Reduction In Interfacial Energy Research Articles

溶融亜鉛中における鋼溶接部の時間依存性破壊の検討

The liquid metal embrittlement cracking (LMEC) of heat affected zone (HAZ) of steel in hot dip galvanizing was investigated. The experiment was conducted using synthetic HAZ of JIS G 3444 STK55 and Sustained Load Test (SLT) at 370°C-470°C heating range in liquid (molten) and solid Zinc.The results obtained are as follows.(1) LMEC behavior is of thermal activated process and LMEC sensitivity is affected by hardness of HAZ.(2) The coarse grain region in HAZ showed the highest LMEC sensitivity.(3) The interfacial energy of steel is reduced by the existence of Zinc.(4) The reaction rate process of LMEC of steel is controlled by grain boundary diffusion of Zinc.(5) The nucleation and the propagation of LMEC in steel are likely to have a close relation to the reduction of interfacial energy due to the grain boundary diffusion of Zinc.

Density of annealing twins

AbstractRecrystallization studies were carried out in a photoemission electron microscope (PEEM) on OF copper and also on nickel and aluminium bronze. Grain sizes and prior cold work were varied over a wide range. The twin density, when expressed as the number of coherent twin interfaces per unit area, is found to correlate well witha parameter reflecting dislocation density. However, the inverse relationship between recrystallized grain size and twin density is not as simple as originally thought. The results show a large scatter which seems to be associated with the variation in recrystallization temperature incurred during heating runs in the PEEM. These variations, although not affecting final grain size, may have a considerable influence on the twin density. The results suggest that twins form because the reorientated matrix provides an easier reaction path for arapid reduction in dislocation density and not because the twinning process may lead to a reduction in interfacial energy.

Wetting under chemical equilibrium and nonequilibrium conditions

The thermodynamics of a solid-liquid-vapor system both under chemical equilibrium and nonequilibrium conditions, based on the model of Gibbs, is discussed. Under chemical equilibrium conditions, the degree of wetting or nonwetting of a flat and nondeformable solid by the liquid is defined by Young's equation in terms of the static interfacial tensions. Under chemical nonequilibrium conditions, mass transfer across an interface results in a transient decrease in the corresponding specific interfacial free energy and the interfacial tension by an amount equal to the free energy of the effective chemical reaction per area at that interface. When the reaction is between the solid and the liquid, this transient lowering of the interfacial tension can cause the liquid drop to spread on the solid substrate if the interfacial energy reduction is large enough and also if the diffusion rates of the reacting components in the solid phase are slow enough relative to the flow rate of the liquid to cause the liquid at the periphery of the drop to be in dynamic contact with unreacted solid.