Deformation and fracture behavior in aluminum and Al–1.0 mass%Mg alloy wire were investigated under cyclic bending test with the maximum strains up to 0.02 at the specimen surface, in order to develop light weight electric wire for automobiles. Microstructural aspects and geometrical characteristics of the fatigue crack initiation sites were examined where electron back scattering diffraction (EBSD) analysis were employed to make the relationship between partially cracked grain boundaries and activated slip systems clarified. Grain size strongly affected the number of cycles to fracture. The fatigue cracks were generated at the grain boundaries with the inclination angles of 40–60 degrees against the tension-compression direction. Both deformation continuity at the grain boundaries and the work hardening inside crystal grains have effects on the number of cycles to fracture in the cyclic bending.
In the present study, we have examined the compression response of single-crystal cylindrical micropillars with different diameters (approximately ranging from 1 to 10 µm) and shape parameters prepared on the sample surface of 4N purity aluminum (Al) sheets with the recrystallized microstructure. The compression tests for micropillars with various sizes demonstrated the flow stress of micropillars increases with decreasing pillar diameter. The observed size dependence of resolved shear stress for slip corresponds well to the previous studies on micropillars prepared from 3N and 5N purity Al sheets. The measured shear stress resolved onto a primary slip system (τi) scaled by shear modulus (G) and the pillar diameter (d) scaled by Burgers vector (b) shows the following correlation: (τi/G)=0.33(d/b)−0.63. The compression response of micropillars with different d1/d2 (ratio of top diameter (d1) to bottom diameter (d2) of cylindrical micropillars) revealed higher d1/d2 than 0.5 is required for precisely measuring the strength of cylindrical micropillars, which was confirmed by the observations of compressed micropillars.