纤维对短切碳纤维/AZ91D复合材料热变形行为和加工性能的影响

Influence of fiber on the hot deformation behavior and workability of chopped carbon fiber/AZ91Dcomposites

采用等温压缩试验研究了不同碳纤维体积分数的镁基复合材料(CFs/AZ91D)和镁合金(AZ91D)在变形温度310~430℃、应变速率10-3~10-1 s-1范围内的塑性变形行为。根据实验结果建立了CFs/AZ91D和AZ91D的热加工图,分析了纤维对CFs/AZ91D塑性加工性能与变形机制的影响。结果表明:相比ZA91D,纤维在提高复合材料流动应力的同时促进了基体动态再结晶和应变软化,但纤维体积分数对流动应力与应变软化程度影响较小,CFs/AZ91D热变形时表现出比ZA91D更高的应变速率敏感指数和变形激活能;ZA91D热加工图不存在变形失稳区且其高温低速率区变形时的能量耗散效率大于30%,CFs/AZ91D高温低应变速率区变形时的能量耗散效率大于50%,此时纤维激励了基体合金动态再结晶而使复合材料表现出极高的能量耗散效率,但在低温高应变速率变形时,基体合金与纤维之间的界面开裂极易导致CFs/AZ91D出现塑性流变失稳行为。

The plastic deformation behavior of magnesium alloy(AZ91D)and chopped carbon fiber(CFs)/AZ91D composites with different fiber volume fractions were investigated at the condition of 310-430℃ and 10-3-10-1 s-1 using isothermal compression testing.According to the experimental results,the hot processing maps of AZ91 D and CFs/AZ91D were constructed to inspect the influence of fiber on the plastic workability and deformation mechanism of CFs/AZ91D composites.The results indicate that the addition of the fiber improves the flow stress as well as the dynamic recrystallization(DRX)and strain softening degree.Nevertheless,the fiber volume fraction has no significant impact on the flow stress and the strain softening degree.The strain rate sensitivity exponent and deformation activation energy of CFs/AZ91D composites are higher than that of AZ91D.It is found there is no deformation instability zone in the processing map of the AZ91D and the power dissipation efficiency exceeds 30% in the deformation safety zone.Due to the stimulation of fiber on the DRX in matrix alloy,the power dissipation efficiency of CFs/AZ91D composite is ultra-high,which exceeds 50%.At the condition of low temperature and high strain rate,the large deformation is liable to induce the interface debonding,which is responsible for the plastic deformation instability of CFs/AZ91 Dcomposites.