Evolution of crystallographic orientation, columnar to equiaxed transformation and mechanical properties realized by adding TiCps in wire and arc additive manufacturing 2219 aluminum alloy

Abstract

2219Al/TiCps composites were deposited by the wire and arc additive manufacturing method. The effects of TiCps content on the phase transformation, average grain size, crystal orientation, and mechanical properties of the deposited 2219 aluminium alloys were investigated as the variation of TiCps fraction is from 0.5 wt% to 2.0 wt%. The results show that the addition of 5 µm TiCps can effectively reduce the nucleation free energy of the system, which provided an opportunity for nuclei to grow on the surface of TiCps. The average grain size first decreased, then increased with the increase of TiCps weight fraction. Also, the EBSD testing results show the texture intensity both the Al-matrix and the θ-CuAl2 phase gradually decreased with increasing TiCps fraction. TiCps played an important role in generating nucleation undercooling (ΔTnu, 0.38 °C), which could be used to counteract the constitutional supercooling (ΔTcs) caused by solute segregation, and further promoted the transformation of granular θ-CuAl2 phase to a fine spot-like one within the grains. The fine spot-like phase possessed a strong interfacial bonding with the Al-matrix, thereby the mechanical properties of the deposited 2219 aluminium alloy were strengthened. Eventually, the deposited alloy exhibited a tensile strength around 405 MPa, and the elongation was up to 15.6%.