Numerical and experimental study of porous NiTi anisotropy under compression

Porous NiTi samples were obtained by self-propagating high-temperature synthesis (SHS) and cut to specific dimensions by electrical discharge machining. Quasi-static compression of the porous SHS-NiTi alloy demonstrated that the deformation was elastic-plastic. Three characteristic types of fracture surfaces of bridges can be distinguished. 1) Ductile fracture of the austenite phase in the form of a cup and cone relief. 2) Brittle fracture with the formation of cleavage steps. 3) Large areas of plastic shear, where cup and cone, and cleavage facets are nucleated. An algorithm for obtaining a porous framework model suitable for finite element method calculations has been developed. The effective moduli of elasticity and shear for the porous volume of the material were determined. It is shown that the studied porous volume has orthotropic elastic properties due to the geometry of the porous framework.