Effect of Radial-Shear Rolling on the Formation of Structure and Mechanical Properties of Al-Ni and Al-Ca Aluminum-Matrix Composite Alloys of Eutectic Type

Results of an analysis of the mechanical properties and macro- and microstructures and the fractographic analysis of the fractures of samples of the Al-6 wt % Ni and Al-7.6 wt % Ca aluminum-matrix composite alloys of eutectic type after thermomechanical treatment, including radial-shear rolling (RSR),-have been presented. The hot deformation of preliminarily annealed ingots of studied alloys with a circular section 60 mm in diameter using RSR method at 400-450A degrees C with total reduction mu = 9.0 can lead to the formation of the gradient microstructure with external more deformed layer characterized by high microhardness and thickness of about 1.5-2.5 mm. The microhardness decreases smoothly from the periphery to the center of samples. Uniaxial tensile tests revealed that the strength of alloys after RSR increases by 2.0-2.5 times compared to the as-cast or the annealed state, the plasticity is the same as in the annealed state or increases by several times as in the case of the Al-7.6 wt % Ca alloy. The latter fact is clearly illustrated by the results of the analysis of the fractures of samples, for which the transition from the brittle or mixed type of the fracture before deformation treatment to the pronounced ductile dimpled type after RSR has been observed.