Fracture Toughness of Martensitic NiTiHf High-Temperature Shape Memory Alloy

摘要

Fracture behavior of a martensitic Ni50:3Ti29:7Hf20 (at.%) high-temperature shape memory alloy (SMA) undermode-I nominally isothermal loading was examined. The material was characterized using diu000berential scanningcalorimetry to identify the transformation temperatures and uniaxial tensile testing to portray the stress{strainbehavior. Pre-cracked disk-shaped compact specimen was tested at room temperature and unstable crack growthwas observed. Fracture toughness was measured using the associated load versus crack-mouth opening displacementrecord. Digital image correlation was implemented to obtain the strain field on the surface and near thecrack-tip. Moreover, fracture surface was examined using scanning electron microscopy. The results provide keyinsights into the fracture properties of NiTiHf high-temperature SMAs.