2Do Informe Cristalizacion TINOCO

Nationa tio nall University Universit y of o f Engine ngin eering FACULTY FACUL TY OF ENGINEERI ENGINEERING NG GEOLOGICAL, GEOLOGICAL , MINING AND METALLURGICAL-FIGMM

STRUCTURE STRUCTURE AND A ND PROPERTIES PROPERTIES OF MATERIALS MATERIA LS I-524R Report: RECRYSTALLIZATION Name:

Tinoco Falero Junior Anderson

Code:

20132220B

Professor:

Ing. Manuel Cruz Torres

LIMA - PERU 2017

ESTRUCTURA Y PROPIEDADES DE LOS MATERIALES: RECRISTALIZACIÓN

Index Objectives …………………………………………………………….... Pág. 2

Theoretical basis …………………………………………….......

Equipment and Materials

Experimental procedure

Pág 3-6

……………………………………………. Pág 7

……..……………………….……...

Pág 7-9

Results ………………..……………………………………………...... Pág 10-18

Conclusions

……………………………………………………....

Pág 19

Recommendations……………………………………………………… Pág 19

Bibliography …………………………….………………………...

Pág 20

Questionnaire

Pág 21-29

Annexs

….……………………………………………………

………………………………………………………….

Natio nal UNIVERSITY OF ENGINEERING - FIGMM - 2017-II

Pág 30-31

1


Objectives I. II.

III.

To study the effect of annealing time on the crystallization to specimens of ASTM A36 steel worked in cold (wires). Determine the average grain size, according to the ASTM E112, for specimens of ASTM A36 steel annealed at different times and to determine the effect of annealing time on the average grain size. Determine the effect of the degree of crystallization on the hardness of the steel ASTM A36.


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Theoretical basis An neal i n g o f t he m at er i al s def or m ed Metallic materials harden when deformed (phenomenon of acrimony and soften when they are annealed. This behavior has been known to man since the beginning of our civilization, and today it is exploited in the industrial production of metals and alloys using the thermo mechanical treatment. During thermomechanical treatment, the metal is exposed to a force of plastic deformation, that hardens and at a high temperature, which leads to a softening either during or after deformation . A thermomechanical pulping process can, for example, be in hot, cold rolling or cold-rolled followed by an annealing, that is to say, a thermal treatment at elevated temperatures. The exposure to the strength and temperature gives rise to the dynamic processes of recovery and recrystallization dynamics. In the case in which the heat (annealing) is applied after the deformation, the processes that are given are the recovery, the recrystallization and grain growth. These processes directly affect the properties of the metal (Figure 1 and 2). This is because there are substantial and important relationships between the structure of metallic materials and their properties.


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Figure N°1: Change of hardness, electrical resistivity and stored energy (represented by a differential of power) for the treatment of pure copper deformed.

Figure N°2: elastic limit (YS) and the ultimate tensile strength (UTS) at room temperature after warming up a sheet of aluminum foil in cold weather.


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2.2. Determi natio n of the average gr ain size The determination of the size of grain is a measurement is very important for the characterization and development of materials, as well as for quality control i n the manufacturing process. The grains are crystals of i rregular shapes whose spatial dimensions are very difficult to measure. The STEREOLOGY allows to infer properties of three-dimensional bodies from their projections in a plane; that is, flat obtained from cross sections of the bodies. There are several methodologies to measure the size of grain on a surface properly prepared and then convert them mathematically in space estimators of grain size. The measurements are usually performed on microstructural features zero, uni-dimensional and the grain size is expressed in units of Linear or two-dimensional (lengths and areas).

The ASTM E112, standard method to determine the size of grain, covers four methods, which are the following: • Planimetric Method or Jeffries • Method of Abrams • Method of Heyn • Method of Hilliard For this job is going to perform the measurement of the size of grain by the method of Jeffries, detailing this procedure.

2.2.1. Method planimeter of Jeffries In the planimetric procedure is part of a circle or rectangle of area known (usually 5000 mm2 to simplify the calculation) in an electron micrograph or glass on the screen, you must select an extension to give you at least 50 grains in the f ield to be counted (this to give more accurate results). Then when the image is centered correctly, count the number of grains within that area, the sum of all the grains included completely within the area known more than half of the number of kernels cut by the circumference of the area gives the number of grains equivalent, as measured by the extension used, within the area. If this number is multiplied by the multiplier of Jeffries, f, the product will be the number of grains per square millimeter NA . The number of grains per square millimeter at 1X, NA , is calculated from: Natio nal UNIVERSITY OF ENGINEERING - FIGMM - 2017-II

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 =  (  +  2 )…………………..ó °1 Where:

: Jeffries (  = ) M: Magnification used To: Area in square millimeters.

