ABSTRACT: The precipitation behaviour and related age-hardening in scandium (Sc) inoculated aluminium alloy (7075 series) aged at 140oC was investigated in detail. The solution treated aluminiumalloy was surface layer modified by a novel solid-state technique like DP-FSP then followed bypost ageing treatment at 140oC for 2h.During DP-FSP, the workpiece was subjected to severe plastic deformation (SPD) by the mechanical stirring action of the rotating tool with 1000 rpm, 70 mm/min traverse speed, and 15kN axial force. The presence of Al3Sc and MgZn2 precipitates promotes continuous dynamic recrystallization (DRX) in matrix during FSP. The mechanism for this phenomenon was examined by using OM, FESEM, SEM, and TEManalysis. After processing, the mechanical properties were improved such as 0.2% PS of 104.4 MPa, UTS of 248.5MPa, elongation of 6.7%, Vicker’s hardness of 139.6HV, and strain hardening exponent (n) of 1.60of the aluminiumalloy.

Key words: Sc inoculation, FSP, Al3Sc precipitates, TEM, mechnaical properties.