The elevated temperature performance of cast aluminium alloys and the development of a cast aluminium-copper metal matrix composite

Forde, John (2015). The elevated temperature performance of cast aluminium alloys and the development of a cast aluminium-copper metal matrix composite. University of Birmingham. Eng.D.

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Abstract

The first phase of this thesis characterised the currently commercially available L169 and A201 aluminium alloys in terms of their response to testing at the operating parameters predicted for next generation aero-engine components. The L169 and A201 alloys were initially subjected to ageing trials at 205°C, specimens of both alloys were then fatigue tested at ambient temperature and at 205°C following 1000 hours exposure at 205°C. Detailed micrographic characterisation was undertaken to assess the impact of prolonged elevated temperature exposure on the alloy microstructure. Fractography was undertaken on the failed fatigue specimens to assess the impact of ageing temperature and temperature exposure on fatigue behaviour. The L169 alloy exhibited a significant reduction in properties following 1000 hours exposure at 205°C due to extensive precipitate coarsening. The A201 exhibited comparably better elevated temperature performance due to the increased stability of the Ω- phase precipitate however the extensive shrinkage porosity observed in the alloy had a negative impact on fatigue performance and will limit its use in a pressure tight environment. In addition to the investigation into currently commercially available alloys a detailed investigation was taken into a novel dilute aluminium-copper based castable metal matrix composite with the potential for use at elevated temperatures. This alloy exhibits unique solidification mechanisms which result in an increased resistance to conventional aluminium copper alloy casting defects such as shrinkage porosity, segregation and hot tearing. A detailed investigation was undertaken to assess the impact of chemical composition on the alloys unique solidification behaviour and to assess whether there was any possibility for further optimisation. Following on from this investigation the alloy was characterised in similar terms to the L169 and A201 alloys in terms of its fatigue behaviour at both ambient and elevated temperatures to provide an assessment of the alloys potential to meet the predicted next generation aero-engine component operating conditions.

Type of Work:

Thesis (Doctorates > Eng.D.)

Award Type:

Doctorates > Eng.D.

Supervisor(s):