1991-02-01

Development of Fiber Reinforced Aluminum Alloy for Diesel Piston Applications 910632

A preliminary study was done to select the more adequate composite material to be used as a reinforcement at the combustion bowl of higher output diesel engine pistons. From the three types of composites produced, namely, Ceramic Reinforced Material (CRM) , Metal Reinforced Material (MRM) and Fiber Reinforced Material (FRM) (1)*, FRM was selected after preliminary tests of mechanical properties, machinability and diesel engine tests, realized in a small monocylinder diesel engine.
After this selection, FRM was characterized and compared to the aluminum base alloy (M- 124R) , and from this analysis the following relevant comments should be made:
a) The reaction degree between the fiber and the matrix of M-124R is highly related to the processing and the heat treatment conditions, and these conditions will strongly influence the microstructure and the final properties of the produced composite.
b) The measured thermal expansion coefficients (CTE) of FRM in the axial and radial directions are the same and their absolute values are 20% below the M-124R aluminum alloy. However, the measured Young's Modulus is higher for axial FRM at room temperature.
c) The measured UTS for axial and radial FRM are the same, and at 300C these values are 80% higher than M-124R. There is an anisotropy of the yield strength of FRM samples that changes with the temperature; at 300C the yield strength of axial and radial FRM are higher than M-124R alloy. The fatigue life at constant load at 300C is one order of magnitude higher for the FRM compared to M-124R.
d) A 2000hs engine test showed a real improvement in piston durability when the FRM was used as a reinforcement at the combustion bowl rim.

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