Effect of loading rate on crystallization of metallic glass supercooled liquids

Abstract

Metallic glasses exhibit unique thermoplastic processing capability, which is enabled by their metastable supercooled liquid state below the crystallization temperature. The thermoplastic processing critically depends on the crystallization time (processing time window), temperature (viscosity), applied load, and strain-rate. Among these parameters, the effects of crystallization time and processing temperature have been extensively studied. However, the effects of load and loading rate have not been thoroughly investigated. In this work, we performed a systematic study of load on the supercooled liquid state of three metallic glass formers: Pt-based, Zr-based, and Pd-based. The results show that the load-response of a metallic glass supercooled liquids is strongly composition dependent. The onset temperature of crystallization decreases with increasing load in Pt-based metallic glass whereas for Zr-based and Pd-based metallic glasses the onset temperature remains unchanged. The crystallization peak time is reduced for all three metallic glasses after thermoplastic forming. The results are discussed in terms of nucleation and growth of crystallites in metallic glasses.