采用等温热压缩试验研究不同变形条件下(变形温度300~450℃、应变速率0.01~10 s?1)喷射成形Al?9.0Mg?0.5Mn?0.1Ti合金挤压坯的流变应力行为,并基于动态材料模型建立2D加工图和3D功率耗散图来分析合金的流变失稳区和优化合金的热变形工艺参数.结果表明,当应变为0.4时,合金在300℃、1 s?1条件下压缩变形,能量耗散效率因子η值最小,主要软化机制为动态回复,晶粒呈扁平状,大角度晶界(>15°)约占34%;合金在400℃、0.1 s?1条件下压缩变形,能量耗散效率因子η值最大,合金的主要软化机制为动态再结晶,组织为完全再结晶组织,大角度晶界(>15°)约占86.5%.2D加工图和3D功率耗散图表明喷射成形Al?9.0Mg?0.5Mn?0.1Ti合金挤压坯的最佳变形条件是:变形温度340~450℃、应变速率0.01~0.1 s?1,合金的能量耗散系数38%~43%.
Hot deformation behavior of extrusion preform of the spray-formed Al?9.0Mg?0.5Mn?0.1Ti alloy was studied using hot compression tests over deformation temperature range of 300?450 ℃ and strain rate range of 0.01?10 s?1. On the basis of experiments and dynamic material model, 2D processing maps and 3D power dissipation maps were developed for identification of exact instability regions and optimization of hot processing parameters. The experimental results indicated that the efficiency factor of energy dissipate (η) lowered to the minimum value when the deformation conditions located at the strain of 0.4, temperature of 300 ℃ and strain rate of 1 s?1. The softening mechanism was dynamic recovery, the grain shape was mainly flat, and the portion of high angle grain boundary (>15°) was 34%. While increasing the deformation temperature to 400 ℃ and decreasing the strain rate to 0.1 s?1, a maximum value ofη was obtained. It can be found that the main softening mechanism was dynamic recrystallization, the structures were completely recrystallized, and the portion of high angle grain boundary accounted for 86.5%. According to 2D processing maps and 3D power dissipation maps, the optimum processing conditions for the extrusion preform of the spray-formed Al?9.0Mg?0.5Mn?0.1Ti alloy were in the deformation temperature range of 340?450 ℃ and the strain rate range of 0.01?0.1 s?1 with the power dissipation efficiency range of 38%?43%.
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