2022 年 72 巻 10 号 p. 585-592
A softening behavior of 3104-H19 aluminum can body materials during the paint baking process in can productions is an impactful factor on can body strength. However, detailed investigations on the mechanism are limited due to simultaneous occurrence of multiple fine precipitations and recovery, as well as difficulty of observing fine precipitates under high-density dislocations. In this research, effects of solid solution of the additional or impurity elements on paint baking softening behavior were investigated by observing microstructural changes with the high resolution FE-SEM, TEM, and synchrotron radiations. Based on this study, the solute atoms are thought to react with lattice defects (dislocations, dislocation cells, subgrain boundaries) to suppress their movement and recovery during the baking process. Then, precipitations and coagulations of the solute atoms occurred as the baking time passed. It could end up with mitigation of the pinning effect and progress of the recovery. The bake softening behavior could be explained with these multiple stages of the precipitations and coagulations of the solute atoms and the recovery progression. On the base of observed microstructural changes during the baking, the softening curve was analyzed using the newly proposed kinetics equation. The results of this analysis support the mechanism mentioned above.
