Investigation of residual stresses in titanium aerospace components formed via additive manufacturing
Additional Publication Information
In the present study gas tungsten arc welding (GTAW) with automated wire addition was used to additively manufacture (AM) a representative thin-walled aerospace component from Ti-6Al-4V in a layer-wise manner. Residual strains, and hence stresses, were analysed quantitatively using neutron diffraction techniques on the KOWARI strain scanner at the OPAL research facility operated by the Australian Nuclear Science and Technology Organisation (ANSTO). Results showed that residual strains within such an AM sample could be measured with relative ease using the neutron diffraction method. Residual stress levels were found to be greatest in the longitudinal direction and concentrated at the interface between the base plate and deposited wall. Difficulties in measurement of lattice strains in some discrete locations within the deposited material were ascribed to the formation of localised grain orientation where α-Ti laths form in aligned colonies within prior β-Ti grain boundaries upon cooling. Neutron diffraction measurements of residual stress were cross-correlated using the contour method with results found to be in close agreement. Observations of microstructure reveal 'basket-weave' morphology typical of fusion welds in Ti-6Al-4V. Microhardness measurements show lower hardness in the deposited material compared to the base plate and a further small decrease in hardness in the top region of the deposit, indicating a dependence on thermal cycling from sequential weld deposition.