Dear Mr. Alcantara, the presence of residual stress and increased dislocation density are the main factors that play a role in the disappearance of discontinuous yielding. Due to the presence of geometrically necessary dislocation (GNDs) at interphases between ferrite and martensite after intercritical annealing the continuous yielding behaviour can be seen.
Dear Mr. Alcantara, the presence of residual stress and increased dislocation density are the main factors that play a role in the disappearance of discontinuous yielding. Due to the presence of geometrically necessary dislocation (GNDs) at interphases between ferrite and martensite after intercritical annealing the continuous yielding behaviour can be seen.
I agree with Maryam
Due to the presence of geometrically necessary dislocation (GNDs) at interphases between ferrite and martensite after intercritical annealing the continuous yielding behaviour can be seen.
Well if I may say it with other words, if a steel is made of two different phases, the tensile behaviour of each phase is probably different from each other. When you start to apply a tensile stress to such kind of steel each phase will react according to its own stiffness. This will result in non homogenous elongation from each structure that will depend of their own presence percentages. The general elongation will result from two different ways of elongation and should be not so clear and marked than a monophasic material.
Dear Victor Alcántara,
In dual phase steels the two main constituents are ferrite and martensite. Now, the transformation from gamma to martensite during cooling process results in preyielding of the adjacent ferrite grains. As a result, geometrically necessary dislocations form in ferrite along ferrite/martensite interphase boundaries to maintain the integrity of the component. Upon further straining, these dislocations act as barriers to dislocation motion leading to rapid sustained strain-hardening and a continuous yielding. However, not all DP steels exhibit continuous yielding. It is feasible only when the fraction of second phase (martensite) is very low and the ferritic matrix is continuous.
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