材料科学基础英文版课件_(13)
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2材料科学基础英文版课件_(9)
Impact Fracture Testing (9)
Factors affecting the DBTT
• Strengthening: solid-solution strengthening, precipitation strengthening, and strain hardening (yield strength increase) DBTT increase – hardening embrittlementຫໍສະໝຸດ TICT1 T2 T3
T4
Temperature
Effects of impurity segregation and strengthening on the DBTT
Also read the paper:
S.-H. Song, J. Wu, L.-Q. Weng, and Z.-X. Yuan, “Fractographic changes caused by phosphorus grain boundary segregation for a low alloy structural steel”, Materials Science and Engineering A 497 (2008) 524-527.
• Grain boundary segregation of impurities: segregation of impurities such as P, S, Sn and Sb Grain boundary cohesion decrease DBTT increase – non-hardening embrittlement
Carbon content Strength DBTT and upper shelf energy
2材料科学基础英文版课件_(8)
1) Composites
Composed of more than one material type – one: matrix; other(s): reinforcing addition
Matrix – polymeric, metallic, or ceramic materials
Reinforcing addition: glass fibers, carbon fibers, ceramic fibers (e.g. basalt fibers) or nanoparticles (e.g. SiC, SiN, etc)
To modify existing materials and develop new materials, we need to know MSE
Classification of materials
In terms of chemical makeup and atomic structure Metals; Ceramics; Polymers
2材料科学基础英文版课件_(8)
Assessment Structure
• Written examination (50%) • Oral presentation (20%, any topics in
Chapter 7 – Mechanical Properties, 4 students as a group, 15 minutes) • Report (20%, any topics in materials science and engineering) • Assignment (10%)
What is materials science and engineering
Composed of more than one material type – one: matrix; other(s): reinforcing addition
Matrix – polymeric, metallic, or ceramic materials
Reinforcing addition: glass fibers, carbon fibers, ceramic fibers (e.g. basalt fibers) or nanoparticles (e.g. SiC, SiN, etc)
To modify existing materials and develop new materials, we need to know MSE
Classification of materials
In terms of chemical makeup and atomic structure Metals; Ceramics; Polymers
2材料科学基础英文版课件_(8)
Assessment Structure
• Written examination (50%) • Oral presentation (20%, any topics in
Chapter 7 – Mechanical Properties, 4 students as a group, 15 minutes) • Report (20%, any topics in materials science and engineering) • Assignment (10%)
What is materials science and engineering
材料科学基础(北京科技大学)13讲
心与4个原子中心相距
a 22
另2个原子中心相距为a/2，所以它不
是正八面体而在一个方向略受压缩
的扁八面体。
在一个晶胞内有6个八面体间隙。 八面体间隙半径r八面为 ：
r八面
1 2
a
2r
1 2
a
3 2
a
0.0670a
或
r八面
1 2
a
2r
1 2
4 3
r
2r
0.1547r
四面体间隙
由4个原子围成，它们的中心的坐标
8
每个原子有8个最近邻原子及6个次 近邻原子。次近邻原子间的距离仅 比最近邻原子距离约大15%，因此往 往要考虑次近邻的作用，有时将配 位数记为8+6，即有效配位数大于8。
扁八面体间隙
由6个原子组成的八面体所围的间
隙，它的中心位置位于晶胞立方体
棱边的中心及立方体6个面的中心。
即1/2 1/2 1/2及其等效位置。间隙中
虽然体心立方结构的致密度比面心立方结构的低，但它的间隙比较
分散，每个间隙的相对体积比较小，因此在体心立方结构中可能填
入杂质或溶质原子的数量比面心立方结构的少。
具有体心立方结构的金属有：钒、铌、钽、钼、钡、-钛（>880C）
-铁（<910C）、-铁（>1400C）、-钨…等。
2.2.最近邻原子，它的配 位数（CN）是12。
面心立方结构的最密 排面是{111}，面心立 方结构是以{111}最密 排面按一定的次序堆 垛起来的。
第一层{111}面上有两个可堆放 的位置：和位置，在第二层 只能放在一种位置，在面上每 个球和下层3个球相切 ，也和 上层3个球相切 。
第一层为 A， 第二放在B 位 置，第三层放 在C 位置，第 四层在放回A 位置。{111}面 按…abcabc…顺 序排列，这就 形成面心立方 结构。
最新2材料科学基础英文版课件_(10)
External Surfaces
• Surface atoms are not bonded to the nearest neighbors above the surface, leading to a higher energy state, i.e., a surface energy
• To be stable, materials need to reduce the surface energy.
