HIGH TEMPERATURE CREEP EVOLUTION IN Al-Si ALLOYS DEVELOPED FOR AUTOMOTIVE POWERTRAIN APPLICATIONS: A NEUTRON IN-SITU STUDY ON HKL-PLANE CREEP RESPONSE

摘要

Recent trend in the automotive industry towards lightweightingrnand downsizing the powertrain components, withoutrncompromising the power output, have led to increased enginernpower density. Increased power density frequently requires thesernlighter components to operate in conditions of increasedrntemperature and pressure, which is challenging for manyrnaluminum alloys in use today in the powertrain manufacturing.rnMeeting the challenge requires not only improving hightemperaturernperformance of known alloys or developing newrnones, but also developing new advanced techniques to understandrnthe long-term behaviour of the alloys.rnThis in-situ neutron diffraction study evaluated creep strain forrnindividual hkl planes in three automotive alloys under tensile load.rnThe conditions of temperature and pressure were typical of orrnsimilar to those experienced by engine heads in service. Highrntemperature plastic and elastic creep properties of three castrnaluminum alloys were characterized. The properties determinedrnfor these alloys can be used as a benchmark for furtherrndevelopment of advanced alloy systems suitable for the enginernhead application.rnThe in-situ neutron diffraction measurements provided data on dspacingrnevolution for various hkl crystallographic planes as arnfunction of temperature, tensile load, and time; thereby revealingrnhkl-specific evolution of elastic strains. This informationrncontributes to in-depth understanding of why a particular alloyrnexhibits particular service properties (eg. creep).