3A21铝合金半固态坯料制备工艺研究

摘要

Equal channel angular pressing and isothermal treatment were combined and the influence of technological pa-rameters on size and pattern of semi-solid microstructures of 3A21 aluminum alloy was analyzed in the view of experiments. Twenty-seven samples were obtained after 3 passes ECAP under route Be and 20, 25,30 min holding under the temperature of 660 ~C. The results indicate that, with the increment of ECAP passes, size of gains becomes smaller, deformation of micro-structure becomes more uniform, and the more accumulation of deformation energy creates a favorable strain inducement con-dition for subsequent isothermal treatment in semi-solid state; gains spheroidize better and gain size becomes larger when the heat holding time elongates. In conclusion, the best technology parameters are as follows: ECAP route Bc, 3 passes, holding temperature 660 ℃, holding time 25 min. The average gain size is 83.7 μm, and the average shape factor is 0.84.%以3A21铝合金为研究对象，将等径角挤压工艺与等温处理工艺相结合，从实验角度研究其中的工艺参数对半固态组织尺寸形貌的影响。采用Bc路径进行ECAP3道次处理，然后在660℃下保温20，25，30min，得到27个试样的半固态组织。结果表明，随着挤压道次的增加，晶粒尺寸减小，变形更加均匀，并且累积变形能的增多，也为后续半固态等温处理提供了更好的应变诱导条件；保温时间越长，半固态组织演化越完全，晶粒球化越完整，但晶粒尺寸会随着保温时间的延长而长大。最后得出最佳工艺参数匹配：室温下沿Bc路径等径角挤压3道次，660℃下保温25min；最终半固态坯料显微组织的平均等积圆直径d=83．7μm，平均形状系数Fc=0．84。