ch 9 prequiz stuff

Alloy

A metallic substance that is composed of two or more elements.

Diffusion

Mass transport by atomic motion.

Lever Rule

A mathematical expression by which the relative phase amounts in a two-phase alloy at equilibrium may be computed; a graphical approach. 

Tie line

A horizontal line constructed across a two-phase region of a binary phase diagram

Phase

A homogeneous portion of a system that has uniform physical and chemical characteristics.

Phase Diagram

A graphical representation of the relationships among environmental constraints (e.g., temperature, pressure), composition, and regions of phase stability, typically under conditions of equilibrium.

Phase Equilibrium

The state of a system where phase characteristics remain constant and the energy is minimized.

Isomorphous system

A system with the same crystal structure or complete solid solubility for all compositions.

Solubility Limit

The maximum concentration of solute that may be added without forming a new phase.

Describe the general form, key features and use of a temperature-composition binary phase diagram for metal alloy systems that are a) isomorphous and b) simple eutectic. (note: don’t worry about the name isomorphous, but be able to read the diagram, if presented)

Isomorphous: Lens shape. Ie Straight line with arc. Above top, liquid. Below bottom, solid. Middle, liquid+solid. Describes complete solubility.

Simple eutectic: V on horizontal line. Bottom tip, liquid turns into two solids. Horizontal line, melting/freezing happens at a constant temp. Sides, solubility limits of the solids. Describes limited solubility.

Given a phase diagram, determine the phases present, composition of phases, and % of the system that is each phase at a given temperature and composition whether you have a one-phase or two-phase region. (see text and bonus slides)

Two phase: Liquid=S/S+R, Solid=R/S+R

S is left, r is right. S is just latin for left.

See slide.