The (20-1)-interfaces in plastically formed NiTi martensite - twins or 'kwinks'?

The talk will focus on a newly proposed deformation mechanism in crystalline metals that arises from merging reversible deformation twinning (typically observed in thermoelastic martensites) with plastic kinking (typically observed e.g. in highly anisotropic magnesium alloys). As this mechanism combines natures of kinking and twinning, I will introduce the term 'kwinking' for it, and the term 'kwinks' for the new class of planar defects on which the kwinking is based. There are several strong indications that kwinking may be the main plastic mechanism in NiTi and NiTi-based shape memory alloys when loaded beyond their shape-recovery limit. If this is true, studying the kwinking mechanism is essential for further development of plastic forming technology for these materials. Main ideas of the kwinking mechanics will be explained, using a continuum mechanics framework.