MSE Chapter 7: Dislocations and Strengthening Mechanism

Dislocations

line defect in a crystal’s atomic structure

slip

plastic deformation caused by a dislocation movement

slip-plane

the plane along which a dislocation moves most easily

slip direction

the direction of easiest movement within that plane

slip system

a particular slip plane combined with a slip direction

grain size reduction

grain boundaries obstruct dislocation motion

solid-solution strengthening

add impurity atoms through alloying. Atoms of different sizes distort the crystal lattice and hinder dislocation motion

strain hardening

plastically deform a metal at a temperature well below its melting point

precipitating strengthening

heat treatment forms small, hard, particles within a meta. These precipitates obstruct dislocation motion

annealing

what happens when you heat a cold-worked metal?

annealing: recovery

dislocations rearrange or annihilate, reducing stored strain energy. This begins to relieve internal stressed

annealing: recrystalization

new, relatively strain-free grains form and replace the cold-worked grains. The metal becomes softer, weaker, and more ductile

annealing: growth

continued heating allows larger grains to grow at the expense of smaller ones