Deformation of Ordered CuAu Alloy

Abstract

The mechanism of deformation of the ordered CuAu alloy is investigated using electron microscopy. The alloy deformation is shown to be accomplished by slipping; a larger degree of deformation involves the mechanism of twinning. The interaction between dislocations and the boundaries of 90° ‐disoriented domains has been studied. It is shown that the interaction between the dislocations and the domain boundaries is responsible for the high deformation strengthening of the ordered alloy.

L10 nanotwinned gold-rich Au–Cu–Pt

“…After the first 120 s of ordering, the hardness increases noticeably in comparison with the initial disordered state: intervariant boundaries are well known to be the main obstacle to dislocations in ordered L1 0 crystals [33,34]. The hardness then decreases somewhat at 540 s and beyond: this corresponds to the observed transition from a microstructure comprising two microtwin systems to the well-known mechanically relaxed polytwin microstructure, in which only one set of parallel microtwins are locally present.…”

Structure and mechanical properties of CuAu and CuAuPd ordered alloys

“…4b). The study of the deformation behavior of this structure revealed that strength properties of the CuAu alloy depend on the domain size (or, which is the same, the number of domain boundaries) [7]. For example, the yield stress of the alloy, which is virtually devoid of domain boundaries, is 115 MPa [8].…”

Thermally activated deformation of two- and three-variant nanotwinned L10 Au–Cu–Pt

“…It is known that intervariant boundaries are the main obstacle to both slip or microtwinning in this alloy class. Several complex mechanisms, documented both by analysis and experiment, exist to explain the transmission of slip or twinning across intervariant boundaries [7,8,23,24,26,28,29,33,46]. Superdislocations, when these are vectors of deformation, must recombine and reorganize to pass intervariant boundaries, a process that can be aided by thermal activation [8,23,24,26,28,29,46].…”

“…Several complex mechanisms, documented both by analysis and experiment, exist to explain the transmission of slip or twinning across intervariant boundaries [7,8,23,24,26,28,29,33,46]. Superdislocations, when these are vectors of deformation, must recombine and reorganize to pass intervariant boundaries, a process that can be aided by thermal activation [8,23,24,26,28,29,46]. Ordinary dislocations, known to be important vectors of deformation in these structures, as well as microtwin Shockley partial series, must change Burgers vector to pass across an intervariant boundary, therefore leaving "debris" (or "residual") dislocations there.…”

“…Ordered AuCu-based alloys can deform by both slip and twinning, depending on their initial state. It has been documented that, when the alloy is devoid of internal stresses, deformation begins by slip only, with twinning setting in only after roughly 10% strain: in an alloy containing high internal stresses, on the other hand, both mechanisms are triggered simultaneously [23]. In L1 0 crystals, both slip and deformation twinning occur along {111} planes [7,8,17,24,25]; this is as in FCC crystals but with significant complications given the more complex L1 0 structure.…”