Hi i need to know what will happen to the impact strength of aluminum 2024 reinforced with Silicon carbide is treated to cryogenic temperature (nearly -200C). Will impact strength increase or decrease. Also will the impact strength vary with respect to the percentage of Silicon carbide.
Aluminum 2024 doesn't have a transition temperature, it absorbs about 18n-m impact strength (via charpy tests I ran three weeks ago at my College course). This was constant between -150?C to +150°C (liquid nitrogen to a furnace). This excerpt from wiki: Cutting tools In 1982 at the Oak Ridge National Laboratories, George Wei, Terry Tiegs, and Paul Becher discovered a composite of aluminium oxide and silicon carbide whiskers. This material proved to be exceptionally strong. Development of this laboratory-produced composite to a commercial product took only three years. In 1985, the first commercial cutting tools made from this alumina and silicon carbide whisker-reinforced composite were introduced by the Advanced Composite Materials Corporation (ACMC) and Greenleaf Corporation. Leads me to believe it depends on how you mix the material in would make a difference. Silicon Carbide and aluminum make very strong tools, but would make it more brittle. The ceramic in a metallic crystal lattice (metal is a crystalline structure) would allow more voids to coalesce leading to a brittle fracture, but the initial strength would be improved because of substitution dislocations in the crystal structure (it would be more rigid, stronger, but more prone to sudden failure). Silicon carbide has low thermal expansion coefficient compared to aluminum also so when it gets really cold the aluminum would contract around the particles increasing the strength, but again, reducing ductility and causing fractures to occur more rapidly. Anyways, very interesting, you should do a bit of research on your own after this as I gave you some good places to work from (and I'm sure plenty of words to look up ;D )
