Published in

Elsevier, International Journal of Fatigue, 10-12(27), p. 1564-1570

DOI: 10.1016/j.ijfatigue.2005.06.023

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The effect of silicon content on long crack fatigue behaviour of aluminium–silicon piston alloys at elevated temperature

Journal article published in 2005 by A. Moffat, S. Barnes, B. Mellor, P. Reed ORCID
This paper was not found in any repository, but could be made available legally by the author.
This paper was not found in any repository, but could be made available legally by the author.

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Abstract

The microstructure of aluminium piston alloys comprises primary and eutectic silicon together with numerous intermetallics. Previous research has shown that primary silicon strongly influences both fatigue crack initiation and subsequent propagation behaviour, however, the detailed effects of varying silicon volume fraction and morphology have not been fully addressed. Therefore, the fatigue properties of a number of candidate piston alloys with varying volume fractions of silicon have been studied. Long crack fatigue tests have been performed at room and elevated temperature typical of the gudgeon pin boss (200°C) using a test frequency of 15Hz (a typical engine frequency at engine idle condition).Microstructural characterisation using image analysis approaches combined with optical profilometry has been used to assess the fracture surfaces of test samples. The role of primary Si in enhancing crack growth rates at high ΔK levels, whilst affording improvements in crack growth rates at lower ΔK levels due to local crack deflections and shielding, has been confirmed. In the absence of primary Si (lower Si content alloys) the low ΔK level crack growth behaviour is dominated by matrix properties (intra-dendritic crack growth pre-dominates) whilst the high ΔK level crack growth behaviour is inter-dendritic and occurs along the weak path of the eutectic Si and/or intermetallic network.