Q1: With increase in carbon percentage in steel, its

ANS:C - tensile strength increases.

As the carbon percentage increases in steel, its tensile strength increases. Explanation:

1. Tensile Strength: Tensile strength refers to the maximum stress that a material can withstand while being stretched or pulled before it fails. Increasing the carbon percentage in steel generally leads to an increase in its tensile strength. This is because carbon forms solid solution strengthening with iron, effectively increasing the strength of the steel. Additionally, higher carbon content promotes the formation of harder and stronger phases, such as pearlite and martensite, which contribute to higher tensile strength.
2. Yield Stress: The yield stress of steel is affected by various factors, including its composition, heat treatment, and microstructure. While increasing the carbon content can lead to an increase in yield stress up to a certain point, excessive carbon content may result in brittleness and reduce the material's ductility, which can impact its yield stress.
3. Elongation Percent: Elongation percent, also known as ductility, refers to the ability of a material to undergo plastic deformation before fracturing. Increasing the carbon percentage in steel typically reduces its ductility, leading to lower elongation percent values. This is because higher carbon content can promote the formation of brittle phases and reduce the material's ability to deform plastically before failure.
4. Impact Strength: Impact strength, or toughness, is the ability of a material to absorb energy and resist fracture under sudden applied loads. The impact strength of steel is influenced by its composition, microstructure, and heat treatment, among other factors. While increasing the carbon content can enhance the hardness and strength of steel, it may also reduce its toughness if not properly controlled. Excessive carbon content can lead to the formation of brittle phases, which may decrease the material's impact strength.

In summary, as the carbon percentage increases in steel, its tensile strength generally increases, but this may come at the expense of ductility and impact strength if the carbon content is too high. Therefore, the carbon content must be carefully controlled to achieve the desired balance of mechanical properties in steel.