The dissolution of second phase particles in a 319-type (Al-Si- Cu-Mg) aluminum casting alloy has been quantified by image analysis of metallographic specimens as well as an electron microprobe technique. The initial phase content of the as-cast material, and the change in volume fraction of each phase following solution treatment for various times at 480°C and 505°C, was determined by analysis of particles observed by backscattered electron microscopy. Furthermore, the change in dendritic alloy content during solution treatment was measured using electron microprobe analysis in order to estimate the relative volume fraction of second phase particles dissolved. Finally, a non-isothermal dissolution model was used to predict the dissolution behaviour during solution treatment and comparisons are made between the model predictions and experimental measurements.

The high-strength aluminum alloy V92Zr, part of the Al-Zn-Mg system, is a self-quenched alloy. Its primary alloying elements include 4.2 wt% Mg, 3.2 wt% Zn, 0.6 wt% Mn, and 0.15 wt% Zr. The most suitable filler wires for welding this alloy are V92W, AMg6, AMg4Zr, and No.11 (Al-Zn-Mg). This alloy is applicable in aircraft production. Prolonged heating at 50-70°C can lead to significant structural changes in the precipitation hardening of aluminum alloys due to the transition from zone aging to phase aging. Studies indicate that zone aging of Al-Zn-Mg alloys, particularly in weld seams, with repeated heating at 50-70°C, substantially increases strength while reducing elongation, cross-sectional area reduction, toughness, stress corrosion resistance, and increasing susceptibility to cracking. Research has shown that even heating at temperatures below the phase aging threshold can significantly alter the properties. This article examines the effects of prolonged low-temperature heating on the mechanical properties, crack sensitivity in impact bending, and corrosion resistance of semi-finished products and weldments of V92Zr aluminum alloys after solution treatment and aging at room and elevated temperatures.

Current heat treatment standards do not adequately define tempers for thin-walled castings that solidify at high rates. Emerging casting processes, such as vacuum high-pressure die casting, benefit from rapid solidification rates, which result in fine microstructures and reduce the need for prolonged solution treatment times. Studies on rapidly solidified samples with secondary dendrite arm spacing between 35-10 μm were conducted, with solution times ranging from 30 minutes to 9 hours, and various aging parameters were evaluated. Metallurgical analysis revealed that increased microstructure refinement could reduce solution time by up to 50% without compromising the alloy’s mechanical properties. The highest strengths, with an ultimate tensile strength of 330 MPa (47.9 ksi) and a yield strength of 300 MPa (43.5 ksi), were achieved under T6 peak aging conditions. Additionally, thermal analysis and dilatometer results are presented to evaluate phase dissolution during solution treatment, aging kinetics, and dimensional stability.