Microstructural evolution in the superplastic-like deformation of Al-Al₃Ni eutectic alloy with [111] fiber texture

The as-extruded Al-Al₃Ni eutectic alloy with [111] fiber texture and purely intergranular particle distribution exhibits superplastic-like behavior. In the current study, microstructure evolution and the role of second-phase particles (Al₃Ni) in superplastic-like deformation are explored. Some intergranular particles become intragranular during the static holding and tensile loading at 500°C. In order to have superior ductility, the number of intragranular particles must be restricted to inhibit dynamic recovery and avoid rapid strain softening. This restriction can be achieved by trapping the particles in newly formed subgrain boundaries through subgrain refining involving particle joining and pinning of primary slip dislocations. Through these refining processes, the subgrains remain in roughly equiaxed shape after superplastic-like deformation. Primary slip is the main dislocation activity in superplastic-like deformation and is persistent until failure, but it can only be observed in limited subgrains. The [111] fiber texture is always retained, but [111] is not necessarily the final stable tensile direction.