Inclusion removal and grain refinement of magnesium alloy castings

Magnesium alloys show promise to be materials for lightweighting of automotive and aerospace vehicles improving fuel efficiencies and vehicle performance. A majority of magnesium alloy components are produced using casting where susceptibility to forming inclusions and coarse grain sizes could result. Development of effective inclusion removal techniques and better understanding of grain refinement of magnesium alloys could help in improving their mechanical properties to advance them to more structurally demanding applications. This research aimed to develop an environmentally friendly alternative to the grain refinement and inclusion removal capabilities of carbon based hexachloroethane as it releases dioxins, chlorine gas and corrodes foundry equipment. A secondary aim was to pioneer in-situ neutron diffraction to examine the solidification of magnesium alloys. The research involved preparing tensile samples of AZ91E magnesium alloy using permanent mould casting. Inclusion removal was conducted by using filtration and argon gas bubbling. Castings grain refined using hexachloroethane (0.25, 0.50 and 0.75 wt.%) were compared against ex-situ aluminum-silicon carbide and in-situ aluminum-carbon based grain refiners combined with filtration and argon gas bubbling. Further, in-situ neutron diffraction was utilized for phase analysis and fraction solid determination of magnesium-zinc and magnesium-aluminum alloys. There was a significant improvement in yield strength, ultimate tensile strength and elongation with filtration plus argon bubbling, carbon inoculation or both filtration plus argon bubbling and carbon inoculation. The results indicated that the mechanism of the observed ~20% reduction in grain sizes with carbon inoculation (hexachloroethane, ex-situ aluminum-silicon carbide and in-situ aluminum-carbon) was explained through duplex nucleation of Mn-Al and Al-Mg-C-O (likely Al2MgC2) phases. Finally, in-situ neutron diffraction was used to follow the formation of Mg17Al12 eutectic phase in a magnesium-9 wt.% aluminum alloy. For the magnesium-zinc alloys, in-situ neutron diffraction enabled characterization of the effects of zirconium to the fraction solid growth of (1010), (0002) and (1011) α-Mg planes. The societal and environmental impact of this research is significant. There is a clear demonstration of alternatives to the universally used hexachloroethane grain refiner promoting harmful emissions. Improved mechanical properties resulting from new grain refinement and iv inclusion filtration are a major advancement in promoting weight reduction, improved castability and decreased environmental impact for automotive and aerospace industries.

Inclusion removal and grain refinement of magnesium alloy castings

Magnesium alloys show promise to be materials for lightweighting of automotive and aerospace vehicles improving fuel efficiencies and vehicle performance. A majority of magnesium alloy components are produced using casting where susceptibility to forming inclusions and coarse grain sizes could result. Development of effective inclusion removal techniques and better understanding of grain refinement of magnesium alloys could help in improving their mechanical properties to advance them to more structurally demanding applications. This research aimed to develop an environmentally friendly alternative to the grain refinement and inclusion removal capabilities of carbon based hexachloroethane as it releases dioxins, chlorine gas and corrodes foundry equipment. A secondary aim was to pioneer in-situ neutron diffraction to examine the solidification of magnesium alloys. The research involved preparing tensile samples of AZ91E magnesium alloy using permanent mould casting. Inclusion removal was conducted by using filtration and argon gas bubbling. Castings grain refined using hexachloroethane (0.25, 0.50 and 0.75 wt.%) were compared against ex-situ aluminum-silicon carbide and in-situ aluminum-carbon based grain refiners combined with filtration and argon gas bubbling. Further, in-situ neutron diffraction was utilized for phase analysis and fraction solid determination of magnesium-zinc and magnesium-aluminum alloys. There was a significant improvement in yield strength, ultimate tensile strength and elongation with filtration plus argon bubbling, carbon inoculation or both filtration plus argon bubbling and carbon inoculation. The results indicated that the mechanism of the observed ~20% reduction in grain sizes with carbon inoculation (hexachloroethane, ex-situ aluminum-silicon carbide and in-situ aluminum-carbon) was explained through duplex nucleation of Mn-Al and Al-Mg-C-O (likely Al2MgC2) phases. Finally, in-situ neutron diffraction was used to follow the formation of Mg17Al12 eutectic phase in a magnesium-9 wt.% aluminum alloy. For the magnesium-zinc alloys, in-situ neutron diffraction enabled characterization of the effects of zirconium to the fraction solid growth of (1010), (0002) and (1011) α-Mg planes. The societal and environmental impact of this research is significant. There is a clear demonstration of alternatives to the universally used hexachloroethane grain refiner promoting harmful emissions. Improved mechanical properties resulting from new grain refinement and iv inclusion filtration are a major advancement in promoting weight reduction, improved castability and decreased environmental impact for automotive and aerospace industries.

