Effects of Annealing on Structural Evolution and Microhardness of Zr50Cu40-xAl10Pdx (x=0-15) Bulk Metallic Glasses and Composites

Abstract

Effects of annealing on structural evolution and microhardness of Zr 50 Cu 40-x Al 10 Pd x (x=0-15) bulk metallic glasses (BMGs) and composites were investigated using X-ray diffraction (XRD) and micro-hardness analysis. The glass transition temperature T g and the crystallization temperature T x of Zr 50 Cu 40-x Al 10 Pd x (x=0-15) BMGs are 703-728 K and 758-764 K, respectively, determined from differential scanning calorimetry (DSC) with heating rate of 10 K/min. The BMG samples were annealed at different temperatures (below T g , between T g and T x , and above T x) and for different time period (5 min, 10 min, 20 min, 30 min), and then cooled in air. Based on XRD analysis, the as-cast BMG samples and the samples annealed at 623 K (i.e. below T g) showed amorphous structures, and the samples annealed at 723-923 K (i.e. above T g) for 30 min showed amorphous-crystalline composite structures. Microhardness measurements indicated that with increasing annealing temperature, microhardness gradually increased and then leveled off.