Grain Refinement under Multiple Warm Deformation in 304 Type Austenitic Stainless Steel.

Abstract

The dynamic process of fine grain evolution as well as deformation behaviour under warm working conditions The interrelations between the mechanisms of plastic deformation and microstructure evolution at warm and high temperatures are analysed in detail and also the multiple compression method for obtaining ultra fine grained structure is discussed as a simple thermomechanical processing.

Effect of Pass Strain on Grain Refinement in 7475 Al Alloy during Hot Multidirectional Forging

“…1) Several techniques, e.g. equal channel angular extrusion, [1][2][3][4][5][6][7][8] torsion under high pressure, 1,4,7) multidirectional forging (MDF) 1,4,[9][10][11][12][13][14] etc., are available for subjecting materials to ultra-high strains required to develop such fine grain structures. MDF seems to be especially attractive in these various SPD methods, because it is the easiest method without any special device and has great potentiality for scaling up of relatively large samples that can be suitable for industrial applications.…”

“…This SPD technique can also be a very valuable scientific tool for studying the microstructure development in large strain deformation. 4,[10][11][12][13][14] The principle of MDF, i.e. multidirectional forging operation, is repeating compression process with changing the axis of the applied strain x !…”

Dynamic Restoration Process of Ni-30Fe Alloy during Hot Deformation.

“…Belyakov et al 8) studied the restoration structures of austenitic stainless steel through the compression test at a strain rate of less than 10 Ϫ1 /s. Recently, Hurley et al 9) and Adachi et al 10) studied the deformation structures of the austenite through high temperature compression test using Ni-30Fe alloys.…”

“…However, there have been few studies that surveyed the dynamic restoration process by changing these parameters systematically within a broad range. [6][7][8][9][10] The present work aims to investigate the dynamic restoration process and its resultant microstructures of austenite under various conditions of strain, strain rate and deformation temperature for Ni-30Fe alloy. Table 1 shows the chemical composition of a 50 kg ingot of the Ni-30Fe alloy that was vacuum melted in a laboratory.…”

Effect of Initial Grain Orientation on Evolution of Deformed Microstructure in Hot Compressed Ni-30Fe Alloy

“…One is the heavy deformation of austenite in non-recrystallized region, which results in the dynamic transformation of unstable austenite to ultrafine ferrite grains [1][2][3] and the other is to introduce the accumulation of strains into ferrite grains by severe warm deformation, which induces the recovered or recrystallized ultrafine ferrite grains. [4][5][6][7] The key element in the method of heavy deformation of austenite in non-recrystallized temperature region is to increase the density of localized inhomogeneous deformation defects within austenite grains. But it is very difficult to investigate systematically the deformation defects in the austenite of the low carbon steel because the austenite grains are transformed to martensite or bainite during quenching to room temperature.…”