欢迎访问 热批发网 登录 【注册】

热批发网B2B商务平台

机械>机械加工>热处理>主要材料检验总结:| 829、92金属化及干货热处理

免费发布产品信息

主要材料检验总结:| 829、92金属化及干货热处理

发布时间:浏览次数:

20 major materials postgraduate entrance examination | 829, 92 metallic and heat treatment practical

information summary wenyan 2019, 08, 1316, 29, 01 wenyan postgraduate entrance examination, this is

the second article of the 20th major material. senior ning was admitted to the material processing

department of the school of materials of chongqing university in 2019. the first test score reached

380, the total score of the second test was 81.6, and the major ranked eighth. as the senior who cam

e ashore for the postgraduate entrance examination in 2019, holding the latest test hotspots and que

stion types, he has a deep understanding and unique learning method for this major! the teacher lect

ured on 829 metalogy and heat treatment (including metallic materials), 928 fundamentals of material

science. chapter 1 crystal structure of metals section 1: general definition of metals: metals are

substances with good electrical conductivity, thermal conductivity, ductility (plasticity) and metal

lic luster. strict definition: metal is a substance with a positive temperature coefficient of resis

tance, that is, the resistance increases with the increase of temperature. test point 2: metal bond

1. definition: atoms that contribute bid electrons become positive ions, immersed in the electron cl

oud, and they are combined by the electrostatic action of public free electrons moving between them,

a mode of binding called metal bonds. two。. features: no saturation and directionality. test point

3: binding energy. definition: the energy of two atoms or molecules held together by electrostatic i

nteraction. section ii crystal structure of metals: crystal and amorphous. crystal refers to the sol

id in which the internal particles (atoms, ions, molecules) are arranged repeatedly periodically in

three-dimensional space. crystals can be divided into single crystals and polycrystals, in which sin

gle crystals have a fixed melting point, anisotropy and polycrystals are pseudo-isotropic. two。. amo

rphous refers to a solid with irregular arrangement or long-range disorder of atoms in three-dimensi

onal space. it is isotropic and has no fixed melting point. but it can be transformed into crystal u

nder certain conditions. test point 2: crystal structure and spatial lattice 1. crystal structure: t

he regular periodic arrangement of atoms, ions, or clusters of atoms in a crystal in three-dimension

al space. features: there are many types, there may be local defects. two。. spatial lattice: a three

-dimensional array formed by abstracting the atoms, ions, or clusters of atoms that make up a crysta

l into geometric points (called array points), which are arranged periodically and regularly. featur

es: there are only 14 types, which is the abstract model of the actual structure. test point 3: latt

ice and unit cell. lattice: a three-dimensional lattice formed by connecting dots with a series of p

arallel lines. its essence is still a spatial lattice. two。. unit cell: the smallest geometric unit

selected from a lattice that can fully reflect the characteristics of the lattice. it is usually a p

arallel hexahedron. test site 4: seven crystal systems and 14 spatial lattice test sites 5: three ty

pical metal crystal structures. the three edges of the body-centered cubic crystal structure (body-c

enteredcubic,bcc) are equal in length and the angles between the three axes are all 90 °, forming a

cube. in addition to having an atom at each of the eight corners of the cell, there is an atom at th

e center of the cube. there are more than 30 kinds of metals with body-centered cubic structure, suc

h as α-fe, cr, v, nb, mo, w and so on. the atoms with 1 atomic radius are in close contact with each

other along the diagonal line of the body. if the lattice constant (or lattice constant) of the cel

l is a, then the length of the diagonal line of the cube is the sum of four atomic radii. therefore,

the atomic number of the atomic radius 2 cell in the body-centered cubic cell is because the lattic

e is stacked by a large number of crystal cells, so the atoms on each corner of the cell are shared

by eight adjacent cells. therefore, only eight atoms belong to this cell, and the atoms in the cente

r of the cell completely belong to this cell, so the coordination number of atoms in the body-center

ed cubic cell (8 × 1) refers to the number of atoms nearest to and equidistant from any atom in the

crystal structure. the larger the coordination number, the tighter the arrangement of atoms in the c

rystal. in the body-centered cubic structure, from the point of view of the atoms in the center of t

he cube, there are 8 nearest neighbors and equidistant atoms, so the coordination number of the body

-centered cubic structure is 8. (4) densification refers to the ratio of the volume of atoms to the

volume of unit cells. that is, after calculation, the density of body-centered cubic structure is 0.