Edge dislocation
Screw dislocation
Mixed dislocation
• Effects of dislocations on the properties of materials
–ormation of materials
Tilt boundary
Twist boundary
Use to represent the extent of CSL e.g., 3, 15, etc.
CSL boundary (coincidence site lattice boundary) Special boundary
Grain boundary segregation
• Observation of dislocations
Dark lines - dislocations
Plane Defects
Features: two dimensional
Outline
• External surfaces • Grain boundaries • Twin boundaries • Stacking faults • Phase boundaries
– Dislocation strengthening is one of the major strengthening mechanisms for metallic materials
材料科学基础双语课件
control the material properties (for example by altering the
grain structure, or the presence of defects in the atom
packing) or to fabricate the material into the desired shape.
extra material, joining parts (e.g., by soldering or welding),
forming (forging, rolling, bending, etc.), or compacting particles which are then fused together (sintering, used for
gases (and most engineering materials are used in solid
form).
1.1 What is Materials Science and Engineering?
It may seem abstract and remote from real engineering to
The Science and Engineering of Materials
Aim
English atmosphere: speaking, reading, writing and lisห้องสมุดไป่ตู้ening; Specialty vocabulary; Specialty knowledge;
form. As this mixture solidifies, different structures form as a function of temperature. The phase diagrams that provide
grain structure, or the presence of defects in the atom
packing) or to fabricate the material into the desired shape.
extra material, joining parts (e.g., by soldering or welding),
forming (forging, rolling, bending, etc.), or compacting particles which are then fused together (sintering, used for
gases (and most engineering materials are used in solid
form).
1.1 What is Materials Science and Engineering?
It may seem abstract and remote from real engineering to
The Science and Engineering of Materials
Aim
English atmosphere: speaking, reading, writing and lisห้องสมุดไป่ตู้ening; Specialty vocabulary; Specialty knowledge;
form. As this mixture solidifies, different structures form as a function of temperature. The phase diagrams that provide
2材料科学基础英文版课件_(12)
• Deformation-induced nonequilibrium vacancies
Point Defects – Point Defects in Metals (4)
The molar free energy of the crystal containing Xv mole of vacancies:
பைடு நூலகம்• There is always some level of impurity or foreign atoms in a metal, leading to the formation of an alloy
• Alloys – solid solutions and intermetallics • Concept: solvent – the matrix or host; solute
• Thermal equilibrium vacancies and interstitials
• Quenching-induced nonequilibrium vacancies and interstitials
• Irradiation-induced nonequilibrium vacancies and interrstitials
Point Defects – Point Defects in Metals (1)
1. Vacancies and Interstitials (self-interstitials)
Frenkel pair: vacancy + interstitial
Schottky defect: moving an atom to the surface produces a vacancy
Point Defects – Point Defects in Metals (4)
The molar free energy of the crystal containing Xv mole of vacancies:
பைடு நூலகம்• There is always some level of impurity or foreign atoms in a metal, leading to the formation of an alloy
• Alloys – solid solutions and intermetallics • Concept: solvent – the matrix or host; solute
• Thermal equilibrium vacancies and interstitials
• Quenching-induced nonequilibrium vacancies and interstitials
• Irradiation-induced nonequilibrium vacancies and interrstitials
Point Defects – Point Defects in Metals (1)
1. Vacancies and Interstitials (self-interstitials)
Frenkel pair: vacancy + interstitial
Schottky defect: moving an atom to the surface produces a vacancy
材料科学基础英文版课件（ＰＤＦ）
Law • Steady State: the concentration profile doesn't
change with time.
Steady State:
J x(left)
J x(right) J x(left) = J x(right)
x
Concentration, C, in the box doesn’t change w/time.
Non Steady State Diffusion
• Concentration profile,
dx
C(x), changes with time. J (left)
J (right)
• To conserve matter:
J (right)
− J (left)
=
dC −
dx
dt
dJ = − dC
ΔJ y
=
− ∂J y ∂y
dxdydzδt
ΔJ z
= − ∂J z ∂z
dxdydzδt
对整个元体积：
−
⎜⎜⎝⎛
∂J x ∂x
+
∂J y ∂y
+
∂J z ∂z
⎟⎟⎠⎞dxdydzδt
若 δt 时间内粒子浓度变化δc ，则在dxdydz
元体积中粒子变化为
δcdxdydz
∴ ∂c ∂t
=
−⎜⎜⎝⎛
∂J x ∂x
Fick’s Second Law
δt 时间内沿x方向扩散
元体积dxdydz
流入的粒子数： J x dydzδt
流出的粒子数：
(J x
+
∂J x ∂x
dx)dydzδt
【大学】材料科学基础(中英版)
Materials in first industrial revolution (1881-1935). Materials in second industrial revolution (1935-1980). Materials today – too,ooo,ooo… many (1980- ）.
