Answer : Option:- D
Retained austenite can be eliminated by tempering, sub-zero treatment, or plastic deformation. These processes stabilize the microstructure and reduce the amount of retained austenite, enhancing the material's properties.
Answer : Option:- D
The super-saturated solution of carbon in iron with a body-centered tetragonal (BCT) structure is known as martensite. Martensite forms when austenite is rapidly cooled, trapping carbon atoms in solution.
Answer : Option:- B
The hardness of white cast iron typically ranges from 350 to 500 BHN (Brinell Hardness Number). White cast iron is characterized by its brittleness and hardness due to its high carbon content and the presence of cementite.
Answer : Option:- B
At room temperature, as grain size decreases, hardness, yield strength, tensile strength, fatigue strength, and impact strength generally increase. Finer grains improve the mechanical properties of the material.
Answer : Option:- B
The iron-carbon phase diagram is a binary phase diagram, representing the equilibrium phases of iron and carbon at various temperatures and carbon concentrations. It helps understand steel and cast iron behavior.
Answer : Option:- B
In scanning electron microscopy, secondary electrons are collected by the anode, which helps form the image. These electrons are emitted from the specimen when it is struck by the primary electron beam.
Answer : Option:- A
Phases like Bainite, Pearlite, and Martensite are transformed from austenite. These phases form during cooling or quenching, depending on the cooling rate and composition of the steel.
Answer : Option:- D
The austenite phase visible in a microscope at room temperature is called retained austenite. It is a metastable phase that remains in steel even after cooling from high temperatures.
Answer : Option:- A
Adding chromium (Cr) to steel significantly improves its corrosion resistance, as it forms a passive oxide layer that protects the steel from environmental degradation. This is why chromium is used in stainless steel.
Answer : Option:- B
The carbon percentage in steel can range up to about 0.21%. Beyond this, steels are often classified as high-carbon steels. Steel with higher carbon content exhibits improved hardness but reduced ductility.