Material Science Foundation - The most comprehensive explanation of the history

1, crystal

The atoms are periodically and regularly arranged in a three-dimensional space in a certain way, with a fixed melting point and anisotropy.

2, the middle phase

When the two groups of elements A and B are alloyed, in addition to the formation of A-based or B-based solid solution, it is possible to form a new phase with a crystal structure different from that of the A and B groups. Since their position on the binary phase diagram is always in the middle, these phases are often referred to as intermediate phases.

3, metastable phase

Metastable phase refers to a phase that cannot be stably existed thermodynamically, but which is temporarily stable due to thermodynamic energy barrier or kinetic factors during rapid cooling to heating.

4, coordination number

The nearest neighbor and equidistant number of atoms around any atom in the crystal structure.

5, recrystallization

After the cold-deformed metal is heated to a certain temperature, new undistorted grains are regenerated in the original deformed structure, and the properties are also changed significantly and restored to the state before the deformation. This process is called recrystallization. (refers to the process of the unequalized equiaxed new grains gradually replacing the deformed grains)

6, pseudo eutectic

Under non-equilibrium solidification conditions, some sub-eutectic or hypereutectic alloys can also obtain the entire eutectic structure. The eutectic structure obtained from the non-eutectic alloy is called pseudo-eutectic.

7, cross slip

When the movement of a screw dislocation on the original slip surface is blocked, it is possible to transfer from the original slip surface to the other slip surface intersecting it to continue the slip. This process is called cross slip.

8, over time

After the solution treatment of the aluminum alloy, the GP zone, θ ′, θ ', and θ will be precipitated in the process of heating and heat preservation. At the beginning of the heat preservation phase, the hardness strength increases with the heat preservation time, and when the heat preservation time is too long, the precipitation will occur. θ ', at this time the hardness of the material will decrease, this phenomenon is called overaging.

9, deformation strengthening

After cold plastic deformation, the strength and hardness of the metal increase, and the ductility and toughness decrease. This phenomenon is called deformation strengthening.

10, solid solution strengthening

The strength of the metal-based alloy is enhanced by the addition of alloying elements (impurities).

11, dispersion strengthening

Many materials consist of two or more phases. If one of the phases is a fine particle and is dispersed in the material, the strength of the material tends to increase, called diffusion strengthening.

12, not all dislocations

A dislocation in which the Bob's vector is not equal to an integer multiple of the lattice vector is called a total dislocation.

13, extended dislocation

Usually refers to a full dislocation decomposition into two incomplete dislocations, with a stacking fault in the middle of the entire dislocation pattern.

14, screw dislocation

Dislocations in which atoms near the dislocation line are arranged in a spiral shape are called screw dislocations.

15, peritectic transformation

In the binary phase diagram, a peritectic transformation is a constant temperature transition in which a solid phase that has crystallized reacts with the remaining liquid phase to form another solid phase.

16, eutectic transformation

A transition of two different solid phases is produced by one liquid phase.

17, eutectoid transformation

The transformation of the other two different solid phases is obtained by a solid phase decomposition.

18. Uphill spread

The process by which solute atoms diffuse from a low concentration to a high concentration is called uphill diffusion. The driving force indicating diffusion is a chemical level gradient rather than a concentration gradient.

19. Gap diffusion

This is a mechanism of atomic diffusion. For interstitial atoms, due to its small size, it is in the lattice gap. When diffusing, the interstitial atoms jump from one gap position to another adjacent gap position to form an atom. mobile.

20, the ingredients are too cold

The actual temperature in the liquid at the interface leading edge is lower than the supercooling produced by the solidification temperature determined by the solute distribution.

21, the first phase change

Where the chemical positions of the old and new phases are equal, the primary polarization of the chemical sites is not equal.

22, secondary phase change:

From the phase transition thermodynamics, the free energy (ç„“) of the two phases before and after the phase transition is equal, the first-order partial derivatives of the free energy (ç„“) are equal, but the phase transitions with the second-order partial derivatives are called the second-order phase transition. Magnetic transition, ordered-disorder transition, constant-superconducting transition, etc.

23, coherent phase boundary

If all the atoms on the two-phase interface have a one-to-one correspondence, that is, the atoms on the interface are simultaneously at the nodes of the two-phase lattice, which are common to the adjacent two crystals, the phase boundary is called a total The phase boundary.

24, amplitude modulation decomposition

The process of decomposing a supersaturated solid solution into two phases of the same structure and different compositions at a certain temperature.

25, temper brittleness

In the tempering process, the plasticity and toughness of the hardened steel generally increase with the increase of the tempering temperature. However, in the specific tempering temperature range, the phenomenon of the decrease in toughness is called temper brittleness. There are first and second types of temper brittleness for steel materials. Their temperature ranges, influencing factors and characteristics are different.

