Effects of dendrite size on dynamic tensile deformation behavior in Zr-based amorphous alloys containing ductile dendrites

In this study, dynamic tensile properties of Zr-based amorphous alloys whose dendrite size was varied with plate thickness (or cooling rate) were investigated, and effects of dendrite size on dynamic deformation mechanisms were verified. The dendrite size of the amorphous alloys was varied from 14.7 μm to 42.8 μm, while their volume fraction was almost constant. The dynamic tensile test results indicated that the ultimate tensile strength increased up to 2.6 GPa because of strain rate hardening effect, whereas the elongation decreased to 1.1-1.6%, although the overall strength and elongation trends followed those of the quasi-static tensile test. According to the observation of dynamic tensile deformation behavior, the dendrite size greatly affected the dynamic tensile strength and elongation by the formation of deformation bands at dendrites, while dendrites themselves took over a considerable tensile load. However, the elongation was deteriorated when dendrites were large above a certain size level. In the alloy containing large dendrites, deformation bands were formed at dendrites in two intersected directions, but the amount of intersected deformation bands was reduced because deformation bands showed slip characteristics on a few slip planes of dendrite.