After taking this value you can go to tables (see annex 2), or by using the following equation to calculate the value of G (number of grain size according to ASTM).

 = 3.321928   − 2.954……………….ó ° 2 It should be noted that the equation N°1 is valid for circles, but for this job will work with square, due to reasons that will be explained below, whose formula is also covered in the standard and is the following:

   =  (  +  2 + 1)…………..ó °3


6


Equipment and Materials The equipment used in the experimental procedure were:

1. Pieces of wire drawing steel ASTM A36.

Figure N°3: Measuring cylinder of steel ASTM A36.

2. Sandpaper Number # 150, 200, 300, 400, 600, 800.1000, alumina 0.5um 2um and nital respectively.

metallographic

preparation

Figure N°4: Equipment preparation.


for

the

and

chemical

attack

metallographic

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3. Oven for heat treatment.

Figure N°5: oven for heat treatment of metals (relays).

4. Metallographic microscope.

Figure N°6: metallographic microscope (Zeiss).


8


EXPERIMENTAL PROCEDURE 1. In the first place, is the metallographic preparation of the specimens of steel (ASTM A36), for this case are six test pieces.

2. Once the metallographic preparation (up to the alumina) proceeds with the heat treatment in the oven, 6 recociendo The pieces to 450°C and 600°C, but with different times of annealing and previously the six specimens without treatment are the development of microstructure (to be used as a standard), as detailed in the table below. Table N°1: annealing times for each

Annealing Temperature: 450°C 0°C 51°C 450°C 450°C Table N°2: annealing times for each

Annealing Temperature: 600°C 0 °C 51 °C 600 °C 600 °C

test piece at 450°C.

Time of annealing 0 minutes 5 minutes 47 minutes 167 minutes test piece at 600°C.

Time of annealing 0 minutes 5 minutes 67 minutes 162 minutes

3. Once the heat treatment is applicable to the development of the microstructure (but not before giving a polished thin the test tubes) using chemical reagents suitable for this case is use the nital to 2.5%.


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RESULTS 1. Metalografias of the cylinders : LAS SEIS PROBETAS STANDARD TRACCIONADAS Probeta 1:

Figura N°7: Probeta 1 estándar (sin tratamiento térmico) donde se observan los granos deformados, 500x.

Probeta 2

Figura N°8: Probeta 2 estándar (sin tratamiento térmico) donde se observan los ranos de ormados, 500x


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Probeta 3:

Figura N°9: Probeta 3 estándar (sin tratamiento térmico) donde se observan los granos deformados, 500x

Probeta 4:



11


Probeta 5:


Probeta 6:



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LAS SEIS PROBETAS TRATAMIENTO TÉRMICO 450°C Probeta 1:

Figura N°13: Probeta 1 con tratamiento térmico 450 °C donde se observan casi todos los granos ya cristalizados,500x.

Probeta 2

Figura N°14: Probeta 2 con tratamiento térmico donde se observan casi todos los granos ya cristalizados, 500x.


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Probeta 3:

Figura N°15: Probeta con tratamiento térmico donde se observa dos zonas con diferentes tamaños de grano, 50 0x.

Probeta 4:

Figura N°16: Probeta con tratamiento térmico donde se observan todos los granos ya cristalizados,500x.


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Probeta 5:


Probeta 6:



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LAS SEIS PROBETAS TRATAMIENTO TÉRMICO 600°C Probeta 1:

Figura N°19: Probeta 1 con tratamiento térmico a 600 °C donde se observan los granos deformados, 500x.

Probeta 2

Figura N°20: Probeta con tratamiento térmico donde se observan casi todos los granos ya cristalizados, 500x.


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Probeta 3:

Figura N°21: Probeta con tratamiento térmico donde se observa dos zonas con diferentes tamaños de grano, 50 0x.

Probeta 4:



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Probeta 5:

Figura N°23: Probeta 5 con tratamiento térmico donde se observan todos los granos ya cristalizados,500x.

