Influence of Aging Parameters on the Tensile Properties and Quality Index of Al-9 Pct Si-1.8 Pct Cu-0.5 Pct Mg 354-Type Casting Alloys

Abstract

The current study was carried out with a view to investigating the influence of age-hardening parameters, aging temperature and time, on the tensile properties and quality indices of a highstrength Al-9 pct Si casting alloy, namely, 354-Al-9 pct Si-1.8 pct Cu-0.5 pct Mg. Quality charts were used as an evaluation tool for selecting the optimum conditions to be applied, in practice, in order to develop high strength and optimum quality in 354 casting alloy. Aging at a low temperature of 428 K (155°C) was observed to produce the greatest strength and optimum quality in the 354-type castings compared to aging at higher temperatures. The peak strength observed for 354 alloy may be attained after shorter aging times on the condition that the aging temperature is increased. The aging times required for reaching peak strength in 354 alloys are 72 hours, 40 hours, 8 hours, 1 hour, and 15 minutes at aging temperatures of 428 K, 443 K, 468 K, 493 K, and 518 K (155°C, 170°C, 195°C, 220°C, and 245°C), respectively. Aging treatment at higher temperatures is accompanied by a reduction in the tensile properties and quality index values of the castings; however, it also introduces the possibility of a significant economical strategy for minimizing the time and the cost of this same treatment. Aging treatment at a lower temperature of 428 K (155°C) produces fine and dense precipitates displaying smaller interparticle spacing, while at higher aging temperatures, such as 518 K (245°C), the precipitates are coarser in size, less dense, and more widely dispersed. The quality charts developed in the course of the current research facilitate the interpretation and evaluation of the tensile properties of the 354 alloy. Such charts provide a logical evaluation tool, from the metallurgical point of view, for an accurate prediction of the influence of aging parameters studied on the properties of the alloys. Depending on the required level of tensile properties and based on the quality charts developed, it is possible to make a rigorous selection as to the most suitable aging parameters to be applied to the 354 alloy so as to obtain the best possible costeffective compromise between alloy strength and quality.

Optimization of A354 Al-Si-Cu-Mg Alloy Heat Treatment: Effect on Microstructure, Hardness, and Tensile Properties of Peak Aged and Overaged Alloy

“…At 160 °C aging temperature, the lowest investigated temperature, a slow initial hardness increase from the as cast condition is registered as a result of the low rate of atomic diffusion related Figure 9, it is clear that the aging temperature plays an important role on precipitation hardening. Similarly to what has been observed by other studies, by increasing the aging temperature, the time required to reach the peak is reduced [24,35] and, with the exception of 160 • C, the peak hardness is generally reduced [30,36,37]. At 160 • C aging temperature, the lowest investigated temperature, a slow initial hardness increase from the as cast condition is registered as a result of the low rate of atomic diffusion related to this temperature.…”

On the Fractography of Impact-Tested Samples of Al-Si Alloys for Automotive Alloys

“…Ammar et al [6] described the microstructure of A356 alloys consisting of primary Al-1% Si dendrites and a eutectic with silicon particles (12 pct volume) embedded in the Al-1% Si matrix. Room temperature constant amplitude fatigue tests revealed that for a low crack-tip driving force, the surface fatigue crack propagated primarily through the Al-1% Si dendrite cells.…”

Effect of intermetallics on the microstructure and tensile properties of aluminum based alloys: Role of Sr, Mg and Be addition

“…8(a) with Fig. 9(a) reveals that increasing the solution heat treatment time did not further improve the mechanical properties and quality index values of the alloys containing Fe and Mg but without Be and Sr [23][24][25][26][27][28] additions.…”