In situ design of ultrafine-grained 7075 Al alloy with laser powder bed fusion

Laser powder bed fusion (L-PBF) is an advanced fast prototyping method for fabricating high-performance metallic components with complex structures. However, the development of L-PBFed high-strength Al alloys is often limited by the hot cracks. To grapple with this difficult issue, a novel solution was proposed by intro-ducing 3 wt% Ti2AlNb intermetallic (IMC) powders into the 7075 Al powders to form an in-situ nucleated 7075 (IN-7075) Al alloy. The results indicated that the as-printed IN-7075 Al alloy was crack-free, and the grain size has been refined from 72.6 mu m to 1.5 mu m, which was attributed to the in-situ formation of Al3(Ti, Nb) particles and the high grain growth restriction factor (Q) values of Ti and Nb elements in the Al matrix. After a suitable heat treatment, the IN-7075 Al alloy exhibited good mechanical properties with an ultimate tensile strength of 429 +/- 2 MPa and an elongation of 9.8 +/- 0.5%.