Abstract
The present study aims to investigate the mechanical properties of a newly developed aluminum Al-6.5% Cu-based alloy, coded HT200, as well as to determine how these properties can be further improved using grain refinement and heat treatment. As a result, the effects of different heat treatments and alloying additions on the ambient and high-temperature tensile properties were examined. Three alloys were selected for this study: (i) the base HT200 alloy (coded A), (ii) the base HT200 alloy containing 0.15% Ti + 0.15% Zr (coded B), and (iii) the base HT200 alloy containing 0.15% Ti + 0.15% Zr + 0.5%Ag (coded C). The properties of the three HT200 alloys were compared with those of 319 and 356 alloys (coded D and E, respectively), subjected to the same heat treatment conditions. The results obtained show the optimum high-temperature tensile properties and Q-values for the five alloys of interest, along with the corresponding heat treatment conditions associated with these properties. It was found that the T6 heat-treated alloy B was the optimum alloy in terms of properties obtained, with values comparable to those of commercial B319.0 and A356.0 alloys.
Highlights
E HT200 base alloy was received in the form of small ingots. ese ingots were melted in a 40 kg capacity SiC crucible using an electrical resistance furnace equipped with a rotary degassing impeller. e melting temperature was maintained at 800°C ± 5°C
Tensile tests were carried out on all the alloys used for this study to obtain their ultimate tensile strength (UTS), yield strength (YS), and the percentage elongation (%El) values
In the first two heat treatment conditions, i.e., S4A and S4W, the improvement in the tensile properties is attributed to the SHTand the high cooling rate achieved with water quenching. e supersaturated solid solution obtained by the dissolution of existing phases like θ-Al2Cu in the ascast structure is preserved by means of rapid cooling to room temperature during the water quenching
Summary
Bal the alloys were heat-treated using different heat treatment conditions, twelve in the case of alloys A, B, and C, and six in the case of alloys D and E. E results reveal that the high-temperature tensile properties of the alloys improved significantly after heat treatment. Heating the samples further in the testing chamber and running the tests at 250°C coarsened the precipitates, decreased their density, increased their size, and increased the interparticle spacing so that the strength decreased and the ductility increased, when compared with the ambient temperature tensile test results. In the first two heat treatment conditions, i.e., S4A and S4W (solution treatment followed by air or water quenching), the improvement in the tensile properties is attributed to the SHTand the high cooling rate achieved with water quenching. As seen from the results for the three alloys, solution treatment with water quenching provided better tensile properties than when the bars were air quenched, due to the higher cooling rate obtained with water quenching. These atoms have different sizes from those of the lattice structure
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