Ttt (Time Temperature Transformation) Diagram Quiz!

Explanation
Austenitizing is the correct answer because it refers to the process of heating the sample to a high temperature to transform its microstructure into austenite, a solid solution of iron and other alloying elements. This step is crucial in constructing a TTT (Time-Temperature-Transformation) diagram as it allows for the subsequent cooling and observation of the transformation of austenite into different phases, providing valuable information about the material's behavior under different cooling conditions. Annealing, normalizing, and quenching are other heat treatment processes but are not specifically involved in constructing a TTT diagram.

Explanation
The correct answer is "Isothermal transformation curve". The TTT diagram, also known as the isothermal transformation curve, is a graph that represents the relationship between time, temperature, and the transformation of austenite to different microstructures. It is commonly used in materials science and metallurgy to understand the phase transformations that occur during the cooling of a material. The S curve and C curve are not alternative names for the TTT diagram, and Baine's Diagram is not a recognized term in this context.

Explanation
The TTT (Time-Temperature-Transformation) diagram is used to show the time and temperature required for the transformation of a material from one phase to another. In the case of non-equilibrium phases, such as the formation of Fe3C in the Fe-Fe3C diagram, the TTT diagram is particularly useful. It provides information on the cooling rate required to achieve specific phase transformations, allowing for precise control of the microstructure and properties of the material. Therefore, the TTT diagram is the most appropriate choice for showing the time and transformation of non-equilibrium phases.

Explanation
At normal cooling rate, pearlite is formed. Pearlite is a microstructure that consists of alternating layers of ferrite and cementite. It forms when austenite (a high-temperature phase of iron) is slowly cooled. The slow cooling allows for the diffusion of carbon atoms, leading to the formation of the layered structure. Pearlite is characterized by its unique appearance under a microscope, with the alternating dark and light bands. It has good strength and toughness, making it a desirable microstructure in certain applications, such as in the production of steel.

Explanation
Cementite is a definite carbide of iron that is known for its extreme hardness, surpassing that of ordinary hardened steel. It is formed through the reaction of iron and carbon, and it is a major component of steel. Cementite is a brittle and hard phase that provides strength and hardness to steel alloys. It is commonly found in high-carbon steels and cast irons, where it contributes to their overall hardness and wear resistance.

Explanation
The correct answer is CCT curve. The CCT (Continuous Cooling Transformation) curve is a plot that shows the start time of transformation during continuous cooling of a material. It provides information about the transformation phases that occur as the material cools down. The S curve is not related to the start time of transformation in TTT (Time-Temperature-Transformation) curve. Phase diagram is a graphical representation of the phases present in a material at different conditions of temperature and composition. Therefore, the correct term for the given explanation is CCT curve.

Explanation
The lower critical temperature (A1) in the iron carbon diagram is 727 degrees centigrade. This is the temperature at which ferrite begins to transform into austenite during the heating process. Below this temperature, the microstructure of iron is primarily ferrite, while above this temperature, it becomes austenite. Understanding the A1 temperature is crucial in heat treatment processes and determining the phase transformations that occur in iron-carbon alloys.

Explanation
The hardness of steel increases with the increase of carbon percentage. Carbon is one of the main alloying elements in steel and it forms hard carbides, which contribute to the steel's hardness. As the carbon content increases, the steel becomes harder and stronger. This is because the carbon atoms occupy the spaces between the iron atoms in the crystal lattice, making it more difficult for the atoms to move and deform. Therefore, an increase in carbon percentage leads to an increase in the hardness of steel.

Explanation
High carbon steel typically contains a carbon content ranging from 0.5% to 0.7%. This level of carbon content provides the steel with increased hardness and strength, making it suitable for applications such as cutting tools, springs, and high-strength wires. Higher carbon content can lead to brittleness, while lower carbon content reduces the steel's hardness and strength. Therefore, the range of 0.5% to 0.7% carbon content strikes a balance between these factors, making it the correct answer.

Explanation
A tie line on a two component solid-liquid phase diagram indicates a region where the composition of the two components is constant.