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The influence of Zn on the strain hardening of as-extruded Mg-xZn (x = 1, 2, 3 and 4 wt%) magnesium alloys was investigated using uniaxial tensile tests at 10-3 s-1 at room temperature. The strain hardening rate, the strain hardening exponent and the hardening capacity were obtained from true plastic stress-strain curves. There were almost no second phases in the as-extruded Mg-Zn magnesium alloys. Average grain sizes of the four as-extruded alloys were about 17.8 μm. With increasing Zn content from 1 2 to 4 wt%, the strain hardening rate increased from 2850 MPa to 6810 MPa at (σ-σ0.2) = 60 MPa, the strain hardening exponent n increased from 0.160 to 0.203, and the hardening capacity, Hc increased from 1.17 to 2.34. The difference in strain hardening response of these Mg-Zn alloys might be mainly caused by weaker basal texture and more solute atoms in the α-Mg matrix with higher Zn content.

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The effect of Al on the strain hardening behavior of as-extruded Mg-xAl (x ¼ 1, 2, 3 and 4 wt%) magnesium alloys is investigated using uniaxial tensile tests at 10 À3 s À1 at room temperature. The strain hardening rate, the strain hardening exponent, and the hardening capacity are obtained from true stress-true plastic strain curves. In as-extruded Mg-Al alloys, the Al element is completely dissolved in the α-Mg matrix. With increasing Al content, the average grain sizes of these samples decrease from 16.9 to 10.7 mm. The strain hardening rate increases from 515 to 924 MPa, then reduces to 818 MPa at (σ-σ 0.2 ) ¼ 90 MPa. The strain hardening exponent n increases from 0.125 to 0.149 and then reduces to 0.142, while the hardening capacity Hc increases from 0.71 to 0.90 and then reduces to 0.80. The train hardening rate, the strain hardening exponent n, and hardening capacity Hc reach peak value in Mg-3Al. The difference in the strain hardening responses of asextruded Mg-Al alloys may mainly be influenced by weaker basal texture and smaller average grain size with increasing Al content.