Microstructure and heat resistance of Al–Cu–Mg–Ag alloy fabricated by wire-arc directed energy deposition

A new type of Al–Cu–Mg–Ag heat-resistant aluminum alloy feed wire was self-developed (named 205B) and was use to prepare a thin-walled structure by wire-arc directed energy deposition (WA-DED) method. Fine equiaxed grains with an average grain size of 18.2 μm were obtained in the WA-DED 205B alloy, and significantly grew to 32.7 μm after T6 heat treatment. Meanwhile, high density of nano-scale Ω phases precipitated in the grains of 205B-T6 sample instead of the θ ′ phases in traditional WA-DED 205A-T6 alloy. The segregation of Ag and Mg atoms at the Ω phase interface was observed, which is beneficial to the thermal stability of the precipitated phases. Though the θ ′ phase began to grow at 200 °C, no obvious growth was found in the Ω phase till the temperature increased to 250 °C. Therefore, excellent high temperature tensile properties were achieved in the WA-DED 205B sample, the ultimate tensile strength (UTS) was as high as 417 MPa together with a high elongation of 9.7 % at the temperature of 200 °C. At a higher temperature of 250 °C, the UTS decreased to 370 MPa, but still larger than that of the 205A sample at 200 °C (356 MPa). Obviously, the service temperature can be improved at least 50 °C in this new WA-DED 205B alloy compared to the traditional heat-resistant 205A alloy. This study provides an effective method to prepare high performance WA-DED heat-resistant aluminum alloys which can be widely used in the short process rapid manufacture of aerospace field.