26. Recrystallization annealing

The so-called recrystallization annealing process generally refers to a process of heating the cold-deformed metal to a temperature above the recrystallization temperature, and then slowly cooling to room temperature after being kept for a while.

27. Tempered Soxite

Quenched tempering structure formed immediately after tempering at a temperature of 400-600 ° C, consisting of equiaxed ferrite and fine granular (worm-like) cementite.

28. Ordered solid solution

When one component is dissolved in another component, each component atom occupies a solid solution of the respective Bravais lattice, forming a solid solution in which the ordered atoms of each component are arranged, and the solute is completely in the lattice. Ordered.

29. Non-uniform nucleation

The new phase preferentially nucleates at the heterogeneous phase present in the parent phase, ie impurities attached to the liquid phase or nucleation of the foreign surface.

30. Martensitic transformation

The phase transition of a high-hardness needle-like structure formed by rapid quenching after heating to austenite in steel.

31. Bainite transformation

The transformation of steel below the pearlite transformation temperature and above the martensite transformation temperature (550 °C - 230 °C) is called bainite transformation.

32, aluminum alloy aging

The phenomenon that the strength and hardness of the quenched aluminum alloy increase significantly with time is called aging, which is also called the aging of aluminum alloy.

33. Thermoelastic martensite

The martensitic transformation causes elastic strain, and when the elastic deformation is applied, the martensite transformation can be reversely transformed. This martensite is called thermoelastic martensite. Or martensitic transformation is coordinated by elastic denaturation. This martensite is called thermoelastic martensite.

34, Kirkendall effect

Reflecting the diffusion mechanism of the replacement atom, two pure components constitute a diffusion couple. During the diffusion process, the interface will move toward the side of the component with a fast diffusion rate.

35. Thermoelastic martensitic transformation

When the shape change of the martensitic transformation is coordinated by elastic deformation, it is called a thermoelastic martensitic transformation.

36, amorphous

Atoms have no long-range periodic arrangement, no fixed melting point, isotropy, etc.

37, density

The atomic volume in the crystal structure as a percentage of the total volume.

38, more slip

Simultaneous slip occurs when the external force has equal shear stress on several slip systems and simultaneously reaches the critical shear stress.

39, undercooling

During the phase change, the transition occurs after cooling to a temperature below the phase transition point, and the difference between the equilibrium phase transition temperature and the actual transition temperature is referred to as subcooling.

40, gap phase

When the ratio of the atomic radius of the non-metal (X) to the metal (M) is rX/rM < 0.59, a phase having a simple crystal structure is formed, which is called a gap phase.

41, full dislocation

A dislocation in which a Bosch vector is equal to a lattice vector or an integer multiple thereof is referred to as a full dislocation.

42. Slip system

The combination of a slip surface in the crystal and a slip direction on the surface is called a slip system.

43. Divorced eutectic

The α phase in the eutectic is attached to the growth of the primary α phase, and the other phase β in the eutectic is pushed to the final solidified grain boundary, so that the structural characteristics of the two phases of the eutectic phase disappear, and the two phases are separated. The crystal is called a divorced eutectic.

44, uniform nucleation

The new phase nucleus is uniformly grown in the parent phase, that is, the crystal nucleus is directly formed by some atomic groups in the liquid phase, and is not affected by the impurity particles or the outer surface.

45, edge dislocation

A crystal plane in the crystal has an extra half-row atomic plane in its upper half, as if a blade is inserted into the crystal, causing atomic misalignment between the two crystals on the surface of the crystal, called the edge type. Dislocation.

46, fine grain strengthening

The finer the crystal grains, the longer the total length of the grain boundaries, the greater the hindrance to dislocation slip, and the higher the yield strength of the material. Grain refinement leads to an increase in grain boundaries, and the slip of dislocations is hindered, thus increasing the strength of the material.

47, double cross slip

If the dislocation after the slip is transferred back to the sliding surface parallel to the original slip surface, it is called double cross slip.

48, unit dislocation

A dislocation in which a Bosch vector is equal to a unit lattice vector is referred to as a unit dislocation.

49, reaction diffusion

The diffusion that forms a new phase with a chemical reaction is called reaction diffusion.

50, grain boundary segregation

The enrichment of solute atoms or impurity atoms on the grain boundaries due to the difference in distortion energy between the crystal and the grain boundaries or due to the presence of vacancies.

51, Koch's air mass

Usually, after the solute atoms interact with dislocations, the phenomenon of segregation around dislocations is called air mass, which was first proposed by Kodul, also known as Kodak air mass.

