Also, it has been observed that: 5. Cu shows its normal hardening effect at room tem- perature, but this effect unexpectedly decreases with rising temperatures.


6. Fe notably reduces the room temperature elonga- tion but has less impact at elevated temperatures.


On the basis of these results, the nominal alloy composition which has been retained is:


AlSi7Cu3.5Mg0.15Mn0.15V0.12 Zr0.12Ti0.12 with Fe <0.15%.


The tensile and creep properties of this alloy can be compared to those of two of the main existing diesel cylinder head alloys (note that the 250C (482F) & 300C (572F) values in Table 2 are those obtained with the former, higher rate of traction as the two reference alloys were characterized this way):


The elevated temperature tensile and creep properties of the new alloy are vastly superior to those of the existing alloys.


How these laboratory results will translate in terms of per- formance in real cylinder heads is the next question. The alloy has been proposed to casting facilities for evaluation on real parts.


referenCeS


1. Garat, M., Laslaz, G., “Improved Aluminium Alloys for Common Rail Diesel Cylinder Heads”, AFS Transactions, vol. 115, pp.89-96 (2007). Reprinted in Hommes et Fonderie, février 2008-No. 382.


2. “Choix d’alliages d’aluminium de moulage pour culasses diesel fortement sollicitées”, René Chuimert - Michel Garat, presented in February 1987 at the Aluminium Zentrale “Aluminium + Automobile” symposium in Neuss (Düsseldorf)


3. Unpublished R&D work at Pechiney CRV by G. Laslaz and A. Delacour, 1991 – 1995.


Table 2. Comparative Tensile and Creep Strengths Common Diesel Cylinder Heads Alloys Versus the Development Alloy


Figure 12. 300C (572F) Creep Strength – Effect of V at Mg 0.10 – 0.15%.


Figure 13. Temperature dependence of thermal conductivity.


24


International Journal of Metalcasting/Summer 2011


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