Physical Simulation and Experimental Examination of ε-Cu Particles Dissolution Evolution During Welding of Copper Precipitation Strengthening Steel

The kinetics of ε-Cu particles dissolution in the matrix during welding of a copper-precipitation strengthening steel was determined by a combination of GleebleTM physical simulation, TEM examination and hardness meas urement. The ε-Cu particles underwent a coarsening and part dissolution and then complete dissolution reaction as the peak temperature increased from 750 to 1 000℃, which resulted in the decrease in the number density of ε-Cu particles and hardness in the heat affected zone （HAZ）. The results can be used to understand the evolution of this transformation and a softening behavior of the HAZ during welding of this type of steel.

An investigation on dissolution kinetics of single sodium carbonate particle with image analysis method

Dissolution kinetics of sodium carbonate is investigated with the image analysis method at the approach of single particle.The dissolution experiments are carried out in an aqueous solution under a series of controlled temperature and p H.The selected sodium carbonate particles are all spherical with the same mass and diameter.The dissolution process is quantified with the measurement of particle diameter from dissolution images.The concentration of dissolved sodium carbonate in solvent is calculated with the measured diameter of particle.Both surface reaction model and mass transport model are implemented to determine the dissolution mechanism and quantify the dissolution rate constant at each experimental condition.According to the fitting results with both two models,it is clarified that the dissolution process at the increasing temperature is controlled by the mass transport of dissolved sodium carbonate travelling from particle surface into solvent.The dissolution process at the increasing pH is controlled by the chemical reaction on particle surface.Furthermore,the dissolution rate constant for each single spherical sodium carbonate particle is quantified and the results show that the dissolution rate constant of single spherical sodium carbonate increases significantly with the rising of temperature,but decreases with the increasing of pH conversely.

Kinetic Model of ε-Cu Particle Dissolution in Welding-Induced HAZ of Copper-Containing Steel

The kinetics of ε-Cu particle dissolution in the matrix of heat affected zone （HAZ） during welding of a copper-containing steel was determined by assembling the welding temperature-time program into a modified Whelan＇s solution. The particle dissolution dependence on the degree of ＂superheating＂ above the equilibrium transformation is demonstrated from the model. In terms of volume fraction of particle dissolution, the HAZ may he classified into three zones, including the undissolving zone, the partially dissolving zone, and the completely dissolving zone, respectively. The numerical solution was in good agreement with the experimental examination finding. The results of model can be used to quantitatively map the ε-Cu dissolution zone dependence on the peak temperature of welding thermal cycles and understand the evolution of this transformation during welding.

CFD-DNS simulation of irregular-shaped particle dissolution

A coupled approach between the conventional computational fluid dynamics platform COMSOL and an in-house-developed direct numerical simulation code DigiDiss is presented to study the dissolution kinetics of an irregular-shaped particle in a stirred cuvette.The complex flow dynamics from COMSOL were imported into DigiDiss as an initial flow condition.A digitised 3D particle structure scanned and reconstructed by X-ray micro-tomography was used in the dissolution simulation.A quantitative assessment of the simulation results was made using as a reference experimental data and a theoretical calculation based on the shrinking spherical model with different flow velocity profiles near the particle.The comprehensive agreement demonstrates the coherence of the simulation method in reproducing the experimental behaviour and is seen as a step closer towards developing a computer software design aide to help with formulation development.

Effects of rotor and stator geometry on dissolution process and power consumption in jet-flow high shear mixers

The jet-flow high shear mixer(JF-HSM)is a new type of intensified equipment with special configurations of the rotor and the stator.The mass transfer property and power consumption were studied in the solid-liquid system for a series of JF-HSMs involving different configuration parameters,such as rotor diameter,rotor blade inclination,rotor blade bending direction,stator diameter,and stator bottom opening diameter.The flow characteristics were examined by computational fluid dynamic simulations.Results indicate that the turbulent power consumption of the JF-HSM is affected by the change in rotor blade inclination and stator bottom opening.With the increase in the shear head size and the change in the rotor into a backward-curved blade,the solid-liquid mass transfer rate can be remarkably increased under the same input power.Dimensionless correlations for the mass transfer coefficient and power consumption were obtained to guide the scale-up design and selection of such a new type of equipment to intensify the overall mixing efficiency.