52. Deformation texture

The phenomenon of crystallographic orientation that occurs during the deformation of polycrystals is called deformation texture.

53. Dot matrix distortion

In the local range, the atoms deviate from their normal lattice equilibrium position, causing lattice distortion.

54. Steady state diffusion

During steady state diffusion, the concentration of the diffusion component changes only with distance and does not change with time.

55, analysis reaction

The process of obtaining a solid phase from two solid phase reactions is an encapsulation reaction.

56. Non-coherent grain boundaries

When the atomic arrangement of the two phases at the phase boundary is very different, that is, when the mismatch δ is large, a non-coherent grain boundary is formed. Similar to the large-angle grain boundary, it can be seen as a very thin transition layer that is irregularly arranged by atoms.

57. Replacement solid solution

When a solute atom is dissolved in a solvent to form a solid solution, the solute atom occupies the lattice of the solvent lattice, or the solute atom replaces part of the solvent atom of the solvent lattice. This solid solution is called a replacement solid solution.

58. Interstitial solid solution

A solid solution in which a solute atom is distributed in a solvent lattice gap is referred to as a gap solid solution.

59, secondary recrystallization

A phenomenon in which a small number of crystal grains abnormally grow when normal growth is suppressed after the completion of recrystallization.

60, pseudo-eutectoid transformation

In the process of non-equilibrium transition, the hypoeutectoid and hypereutectoid alloys near the eutectoid component point are all in the form of eutectoid organization.

61, Schottky vacancies

In an individual's crystal, when an atom has sufficient vibrational energy to increase the amplitude to a certain extent, it may overcome the restriction of the surrounding atoms, jump away from its original position, and migrate to the crystal surface or inner surface. The normal junction position leaves a vacancy inside the crystal, called the Schottky vacancy.

62, Frankel vacancies

The atoms leaving the equilibrium position squeeze into the interstitial locations in the lattice while forming equal numbers of vacancies and interstitial atoms in the crystal.

63, non-steady state diffusion

The concentration of the diffusion component varies not only with the distance x but also with time as the non-steady state diffusion.

64, timeliness

The supersaturated solid solution is subsequently subjected to a solute atom desolvation process at or above room temperature.

65, reply

Refers to the stage of substructure and performance changes that occur before the emergence of new undistorted grains.

66, phase law

The phase law gives the relationship between the number of phases and the number of components and the temperature and pressure in the equilibrium state. It can be expressed as: f=C+P-2, f is the degree of freedom of the system, and C is the system. The number of components, P is the number of phases.

67, alloy

Two or more metals or metals and non-metals are combined by melting, sintering or other methods and have metallic properties.

68, twin

Twinning refers to the fact that two crystals (or two parts of a crystal) form a mirror-symmetric orientation along a common crystal plane. These two crystals are called twins, and the common crystal plane is called twin plane.

69, phase diagram

A diagram depicting the existence or coexistence of equilibrium in each phase, also known as the geometric trajectory of the thermodynamic parameters at equilibrium.

70, twins

After the crystal is stressed, the shearing process in the manner of generating twins is called twinning.

71, grain boundary

The grain boundary is the interface between the same crystal grains having the same compositional structure.

72, unit cell

A representative basic unit (minimum parallelepiped) is taken out in the lattice as a constituent unit of the lattice, called a unit cell.

73. Dislocation

It is a kind of line defect in the crystal, which is characterized by the regular misalignment of atoms along a line; such defects are described by a line direction and a Berth's vector.

74, segregation

Inhomogeneity of chemical composition in the alloy.

75, metal key

The bonding force generated by the electrostatic interaction between free electrons and the nucleus.

76, solid solution

It is a uniformly mixed solid solution formed by dissolving a certain element atom (solvent atom) in a crystal lattice of a certain component as a solvent, which maintains the crystal structure type of the solvent.

77, subgrain

A number of grains in which a plurality of phases are slightly different in one grain are referred to as subgrains.

78, sub-grain

The interface between adjacent subgrains is called the subgrain boundary.

79, grain boundary energy

Whether it is a small-angle grain boundary or a large-angle grain boundary, the atoms here are more or less deviated from the equilibrium position, so the grain boundary is in a higher energy state relative to the inside of the crystal, and the higher part of the energy is called the grain boundary. Can, or the free energy of the grain boundary.

80, surface energy

The surface atoms are in an uneven force field, so their energy is greatly increased, and the higher energy is called surface free energy (or surface energy).

81, interface energy

The atoms on the interface are in a broken state with excess energy. The excess energy on average per unit area of ​​the interface is called interface energy.

82, hardenability

Hardenability refers to the ability of an alloy to be quenched into martensite, mainly related to critical cooling rate, and the size is expressed by the depth of the hardened layer.