第21页
Materials science and engineering
The relationship between materials science and materials engineering
Materials science Why it has…
Materials engineering How to make…
Time: Location: Activities:
Present new study material Announce reading and homework Take quizzes
第4页
授课信息
授课人： 时间： 地点： 主要活动：
教授新课 布置作业 课堂测验
第5页
Recitations
第1Байду номын сангаас页
What is material?
Classifications of materials
Based on the chemical composition: Metals, Non-metal inorganic materials (ceramic mateials) Polymers, Composites
Materials, energy and information are the three pillars of current human civilization.
第21页
Materials science and engineering
The relationship between materials science and materials engineering
Materials science Why it has…
Materials engineering How to make…
Time: Location: Activities:
Present new study material Announce reading and homework Take quizzes
第4页
授课信息
授课人： 时间： 地点： 主要活动：
教授新课 布置作业 课堂测验
第5页
Recitations
第1Байду номын сангаас页
What is material?
Classifications of materials
Based on the chemical composition: Metals, Non-metal inorganic materials (ceramic mateials) Polymers, Composites
Materials, energy and information are the three pillars of current human civilization.
材料科学基础英文版课件-(13)
Ductility
The ability of a material to be stretched without breaking.
Toughness
The ability of a material to absorb energy before fracturing.
Physical Properties
Some common examples of polymers include plastic, rubber, and fiberglass.
Polymers can be natural or synthetic.
Composites
Composites are materials that consist of two or more materials with different physical and chemical properties.
Nondestructive testing techniques: 超声波检测，射线检测，涡流检测等 。
02
Materials Properties
Mechanical Properties
Elasticity
The ability of a material to return to its original shape after being deformed by an external force.
Metals
Metals are materials that are typically ductile, malleable, and conduct electricity well.
They are often used in the manufacturing of various
材料科学基础英文版课件_(11)
d
e
g
f
7c/8
(2/3,1/3,3/4)
dae a
Ro = a2/2 – R
= 2R – R =
g
f
0.414R (a=2R)
(2/3,1/3,7/8)
Rt = (3/8)c – R = (3/8)x1.633a –R = 0.225R (a=2R)
Metallic crystal structures (11)
Metallic crystal structures (7)
3) Hexagonal close-packed (HCP) crystal structure
Each unit cell contains 6 atoms (12(1/6) + 2(1/2) + 3 = 6)
2R = a R = a/2
Two other features: coordination number (CN) and atomic packing factor (APF) CN: the number of nearest-neighbour atoms – 12 for FCC APF: the fraction of atom-occupied volume in a unit cell
4.2198 10-22 g Unit cell volume = a3 = (0.36148)3 = 0.04723 nm3 = 4.7234 10-23 cm3 = (weight of atoms in each unit cell)/unit cell voulme = 4.2198 10-22
CN = 12 c/a = ? APF = ?
Equilateral triangle
2材料科学基础英文版课件_(8)
Designed to display a combination of the best properties of each of the components
2) Semiconductors
Electrical properties being intermediate between conductors and insulators and being very sensitive to their composition and environmental conditions (e.g., functional ceramics: microwave dielectric ceramics, ferroelectric and piezoelectric ceramics)
Why study materials science and engineering
All applied scientists and engineers in any engineering areas: design problems involving materials
To select a right material from many thousands according to service conditions and property requirements, we need to have the knowledge of MSE
To modify existing materials and develop new materials, we need to f materials
In terms of chemical makeup and atomic structure Metals; Ceramics; Polymers
2) Semiconductors
Electrical properties being intermediate between conductors and insulators and being very sensitive to their composition and environmental conditions (e.g., functional ceramics: microwave dielectric ceramics, ferroelectric and piezoelectric ceramics)
Why study materials science and engineering
All applied scientists and engineers in any engineering areas: design problems involving materials
To select a right material from many thousands according to service conditions and property requirements, we need to have the knowledge of MSE
To modify existing materials and develop new materials, we need to f materials
In terms of chemical makeup and atomic structure Metals; Ceramics; Polymers
材料科学基础英文版
Chapter 1 Fundamental Concepts of
Crystal
1
1-1. Basic Concepts of Crystal
1) Definition of Crystal
• What is Crystal？
• Crystal and Amorphous
2
• People realized that there are two kinds of mineral in nature: Crystal and Amorphous.
