Microstructure and mechanical properties of wire arc additive manufactured ZL205A alloy

Abstract

The evolution of grain structure, precipitates and mechanical properties of the ZL205A alloy prepared by wire arc additive manufacturing were investigated. The results show that the as-deposited alloy consists of equiaxed and columnar grains in the bottom region. As the deposition height increases, the alloy mainly consists of equiaxed grains. The evolution of columnar to equiaxed grains is explained by the solidification theory. The needle-like θ′-Al2Cu precipitates in Cu-rich regions surrounding the α-Al+θ-Al2Cu eutectics. As the part deposited first is subjected to multiple cycles of heating by the subsequently deposited layers, the volume fraction and average size of θ′ precipitates gradually decrease with the increase of deposition heights. The microhardness of the as-deposited alloy fluctuates in the range of 74.6–84.5 HV. The mechanical properties of the horizontal specimens at different heights are affected by the combination of grain structure, precipitates and pores, and that of the specimens in the middle region are optimal. The mechanical properties of the horizontal and vertical specimens show isotropic. Attributed to the grain boundary strengthening and precipitation strengthening, the yield strength (132.9 MPa) and elongation (15.9%) of the as-deposited alloy are approximately 31.3% and 211.8% higher than that of the as-cast alloy, respectively.