Ultrafine-grained Al-La-Mg-Mn alloy fabricated by melt spinning and hot extrusion with ultrahigh strength and thermal stability

To enhance the mechanical properties of Al-(La, Ce) alloys, melt spinning and hot extrusion were employed to fabricate Al-La-Mg-Mn alloy with an ultrafine-grained structure (similar to 0.56 mu m). The as-extruded alloy exhibits the highest tensile strength of 621 +/- 4 MPa among Al-(La, Ce) alloys fabricated by various methods while retaining an appreciable elongation of 6.8 +/- 1.1 %. The high strength is mainly ascribed to the ultrafine grains and high-volume intermetallics, conferring robust grain boundary strengthening and Orowan strengthening effects. Additionally, this study delved into the high-temperature (400 degrees C) coarsening behavior of the intermetallic and grain size. The findings unveil an exceptionally low coarsening rate of the intermetallic at 400 degrees C (3.19x10(-33) m(4) s(-1)), accompanied by only slight grain coarsening, underscoring the remarkable thermal stability of the ultrafine-grained structure.