Effect of grain diameter, strain rate and deformation temperature on the work hardening characteristics of Al–0.86 wt%Mn–0.28 wt%Fe

Stress–strain characteristics of Al–0.86 wt%Mn–0.28 wt%Fe specimens with different grain diameters were studied in the temperature range from 300 to 393 K. Tensile tests were performed at different strain rates ranged from ε˙ = 2.2 × 10−4 to 1.0 × 10−2 s−1. The work hardening parameters; yield stress σy, fracture stress σf, strain hardening exponent n, and the total elongation ɛT were found to be markedly affected by the strain rate ε˙, deformation temperature T and grain diameter D of the tested sample. From the grain diameter dependence of these hardening parameters, two distinct stages were observed. In the first stage, increasing D results in increased σy, σf, n and ɛT to maxima at ∼53 μm. In the second stage, these parameters drastically decreased with further increase of D. The decrease of σy with D in the second stage reaches its minimum (σy,min) at values depend on the strain rate ε˙. Both σy and σy,min were found to increase with increasing ε˙ while ɛT decreased. The obtained results were interpreted on the basis of solid solution decomposition caused by annealing treatment. The grain diameter dependence of the work hardening parameters may characterize a dislocation movement by cross slip mechanism. The microstructure of the tested samples was examined by optical microscopy and X-ray diffraction measurements.