Prediction of the recrystallised grain size distribution after deformation for the Nb free and model steel

Kaonda, Mususu Kosta Mpongo (2017). Prediction of the recrystallised grain size distribution after deformation for the Nb free and model steel. University of Birmingham. Ph.D.

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Abstract

Grain size refinement can be achieved by recrystallisation during hot deformation, with multiple deformation steps during rolling or forging being used to generate fine grain sizes. Whilst the mode (or average) grain size after recrystallisation can be determined from standard equations the full grain size distribution is required for predicting a range of mechanical properties. In this work an approach has been proposed to allow prediction of the full grain size distribution by varying the value of the D’ parameter value in the Dutta - Sellars equation developed to predict the recrystallised mode/average grain sizes. It has been found that D’ is a function of strain at high strain values (above 0.3) and the relative position of the grain size in the grain size range (D*). Results for recrystallised grain size distributions for a range of steel grades (including model Fe - Ni steels, commercial Nb-microalloyed plate and high alloy (9Cr) forging steel) with different initial grain sizes and following deformation to different deformation strains, show that the predictions give good agreement with the experimental data except for samples with larger mode grain sizes deformed to a strain of 0.15.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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