The Effects of Solidification Cooling Rates on the Mechanical Properties of an Aluminum Inline-6 Engine Block

A shift from ferrous to aluminum alloys for use in automotive engine blocks has significantly reduced the weight of vehicles and has consequently improved fuel economy while reducing harmful emissions. During the casting process of aluminum engine blocks, chilling devices are typically incorporated into the sand castings for faster cooling and to allow for a more uniform cooling rate. The effects that chills have on the alloys microstructure (i.e. size, morphology and SDAS) and mechanical properties have been studied in this paper. This study characterizes the microstructure throughout a modified 319 type aluminum inline-six engine block using scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. In addition, mechanical testing (i.e. uniaxial tensile testing) have been performed at various depths along the cylinder web to determine the effects that varying microstructure has on the mechanical properties of the alloy. The results from this study indicate that the minor variation in cooling rates led to a fine and relatively uniform microstructure; resulting in the observation of similar mechanical properties throughout the entire cylinder bridge.