Probeta 6:

Figura N°24: Probeta 6 con tratamiento térmico donde se observan todos los granos ya cristalizados,500x.


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Conclusions 1. The annealing time significantly influences the degree of crystallization and about the size of grain crystallized and this influences the mechanical properties of the material, that is to say, more time of annealing decreases the temperature of recrystallization.

2. Once you reach the complete crystallization and recociendo annealing (longer) increases the size of grain influencing negatively on the mechanical properties of the material.

3. The main objective of the annealing is to reduce the excessive hardness of the material product of the phenomenon of "sourness" and this is with the recrystallization as shown in TABLE N° 1 and N° 2.

4. When an excessive amount of time of annealing occurs the process known as "Grain" that is the growth of grain, so that the hardness decreases to values lower than his cold worked and this is a negative aspect in the material by what must be avoided.

5. Another important factor to point out for the crystallization is the degree of deformation of the material that translates into elastic energy stored and this is the cause of the existence of the recrystallization of the material. The greater the degree of deformation it is said that decreases the temperature of recrystallization of the material.

Recommendations 1. It is recommended to work carefully in the metallographic preparation and especially in the chemical attack to avoid burning the specimen is tested with different times and different concentrations of reagent Nital, for this case used the reagent with a concentration of 2.5%.

2. For the measurement of the size of grain before everything must be calibrated by means of the microscope micrometers in order to have a real scale of the image and be able to work properly as you said the ASTM E 112.

3. The method of Jeffries tells us that we can work with circles or rectangles, but for this case is going to work with rectangles since the error is less than working with circles as will be explained below.


19


Bibliography 1. SYDNEY H.AVNER (1988). Introduction to the Physical Metallurgy. Mc Graw Hill.

2. ASTM International - E112 - 10. Current edition approved Nov. 1, 2010. Published December 2010.Originally approved in 1955. Last previous edition approved 2004 as E112 - 96(2004). United States.

3. TASM

INTERNATIONAL (1987). Metal's METALLOGRAPHY and Structure.

Handbook

Volume

09

4. "Evaluation of the estimation methods for the measurement of grain size, and effects the size of grain in the microhardness", University Thesis, Lima-peru, 2013.

5. "Theory of the recrystallization", Ing. July Uzzah Teruya, class notes, Lima-peru, 2016.


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Questionnaire 1.

Mechanisms that occur in the recovery phase, recryst allization and grain size. Plastically deforms when a metal at temperatures well below its melting point, it is said that the metal has been cold worked. Most of the energy used in this deformation is dissipated as heat, storing a small fraction as deformation energy. The latter is accumulated in the form of dislocations and point defects, for example: broken links and vacancies. How increasing the density of dislocation is not smooth, there are areas of higher density, which leads to the generation of cells. When heated this material occur two processes that decrease the internal energy stored, recovery and recryst allization. In addition to the above-mentioned processes and depending on the time and the temperature at which heat the material, there may be a third process called grain grow th , this occurs when annealing is continued after the completion of the recrystallization.

Recovery mechanisms: The recovery is the first stage of the annealing process. The relief of internal efforts caused by cold working, ( residual stresses), on the other hand, microstructural changes and modification of some properties, among which we can highlight: the annihilation of point defects, the poly and the decrease in electrical resistance.


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Temperature Low

Mechanism 

Migration of point defects toward sinks (grain boundaries, dislocations, etc.)

Media

High



Combination of point defects



New array of dislocations



Annihilation of dislocations



Growth of subgranos



Climbed dislocations



Agglutination of dislocations



Poly

Of recrystallization mechanisms: The recrystallization occurs due to the nucleation and growth of new grains that contain few dislocations. The growth of these new grains occurs at the edges of the cell structure pollinated, eliminating most of the dislocations. The new recristalizados grains taken at more or less regular forms, due to the anisotropies their rate of growth. When beans come in contact with each other, it is just the phase knock recrystallization and enters the phase called grain growth. How has significantly reduced the number of dislocations, the metal recrystallized has low resistance, but a high ductility.

Grain grow th mechanisms: In a metal completely crystallized, the driving force for the growth of the grains corresponds to the decrease in the energy associated with the edges of grain. The growth of the new grain is produced by movement of the recrystallized grain-grain interface deformed. The edges of grain tend to move toward the center of the curve. The angle between three edges of grain is of about 120°. Natio nal UNIVERSITY OF ENGINEERING - FIGMM - 2017-II

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2.

