Casting of aluminum-based wrought alloys using controlled diffusion solidification
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Further available data[7,8] where Eq. [1] may be valid have not been considered in this article. Here, it should be noted that not all overaging data could be expected to fit into this equation. This is thought to be due to interactions with mechanism(s), other than coarsening, e.g., the disappearance, dissolution, and change of metastable phase precipitates. While the simple theories and their application presented in this article apply only for overaging, further analysis along these lines may provide a useful basis for general modeling of the precipitation hardening process. This article has shown that, on a basis of good correlation with published test results, a very simple mathematical description can be used to describe the overaging kinetics for a number of aluminum alloys. The approach provides a quantitative framework for understanding overaging, which is one of the key phenomena that these alloy systems rely on and is highly important in transport technology. In contrast, the Shercliff/Ashby model,[9] which describes the entire aging curve, is more complex to apply. REFERENCES
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1. E.A. Wilson: Scripta Mater., 1997, vol. 36, pp. 1179-85. 2. W. Sha: Scripta Mater., 2000, vol. 42, pp. 549-53. 3. W. Sha: PRICM4: 4th Pacific Rim Int. Conf. on Advanced Materials and Processing, Honolulu, HI, Dec. 11–15, 2001, S. Hanada, Z. Zhong, S.W. Nam, R.N. Wright, eds., The Japan Institute of Metals, Sendai, vol. II, pp. 2559-62. 4. K. Raviprasad, C.R. Hutchinson, T. Sakurai, and S.P. Singer: Acta Mater., 2003, vol. 51, pp. 5037-50. 5. Z. Guo and W. Sha: Mater. Trans., 2002, vol. 43, pp. 1273-82. 6. M.-C. Chou and C.-H. Chao: Metall. Mater. Trans. A, 1996, vol. 27A, pp. 2005-12. 7. S. Esmeiili, X. Wang, D.J. Lloyd, and W.J. Poole: Metall. Mater. Trans. A, 2003, vol. 39A, pp. 751-63. 8. H.K. Hardy and T.J. Heal: Progr. Met. Phys., 1963, vol. 16, pp. 149-391. 9. H.R. Shercliff and M.F. Ashby: Acta Metall. Mater., 1990, vol. 38, p. 1789.
Casting of Aluminum-Based Wrought Alloys Using Controlled Diffusion Solidification (d)
DEEPAK SAHA, SUMANTH SHANKAR, DIRAN APELIAN, and MAKHLOUF M. MAKHLOUF Aluminum-based alloys containing elements such as silicon, copper, magnesium, and manganese are widely used in domestic, automotive, and aerospace applications. These alloys are broadly classified into two groups: casting alloys and wrought alloys. The latter group of alloys cannot be used in the as-cast condition because they develop hot tears during solidification and are shaped by rolling, drawing, forging, etc. Of the two groups of aluminum-based alloys, the wrought alloys are the most widely used in aerospace
Fig. 2—(a) Vickers microhardness and (c) Rockwell hardness as a function of aging time for the Al-Zn-Mg-Cu monolithic alloys with various Mg contents and their corresponding Al-Zn-Mg-Cu/Al2O3 metal matrix composites aged at 120 °C[6] and plots of H3 vs aging time of the Al-1.23 pctMg-1.64 pct Cu-6.15 pct Zn (wt pct) alloy using (b) Vickers microhardness and (d) Rockwell hardness
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