Search

Fine-grained bulk AA2219 material was successfully manufactured by means of milling and hot compression/extrusion of metallic chips. Preliminary milling of the metallic scrap either for 8 or for 30 h was found to result in the development of two components of the material structure, i.e. a highly refined matrix and coarse remnants of unmilled chips. The average volume of the highly refined matrix reached 45% and 84% for materials milled for 8 h and 30 h (MA8h and MA30h samples), respectively. Hot compression tests confirmed high strength of preliminarily milled materials attributed to the grain refinement and properly carried out mechanical consolidation methods. An additional solid solution strengthening effect was observed for samples water-quenched after annealing at 808 K/300 min both for preliminarily milled materials and samples made from an industrial material (IM). However, subsequent hot deformation tests did not reveal noticeable hardening of the solution treated MA30h samples due to dynamic precipitation unlike in the case of IM samples. Transmission electron microscopy analyses may lead to the conclusion that the aging of solution treated MA material result in the growth of θ-type stable particles in heavily-refined areas without the preceding precipitation of metastable θ′ particles. Therefore, precipitation hardening of the tested MA-materials becomes inhibited with increased milling time. [ABSTRACT FROM AUTHOR]

The present study has investigated the influence of scandium additions on the structure and mechanical properties of AA2219 gas tungsten arc (GTA) weldments. Controlled amounts of scandium modified AA2319 fillers were introduced into the molten pool of AA2219 by predeposited cast inserts under different welding conditions in GTA welding. Full penetration GTA welds were prepared using alternating current. It was observed that grain size decreased with increasing amounts of scandium and gradual transformation from columnar to equiaxed grain morphology. The observed grain refinement was shown to result in an appreciable increase in fusion zone hardness, strength, and ductility. Room temperature hardness and tensile properties at different temperatures (room temperature, 100, 150, 200 and 250 °C) of weldments in the as-welded condition were observed and correlated with microstructure. The results show that the welds subjected to post-weld aging treatment have displayed superior hardness and tensile strength. [ABSTRACT FROM AUTHOR]