No description available.

Thesis (Ph. D.)--Worcester Polytechnic Institute. / Keywords: Microstructure; Elastic-Plastic Fracture Mechanics; Crack closure; A356; J-integral; Conventionally cast and SSM Al-Si-Mg alloys; Residual stress; Heat treatment; Fatigue crack growth mechanisms; Threshold stress intensity factor; Plastic zone; Paris law; Fracture toughness; Roughness. Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xi, 71 p. : ill. Vita. Includes abstract. Includes bibliographical references (p. 53-56).

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The dissolution mechanism and kinetics of a number of strontium master alloys in liquid aluminum and A356 alloys have been investigated. The dissolution behaviour of the strontium alloys was found to show marked differences depending on strontium content. Dilute strontium alloys containing less than 63 weight percent Sr were observed to exhibit simple dissolution in both melts. The dissolution rate and the recoveries of these alloys were found to increase with increasing melt temperature. Over the temperature interval of 675-775$ sp circ$C dissolution was determined to be mass-transfer controlled with associated activation energies of 10-20 kcal/mole. Experimental rate constants for dissolution showed good agreement with a mass transfer correlation expressed as k = (0.67(Gr.Sc)$ sp{1/4}$ + 0.58(h/r)) (D/h). The dissolution of high strontium master alloys $(>$63 wt. pct. Sr), unlike the dilute alloys, was accompanied by the formation of various intermetallics. Additions at low melt temperatures yielded the exothermic formation of those intermetallics that have the lowest Sr content as seen in the relevant phase diagram, i.e., SrAl$ sb4$ in liquid Al and SrAl$ sb2$Si$ sb2$ in liquid A356. Due to low reaction rates at these low melt temperatures, these intermetallics formed as dispersed particles that could easily dissolve in the melt yielding high recoveries. At high melt temperatures, the associated chemical reactions yielded, as products, the higher Sr intermetallics which formed with little or no exothermicity. These intermetallics were observed to be scarcely soluble in the melt resulting in low strontium recoveries. The dissolution times of these alloys were found to show good agreement with calculated values based on a two-stage dissolution model comprising an initial exothermic reaction period and a subsequent free dissolution period. The strontium master alloys were classified in two groups; the high Sr alloys that are efficient at low temperatures of 675-7

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Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 108-117). Also available via the Internet.

Thesis (MEng--Engineering) -- Auckland University of Technology, 2005. / Also held in print (xiv, 125 leaves, ill., 30 cm.) in Wellesley Theses Collection. (T 673.722 WIL)

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2006. / Thomas E. Michaels, Committee Chair ; Jianmin Qu, Committee Member ; Laurence Jacobs, Committee Member.