Papers by Keyword: Polycrystalline Structure

Abstract: In the production of steel parts exigent of high durability to abrasive wear at high temperatures and / or corrosive environment, the method is used for the deposition welding with the addition material MSG-6-GZ-C-60G. With this material layer it is made of 55-60 HRC hardness, corrosion and wear resistant, with properties that are kept up to temperatures of 5000 C. There can be manufactured new parts (pressure casting forms, components for dies, molds, etc.), or dynamically and abrasion-torn reconditioned parts may be required. Deposits have been made with wear-resistant layer on the steel 42CrMo4, with and without the generation of vibration during welding. For the samples swing, a device was used with an electrodynamic exciter to generate vibrations with frequencies up to 20 kHz. Vibration tests were performed at a frequency of 50 Hz, because the frequency can be applied in industrial conditions, by means of excitation of electromagnetic or vibration driven motor. There have been registered horizontal and vertical accelerations which lead to changes in the conditions of crystallisation of the melt, respectively the formation of a microstructure with superior features. Microstructures and hardness recorded on specimens welded with and without vibration are comparatively presented. Micrographs which were made demonstrate the favourable influence of the vibration on the quality of the deposited layer and the base material. Whith the vibration with accelerations of a_x = 55 m/s² and a_z = 70 m/s² resulted: much lower deformation of the base material, HAZ - a lower content of residual austenite, in the TZ there was a great interlock of the two materials, in the deposited material the dendritic crystals strongly fragmented and the grain was finished.

Abstract: A modified multi-phase-field model for regenerating a homogeneous polycrystalline microstructure was presented. An extra term was introduced to the original formula by Steinbach et al. by assuming that the stability of every grain constituting the microstructure depends on the grain size distribution. The effect of the term on the obtained microstructure was then verified by numerical simulations, and it was found that a homogeneous microstructure having nearly the same shape and size was generated. The influence of the parameter was also investigated, and it revealed that the parameter was dominative on the grain size at the steady state.