682. the face-centered cubic crystal structure (face-centeredcubic,fcc) has an atom at each of the e

ight corners of the cell to form a cube and an atom at the center of each of the six faces of the cu

be. about 20 kinds of metals, such as γ-fe, cu, ni, al, ag and so on, have this crystal structure. 1

atomic radius atoms are in close contact along the face corner line, and if the lattice constant (o

r lattice constant) of the cell is a, then the length of the face corner line of the cube is the sum

of four atomic radii, so the atomic number of the atomic radius 2 unit cell in the face-centered cu

bic cell has one atom on each of the eight corners of the cell, forming a cube. there is one atom in

the center of each of the six faces of the cube, but only 1/2 belongs to this cell. therefore, the

number of atoms in the unit cell is 8 × 1. 8 × 6 × 1. 2. 43 for example, the nearest atom is the fou

r atoms on the vertex around it, and the five atoms form a plane. there are three such planes, and t

he three planes are perpendicular to each other and have the same structure, so there are 4 × 3 atom

s in the nearest neighbor and equidistant from the atom. (4) the density of face-centered cubic crys

tal structure is 0.743. the closely packed hexagonal crystal structure (hexagonalclosed-packed,hcp)

has one atom on each of the 12 corners of the cell, forming a hexagonal cylinder, one atom in the ce

nter of the upper bottom and the lower bottom, and three atoms in the cell. the metals with closely

packed hexagonal structure include zn, mg, be, α-ti, α-co, cd and so on. there are two lattice const

ants of the closely packed hexagonal structure: one is the side length a of the regular hexagon, and

the other is the ratio of the distance between the upper and lower bottoms c to a, which is called

the axis ratio. 1 the atomic number of the unit cell has one atom on each of the 12 corners of the u

nit cell, forming a hexagonal cylinder, one atom in the center of the upper and lower surface, and t

hree atoms in the unit cell. the number of atoms in each cell is 62. in the typical close-packed hex

agonal structure, the atomic rigid spheres are stacked very closely. taking the atom in the center o

f the upper bottom of the cell as an example, it not only comes into contact with the atoms on the s

urrounding six angles, but also20专业材料考研|829、92金属与热处理实用资料汇总文研2019-08-1316-29-01文研考研,这是第20期专业材料的第二篇。20

19年,大宁考入重庆大学材料学院材料加工系。初试成绩达到380分,复试总分为81.6分,专业排名第八。作为2019年上岸考研的大四学生,掌握着最新的考试热点和题型,他对这个专业有着深刻的理解和独特的学

习方法!老师讲授829金相学与热处理(含金属材料)、928材料科学基础。第一章金属的晶体结构第一节:金属的一般定义:金属是具有良好的导电性、导热性、延展性(塑性)和金属光泽的物质。严格定义:金属是电阻

温度系数为正的物质,即电阻随温度升高而增大。测试点2:金属键1.定义:贡献bid电子的原子变成正离子,沉浸在电子云中,它们通过在它们之间移动的公共自由电子的静电作用结合在一起,这种结合方式被称为金属键

。二.。。特点:无饱和度和方向性。测试点3:结合能。定义:两个原子或分子通过静电相互作用保持在一起的能量。第二节金属的晶体结构:晶态和非晶态。晶体是指内部粒子(原子、离子、分子)在三维空间中周期性排列

的固体。晶体可分为单晶和多晶,其中单晶具有固定的熔点,各向异性,多晶为伪各向同性。二.。。非晶态是指原子在三维空间中不规则排列或长程无序的固体。它是各向同性的,没有固定的熔点。但在一定条件下可以转化为

晶体。测试点2:晶体结构与空间点阵1.晶体结构:晶体中原子、离子或原子团簇在三维空间中的规则周期性排列。特点:有多种类型,可能存在局部缺陷。二.。。空间点阵:通过将构成晶体的原子、离子或原子簇抽象为几

何点(称为阵列点)而形成的三维阵列,这些几何点定期且规则地排列。特点:只有14种类型,是实际结构的抽象模型。测试点3:点阵和单胞。格子:用一系列平行线将点连接起来形成的三维格子。它的本质仍然是一个空间

格子。二.。。单元格:从晶格中选择的能够完全反映晶格特征的最小几何单位。它通常是一个平行的六面体。试验点4:7个晶系和14个空间点阵试验点5:3个典型的金属晶体结构。体心立方晶体结构(体心立方,bcc

)的三条边等长,三轴夹角均为90°,形成立方体。除了在细胞的八个角上各有一个原子外,立方体的中心还有一个原子。具有体心立方结构的金属有30多种,如α-fe、cr、v、nb、mo、w等。原子半径为1的原

子沿着物体的对角线紧密接触。如果晶胞的晶格常数(或晶格常数)是a,那么立方体的对角线的长度就是四个原子半径之和。因此,体心立方晶胞中原子半径为2的晶胞的原子序数是因为晶格

关键词: 材料   金属   金属化   热处理  
温馨提示:“主要材料检验总结:| 829、92金属化及干货热处理”信息由发布人自行提供,其真实性、合法性由发布人负责。交易汇款需谨慎,请注意调查核实。

网站首页 | 关于我们 | 联系方式 | 交易须知 | 免责声明

©2020 热批发网版权所有 All Rights Reserved    豫ICP备18040082号-4