通过恒应力和恒塑性应变控制疲劳实验, 比较了等通道转角挤压四道次的Al-0.7%Cu(质量分数)合金的疲劳寿命、表面变形形貌、疲劳开裂和疲劳断口。结果表明：样品发生明显的循环软化, 致使应变和应力疲劳寿命在高、低应力范围存在差别。在应变控制疲劳样品中, 塑性变形既可由剪切带来承担, 也可以由剪切带和形变带共同承担, 进而疲劳裂纹分别沿剪切带或形变带萌生。而应力控制疲劳的塑性变形只集中在剪切带中, 并导致剪切疲劳开裂。疲劳断口上存在典型的疲劳裂纹萌生区、缓慢扩展区、快速扩展区和最后瞬断区。
Fatigue life, surface deformation morphology, fatigue cracking and fatigue fractography of Al-0.7%Cu (mass fraction) alloy, produced by equal channel angular pressing (ECAP) for 4 passes, were investigated under constant stress or plastic strain control. It is shown that the specimens displayed obvious cyclic softening, which caused some difference in fatigue life at low or high stress range under constant stress and strain conditions. The plastic strain is carried either by shear bands only, or by shear bands and deformation bands, in the specimens fatigued under strain control. Consequently, fatigue cracks nucleated either along shear bands or along deformation bands. However, the plastic strain only localized in the shear bands of the specimens under stress control, as a result, leading to shearing fatigue cracking. The fatigue fractography consists of several different zones, including fatigue crack initiation, slow, fast propagation and final fracture.
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