A Novel Rolling Approach to Refining the Microstructure and Enhancing the Mechanical Strength of Pure Aluminium

Abstract

In the present study, a novel rolling method is proposed, which is called Multi-Rotational Flat Rolling (MRFR). The novelty of this work is the application of this special method of flat rolling to severely deform metal. The rolling is performed so as to preserve the square shape of the transverse section of the sample. During the process, the transverse-sectional area of the workpiece is gradually reduced, while the sample length is simultaneously increased. The experiment was carried out on commercially pure aluminium. An annealed sample was subjected MRFR up to the attainment of a maximum fourfold reduction in the transverse-sectional area. A microstructure analysis showed that the process resulted in a material having a refined microstructure of less than 1\xa0 µ m. Nevertheless, the majority of the grain boundaries (over 70 pct) were of the low-angle type. As a result of the grain refinement and the increase in dislocation density, a clear improvement in the strength of the deformed material was observed. The increase in yield stress was 157 pct, the increase in ultimate tensile strength was about 56 pct, while the decrease in the value of elongation to failure was 12.8 pct.