Iron Carbon Phase Diagram Questions And Answers Pdf
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It is related to consistency in the physical and chemical characteristics of the phase with respect to time.
- Classification of Steels and Alloy Steels - Mechanical Engineering (MCQ) questions and answers
- Phase Diagram
- Microstructure and Properties
- Iron-Carbon Phase Diagram Explained
Classification of Steels and Alloy Steels - Mechanical Engineering (MCQ) questions and answers
Stop wasting time on admin! Order your sheet metal fabrication online. Immediate pricing and short lead times all over the UK. Alloy metals can exist in different phases. Phases are physically homogeneous states of an alloy. A phase has a precise chemical composition — a certain arrangement and bonding between the atoms. This structure of atoms imparts different properties to different phases. We can choose the phase we want and use it in our applications.
Only some special alloys can exist in multiple phases. Heating the metal to specific temperatures using heat treatment procedures results in different phases. Some special alloys can exist in more than one phase at the same temperature. Phase diagrams are graphical representations of the phases present in an alloy at different conditions of temperature, pressure, or chemical composition. The diagram describes the suitable conditions for two or more phases to exist in equilibrium.
For example, the water phase diagram describes a point triple point where water can coexist in three different phases at the same time. This happens at just above the freezing temperature 0. When it comes to alloy development, phase diagrams have helped prevent overdesign for applications. This keeps cost and process time down. They also help develop alternative alloys or same alloys with alternative alloying elements.
It can help to reduce the need for using scarce, hazardous, or expensive alloying elements. Performance-wise, phase diagrams help metallurgists understand which phases are thermodynamically stable, metastable, or unstable in the long run.
Appropriate elements can then be chosen for alloying to prevent machinery breakdown. Material for exhaust piping, for example, if not chosen properly, may lead to breakdown at higher temperatures. The service life also improves as phase diagrams show us how to solve problems such as intergranular corrosion, hot corrosion, and hydrogen damage. The iron-carbon phase diagram is widely used to understand the different phases of steel and cast iron.
Both steel and cast iron are a mix of iron and carbon. Also, both alloys contain a small amount of trace elements. The graph is quite complex but since we are limiting our exploration to Fe3C, we will only be focusing up to 6. This iron carbon phase diagram is plotted with the carbon concentrations by weight on the X-axis and the temperature scale on the Y-axis.
The carbon in iron is an interstitial impurity. Up to a maximum carbon content of 0. From 0. Within this range, there are different grades of steel known as low carbon steel or mild steel , medium carbon steel, and high carbon steel. When the carbon content increases beyond 2. Cast iron is very hard but its brittleness severely limits its applications and methods for forming.
As the temperature of the metal increases or decreases, phase change occurs at these boundaries when the temperature reaches the value on the boundary. Normally, when heating an alloy, its temperature increases. But along these lines A1, A2, A3, A4, and ACM the heating results in a realignment of the structure into a different phase and thus, the temperature stops increasing until the phase has changed completely.
This is known as thermal arrest as the temperature stays constant. Alloy steel elements such as nickel, manganese, chromium, and molybdenum affect the position of these boundaries on the phase diagram.
The boundaries may shift in either direction depending on the element used. For example, in the iron carbon phase diagram, addition of nickel lowers the A3 boundary while the addition of chromium raises it. Eutectic point is a point where multiple phases meet.
The formation of these points is coincidental. At these points, eutectic reactions take place where a liquid phase freezes into a mixture of two solid phases. This happens when cooling a liquid alloy of eutectic composition all the way to its eutectic temperature. The alloys formed at this point are known as eutectic alloys.
Within each region, a different phase or two phases may exist together. At the boundary, the phase change occurs. These regions are the phase fields. They indicate the phases present for a certain composition and temperature of the alloy.
This phase is stable at room temperature. In the graph, it can be seen as a sliver on the left edge with Y-axis on the left side and A2 on the right. It has a maximum carbon content of 0. This phase is a solid solution of carbon in FCC Fe with a maximum solubility of 2. This phase is non-magnetic. The phase can be spotted at the top left corner in the graph. Cementite is a metastable phase of this alloy with a fixed composition of Fe3C.
It decomposes extremely slowly at room temperature into Iron and carbon graphite. This decomposition time is long and it will take much longer than the service life of the application at room temperature. Some other factors high temperatures and addition of certain alloying elements for instance can affect this decomposition as they promote graphite formation. Cementite is hard and brittle which makes it suitable for strengthening steels. Its mechanical properties are a function of its microstructure, which depends upon how it is mixed with ferrite.
As the name suggests, it is a liquid solution of carbon in iron. Get instant quote. Knowledge base. Delivery All Over the World. Guaranteed Quality. Table of Contents hide. I What Are Phase Diagrams? III Different Phases. Iron crystal structures explained.
Stop wasting time on admin! Order your sheet metal fabrication online. Immediate pricing and short lead times all over the UK. Alloy metals can exist in different phases. Phases are physically homogeneous states of an alloy.
In metallurgy, the term phase is used to refer to a physically homogeneous state of matter, where the phase has a certain chemical composition, and a distinct type of atomic bonding and arrangement of elements. Within an alloy, two or more different phases can be present at the same time. The images below show the phases in aluminum-copper and iron-carbon alloys. Al2Cu precipitates in an aluminum matrix. Ferrite white and cementite dark in steel. Each phase within an alloy has its own distinct physical, mechanical, electrical, and electrochemical properties.
Which microstructure in eutectoid steel has maximum hardenss? Give reason. Answer: 1. There are 2 types of interstitial sites octahedral & tetrahedral. In FCC the.
Microstructure and Properties
The melting point of iron in o C is? Here, the two components may be mixed in an infinite number of different proportions, which indicates that composition also becomes a variable, along with pressure and temperature. Iron-carbon phase diagram, Pb-Sn diagram are the best examples of this category.
Melting point of iron in degree centigrade is equal to a b c d Answer: b Explanation: Melting point of iron in degree centigrade is equal to degree centigrade. Iron carbon phase diagram is a Unary phase b Binary phase c Tertiary phase d None of the mentioned Answer: b Explanation: Iron carbon diagram is binary phase diagram. Diagram which contains only two phases are known as binary phase diagram.
Materials Science pp Cite as.
Iron-Carbon Phase Diagram Explained
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