Effect of addition of SiC particles on the Microstructure and Hardness of Al-SiC composite

This work aims to investigate the effect of the addition of silicon carbide particles on the microstructure and the hardness of the Al-SiC metal matrix composites. The said composite is prepared using the stir casting technique for different weight percentages of the SiC particles. The higher composition of the reinforcement causes the clustering of the particles in the matrix. Thus, research has to be carried out on the aluminum-silicon carbide composites with the reinforcement 3wt%, 6wt%, 9wt%, and 12wt% of SiC particles to obtain the optimized composition. In order to study the microstructure and the reinforcement distribution in the matrix, a scanning electron microscope is utilized. The hardness testing has been carried out using the Vickers’ indentation technique for the as-cast and age hardening conditions. From the microstructural study, it is observed that the microstructure of the said composite exhibits the uniform distribution of the reinforcement. The EDX results show the presence of the reinforcing elements in the Al-SiC composite. From the results obtained from the hardness testing, it is observed that the presence of the carbide element in the composite increases the hardness of the Al-SiC particulate composites.

An Assessment of Mechanical Characteristics of Al 6061 Reinforced with SiC and Bagasse Fly Ash Hybrid MMC

Material is one or more substances that form an object. Due to an attractive mechanical characteristic, materials are commonly selected for structural applications. Recently, the hybrid MMC has been developed and highly an innovative trend in material science. The current study is concentrated on the formation of an innovative hybrid MMC by utilizing aluminum, silicon carbide and fly ash particulates of bagasse. In this study, the physical characteristics of Aluminum 6061 were evaluated by adding Sic, fly ash particulates of bagasse and observed that this is the hardest substance. The compositions were added until the final level and a method of stir casting has been utilized to fabricate Al MMC. XRD ie x-ray diffraction was utilized to analyze the structural characterization of MMC and optical microscopy was utilized to analysis the microstructure on MMC. In this study, the mechanical characteristics like hardness, elongation, yield strength, UTS and density have been performed on MMC. Aluminum was added with 5% of silicon carbide and 10% of fly ash particles of bagasse in one case and in other case aluminum was added with 10% of fly ash particles of bagasse and 10% of silicon carbide. As a result, it was detected that there is an improvement in the hardness and UTS and a reduction in the density and elongation of the composites in comparison to plain aluminum. This shows that the aluminum-silicon carbide-fly ash particles of bagasse MMC substantially differ throughout all characteristics.

Structural Simulation and Optimization of Diesel Engine Piston Material using ANSYS

During the combustion of fuel in diesel engine, high temperature and pressure will be created as engine runs at high speed and loads. This results in development of high thermal and structural stresses in the piston and if these stresses exceed the design value, failure of piston may take place. To avoid these failures, intensity of stresses should be avoided. In this work an attempt is made to reduce the intensity of stresses by replacing conventional aluminum alloy material of piston with aluminum silicon carbide composite by commercial analysis software package ANSYS

Liquid-Cooled Aluminum Silicon Carbide Heat Sinks for Reliable Power Electronics Packages

With recent advances in the state-of-the-art of power electronic devices, packaging has become one of the critical factors limiting the performance and durability of power electronics. To this end, this study investigates the feasibility of a novel integrated package assembly, which consists of copper circuit layer on an aluminum nitride (AlN) dielectric layer that is bonded to an aluminum silicon carbide (AlSiC) substrate. The entire assembly possesses a low coefficient of thermal expansion (CTE) mismatch which aids in the thermal cycling reliability of the structure. The new assembly can serve as a replacement for the conventionally used direct bonded copper (DBC)—Cu base plate—Al heat sink assembly. While improvements in thermal cycling stability of more than a factor of 18 has been demonstrated, the use of AlSiC can result in increased thermal resistance when compared to thick copper heat spreaders. To address this issue, we demonstrate that the integration of single-phase liquid cooling in the AlSiC layer can result in improved thermal performance, matching that of copper heat spreading layers. This is aided by the use of heat transfer enhancement features built into the AlSiC layer. It is found that, for a given pumping power and through analytical optimization of geometries, microchannels, pin fins, and jets can be designed to yield a heat transfer coefficients (HTCs) of up to 65,000 W m−2 K−1, which can result in competitive device temperatures as Cu-baseplate designs, but with added reliability.

Suppressing Aluminum Carbide in Welding Aluminum Silicon Carbide Composite

Weldability of aluminum-based metal matrix composite A359/SiC/10p using gas tungsten arc welding and R356.0 filler material is investigated. The welding current, welding speed, and preheat temperature affect the weld quality significantly. Finite element analysis is successfully applied to map the weldment temperature during preheating and welding. During mechanical testing of welded specimens, a crack propagates in the parent composite or in the weld, but not in the stronger zone between the weld and the parent material. The weld region contains reasonably uniform distribution of SiC particles due to high viscosity of the molten weld and its fast cooling rate. Proper control of heat input and addition of silicon-rich filler material hinder the interface reaction between aluminum matrix and the reinforcing SiC particles, and successfully suppresses the formation of harmful aluminum carbide flakes in the weld. The average tensile and flexural strengths of optimally welded specimens approach those of the parent composite while its ductility exceeds that of the parent material.