No description available.

"Theoretical issues relating to the aerospace sand casting simulation are laid out, identifying parameters used in the model. A sensitivity analysis is performed to examine the mold-metal heat transfer coefficient, mold thermal conductivity, wall friction factor, pouring basin pour temperature, and pouring basin head pressure through doing coupled flow simulations on thin-walled castings using the commercial casting simulation software, MAGMASOFT. A verification exercise is done to match simulation with reality with the knowledge that mold-metal heat transfer coefficient and mold thermal conductivity are the most influential parameters of the five. Validation on a real production casting is performed using the tuned parameters from the verification exercise."

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: hydrogen removal; metal cleaning; particle removal. Includes bibliographical references (p. 42-43).

No description available.

Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

To minimize the production cost and time of the heat treatment of critical application aluminum castings within the automotive industry a combined hot isostatic pressing (HIP)/solution heat treat process is desired. A successfully combined process would produce parts of equal quality to those produced by the individual processes of HIP and subsequent heat treatment with increased efficiency in time and energy. In this study, an experimental combined process was designed and implemented in a production facility. Industrially produced aluminum castings were subjected to the combined process and results were quantified via tensile and fatigue testing and microscopic examination. Comparisons in fatigue and tensile strength were made to raditionally HIPed and heat treated samples, as well as un-HIPed samples in the T6 condition. Results show that castings produced with the combined process show fatigue properties that are equal in magnitude to castings produced with the independent HIP and heat treatment processes. Furthermore, an order of magnitude improvement in the fatigue life in those castings that were produced with the combined process exists compared to the castings that were only heat treated. This study shows no difference in the tensile properties that result from any of the processing routes compared. Also, microstructural comparison of the castings processed show no difference between the process routes other than porosity, which is only evident in the un-HIPed samples. Dendrite cell size and dendritic structure of the samples that were solutionized for the same time is identical. Theoretical examination of the combined process was also completed to quantify the energy consumption of the combined process compared to the independent processes. Thermodynamic calculations revealed that the energy consumed by the combined process for a typically loaded HIP vessel is fifty percent less than the energy required to process the same quantity of castings with the two individual processes. However, it was determined that a critical ratio of the volume occupied in the HIP vessel by castings to the total HIP vessel volume exists that ultimately determines the efficiency of the combined process. This critical ratio was calculated to be approximately fifteen percent. If the volume ratio is less than fifteen percent then the combined process is less energy efficient then conventional processing. These thermodynamic calculations were experimentally verified with power consumption process data in a production facility. In addition, the time required for the combined process of HIP and solution heat treatment was calculated as thirty-percent less than the conventional two-step process. This calculation was verified via the comparison of data compiled from the experimental combined process.

"Research and development of magnesium casting alloys depends largely on the metallurgist’s understanding and ability to control the microstructure of the as-cast part. Currently few sources of magnesium solidification information and as-cast microstructures exist. Therefore, the goal of this research is to increase the general knowledge base of magnesium solidification behavior and to characterize the resultant microstructures. Equipment has been developed and constructed to study the solidification behavior of magnesium-aluminum casting alloys via non-equilibrium thermal analysis and continuous torque dendrite coherency measurements. These analyses have been performed on six magnesium-aluminum alloys, including industry dominant alloys such as AM60 and AZ91E, and experimental alloys which show commercial potential such as AXJ530. The resultant microstructures have been characterized for general microstructure trends and the various phases present were analyzed using optical and scanning electron microscopy, as well as energy dispersive x-ray spectroscopy. The measurements were performed using a cooling rate on the order of 1-2°C/s, and results of these analyses show that in general, magnesium-aluminum casting alloys have relatively large solidification ranges, non-dendritic microstructures, and coherency points that are similar to those of aluminum casting alloys. These results should prove useful for research directed towards development of new magnesium alloys that are targeted for specific applications, as well as for optimizing casting procedures for Mg-Al alloys to obtain defect free cast structures."

Thesis (M.Phil.) - University of Queensland, 2006. / Includes bibliography.

Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

The enactement of the Energy Policy and conservation Act of 1975, led to a paradigm shift in material selection and design in the automotive industry. The net effect was an increased focus by the automotive industry toward the use of light metals leading for the reduction of weight and hence, the dependence of imported oil. Increasing use of aluminum was a transition in that direction. However, raw aluminum on an average is 1.5 - 2 times as expensive as steel. Near net shape manufacturing processes (Die casting, Thixo-forging, etc) provided the much needed competitive advantage vis-à-vis steel / iron parts by permitting the manufacturing of Al components. Semi solid processing involves the net shape manufacturing of alloys in a two phase region (liquid + solid). The reduced turbulence (during casting), less entrapped gases and lower operating temperatures (processes below the liquidus) make semi solid processing ideal for the manufacturing of high integrity Al parts. Traditionally, semi solid processing involved the heating of billets to a two phase region (called Thixcasting). Rheocasting is a new semi solid processing technique wherein the alloy is cooled from a liquid state (a combination of controlled heat / nucleation and growth phenomena) to yield structures similar to the Thixocasting process. Rheocasting or Slurry-On-Demand is in its early stages of development (the first industrial prototype of rheocasting was invented in the late 1990's) and forms the central point of interest in this work. Much research is underway around the globe to understand the controlling mechanism as well as the structure - property relationships in rheocast parts, primarily limited to the hypoeutectic Al-Si alloys (less than 12.6% Si). This work is dedicated in the development of novel methods for the rheocasting of hypereutectic Al-Si alloys (greater than 12.6% Si) and Al based wrought alloys (alloys with Cu, Zn, Mg and Si as alloying elements). The thesis presents the problems associated with microstructure control of hypereutectic Al-Si (primary Si coarsening and accelerated growth) and Al based wrought alloys (dendritic structures and hot tearing) with currently available technologies. Novel processing techniques are presented for the casting of hypereutectic Al-Si alloys and Al based wrought alloys with a combination of industrial trials and a through analysis of the underlying mechanisms.