Surface wrinkling of the twinning induced plasticity steel during the tensile and torsion tests

• Heterogeneous twinning during deformation of TWIP steel.
• Comparing twin developments in TWIP steel during tensile and torsion tests.
• No heterogeneous twinning of TWIP torsion samples subjected to high shear strains.
• Experimental aspects of heterogeneous twinning.

‘Heterogeneous twinning’ is defined as plastic deformation due to the formation and progress of twins resulting in surface wrinkles on the deforming part when the initial grain size is relatively large compared to the typical size of the part. In the case of a Twinning Induced Plasticity (TWIP) steel with an initial grain size of ∼160 m, the heterogeneous twinning generated visible wrinkles, an orange peel effect, under medium uni-axial strains. The heterogeneous twinning did not occur in the material subjected to high shear strains. The complications resulting from this phenomenon on strain hardening characterization of the TWIP steels using two commonly used mechanical tests, tensile and torsion are discussed along with some experimental aspects of heterogeneous twinning.