Microstructure and mechanical behavior of high toughness Al-based metal matrix composite reinforced with in-situ formed nickel aluminides.

A powder blend of Ni particles embedded in Al flakes obtained after high energy ball milling was used to reinforce an Al Mg alloy using friction stir processing (FSP). The mechanical activation provided by both ball milling and FSP resulted in the in-situ formation of nickel aluminides during FSP, which was distributed throughout the nugget zone. The average grain size after FSP was 8.3 μm. High dislocation density was observed in the vicinity of the reinforcements. The yield and ultimate tensile strengths of the composite improved by 123% and 78% respectively. The tensile elongation of the composite was 23% and the base material, 32%. The toughness of the composite improved by 42%. At elevated temperatures (200 °C and 300 °C), the composite exhibited a decrease in strength but an increase in ductility with increasing temperature. • Al5052 alloy was reinforced with a powder blend of Ni particles and Al flakes using friction stir processing (FSP). • Ni reacted with Al during FSP to form a core-shell type structure with Ni 3 Al as the shell and Ni as the core. • The shell then fragmented into much finer sizes during FSP and formed Al 3 Ni with further reaction with Al. • Improvement in the mechanical properties was observed, especially, toughness. • A transition from strain hardening to strain softening was observed at elevated temperatures. [ABSTRACT FROM AUTHOR]