Reducing time and cost of the heat treatment post-processing of additively manufactured Ti6Al4V

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The unique microstructure of Ti6Al4V produced through laser powder bed fusion (LPBF) displays high tensile strength with low elongation in the as-built state. To obtain desired material properties which comply with standards for Ti6Al4V products, further post-processing is needed. Conventional practice prescribes that the required tensile properties can be achieved with time-consuming post-processing heat treatment of LPBF parts, most of which use air or water quenching that causes surface modification, such as oxidation, when applied to Ti6Al4V. The aim of this work was to develop an alternative heat treatment process that would retain the benefit of additive manufacturing (AM), but reduce the related processing time and cost, while still complying with the part property specifications. A new heat treatment cycle was hypothesized and tailored, resulting from a critical analysis of current practice found in literature and practised in the Centre for Rapid Prototyping and Manufacturing (CRPM) of the Central University of Technology, Free State, based on the need for a quick and cost-effective cycle. By comparing the obtained material properties and microstructure with those of other common heat treatments, the cycle was found to be faster, lasting only four hours in total, and the material properties were superior to those of existing cycles. A high yield stress of 987 MPa was obtained while retaining a good elongation of 16 %.