In our recent work, anelastic relaxation-time spectra, obtained over eight orders of magnitude, have revealed an atomically quantized hierarchy of shear transformation zones (STZs). These can explain both alpha and beta relaxations. Some La-based alloys exhibit pronounced beta relaxation, which correlate with high ductility. The purpose of the present work is to characterize the STZ spectra of such alloys. Two regimes of atomic volume increments are observed, suggesting a size dependence of STZ composition. Separately, in order to determine the STZ volume and transformation shear strain independently, we developed a measurement method for the non-Newtonian regime, based on constraining samples at nominally elastic strains of up to ~ 1.45%.
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