Study of heat treatment effects on properties and structures of A356 and B319 cast aluminum alloys

This work examines the effect of heat treatment parameters on hardness, electrical conductivity and microstructure of A356 and B319 cast aluminum alloys. The use of Jominy End Quench test to investigate quench effect and its important role to control of properties of these alloys was developed. Also, prediction of these properties in different points of large section castings was developed. Analyzing the hardness versus Jominy distance gave the determination of the importance of each heat treatment parameter. Also, Avrami parameters for each heat treatment cycle were validated to fit the Avrami curves to the hardness versus Jominy distance curves. In order to investigation of effects of variable heat treatment parameters on hardness of each of A356 and B319 alloys, nine different heat treatment parameters were chosen. Sixteen different heat treatment cycles were done on Jominy End Quench bars of each alloy based on the variable heat treatment parameters. These were evaluated by a Design of Experiment matrix which uses sixteen samples for each alloy. Techniques used included hardness testing; electrical conductivity measurements; Differential Scanning Calorimetry; and also microstructure observation using optical microscopy, Scanning Electron Microscopy, and Field Emission Scanning Electron Microscopy were employed to examine properties and microstructures of these alloys --Abstract, page iii