<p>Aluminum alloys are widely used in many manufacturing areas due to good castability, lightness and mechanical properties. The purpose of this research is to investigate copper’s influence on an Al-Si-Mg alloy (A356). Copper in the range of 0.6 – 1.6 wt. % has been used in an A356 aluminum based alloy. In this work a simulation of three different casting processes, sand-, die- and high pressure die-casting has been employed with the help of gradient solidification equipment. The microstructure of the samples has been studied by optical and scanning electron microscopy. Materials in both as-cast and heat treated states have been investigated through tensile test bars  to get the mechanical properties of the different conditions.</p><p> </p><p>Questions that have been subjected to answer are what influence does copper have on the plastic deformation and on fracture behavior and whether there is a relationship between the content of copper and increased porosity or not; and in that case explore this relationship  between the amount of copper and the mechanical behaviour.</p><p> </p><p>It has been analyzed that a peak of mechanical properties is obtained with a content about 1.6 wt. % copper. The increment of copper seems to have a remarkable impact on the mechanical properties and especially after the aging process showing a large raise on the ultimate tensile strength and yield strength.</p><p>Relationship between the copper content and increased porosity could not be found.</p>

Thesis. 1975. Sc.D.--Massachusetts Institute of Technology. Dept. of Materials Science and Engineering. / Vita. / Includes bibliographical references. / Sc.D.

Numerical simulation of mold filling in low pressure die casting is considered in this study. The physical model includes modeling of free surface flow, heat transfer with phase change, surface tension, natural convection together with effect of trapped air in the mold. The governing equations are discretized by control volume finite difference method. The pressure field is computed by two-step projection method and the free surface is tracked by PLIC-VOF method. Water analog model is used for the validation purpose. Good agreement between numerical and experimental results is observed which supports the feasibility of the presented method.

Aluminum alloys are widely used in many manufacturing areas due to good castability, lightness and mechanical properties. The purpose of this research is to investigate copper’s influence on an Al-Si-Mg alloy (A356). Copper in the range of 0.6 – 1.6 wt. % has been used in an A356 aluminum based alloy. In this work a simulation of three different casting processes, sand-, die- and high pressure die-casting has been employed with the help of gradient solidification equipment. The microstructure of the samples has been studied by optical and scanning electron microscopy. Materials in both as-cast and heat treated states have been investigated through tensile test bars  to get the mechanical properties of the different conditions.   Questions that have been subjected to answer are what influence does copper have on the plastic deformation and on fracture behavior and whether there is a relationship between the content of copper and increased porosity or not; and in that case explore this relationship  between the amount of copper and the mechanical behaviour.   It has been analyzed that a peak of mechanical properties is obtained with a content about 1.6 wt. % copper. The increment of copper seems to have a remarkable impact on the mechanical properties and especially after the aging process showing a large raise on the ultimate tensile strength and yield strength. Relationship between the copper content and increased porosity could not be found.

The central goal of this research is to quantitatively characterize the relationships between processing, microstructure, and mechanical properties of important high-pressure die-cast (HPDC) Mg-alloys. For this purpose, a new digital image processing technique for automatic detection and segmentation of gas and shrinkage pores in the cast microstructure is developed and it is applied to quantitatively characterize the effects of HPDC process parameters on the size distribution and spatial arrangement of porosity. To get better insights into detailed geometry and distribution of porosity and other microstructural features, an efficient and unbiased montage based serial sectioning technique is applied for reconstruction of three-dimensional microstructures. The quantitative microstructural data have been correlated to the HPDC process parameters and the mechanical properties. The analysis has led to hypothesis of formation of new type of shrinkage porosity called, gas induced shrinkage porosity that has been substantiated via simple heat transfer simulations. The presence of inverse surface macrosegregation has been also shown for the first time in the HPDC Mg-alloys. An image analysis based technique has been proposed for simulations of realistic virtual microstructures that have realistic complex pore morphologies. These virtual microstructures can be implemented in the object oriented finite elements framework to model the variability in the fracture sensitive mechanical properties of the HPDC alloys.

High Pressure Die Casting (HPDC) is low-cost technique for the mass production of complex, non-ferrous parts. Despite its benefits such as dimensional accuracy, surface quality and high production rate / some mechanical drawbacks limit use of HPDC in production of critical parts especially under dynamical loads. This study aims to improve impact resistance and surface hardness of die cast parts by means of tool steel inserts. These inserts act as a barrier between the impactor and die casting alloy, in order to avoid surface deformation and reduce stress localization which leads crack formation. Except the impact surface, whole insert is embedded into the die casting alloy by placing them on specially machined die casting molds prior to the metal injection. The mentioned method was evaluated by mechanical test and micro-examinations which were applied on AISI D2 tool steel inserted A518.0, A413.2 and Zamak5 alloy samples. To see the effect of inserts on energy absorbance under single destructive loads, both monolithic (conventional) and inserted (produced by mentioned technique) samples were subjected to Charpy impact test. In order to observe its behavior under non-destructive, cyclic, low velocity impacts / a dedicated real rifle part was produced by this method and tested in the real service loads. Explicit Finite Elemental Analysis was also carried out to understand how the inserts increases the energy absorbance and protect the die cast body by simulating both destructive and non-destructive impact loads. In addition to these, micro-examinations were also conducted especially on insert-die casting alloy interface for chemical and physical interactions, defects and stability. In regards of experimental findings, mechanical feasibility of the method was achieved. It was proved that steel inserts improve energy absorbance, stress distribution and impact-surface hardness of die cast products.

