Development of manufacturing technologies and characterization of microstructure, residual stress, and resultant in-service properties for production of I6 aluminum cylinder block

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Nemak Canada is currently introducing a new aluminum engine block into its product line that is based on I6architecture. This involves development of new casting technology, which shall address exceptionally thin wallsections, interbore cooling channels, and localized integrated chills. The focus of this research is themicrostructure, mechanical properties and residual stresses in an aluminum alloy engine block that have beenmanufactured with the new technology. Aluminum alloys do not have as high mechanical strength and wearresistance as compared to, for example, ferrous alloys and are often susceptible to deformation or distortionduring service while under high loads and elevated temperatures, and excessive wear at friction surfaces. Thispermanent deformation and excessive wear can lead to improper sealing of the combustion chamber, whichwill result in leakage of the air-fuel mixture past the piston rings into the crankcase, known as blow-by. Withthe occurrence of any amount of blow-by, the engine efficiency decreases and fuel consumption and carbon andNOx emissions rapidly increase. Due to strict environmental laws now commonly enforced in mostjurisdictions, engines suffering from blow-by would require expensive recalls, resulting in significant financiallosses for the automotive industry. Mechanical properties are highly dependent on alloy composition andmicrostructure. To secure the engine block quality is it therefore important to understand how microstructureand residual stress evolve at each stage of the manufacturing process (casting, heat treatment, and machining).The first objective of this research is to analyze the microstructure and residual stresses for each stage of themanufacturing process. This will allow to identify the stage(s) during manufacturing that may lead todetrimental microstructural changes or high residual stresses that contribute to component premature failureduring service. The second objective is to study how cast-in chills influence the post casting heat treatment.This will enable optimization of the casting and heat treatment process to enhance alloy mechanical propertiesand thus provide OEMs a new lighter material for engine blocks that will increase automobile fuel efficiency.