Describe and substantiate the acrimony and annealing. The acrimony:

It is a mechanical property that acquire the metals as a result of the cold deformation, also known as hardening process by acrimony, that increases its hardness, brittleness and resistance, although the loss, at the same time, its ductility and malleability. In fact, the materials with a high pungency are also referred to as citrus fruits.

The annealing: It is one tratamiento térmico of whose purpose is the softening, the recovery of the structure or the elimination of internal tensions generally in metals.Any metal that has been treated has resulted in an alteration of the physical properties of the same. The annealing consists in heating the metal to a certain temperature to then leave it to cool slowly, usually, by turning off the oven and leaving the metal in its interior to its temperature decreases gradually. The process ends when the metal has reached room temperature. Through the combination of several jobs in cold and several soft annealed coils are able to obtain large deformations in metals that, otherwise, we would not be able to achieve.

Anneal ing against acrimony The acrimony against annealing is a heat treatment of metals whose goal is to return to the metal, that has gone through a cold deformation, features such as the plasticity, ductility, toughness, in addition to eliminating internal tensions, all of which results in that the metal retrieves conditions to be worked again. It is a process that has three phases: heat the material up to the annealing temperature, keep it at that temperature for a period of time, and, finally, let it cool down slowly and gradually.


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3. The

photomi crographs

of

the

measuring

standard

and

recristalizadas to 450 °C and 600 °C. Find the speed of global warming oven yes ( 600 °C= 27 minut es and 450 °C). T 450°C : Time (min)

T °C

0 5 47 167

0 51 450 450

Note: Due to the fact that they took a few points cannot be taken as a heating profile, since according to criterion was due to take temperature every 30 minutes

Rate of heating The Oven 450° C 500 450 400 C ° 350 e r 300 u t a r 250 e p 200 m e T 150

Speed global warming

100 50 0 0

50

100

150

200

Time (minutes)

T 600°C : Time (min)

T °C

Note: Due to the fact that they took a

0 5 67 162

0 51 600 600

few points cannot be taken as a


heating profile, since according to criterion was due to take temperature ever 30 minutes

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9.54552276


Rate of heating of the Oven 600° C 700 600 500 C ° e r u t 400 a r e 300 p m e T 200

Pending= speed

100 0 0

50

100

150

200

Time (minutes)

Speed global warming

8.91277818

4. Find the grain size of the measuring standards ASTM A36 of recryst allization temperature to 450 °C and 600 °C by the planimetric method of J EFFRIES. and method of Hillary. As we mentioned before is going to perform this method by using rectangles, as this avoids the error produced by the count of grains in the circumference using the equation N°3.

   =  (  +  2 + 1)…………..ó °3 1-piece: "Standard" Steps: 1) Using the Image program "J" we opened the image and to put my scale of work:


25


Where:

=


26


2) By using the tools then selects the first rectangle in the first quadrant in the following way:

3) Then we proceed to improve the image to count the grains inside and the queestan that intersect the rectangle:


27


4) The data found are the following:

=500  = 16  = 12  = 520.576  Replacing in the equation N°3:

 500  = 520.576 ( 16 + 122 + 1)

 =11045.46   , 1 Replacing in the equation N°2:

 = 3.321928   − 2.954……………….ó ° 2  = 10.4771 Approaching this value to your nearest integer:

=10 In the same way you work for the following rectangles, way to have grain sizes since metalografias for each test piece


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5. Define Ostwald ripening in recrystallization for both liquids and solids. The molecular diffusion or Ostwald r ipening is an observed phenomenon in solid or liquid solutions soles that describes the change of a homogeneous structure with time. With time, the small crystals or particles of sun dissolved, and become deposited in large crystals or particles of sun.[] The dissolution of small crystals or particles of sun and soil redeposition of the species dissolved in the surfaces of the larger crystals or particles of sun was described for the first time Wilhelm Ostwald in 1896.[] Ostwald ripening is usually found in water-in-oil emulsiones, while the floculación is in oil-in-water emulsions

Figure N°25: outline of the process of ripening Ostwald


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X. Annexs 1. Digital Archive.


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2Do Informe Cristalizacion TINOCO

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