Rapid Heat Treatment of Aluminum High-Pressure Diecastings
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Recently, it has been demonstrated that common high-pressure diecasting (HPDC) alloys, such as those based on the Al-Si-Cu and Al-Si-Mg-(Cu) systems, may be successfully heat treated without causing surface blistering or dimensional instability. In some compositions, the capacity to exploit age hardening may allow the proof stress values to be doubled when compared to the as-cast condition. This heat treatment procedure involves the use of severely truncated solution treatment cycles conducted at lower than normal temperatures, followed by quenching and natural or artificial aging. The potential therefore exists to develop and evaluate secondary HPDC alloys designed specifically for rapid heat treatment, while still displaying high castability. This article reports results of an experimental program in which responses of various alloy compositions to age hardening have been investigated with the primary aim of further reducing the duration and cost of the heat treatment cycle while maintaining high tensile properties. Composition ranges have been established for which values of 0.2 pct proof stress exceeding 300 MPa (i.e., increases of ~100 pct above as-cast values) can be achieved using a procedure that involves a total time for solution treatment plus age hardening of only 30 minutes. This rapid aging behavior is shown to be related to precipitation of the complex Q′ phase, which forms primarily when Mg contents of the alloys are above ~0.2 wt pct.
KeywordsHabit Plane Artificial Aging Peak Hardness Heat Treatment Cycle Differential Scanning Calorimeter Result
The authors thank Andy Yob, Maya Gershenzon, and Dayalan Gunasegaram for assistance with diecasting of test samples.
- 1.R.N. Lumley, R.G. O’Donnell, D.R. Gunasegaram, and M. Givord: International Patent Application WO2006/066314, 2005.Google Scholar
- 4.R.N. Lumley, R.G. O’Donnell, D.R. Gunasegaram, and M. Givord: 13th ADCA Conf. Proc., Melbourne, Australia, 2006, Australian Die Casting Association (ADCA), Melbourne, Australia, paper no. 25.Google Scholar
- 5.R.N. Lumley, D.R. Gunasegaram, M. Gershenzon, and R.G. O’Donnell: Conf. Proc. 111th Metalcasting Congr., Houston, TX, 2007, North American Diecasting Association (NADCA), Wheeling, IL, paper no. T07-013.Google Scholar
- 6.R.N. Lumley, R.G. O’Donnell, D.R. Gunasegaram, and M. Givord: Geissereiforschung, 2007, vol. 59 (3), pp. 8–13.Google Scholar
- 7.R.N. Lumley: Conf. Proc. 2008 SAE Small Engine Technology Conf., Milwaukee, WI, 2008, paper nos. 2008-32-0058 (SAE) and 20084758 (JSAE).Google Scholar
- 8.R.N. Lumley and S. Tartaglia: Conf. Proc. 111th Metalcasting Congr., Houston, TX, 2007, North American Diecasting Association (NADCA), Wheeling, IL, paper no. T07-023.Google Scholar
- 14.H.J. Axon: J. Inst. Met., 1952–53, vol. 81, pp. 209–13.Google Scholar
- 15.L.A. Willey: in Aluminum, vol. 1, Properties, Physical Metallurgy and Phase Diagrams, K. van Horn, ed., ASM INTERNATIONAL, Metals Park, OH, 1967, Appendix 1, p. 394.Google Scholar
- 16.L. Sagalowicz, G. Hug, D. Bechet, P. Sainfort, and G. Lapasset: Conf. Proc. ICAA4, Atlanta, GA, 1994, Georgia Institute of Technology, School of Materials Science and Engineering, Atlanta, GA, pp. 636–43.Google Scholar