Effect of loading rate on crystallization of metallic glass supercooled liquids

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.

Heat Effects Occurring in the Supercooled Liquid State and Upon Crystallization of Metallic Glasses as a Result of Thermally Activated Evolution of Their Defect Systems

We show that the kinetics of endothermal and exothermal effects occurring in the supercooled liquid state and upon crystallization of metallic glasses can be well reproduced using temperature dependences of their shear moduli. It is argued that the interrelation between the heat effects and shear modulus relaxation reflects thermally activated evolution of interstitial-type defect system inherited from the maternal melt.

FEATURES OF TEXTURE FORMATION IN POLYMORPHIC METALS BEING ELECTRODEPOSITED

<p class="AMSmaintext"><span lang="EN-GB">The aim of this work was further experimental verification of the existence of the phenomenon of electrochemical phase formation in metals and alloys via a supercooled liquid state stage. According to proposed idea the slowing down of the process of polymorphic transformation in a metal being electrodeposited should be accompanied by an intensive formation of the texture of the metastable modification and suppression of the texture development of the stable modification. The results of the texture analysis of electrodeposited cobalt as a model metal showed that under slowing down the polymorphic transformation process in a metal being electrodeposited, the texture formation is intensified in the metastable modification, but suppressed in the stable modification. The finding is another proof of the existence of the phenomenon of electrochemical phase formation in metals and alloys through a supercooled liquid state stage.</span></p>