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Transcript of Phase Diagrams
MENG 3319 Necessary Definitions Component - chemically recognizable species (Fe and C in carbon steel)
Alloys contain two or more components, one of which must be a metal
Binary alloy -- alloy contains two components, a ternary alloy – three, etc.
Phase - homogenous mass of material, such as zinc dissolved in copper One element is dissolved in another to form a single-phase structure
Base element is a metal, the dissolving element can be eithe metal or non-metal
Resulting alloy is typically stronger then either of the components
Two types -- substitutional and interstitial Solid Solutions Metal Phases There is usually a limit to how much of one element can be dissolved into another
When this happens, an intermediate phase is formed
Two phase alloys can be formulated and heat treated for significantly higher strength Image source: http://www.chem.ufl.edu/~itl/2045/lectures/lec_i.html Metal Alloys Phase Diagrams Graphical means of representing the phases of a metal alloy in terms of temperature and composition Example: Copper-Nickel Phase Diagram Looking at this diagram we see
that if we heat a mixture of 20% Cu
and 80% Ni to 1150C, the result is a mixture of liquid and solid
The more nickel present, the more heat is required to melt the mixture entirely Example Lead-Tin Alloy The lead-tin alloy is a more complicated phase diagram --
It has two solid phases present! Alpha phase and Beta phase Iron-iron carbide Phase Diagram Some facts . . .
Austenite: also known as gamma iron
Alpha iron: cast iron, 2.1% to 4 - 5% C
Steel: 0.02% to 2.1% C
Cementite: Iron carbide, mixture of iron and carbon that is hard and brittle Example Problem Another Look . . . Eutectoid point - 3 phases (ferrite, austenite, cementite) in equilibrium at one temperature.� All phases are solid, therefore this is a solid-solid transformation
Eutectoid composition - 0.76% carbon
Eutectoid Structure - pearlite http://www.rose-hulman.edu/~stienstr/me%20328/2003/p-review%20e3%202003%28phase%29.htm Consider this . . . http://web.utk.edu/~prack/mse201/Chapter%209%20%20Total.pdf