High temperature creep evolution in al-si alloys developed for automotive powertrain applications: A neutron insitu study on hkl-plane creep response

Abstract

Recent trend in the automotive industry towards lightweighting and downsizing the powertrain components, without compromising the power output, have led to increased engine power density. Increased power density frequently requires these lighter components to operate in conditions of increased temperature and pressure, which is challenging for many aluminum alloys in use today in the powertrain manufacturing. Meeting the challenge requires not only improving high- Temperature performance of known alloys or developing new ones, but also developing new advanced techniques to understand the long-term behaviour of the alloys. This in-situ neutron diffraction study evaluated creep strain for individual hkl planes in three automotive alloys under tensile load. The conditions of temperature and pressure were typical of or similar to those experienced by engine heads in service. High temperature plastic and elastic creep properties of three cast aluminum alloys were characterized. The properties determined for these alloys can be used as a benchmark for further development of advanced alloy systems suitable for the engine head application. The in-situ neutron diffraction measurements provided data on d- spacing evolution for various hkl crystallographic planes as a fUnction of temperature, tensile load, and time; thereby revealing Mi-specific evolution of elastic strains. This information contributes to in-depth understanding of why a particular alloy exhibits particular service properties (eg. Creep).