ANS:B - modulus of toughness

When the yield strength of a steel increases from 450 to 650 MPa:

1. Ultimate Tensile Strength (UTS): The ultimate tensile strength may or may not increase. The UTS is the maximum stress a material can withstand while being stretched or pulled before breaking. While increasing the yield strength might correlate with an increase in UTS, it's not always guaranteed, as other factors such as alloying elements and microstructure also influence UTS.
2. Modulus of Toughness: The modulus of toughness might increase. Modulus of toughness is a measure of the ability of a material to absorb energy before rupturing. An increase in yield strength could potentially lead to greater toughness if it corresponds to a change in the material's microstructure or other mechanical properties.
3. Percent Elongation: The percent elongation will likely decrease. Percent elongation is a measure of the amount a material will stretch or deform before fracturing under tensile loading. Higher yield strength typically indicates a more brittle material, which tends to have lower elongation at fracture.
4. Modulus of Resilience: The modulus of resilience may or may not increase. Modulus of resilience measures the amount of strain energy that a material can absorb without undergoing permanent deformation. Increasing yield strength might lead to a higher modulus of resilience if it corresponds to an increase in the material's ability to absorb energy without undergoing plastic deformation.