Soldering results from the interfacial interactions between the die and the casting alloy during high pressure die casting and is one of the major die failure modes. To prevent this occurring, lubricant layers and surface coatings are used to act as a barrier between the die and the casting alloy. The microstructures of a series of soldered layers on H13 tool steel core pins were examined after conducting high pressure die casting experiments with a specially designed die using removable core pins and Al-11Si-3Cu casting alloy. This showed that first, a casting alloy build-up layer formed, and then intermetallic phases nucleated at the die steel interface and grew to cover the entire surface in subsequent casting cycles. The structures of intermetallic layers formed during immersion of H13 tool steel into an Al-11Si-3Cu casting alloy melt were studied by X-ray diffraction and energy dispersive spectroscopy (EDS). A thick composite layer away from the H13 steel substrate consisted of irregular intermetallic phases and solidified casting alloy. A thin intermetallic layer was present between the composite layer and an inner compact layer next to the steel substrate. The irregular intermetallic phase in the thick composite layer away from the H13 steel substrate was identified to have a body centre cubic (bcc) structure, abcc-( FeSiAlCrMnCu). The thin and continuous intermetallic layer between the composite layer and the inner compact layer was found to be structurally isomorphous with aH-Fe2SiAl8. The compositional differences observed between aH and abcc phases indicated that the latter consisted of a higher amount of chromium, manganese, copper, and a lower amount of iron. It was likely that the presence of chromium, manganese and copper in the H13 tool steel caused the transformation of aH®abcc. The inner compact layer next to the steel substrate was identified to be orthorhombic h-Fe2Al5 containing silicon and chromium. An examination of lubricants to prevent soldering in high pressure die casting in conjunction with Nissan Casting Australia Pty Ltd. found that soldering was reduced by using a suitable lubricant. The chemistry of the lubricant, spray parameters, and die surface temperature were important factors in producing a protective lubricant layer. It was found that lubricant containing polypropylene waxes prevented soldering significantly better than lubricant containing polyethylene waxes. It was also found that the lubricant containing polypropylene waxes had lower surface tension. An examination of the use of iron oxide layers to prevent soldering in high pressure die casting was performed. H13 tool steel was oxidised in air and produced porous iron oxide with a mixture of haematite (Fe2O3) and magnetite (Fe3O4). These porous iron oxides did not completely prevent the H13 steel from soldering in immersion tests as intermetallic cones formed at the surface of the steel. Commercial steam tempering of H13 steel produced more compact iron oxide layers with magnetite (Fe3O4) and haematite (Fe2O3) structures. It was found that these compact iron oxide layers offered better protection against soldering than the porous layers created in air. Pure iron oxidised in a CO2/H2 gas mixture at a ratio of 95:5 at 550°C produced structurally pure, compact magnetite (Fe3O4) layers. H13 steel oxidised in a CO2/H2 gas mixture at a ratio of 95:5 at 550°C produced compact iron oxide layers that showed only magnetite (Fe3O4) structure. The magnetite (Fe3O4) layer containing chromium, manganese, silicon and vanadium formed next to the H13 substrate was found to be a very adherent layer and protected H13 steel from soldering in high pressure die casting experiments with a specially designed die using removable core pins and Al-11Si-3Cu casting alloy. An examination of aluminium oxide layers to prevent soldering in high pressure die casting was performed. Incoloy MA956 containing 4.5 wt.% aluminium, oxidised in air at 1100°C, produced a single, compact, adherent oxide layer with a-alumina (Al2O3) structure, that prevented the formation of intermetallic phases between aluminium alloy and Incoloy MA956 during high pressure die casting. However, non-reactive casting alloy build-up formed on the oxide coatings, similarly to physical vapour deposition (PVD) and vanadium carbide coatings. It was found that the thickness of the non-reactive casting alloy build-up was reduced by decreasing the roughness of the oxide coatings by lightly grinding of the surface of the coatings. The industrial application of these findings are discussed and directions for further research are presented.

Thesis (Ph. D.)--Carleton University, 2004. / Includes bibliographical references (p. 123-134). Also available in electronic format on the Internet.

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 172-177).

Thèse (M.Eng.) -- Université du Québec à Chicoutimi, 2006. / La p. de t. porte en outre: Mémoire présenté à l'Université du Québec à Chicoutimi comme exigence partielle de la maîtrise en génie. CaQCU Bibliogr.: f. [142-145]. Document électronique également accessible en format PDF. CaQCU