清华大学：《材料科学基础》课程教学资源（PPT课件讲稿）Chapter 6.1 Introduction

Chapter y Diffusion in Solids Lesson twenty-sIX

§6.1 ntroduction Atom movement in solids mechanical movement thermal vibration (short-range migration) Thermal motion diffusion(long-range migration)

mechanical movement thermal vibration (short-range migration) Thermal motion diffusion (long-range migration)

surface diffusion evaporation solidification volume diffusion

evaporation & solidification surface diffusion volume diffusion

e. Classification of diffus ion in solids 1. According to Steady state diffusion and Non-steady state diffusion

Steady state diffusion and Non-steady state diffusion ( )  C

aC Gp. =0. self-diffusion. both in pure metal and in homogeneous alloy aC dr+0. inter-diffusion, down-hill up-hil

( )  0   x C ( )  0   x C