83, hardenability

Hardenability refers to the highest hardness that steel can achieve after quenching, mainly related to the carbon content of steel.

84, habitual face

In the solid phase transition, the new phase tends to form at a certain crystal plane of the parent phase, which is called the habit.

85, Sorbite

The pearlite transformation product in the middle temperature section is composed of flaky ferrite cementite, the interlayer spacing is small, and the sheet layer is thin.

86, pearlite

The product of the eutectoid transformation of iron-carbon alloy is a lamellar mixture of eutectoid ferrite and eutectoid cementite.

87, Leysite

The product of the iron-carbon phase diagram eutectic transformation is a mechanical mixture of eutectic austenite and eutectic cementite.

88, Berkeley vector

An important vector describing the dislocation feature, which reflects the magnitude and direction of the total amount of distortion in the dislocation area, and also the amount of relative sliding of the crystal after the dislocation is swept.

89. Space lattice

It refers to the three-dimensional array formed by the regular arrangement of geometric points in a three-dimensional space, which is an artificial abstraction of the crystal structure.

90, Van der Waals key

A physical bond made up of intermolecular gravitational forces generated by an instantaneous dipole moment and an induced dipole moment.

91, dislocation slip

The dislocation motion of the dislocation line moving along the slip surface under a certain stress.

92, heterogeneous nucleation

The nucleus is formed in the liquid metal by virtue of the surface of the foreign matter or at a temperature unevenness.

93, structural fluctuations

The atomic arrangement of the liquid structure is long-range disorder, short-range order, and the short-range ordered atomic group is not fixed. It is a structure that is constantly changing, rapidly changing, and unstable in size. This phenomenon is called structural fluctuation.

94, the principle of gravity

For alloys in a three-phase equilibrium, the component points must be located at the center of gravity of the conjugate triangle.

95, strain aging

After the first stretching, a second stretching is performed immediately, and the yielding phase does not appear on the stretching curve. However, after the first stretched low carbon steel sample is allowed to stand for a second time at room temperature, a yielding phase appears again on the tensile curve. However, the strength of yielding again is higher than the strength of the initial yielding. This test phenomenon is called strain aging.

96, dendritic segregation

Under the condition of non-equilibrium cooling, the composition of the newly obtained solid solution grains is not uniform after the homogenization, the core of the first crystal contains more high-melting group atoms, and the outer edge of the crystal contains more The low melting point of the constituent atoms, and usually the solid solution crystal grows in a dendritic manner. Thus, the branches contain more high melting point components, and the branches contain many low melting point constituent atoms, resulting in unevenness of internal components of the same crystal grain. .

97, critical deformation degree

The minimum amount of pre-cold deformation required for recrystallization of the metal at a given temperature.

98, electronic compounds

An electronic compound is a class of compounds whose crystal structure is determined by the concentration of major electrons, also known as the Hume-Roserite phase. Where the same electron concentration is present, the crystal structure type of the phase is the same.

99, isomer

The chemical composition is the same as the different crystal structures formed due to different thermodynamic conditions.

100, recrystallization temperature

The deformed metal just completes the minimum temperature of recrystallization within a certain period of time (generally 1 h).

101, Brafi dot matrix

In addition to considering the shape of the unit cell, the lattice formed by the position of the lattice is also considered.

102, coordination polyhedron

A polyhedron composed of atoms or ions that are directly adjacent to an atom or ion, and is called a coordination polyhedron of an atom or ion.

103, Schmidt factor

Also known as the orientation factor, it is cosΦcosλ, Φ is the angle between the slip plane and the center axis of the external force F, and λ is the angle between the slip direction and the external force F.

104, topological close phase

A type of mesophase consisting of two metal atoms of different sizes, in which the large and small atoms form a complex structure with high space utilization and coordination number by appropriate coordination. Since such structures have topological features, these phases are referred to as topologically dense phases.

105, gap compound

When the ratio of the atomic radii of the non-metal (X) to the metal (M) is rX/rM &gt; 0.59, a phase having a complicated crystal structure is formed, which is generally called a gap compound.

106, large angle grain boundary

The grain boundary between the crystal grains in the polycrystalline material is called a large-angle grain boundary, that is, a grain boundary in which adjacent crystal grains have a phase difference of more than 10 o .

107, small angle grain boundary

The phase difference between adjacent subgrains is less than 10 o . The grain boundary between subgrains is called small angle grain boundary, generally less than 2 o , and can be divided into oblique grain boundary, torsional grain boundary, coincidence grain boundary, etc. .

108, critical slitting stress

The minimum shear stress required for the slip system to act; it is a fixed value that is related to the nature of the material itself and is independent of the orientation of the external force.

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