A methodology for temperature evaluation in T6 heat treated aluminium engine components by hardness curves and CFD/FEM simulation

One of the main limitation in designing of T6 heat treated Al-Si-Mg castings for high temperature applications, such as cylinder heads or pistons, is the considerable influence of thermal exposure on the local mechanical properties. Moreover, the evaluation of the temperature distribution in such crucial engine components is necessary for a correct structural simulation even if sometimes a direct measure is not possible. This work presents an experimental methodology for the evaluation of the local working temperature of an A356 T6 gravity die cast cylinder head by using the constant-hardness curves of the alloy. The loss of hardness due to thermal exposure is in fact strongly dependent from time and temperature exposure and can be used to evaluate the working temperature, when time of exposure and residual hardness are known. The temperatures evaluated with this approach were compared with those obtained by an advanced CFD/FEM simulation methodology for the prediction of the inner thermal diffusion.