An investigation on the impact toughness properties of wrought and additively-manufactured (AM) Ti 6Al 4V was conducted at NIST Boulder, by means of instrumented impact tests on miniaturized Charpy specimens. Full transition curves for absorbed energy and lateral expansion were obtained by performing tests in the temperature range between -196 °C and 700 °C. Testing was performed on a small-scale (50 J) impact tester equipped with an instrumented striker, and using Reduced-Half-Size (RHS) miniaturized Charpy specimens. For tests below room temperature, specimens instrumented with thermocouples were cooled down to liquid N2 temperatures, before being manually transferred to the impact position. When testing above room temperature, specimens were heated in a small furnace and their temperature was monitored by means of an infra-red thermometer until the moment of impact. The effect of various parameters was investigated for AM specimens, namely specimen orientation, Hot Isostatic Pressing (HIPping), and notch configuration (printed or machined). Our results indicate that AM specimens exhibit equivalent or better impact toughness than wrought material after HIPping, and that the material is more resistant to cracks growing in the plane perpendicular to the build direction than in the plane containing the build direction. HIPping has a significantly beneficial effect for the AM material, while no effect of notch configuration was observed from the results obtained. Characteristic instrumented forces allow a qualitative assessment of dynamic tensile properties, which appear to be similar for wrought and AM Ti 6Al 4V.
Citation: Materials Performance and Characterization
Pub Type: Journals
Hot Isostatic Pressing, impact toughness, instrumented impact tests, miniaturized Charpy specimens, Ti-6Al-4V