Driving force of zero-macroscopic-strain deformation twinning in face-centred-cubic metals

ABSTRACT

Zero-macroscopic-strain deformation twinning (ZMS-DT) is widely observed in many face-centred-cubic (FCC) metals and alloys. However, the driving force of ZMS-DT is a controversial issue and has not been fully clarified for a long time. Based on molecular dynamics simulations to various FCC metals, we found that ZMS-DT, i.e. Σ₃{112} incoherent twin boundary migration can be driven by simultaneously applying both normal and shear strains/stresses to the twin boundary (TB), and changing the sign of the normal or the shear strain/stress can change the direction of the incoherent TB migration. With analysing the results of atomistic strain energy calculation and anisotropic elasticity theory, we revealed the strain energy imbalance, which originates from elastic anisotropic response of materials, between the two sides of the twin boundary under normal–shear strain (or stress) coupling condition essentially drives the TB migration and twin growth. Eventually, we deduce that the elastic anisotropy ratio can be one of the key material constants which affect the twinnability of FCC metals.

KEYWORDS:

• Face-centred-cubic (FCC)
• twinning
• dislocation
• molecular dynamics (MD)
• elastic anisotropy

Acknowledgments

This work was financially supported by the Natural Science Foundation of China (grant number 11875015) and the National Key R&D Program of China (2018YFE0308101). This work was also financially supported by the Natural Science Foundation of Hebei Province (A2019202196). This research was also supported by JSPS KAKENHI Grant Nos. JP18H05453, JP17H01238, JP17K18827 and Element Strategy Initiative for Structural Materials (ESISM).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Japan Society for the Promotion of Science: [Grant Number JP17H01238,JP17K18827,JP18H05453]; National Natural Science Foundation of China: [Grant Number 11875015]; the Natural Science Foundation of Hebei Province (Grant Number A2019202196); the National Key R&D Program of China (Grant Number 2018YFE0308101).