Significant strengthening effect in ultra-fine grained Al alloy made by fast solidification and hot extrusion processes

Abstract

Grain refinement with a facile process without additional alloying is quite desired for strengthening the Al alloys. Using the melt spinning process, we obtained the ultra-fine grained foils of Al–Mg–Si–Cu alloy (AA6061), then the foils followed by hot extrusion to produce the rods for industrial applications. The yield strength of the extruded melt-spun rod is 102% higher than that of the extruded rods of the alloy by a conventional direct chill casting. The electron backscatter diffraction results reveal that the average grain diameter in the extruded melt-spun sample is only 1.35 μm, indicating that the sample is an ultra-fine grained alloy. Through the Hall–Petch relationship, the finer grains contribute to a 66.9% increase in yield strength of the extruded rod. Moreover, the fiber texture occupied 68% of the volume fraction after hot extrusion, contributing to 30.5% improvement of the yield strength in the extruded melt-spun sample. This study shows that the ultra-fine grained Al–Mg–Si–Cu alloy rods have excellent mechanical properties, which provides a strong potential for industrial application.

Keywords

• Grain refinement
• Rapid solidification
• Texture evolution
• Al–Mg–Si–Cu alloy