Quote:
Originally Posted by headpunter
the hypereurectic pistons are a type of forged, so when they fail they shatter instead of becoming a fist sized projectile they break into a hundred little pieces and fall into the oil pan
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i dont know about them breaking into many little pieces, and they can be forged or cast (forged is stronger), now what makes a piston hypereurectic is just a special way of mixing the metals. For ex, pistons are made of many different metals (the good ones anyways) one primary component is aluminum for its weight savings and good strength. However aluminum expands greatly when it heats up, this large difference in size at different temps makes a tight tolerance engine impossible. So to reduce the expansion of aluminum we can add other ingredients to the mixture.
Which brings us to "eurectic" which means two elements can be alloyed together, BUT only up to a certain percentage, ie you can only add so much salt to a pot of water before it wont dissolve anymore. So for our case of the pistons and aluminum, we add silicon to the aluminum which reduces the amount of expansion. now only about 12% of this mixture can be silicon before it wont "dissolve" anymore, so special processes are used to force extra silicon into the mixture, bringing it to around 20%, this greatly reduces thermal expansion, which allows us to make tighter tolerance engines. the fact that we have now "super-saturated" the mixture of silicon to aluminum above the "eurectic" point of 12% makes it over or hyper eurectic
hope that helps