Anyone with young kids or a curious mind has experienced crystals growing. Typically, you dissolve something like sugar into very hot water, or aluminum foil into aqueous copper sulphate with table salt, and then leave it to cool while the water evaporates. As the water evaporates, the solution becomes “super-saturated” and crystals start to form because the water can no longer hold all that aluminum or dissolved copper sulphate.
Metal alloys behave in very similar ways, just not so easy to see. The concept of metals being crystalline can be hard to imagine. An ingot of aluminum alloy does not look crystalline, but it is, and the shape and direction of those crystals is important.
Dendrites are what metallurgists call the crystals that start to form as metals cool from liquid to solid. They typically take a form similar to a growing pine tree as they develop due to rather complicated issues related to alloy content and heat flow. But what’s really important to Vforge is that long, tree-like dendrites floating in an ocean of partially melted liquid, aka a semi-solid state, will keep tangling up with each other as you might imagine if you try to inject them into a die.
That’s why Vforge uses our MHD casting system to break down those long tree-like dendrites and make them “equiaxed” with roughly the same dimension in all directions. Then, once we have them captured in our bar, we convert them to globules that flow easily past one another as the bar transitions through our induction heating systems prior to thixocasting parts.
Dendrites and dendritic shapes are important to Vforge. For our customers, our careful control of the dendritic shapes is the enabling technology that facilitates our ability to make high strength, heat-treatable, pressure tight structural parts.
