# Shared Flashcard Set

## Details

Chapter 8 HW Questions
ET 2371
6
Mechanical Engineering
04/17/2016

Term
 Define aa) phase in a materialb) phase diagram.
Definition
 a) Phase is a physically homogeneous and distinct portion of a material system. Phase in a material is a region that differ in its microstructure and/or composition from another region. b) A graphical representation of phases present in a materials system at various temperatures, pressures and compositions. Phase diagrams are constructed by using equilibrium conditions. Most of the phase diagrams involve temperature versus composition.
Term
 Refer to figure 8.1 in the textbook (pressure-temperature equilibrium phase diagram for pure water and answer the following:a)How many degrees of freedom are there at the triple point?b) How many degrees of freedom are there along the freezing line?
Definition
 a) P + F = C + 2 3 + F = 1 + 2 F = 0b) 2 + F = 1 + 2 F = 1
Term
 a) What is a cooling curve?b) What type of information may be extracted from a cooling curve?c) Draw a schematic of a cooling curve for a pure metal and one for an alloy. Discuss the differences.
Definition
 a) A cooling curve is the plot temperature vs time aquired during solidification of a metal. It is used to determine phase transition temperature of metal vs time as it cools from a temperature at which it is molten through solidification and finally room temperature.b) (1) Phase transition temperatures for pure metals and alloys are the latent hears of metal or mixtures for which solidifications are achieved. (2) Solid state phase transformation in the metals. c) Refer to figure 8.3 and figure 8.6 in the textbook.The cooling curve for metal alloys in an isomorphous system does not contain the thermal arrest region at a specific temperature and ends at a lower temperature as presented by L & S symbols. As a result, unlike pure metals, alloys solidify over a range of temperatures.
Term
 What is a binary isomorphous alloy system?
Definition
 A mixture of two metals is called a binary alloy. It is two component system systems since each metallic element is an alloy which is considered a separate component. In a binary metallic system, two elements that are completely soluble into each other in both solid and the liquid state are said to be a binary isomorphous alloy system.
Term
 What are the four Hume-Rothery rules for the solid solubility of one element in another?
Definition
 1) The size of the atom of each of the two elements must not differ by more than 15%2) The element should not form compound with each other, i.e. there should be no appreciable difference in the electronegativities of the two elements3) The crystal structure of each element of the solid solution must be the same4) the elements should have the same valance
Term
 Write equations for the following invariant reaction:eutectic eutectoidperitecticpertectoidHow many degrees of freedom exist at invariant reaction points in binary phase diagrams?
Definition
 eutectic - liquid to a two phase solideutectoid - solid to a two phase solidperitectic - liquid + solid to a different solid phasepertectoid - two solids to a different solidP + F = C + 13 + F = 2 + 1 F = 0P = 3 (3 phases in the invariant reactions)C = 2 (since binary phase diagrams)1 because pressure is kept constant
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