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

Nemak Canada目前正在其产品线中引入一种基于I6架构的新铝发动机机体。这包括开发新的铸造技术，该技术将解决异常薄的壁面、孔间冷却通道和局部集成冷铁。本文研究的重点是采用该新工艺制造的铝合金发动机机体的组织、力学性能和残余应力。例如，与黑色金属合金相比，铝合金的机械强度和耐磨性并不高，在高负荷和高温下使用时，铝合金往往容易变形或变形，摩擦表面磨损过大。这种永久性变形和过度磨损可能会导致燃烧室密封不当，这将导致空气-燃料混合物通过活塞环泄漏到曲轴箱，即所谓的漏气。当发生任何程度的漏风时，发动机效率下降，油耗、碳和NOx排放迅速增加。由于目前大多数司法管辖区普遍执行严格的环境法，发动机遭遇井喷将需要代价高昂的召回，从而导致汽车业的巨额财务损失。力学性能在很大程度上取决于合金成分和组织。因此，为了确保发动机机体的质量，了解制造过程的每个阶段(铸造、热处理和机械加工)的组织和残余应力的演变是很重要的。本研究的第一个目标是分析制造过程每个阶段的组织和残余应力。这将允许识别制造过程中可能导致有害组织变化或高残余应力的阶段(S)，这些变化或残余应力导致部件在使用过程中过早失效。第二个目标是研究铸态冷铁对铸件后热处理的影响，从而优化铸件和热处理工艺以提高合金的机械性能，从而为原始设备制造商提供一种新的更轻的发动机机体材料，从而提高汽车的燃油效率。

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.