Ge2-type and Gd5Si4-type double-phase structure. However, there is no change in the structure on the bulk Gd5Si2Ge2 samples heat-treated at 400 deg C for 0.5 and 10h. These results indicate that the inner stresses can induce the Gd5Si2Ge2 beta-gamma phase transformation to occur at lower temperatures.