Microstructure and mechanical properties of Al-Mg-Si-Mn alloy fabricated by a continuous rheological extrusion

Microstructure and mechanical properties of continuous rheological extrusion (CRE) 6082 alloy were systematically investigated in comparison with those of the corresponding as-cast alloy. The as-cast 6082 alloy exhibited coarse dendrites and mainly consisted of a non-equilibrium Mg 2 Si eutectic phase and a significant amounts of Al(Fe, Mn)Si phases distributed at the grain boundaries and formed a continuous network structure. The continuous rheological extrusion induced significant dendrite refinement, pronounced fragmentation of the second phase, and extensive precipitation of nano-sized Mg 2 Si phase in Al matrix of the as-cast 6082 alloy, attributable to the high-pressure shearing effect. Moreover, the dislocation density and quantity of the second phase in the CRE 6082 alloy were significantly higher compared to those in the as-cast state. The tensile test results indicated that the CRE 6082 alloy exhibited an excellent balance of strength and ductility, with an ultimate tensile strength (UTS), a yield strength (YS), and an elongation (EL) of 232.6 MPa, 172 MPa, and 24.23 %, respectively, at room temperature. The high tensile strengths of the CRE 6082 alloy were primarily attributed to grain refinement, dislocation strengthening and particle strengthening provided by nano-scale Mg 2 Si phases.