清华大学：《材料科学基础》课程教学资源（PPT课件讲稿）Chapter 3. 1 Basic concepts of al loys

Chapter The Structures of Alloys

Chapter Ⅲ The Structures of Alloys

33 1 Bas ic concepts of al loys I Definition An alloy is the combination of metal(s)with other elements through chemical bonding l. Terminology

§3.1 Basic concepts of alloys ◆ Ⅰ.Definition An alloy is the combination of metal(s) with other elements through chemical bonding. ◆ Ⅱ.Terminology

Alcohol Water ○- Liquid solution Mixing on the molecular scale Ni O H2O ●C2H3OH Cu

1. Component (or constituent) ◆ one component system e two component system binary system three component system ternary system four component system quarternary system ◆ five component system quinary system multi-component system

1. Component (or constituent) ◆ one component system ◆ two component system binary system ◆ three component system ternary system ◆ four component system quarternary system ◆ five component system quinary system multi-component system

2. Compo osition It can be expressed either by atomic percentage(mol fraction) Xa or by mass percentage Xm W/ m X:M ml ∑(Xm,/M) ∑(Xg9M/)

2. Composition It can be expressed either by atomic percentage (mol fraction) Xa or by mass percentage Xm  = = n j j i X M W M X j i i 1 m m a ( )  = = n j j j i i i X M X M X 1 a a m ( )

3. Phase A phase is a homogeneous part of the material in which no abrupt change in composition, structure and properties occurs An alloy may be single phase or multi-phase material 4. Structure Structure is a general term for the combination of atom arrangement including the types amounts and distribution of all types of material as well as grain size, defect etc

3. Phase A phase is a homogeneous part of the material in which no abrupt change in composition, structure and properties occurs. An alloy may be single phase or multi-phase material. 4. Structure Structure is a general term for the combination of atom arrangement including the types amounts and distribution of all types of material as well as grain size, defect etc

ll. Classification of al loy phases 1. According to structure Solid Solution Compound In Solid Solution, atoms of different component share a common lattice in variable proportion

◆ Ⅲ. Classification of Alloy Phases 1. According to structure Solid Solution Compound In Solid Solution, atoms of different component share a common lattice in variable proportion

oOOOOOOOCu oOOOOOOOCu Solid solution 0000Q of Zn in cu Compound of Cu and zn

2. According to position of ine alloy in_prase diagram erminal ss Intermediate SS + or secondary Ss A B

2. According to position of the alloy in phase diagram Terminal S.S. Intermediate S.S. or secondary S.S. α A B β α+β

83. 2 Factors Affecting the Structure of Alloy Phase 1. What is size factor metallic radi AB Atomic ionic radi r++r-=d radii covalent radii single bond radius Van der Waals radii

§3.2 Factors Affecting the Structure of Alloy Phase 1. What is size factor metallic radii rA+rB =d ionic radii r ++r- =d covalent radii single bond radius Van der Waals radii Atomic radii