Spinodal strain glass in Mn-Cu alloys

Strain glasses (STGs), which are characterized by nanodomains of martensite formed via a strain glass transition, can produce many unusual properties not possessed by normal martensitic alloys. These nanodomains originate from the formation of short-range strain ordering by the disruption of otherwise long-range strain ordering or normal martensitic transformation through sufficient atomic/nanoscale random stress/strain field. So far the atomic/nanoscale randomness is known to be from either point defects, dislocations, or nanoprecipitates. Here we report a spinodal STG alloy Mn60Cu40, which stems from nanoscale composition modulations (5-20 nm) formed in the early stage of spinodal decomposition, which is identified by STEM-EDS and HRTEM. For short-time ( < 50 min) aged sample, a strain glass transition was identified by its typical signatures including invariance of global face-centered cubic (fcc) structure with cooling, frequency dependence of elastic moduli at STG transition temperature (T-g) following a Vogel-Fulcher relationship, non-ergodicity as manifested by zero-field-colling/field-cooling curves, and the formation of martensitic face-centered tetragonal (fct) nanodomains. For long-time (>= 50 min) aged sample, a normal martensitic transition from fcc to fct appears with cooling, being consistent with literatures. As the result, a temperature vs. aging-time phase diagram of spinodal STG was established and shows a crossover from STG to martensite above a critical aging time. The spinodal STG exhibits a non-magnetic Elinvar behavior, i.e., nearly constant elastic modulus over a wide temperature range, together with high-damping capacity. We anticipate that the spinodal STG and associated novel properties may also be found in other metallic and ceramic spinodal materials. (C) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

The study focuses on the characteristics and properties of a spinodal strain glass alloy Mn60Cu40, which exhibits a transition from strain glass to normal martensite with aging. The spinodal strain glass shows non-magnetic Elinvar behavior and high damping capacity. The findings suggest that spinodal strain glasses and their novel properties may also be found in other metallic and ceramic spinodal materials.