Microscopic mechanisms contributing to the synchronous improvement of strength and plasticity (SISP) for TWIP copper alloys

R Liu,L L Li,Z F Zhang,Z J Zhang,X H An

doi:10.1038/srep09550

Abstract

In this study, the concept of “twinning induced plasticity (TWIP) alloys” is broadened, and the underlying intrinsic microscopic mechanisms of the general TWIP effect are intensively explored. For the first aspect, “TWIP copper alloys” was proposed following the concept of “TWIP steels”, as they share essentially the same strengthening and toughening mechanisms. For the second aspect, three intrinsic features of twinning: i.e. “dynamic development”, “planarity”, as well as “orientation selectivity” were derived from the detailed exploration of the deformation behavior in TWIP copper alloys. These features can be considered the microscopic essences of the general “TWIP effect”. Moreover, the effective cooperation between deformation twinning and dislocation slipping in TWIP copper alloys leads to a desirable tendency: the synchronous improvement of strength and plasticity (SISP). This breakthrough against the traditional trade-off relationship, achieved by the general “TWIP effect”, may provide useful strategies for designing high-performance engineering materials.

Highlights

Microscopic mechanisms contributing to the synchronous improvement of strength and plasticity (SISP) for twinning induced plasticity (TWIP) copper alloys
The tensile stress-strain curves in Fig. 2a and the relationships between yield strength (YS, the off-set yield at 0.2 percent, s0.2), ultimate tensile strength (UTS) and uniform elongation in Fig. 2b show an obvious SISP tendency with increasing Al content. These experimental results, together with our previous findings, indicate that the trend of SISP is an intrinsic characteristic of Cu-Al alloys, which is quite different from the traditional trade-off relationship[2,3,4,5]
While the increase of YS mainly reflects the effect of solid solution strengthening, the extra increase of UTS probably derives from the following work-hardening process, which is possibly associated with the participation of deformation twinning during plastic deformation

Summary

Introduction

Microscopic mechanisms contributing to the synchronous improvement of strength and plasticity (SISP) for TWIP copper alloys. ‘‘dynamic development’’, ‘‘planarity’’, as well as ‘‘orientation selectivity’’ were derived from the detailed exploration of the deformation behavior in TWIP copper alloys These features can be considered the microscopic essences of the general ‘‘TWIP effect’’. The effective cooperation between deformation twinning and dislocation slipping in TWIP copper alloys leads to a desirable tendency: the synchronous improvement of strength and plasticity (SISP). This breakthrough against the traditional trade-off relationship, achieved by the general ‘‘TWIP effect’’, may provide useful strategies for designing high-performance engineering materials. To achieve a better understanding and make full use of the TWIP effect, the following two problems should be addressed: (i) is this ‘‘TWIP effect’’ a general mechanism that can be shared by other face centered cubic (FCC) alloys? If so, there should be a ‘‘TWIP family’’ that contains ‘‘TWIP steels’’ and some other ‘‘TWIP alloys’’. (ii) How does deformation twinning benefit the strength and plasticity simultaneously in ‘‘TWIP alloys’’?

Methods

Results

Conclusion