Comparison of microstructure and mechanical properties of Al-Mg-Li-Sc-Zr alloys processed by ingot metallurgy and rapid solidification

The microstructural evolution and mechanical properties of Al-Mg-Li-Sc-Zr alloys fabricated by ingot metallurgy (IM) and gas atomization (GA) with hot isostatic pressing (HIP) were investigated. The results showed that the as-cast alloy exhibits a coarse grain microstructure with large amounts of Al2MgLi and primary Al3(Sc, Zr) particles in the matrix. While a fine and uniformly structured HIPed alloy with a relative density of 99.9% can be obtained at 400 degrees C for 2 h, and no primary Al3(Sc, Zr) phase nor macro-segregation existed in the HIPed alloy. After a two-stage homogenization treatment, the Al3Li, Al2MgLi, and AlLi phases dissolved into the matrix, and simultaneously dense Al3(Sc, Zr) dispersoids precipitated in the two alloys. The number fraction of the Al3(Sc, Zr) phase in the HIPed alloy was much higher than that in the as-cast alloy. An excellent ultimate tensile strength of 352 MPa was obtained for the HIPed alloy, an increase of approximately 14% compared with the as-cast alloy. The increased strength in the HIPed alloy is mainly attributed to grain boundaries, precipitation, and solid-solution strengthening mechanisms. (c) 2021 Elsevier B.V. All rights reserved.