YBa₂Cu₃O_x Superconducting Thin-Film Formation Studied by Rutherford Backscattering Spectroscopy for the Multilayer Deposition Method

Abstract

The deformation behaviour of 304L stainless steel was evaluated, under compression in the temperature range of 600-1200˚C and strain-rate range of 0.001-100 s −1 from the viewpoint of establishing processing-microstructure relationships during hot working. Ferrite forms at temperatures above 1150˚C during deformation. The material exhibits a dynamic recrystallization (DRX) domain in the temperature range of 1000-1200˚C and strain-rate range of 0.01-5 s −1 , which is the optimum one for hot working. The development of microstructure in 304L stainless steel during industrial hot-forming operations such as press forging, rolling, extrusion, and hammer forging at different temperatures in the range 600-1200˚C, was studied and compared with the results of the laboratory tests for assessing the applicability of simulative tests in the optimization of processing parameters.In order to control the final microstructure of the product, an analytical model for the evolution of microstructure during hot working (in the DRX domain) was obtained. Using the above model, the optimum strain, strain-rate, and temperature trajectories were arrived at for obtaining a grain size of 35 µm in an extruded product. Process control parameters, such as ram velocity, die profile, and billet temperature, which achieve the optimal trajectories were calculated using a process model. Extrusion trials were conducted at optimal conditions and a good agreement with those results predicted in the design stage has been achieved.