Twinning deformation in martensite microstructure

Molecular dynamics is used to study twinning deformation in a martensite microstructure obtained from rapid cooling β zirconium through the bcc-hcp transition. The microstructure is composed of (101̄1) twin boundaries and boundary dislocations which sometimes spread across the twins to form stacking faults. A series of such equilibrium microstructures subjected to discrete, increasing <1012̄ > (101̄1) shear strain. The stress-strain curve has stick-slip behaviour with yield stress of ≈ 5.0Kbar and yield strain of ≈ 3.8%. Deformation occurs through movement of twin boundaries in segments between boundary dislocations. Straight perfect twin boundaries do not move.