Development of aluminum alloys for diesel-engine applications.

摘要

Weight reduction in vehicles has important benefits of fuel economy and reduction in greenhouse gas emissions as well as improved vehicle performance. The current material for the diesel-engine block/head is mostly ductile iron and replacing it with aluminum alloys would result in very effective weight reduction (30--40%). Current commercial cast aluminum alloys, however, soften at engine operating temperatures exceeding 200°C and would cause early fracture in the diesel engine.;Two new alloys derived from the commercial alloy (A356) are described in terms of microstructure, creep, aging behavior and tensile properties at elevated temperatures. The alloy containing both peritectic (Cr, Zr and Mn) and age hardenable elements (Cu and Mg) shows superior aging response at 200°C (for 200 hours) and creep properties at 300°C (for 300 hours). Interestingly, the alloy has better tensile strength (161MPa) at 250°C with adequate ductility compared to the current engine alloys, A356 and A356+Cu. The improvement in mechanical properties is attributed to the newly formed thermally stable fine precipitates (epsilon-AlZrSi, alpha-AlCrMnFeSi...) inside the alpha-Al dendrites.