Study on defects of Zr-containing Al–Cu–Mn–Mg alloys manufactured by selective laser melting

Abstract

The effects of selective laser melting (SLM) parameters on the formability, microstructure, and mechanical properties of Zr-containing Al–1Cu–1Mg–3Mn alloys were investigated. It was observed that, under different energy density, the type, shape, volume, and number of defects were different. At a lower energy density, cracks and irregular holes occurred, and with an increase in the energy density, the holes gradually became spherical. The mechanism diagram for the hole formation was drawn, and the reason for crack formation was described. The microstructure of the specimen was made of equiaxed and columnar grains, and Al2Cu and Al6Mn precipitates were found both at the grain boundaries and inside the grains. The electron backscattered diffraction (EBSD) indicated that the large columnar grains in the centre primarily exhibited the {001} and {101} orientations. In the equiaxed grain region, the grain orientation along {111} was enhanced. A hardness test revealed that the hardness of cross section and longitudinal section of the alloy was basically the same. When the energy density was 3.06 J/mm2, the tensile and yield strength of the alloy were 434 MPa and 336 MPa, respectively, and the elongation was 4.8 %.