• Crystal Structure = The periodic arrangement of atoms in the crystal.
11
=
? =
?
Lattice: Periodic repeating array
12
Lattice, Basis, Crystal Structure
Don't mix up atoms with lattice points
Diamond 4
Salt
Beryl
Quartz
Red Bee The building blocks of these two are identical, but different crystal faces are developed
Cleaving a crystal of rocksalt
• Lattice = An infinite array of points in space, in which each point has identical surroundings to all others.
• It can be described by associating with each lattice point a group of atoms called the Motif (Basis)
Crystal
1
1-1. Basic Concepts of Crystal
1) Definition of Crystal
• What is Crystal？
• Crystal and Amorphous
2
• People realized that there are two kinds of mineral in nature: Crystal and Amorphous.
• Crystal Structure = The periodic arrangement of atoms in the crystal.
11
=
? =
?
Lattice: Periodic repeating array
12
Lattice, Basis, Crystal Structure
Don't mix up atoms with lattice points
Diamond 4
Salt
Beryl
Quartz
Red Bee The building blocks of these two are identical, but different crystal faces are developed
Cleaving a crystal of rocksalt
• Lattice = An infinite array of points in space, in which each point has identical surroundings to all others.
• It can be described by associating with each lattice point a group of atoms called the Motif (Basis)
材料科学基础 英文版
Fundamentals of Materials Science and Engineering
To sum up, by learning this course, you could
Improve your English, learning new phrases or terms and concepts of materials science. Expand your knowledge about the Principal of Materials Science and Engineering. Know how to write an abstract ,a resume properly, how to do translation between English and Chinese; how to communicate effectively.
Course Organization(课堂组织)
We meet twice a week for two successive 50minute periods. The time will be used for text study, problem discussing, in-class practicing and practical skills training for example, translation skills training. You are allowed to use both English and Chinese, but the former is encouraged.
2．The iron-carbon system
Fundamentals of Materials Science and Engineering
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Minus sign indicates the diffusion is down the concentration gradient Negative
Fick’s first law
Mathematics of Diffusion (4)
• Nonsteady-stDiffusion in Solids
Diffusion - Introduction
• A phenomenon of material transport by atomic migration The mass transfer in macroscopic level is implemented by the motion of atoms in microscopic level • Self-diffusion and interdiffusion (or impurity diffusion) • Topics: mechanisms of diffusion, mathematics of diffusion, effects of temperature and diffusing species on the rate of diffusion, and diffusion of vacancy-solute complexes
Position of interstitial atom after diffusion
The activation energy is the migration energy of the interstitial atom.
Mathematics of Diffusion (1)
• Steady-state diffusion
– Time-dependent process, the rate of mass transfer is expressed as a diffusion flux (J)
M J At
In differential form
Mass transferred through a crosssectional area Diffusion time Area across which the diffusion occurs
dC J D dx
For this case, the unit of C is in mass per unit volume, e.g. g/m3
where D is the diffusion coefficient (m2/s), showing the rate of diffusion
The diffusion flux at a particular point varies with time.
Mathematics of Diffusion (5)
The diffusion equation is represented by
C C (D ) t x x
e.g. the diffusion of atoms of a gas through a metal plate
concentration gradient = dC/dx
dC/dx
J
Mathematics of Diffusion (3)
For steady-state diffusion, the diffusion flux is proportional to the concentration gradient The mathematics of steady-state diffusion in one dimension is given by
For self-diffusion, the activation energy is vacancy formation energy + vacancy migration energy.
Diffusion – Mechanisms (3)
• Interstitial diffusion In interstitial solid solutions, the diffusion of interstitial solute atoms is the migration of the atoms from interstitial site to interstitial site
Demonstration of diffusion
Before heat treatment
After heat treatment
Diffusion – Mechanisms (1)
Two mechanisms:
• Vacancy diffusion • Interstitial diffusion
1 dM J A dt
J = Mass transferred through a unit area per unit time (g/m2 s))
Mathematics of Diffusion (2)
Concentration profile does not change with time – steady-state diffusion
Fick’s second law C is a function of x and t If D is independent of the composition, the above equation changes to
C 2C D 2 t x
Unit area cross-section C = mass per unit volume (concentration)
Diffusion – Mechanisms (2)
• Vacancy diffusion In substitutional solid solutions, the diffusion (both self-diffusion and interdiffusion) must involve vacancies