NanoSteels (The Newest Approaches Toward the Training and Applications of Nanotechnology in Mass Production of Nanostructure Steels)

The term NanoSteels is called to some special steels consisting of nanosize phases (i.e. ferrite, cementite, and austenite), grains, and carbides (e.g. vanadium and M2C) produced by nanotechnology. It is proof that exotic physical, mechanical, and magnetic properties can be obtained from nanostructured steels. Fabrication methods of nanostructure steels can be divided into two main categories, SPD (severe plastic deformation) and melt base (crystallization from amorphous state) methods. Among all of the severe plastic deformation techniques (i.e. ECAP, HPT, and ARB), equal channel angular pressing (ECAP) is especially attractive because it can economically produce bulk of ultra- fine grain (UFG) materials. On the other hand, crystallization from amorphous state in bulk metallic glasses is a unique approach toward the mass production of nanostructure ferrous alloys. In the experimental process, crystallization of α – Fe phase during annealing process of Fe55Cr18Mo7B16C4 bulk amorphous alloy has been evaluated by X- ray diffraction and TEM observations. It is known from the TEM observations that crystalline α – Fe phase nucleated in the structure of the alloy in an average size of 10 nm and completely mottled morphology

EFFECTS OF ELECTRO-SLAG REMELTING PROCESS (ESR) ON MACROSTRUCTURE AND REFINEMENT OF A MEDICAL GRADE OF STAINLESS STEEL

This study is focused on the effects of electroslag remelting by prefused slag (CaO, Al2O3, and CaF2) on macrostructure and reduction of inclusions in the medical grad of 316LC (316LVM) stainless steel. Results showed that in order to obtain uniform ingot structures during electroslag remelting, the shape and depth of the molten pool should be carefully controlled. High melting rates lead to deeper pool depths and interior radial solidification characteristics. Furthermore, decrease in the melting rate caused more reduction of non-metallic inclusions. In practice, large shrinkage cavities formed during the conventional casting process in the primary ingots were the cause of the fluctuation in the melting rate, pool depth and extension of equiaxal crystals zon

Investigation of Crystallization Kinetics of Fe36Cr12Mo10 and α-Fe Phases in Devitrification of Fe51Cr18Mo7B16C4Nb4 Amorphous Alloy

In this research, crystallization of Fe36Cr12Mo10 and α-Fe phases in devitrification of Fe51Cr18Mo7B16C4Nb4 amorphous alloy was studied using X-ray diffraction and transmission electron microscopy. For evaluation of crystallization kinetics, differential scanning calorimetric tests were carried out at different heating rates. Results showed that two-step crystallization led to the formation of Fe36Cr12Mo10 and α-Fe phases in the structure of alloy. Activation energy of crystallization of Fe36Cr12Mo10 and α-Fe phases measured according to Kissinger-Starink model were 747 and 880 kJ/mol, respectively. Results growth mechanism along with the decreasing nucleation rate in crystallization of Fe36Cr12Mo10 and α-Fe phases