Small Punch Testing to Estimate the Tensile and Fracture Properties of Additively Manufactured Ti-6Al-4V

Small punch (SP) testing is a methodology that uses tiny disks (generally 8 mm in diameter and 0.5 mm thick) to estimate mechanical properties of metallic materials, such as tensile properties, fracture toughness, and ductile-to-brittle transition temperature. Empirical correlations are typically used to infer conventional mechanical properties from characteristic forces and displacements obtained from the test record. The majority of the available literature relates to SP testing of steels, while relatively little is available for other metallic materials. At NIST in Boulder, Colorado, we conducted SP tests on additively manufactured (AM) Ti-6Al-4V with different processing parameters and heat treatment conditions. Force/punch displacement curves appeared different than those typically reported for conventionally manufactured steels, and correlations with tensile and fracture parameters were generally weaker than those published for steel samples. It appears that the application of the SP technique (characterized by a biaxial loading mode) to materials with high anisotropy such as AM materials may be somewhat problematic and therefore of limited applicability.