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Grand Falls-Windsor, Canada

MacKay R.I.,Nemak of Canada Corporation | Sokolowski J.H.,University of Windsor
International Journal of Cast Metals Research

Recent metal casting literature has focused on the effect of Al melt practices and alloy chemistry on the formation of dispersed microshrinkage porosity in the cross-section of sand castings. In the present work, an attempt is made to explain observations on the severity of microshrinkage porosity formation in wedge castings of four alloys having different Si and Cu concentrations, with cooling rates ranging from 0.75 down to 0.045°C s -1. The Al-9Si-1Cu alloy provided the lowest level of dispersed microshrinkage along the wedge and the Al-7Si-4Cu alloy had the highest porosity. It is concluded on the basis of interpretative thermal analysis with fraction solid calculation that the requirements for the lowest level of porosity are primary α-Al dendritic mass being low in volume and more permeable, a high volume of Al-Si eutectic phase but within a shorter freezing range, and a low volume fraction of the Cu and Mg containing phases post-Al-Si eutectic reactions. © 2010 W. S. Maney & Son Ltd. Source

Mackay R.,Nemak of Canada Corporation | Sokolowski J.,University of Windsor
International Journal of Metalcasting

A significant portion of the literature on new and/ or modified alloy compositions that could serve as a replacement for the traditional 300 series aluminum alloys used for engine components are performed on test castings, which at times have limited complexity, lending themselves to advantageous liquid feeding conditions in the semi-solid state. More specifically the limited complexity of the test casting design may lead to conditions where progressive solidification provides enhanced soundness and limited segregation, which may not repeat in the component casting, made of the same alloy with the same melt treatment strategy. The research contained in this paper will investigate both a directionally chilled wedge test casting and a component engine block (CEB) poured with four development test alloys having the same melt treatment, with the aim to establish similarities and differences encountered in the test results of both casting designs used. The authors will make a recommendation regarding the best approach for successful alloy conversion strategies for production castings. Copyright © 2010 American Foundry Society. Source

Lombardi A.,Ryerson University | Sediako D.,National Research Council Canada | Ravindran C.,Ryerson University | Mackay R.,Nemak of Canada Corporation
SAE International Journal of Materials and Manufacturing

The development of an optimized heat treatment schedule, with the aim of maximizing strength and relieving tensile residual stress, is important to prevent in-service cylinder distortion in Al alloy engine blocks containing cast-in gray iron liners. However, to effectively optimize the engine block heat treatment schedule, the current solutionizing parameters must be analyzed and compared to the as-cast condition to establish a baseline for residual stress relief. In this study, neutron diffraction was carried out to measure the residual stress along the aluminum cylinder bridge following solution heat treatment. The stresses were measured in the hoop, radial and axial orientations and compared to a previous measured as-cast (TSR) engine block. The results suggest that solution heat treatment using the current production parameters partially relieved tensile residual stress in the Al cylinder bridge, with stress relief being more effective near the bottom of the cylinder. Copyright © 2014 SAE International. Source

Lombardi A.,Ryerson University | Ravindran C.,Ryerson University | MacKay R.,Nemak of Canada Corporation
Journal of Materials Engineering and Performance

The use of Al engine blocks has increased significantly to improve vehicle fuel efficiency. However, the gray cast iron cylinder liners cause the development of large tensile residual stress along the cylinder bores which necessitates the optimization of mechanical properties in this region to prevent premature engine failure. This study compared the microstructure of T4-treated Al billet castings of varying cooling rate to that of the cylinder region of T4-treated (current production schedule) Al engine blocks. The aim of this study was to develop a cost-effective small scale heat treatment optimization method for engine block production. Comparisons in microstructure between the engine block and the billet castings were carried out using optical and scanning electron microscopy. The results suggest that the microstructure and hardness at the top, middle, and bottom of the cylinder were similar to those of each representative billet casting, indicating that heat treatment resulted in successful replication of the engine block locations. In addition, tensile testing revealed that the YS and UTS increased slightly following T4 treatment for all billet castings, which was also observed at the middle of the engine block cylinder bridge. As such, this method can be an effective forerunner for future heat treatment optimization in Al engine block production. © 2014 ASM International. Source

Lombardi A.,Ryerson University | Ravindran C.,Ryerson University | MacKay R.,Nemak of Canada Corporation
Journal of Materials Engineering and Performance

The increased use of Al for automotive applications has resulted from the need to improve vehicle fuel efficiency. Aluminum alloy engine blocks fulfil the need of lightweighting. However, there are many challenges associated with thermo-mechanical mismatch between Al and the gray cast iron cylinder liners, which result in large tensile residual stress along the cylinder bores. This requires improced mechanical properties in this region to prevent premature engine failure. In this study, replicating billet castings were used to simulate the engine block solution heat treatment process and determine the onset of incipient melting. Microstructural changes during heat treatment were assessed with SEM and EDX, while thermal analysis was carried out using differential scanning calorimetry. The results suggest that solution heat treatment at 500 °C was effective in dissolving secondary phase particles, while solutionizing at 515 or 530 °C caused incipient melting of Al2Cu and Al5Mg8Cu2Si6. Incipient melting caused the formation ultra-fine eutectic clusters consisting of Al, Al2Cu, and Al5Mg8Cu2Si6 on quenching. In addition, DSC analysis found that incipient melting initiated at 507 °C for all billets, although the quantity of local melting reduced with microstructural refinement as evidenced by smaller endothermic peaks and energy absorption. The results from this study will assist in improving engine block casting integrity and process efficiency. © 2015, ASM International. Source

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