Strain – rate effects on the tensile properties of some heat – treated high pressure die cast aluminium alloys

Blackstock , Ross (2011). Strain – rate effects on the tensile properties of some heat – treated high pressure die cast aluminium alloys Honours Thesis, School of Engineering, The University of Queensland.

       
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Author Blackstock , Ross
Thesis Title Strain – rate effects on the tensile properties of some heat – treated high pressure die cast aluminium alloys
School, Centre or Institute School of Engineering
Institution The University of Queensland
Publication date 2011-01-01
Thesis type Honours Thesis
Supervisor Carlos Caceres
Total pages 70
Language eng
Subjects 0913 Mechanical Engineering
Formatted abstract
This report investigates the effect of three different strain rates for six different high pressure die casted (HPDC) alloys that have undergone three different heat treatments namely, As Cast, T4 and T6. HPDC alloys are the most important types of castings in terms of the number of castings that can be produced. They are used widely in the automotive industries and among other industries. The literature review highlights some important metallurgical concepts related to aluminium alloys and the topic at hand. Precipitation hardening is a key concept because alloys five and six were identified to have a significant amount of precipitate formation after heat treatment.

Samples for tensile testing were provided by Roger Lumley of CSIRO. CSIRO required the 0.2% proof stress and fracture strain data, and their susceptibility to different strain rates. The complementary aim of the report was to investigate the effects of strain rate and the Portevin – Le Chatelier (PL) effect.

The report discusses the testing and data analysis procedure. Engineering stress – strain, true stress – strain and true stress – true plastic strain plots were generated for each plot to determine all the necessary mechanical properties. All the results are tabulated within the report. In addition to the standard mechanical properties, the strain rate effect was also studied. A number of charts detail the effect of strain rate on ductility, strength and Work Hardening Rate. The PL effect (or “jerky flow”) was identified in most of the tests except those conducted at very low strain rates

A number of conclusions were drawn from this project. Firstly the alloys all have favourable properties depending on what is required. In terms of ductility alloys one to four were the best, with alloy three being the stand out alloy. Alloys five and six (particularly after T4 heat treatment) had the highest yield strengths.

Strain rate effects were also studied. Charts of 0.2% proof stress showed that they decreased with increasing strain rate for alloys one to four. The effect was similar with regards to fracture stress versus strain rate. The most notable strain rate effect was on the fracture strain of the alloys. It was quite clear that total elongation to failure decreases with increasing strain rates for all six alloys.
Keyword Alluminium Alloys

Document type: Thesis
Collection: UQ Theses (non-RHD) - UQ staff and students only
 
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