Case Study of Ambient Pressure Effects on Pore Shape in Solid

摘要

The shape of a pore resulting from a bubble entrapped by a solidification front for different ambient or terrestrial pressures is predicted. Ambient pressure affects pressure and solute concentration in the pore, and the pore shape in solid. Pore formation widely influences microstructure of materials and contemporary issues of aerospace, engineering, biology, foods, geophysics, climate change, and so on. This model accounts for a realistic shape of the bubble cap subject to balance of pressures and physicochemical equilibrium, as well as different directions and magnitudes of solute transport. Cases1 and 2 are, respectively, referred to solute transport from the pore across the cap into surrounding liquid and surrounding liquid across the cap into pore in the early stage. Case2 can also be subdivided into cases 2a and 2b. In contrast to case 2b, case 2a exhibits a stronger effect of solute transport across the cap on solute gas pressure in the pore than pore volume expansion in the late stage. The results show that an increase in ambient pressure decreases pore radius and time for bubble entrapment in case 1. Irrespective of ambient pressure, the bubble cannot be entrapped as an isolated pore in solid in case2, as a result of significant variation of solute gas pressure in the pore in the late stage. The predicted pore shape agrees with experimental data. Relevant prediction and control of the pore shape in solid are obtained.