【摘要】 对Al-Cu-Li合金进行温度300⁵00℃、应变速率0.001¹0s^-1的等温热压缩,分析合金的流变行为:结合TEM和EBSD研究合金热变形过程中的组织演变。结果表明:合金流变曲线分为3个阶段:加工硬化阶段、过渡阶段和稳态变形阶段;变形温度越高,流变应力达到动态平衡所需应变量越小。基于应变硬化率（θ）与流变应力（σ）之间的关系,确定动态再结晶的临界应变（ε_c）;不同热变形条件下的临界应变（ε_c）与峰值应变（ε_p）之比为0.30342⁰.92828;临界应力（σ_c）与峰值应变（σ_p）之比为0.88492⁰.99782。引入最大软化率应变（ε^*）和中间变量Z/A,建立ε_c和ε^*与Z/A的关系表达式。构建Al-Cu-Li合金动态再结晶动力学模型,模型表明,温度越高或应变速率越低,越有利于促进动态再结晶分数的增加;显微组织分析结果与模型预测规律一致。Al-Cu-Li合金动态再结晶形核机制主要为晶界突出形核机制、亚晶合并长大机制以及粒子促进形核机制,随温度升高和应变速率的降低,晶内亚晶合并长大机制得到加强。更多还原

【Abstract】 The flow behaviors of Al-Cu-Li alloy were investigated by isothermal hot compressive tests,which were carried out at the deformation temperature range of 300-500℃,and strain rate of 0.001-10 s^-1.Microstructure evolution process was studied by TEM and EBSD analysis.The results show that flow curve can be divided into three stages:work hardening stage,transition stage and steady stage.The higher the deformation temperature is,the smaller strain required for dynamic balance of flow stress is.According to the flow behaviors of Al-Cu-Li alloy,critical strain（ε_c）of dynamic recrystallization is determined based on the relationship of strain hardening rate and flow stress.Under different hot deformation conditions,the ratio of critical strain（ε_c） to the peak strain（ε_p） is 0.30342-0.92828,and the ratio of the critical stress（σ_c） to the peak stress（σ_p） is 0.88492-0.99782.Introducing the strain for maximum softening rate strain（ε^*） and intermediate variable（Z/A）,and the relationships among ε_c,ε^* and Z/A are obtained.Dynamic recrystallization kinetics model is identified to express the evolution of dynamic recrystallization.The higher the deformation temperature or the lower strain rate,the more beneficial to increase the dynamic recrystallization fraction.Predicted rules by proposed model show a good agreement with microstructure analysis results.Dynamic recrystallization nucleation mechanisms are constituted of grain boundaries bulging nucleation,subgrain rotated induced nucleation and particle stimulated nucleation mechanism.Subgrain rotated induced nucleation transgranular is strengthened with increasing temperature and decreasing strain rate.更多还原