Strain glassy behavior and premartensitic transition in Au7Cu5Al4alloy

Abstract

Strain glassy behavior (SGB) in correlation with premartensitic tweed (PMT) morphology was observed in an Au 7 Cu 5 Al 4 alloy, which is different from previously observed SGB that is incompatible with PMT in doped Ti-Ni alloys. Additionally, an "inverse freezing" transition from martensite to premartensitic strain glass upon heating was experimentally discovered, confirming a recent theoretical prediction. Investigations of rich phenomena in nonmagnetic Au-Cu-Al alloys are expected to shed light on the origin of both premartensitic transition and glasses.

Origin of tweed in Au–Cu–Al alloys

“…Ren and collaborators [12][13][14] suggested that the premartensitic tweed is a frozen 'strain glass' stems from point defects (such as the doping excess atoms), which is similar to the proposal of Kartha et al [2,10] and Loveras et al [1]. Our previous paper [15] and Zhang [14] have experimental proved that the premartensitic tweed indeed shows the 'strain glassy behavior' in Au-Cu-Al alloys and Ti-Ni-based alloys, respectively.…”

“…The premartensitic tweed in Au-Cu-Al alloys was reported in our previous paper [15]. In the present work aiming to a better understanding of the origin of premartensitic tweed, the BCC parent (L2 1 -type β phase) → BCC (Cu 9 Al 4 -type premartensitic phase) transition giving rise to the tweed morphology was investigated further detailedly.…”

“…This indicates that a premartensitic phase (or intermediate phase, denoted as I phase) may exists between the martensite and parent phases. In fact, the P1 peak of S1 (with nominal composition Au 7 Cu 5 Al 4 ) showing the frequency-dependent internal friction was found to be responsible for the 'premartensitic strain glassy behavior' [15].…”

“…However, the mechanism of 1/6 h2 2 0 i atomic displacement waves in parent remains unclear (also seen in Ref. [15]). Bright-field image of S1 (aged at 200°C for 1 h, followed by slowly cooled to RT at 1°C/min) and its EDP along [1 0 0] zone axis and dark-field image of circled spot.…”

Is “strain glass” a nanodomain frozen transition?

“…Based on this concept, Kartha et al and Ren and collaborators developed the theory and proposed the “spin/strain glass nature” of premartensitic tweed due to frozen point defects or intrinsic compositional disorder. Also, our previous paper and Zhang et al have experimentally proved that the premartensitic tweed or mottled phase indeed shows the “strain glass behavior” in Au–Cu–Al and Ti–Ni‐based alloys respectively.…”