E45 Lab 2 Phase - Engineering 45 Properties of Materials Laboratory Copyright 2001 Professor Ronald Gronsky the Arthur C and Phyllis G Oppenheimer

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E E n n g g i i n n e e e e r r i i n n g g 4 4 5 5 P P r r o o p p e e r r t t i i e e s s o o f f M M a a t t e e r r i i a a l l s s L L a a b b o o r r a a t t o o r r y y © Copyright 2001 Professor Ronald Gronsky the Arthur C. and Phyllis G. Oppenheimer Chair in Advanced Materials Analysis University of California Berkeley, California 94720-1760
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E 45 2 Lab 2 Phase Diagrams Objectives To understand how phase diagrams are constructed from cooling curves To compare the as-solidified microstructures of different alloys in the lead-antimony system Overview This lab is designed to help obtain a better understanding of how phase diagrams are experimentally determined. Students will construct a simple phase diagram using the cooling curves provided for a series of lead - antimony alloys. The cooling curve of an alloy with unknown composition will be obtained by each student. The composition of the alloy will be determined from this information and from observing the microstructure. Equipment •Computer data acquisition system •Chromel™ + alumel™ thermocouple •Pyrex® test tube, 15 x 125 mm, containing Pb-Sb alloy (5%, 11.8%, or 15% Sb) •Pyrex® glass tubing, 4 mm diameter, 5" long, one end sealed •Bi-grip test tube clamp •Lava plug •Coil furnace •Mold heater •Aluminum spacer •Thermocouple tube stop •Aluminum mold •Glass slide in mold •Tongs •Gloves •Etching reagent •Glycerol 16 parts •Acetic acid 1 part •Nitric acid 1 part •Microscope, 100x, 500x •Stereomicroscope, 7x, 30x •Microscope slide and plasticene •Graph paper (20 to the inch), to be furnished by student
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E 45 3 Background Phase diagrams are used to depict the equilibrium state of a multi-component system, normally as a function of temperature and composition. For example, solid water (ice) and liquid water have the same composition, but differ in atomic arrangements at their respective equilibrium temperatures. Tin has two distinct solid-state phases, with different atomic structures. Brine (a liquid solution of water and salt) has a different composition and structure than a mixture of solid salt and ice. The set of curves in a phase diagram delineate the regions of temperature and composition over which a given phase will exist. For points on the curves, the two (or at the eutectic temperature, three) phases that are separated by the curve coexist and are said to be “in equilibrium.” Pure elements have well-defined melting points whereas alloys (materials containing more than one element) generally do not. If heat is applied to a pure metal, its temperature will rise as heat is absorbed until the melting point is reached. Then the heat will be absorbed at a constant temperature until melting is complete, when the temperature will again begin to rise. The heat absorbed during the melting process is called the heat of fusion. Cooling the metal to the melting point will result in the release of the heat of fusion, which will halt
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This note was uploaded on 01/26/2010 for the course ENGLISH 45 taught by Professor Morris during the Spring '10 term at University of California, Berkeley.

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E45 Lab 2 Phase - Engineering 45 Properties of Materials Laboratory Copyright 2001 Professor Ronald Gronsky the Arthur C and Phyllis G Oppenheimer

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