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Different amounts of Al-5Ti-1B master alloy (TiBAl) were added to the AZ31 magnesium alloy (Mg-3Al-1Zn-0.2Mn) as grain refiner and the resulting microstructure and grain size distributions were studied after extrusion and equal channel angular pressing (ECAP). Results showed that the addition of 0.6% TiBAl had the strongest grain refinement effect, reducing the grain sizes by 54.5 and 48.5% in the extruded and ECAPed conditions, respectively. The observed grain refinement was partly due to the presence of the thermally-stable micron- and submicron-sized particles in the melt which act as nucleation sites during solidification. During the high-temperature extrusion and ECAP processes, dynamic recrystallization (DRX) and grain growth are likely to occur. However, the mentioned particles will help in reducing the grain size by the particle stimulated nucleation (PSN) mechanism. Furthermore, the pinning effect of these particles can oppose grain growth by reducing the grain boundary migration. These two phenomena together with the partitioning of the grains imposed by the severe plastic deformation in the ECAP process have all contributed to the achieved ultrafine-grained structure in the AZ31 alloy.

High Si bainitic steel has received much interest because of combined ultra high strength, good ductility along with high wear resistance. In this study, the microstructural evolution of dual phase bainitic ferrite-austenite steel after heavy compression was investigated. Compression tests were conducted at temperature of 298K on the rectangular billets at the strain rate of 0.001s_-1. The samples were deformed to 40% and 70% of their original thickness. The EBSD results show formation of nano grains with high angle grain boundaries through 70% compression, which confirms grain refinement. Additionally, 40% deformation resulted in enhancement of the dislocation density and formation of subgrains at ferrite unites. Also, it was found during 70% compression of the steel, the austenite transforms to the martensite, which is in agreement with thermodynamic calculations.

Nano/Submicron crystalline grains of about 250 nm were obtained in a metastable austenitic stainless steel AISI304L by an advanced thermomechanical process consisting of heavy conventional cold rolling and annealing. Effects of cold thickness reduction and temperature and time of the reversion treatment on microstructure and mechanical properties of the steel were investigated. The nano-structured austenitic steel exhibited not only high strength (above 1 GPa) but also good elongation (above 50%).