| Lotus-type porous Cu-1.3wt%Cr alloy is a new type material of in-situ composites, which are prepared by Gasar under high pressure atmosphere. Pore growth direction of lotus-type porous Cu-Cr alloy material prepared by this way are same with the metal solidification direction. It has good anisotropy and uniformly distributed pores. Besides, pore structure and morphology can be controlled by hydrogen pressure, solidification rate and other parameters. Currently, because the lotus-type porous alloy has better strength and hardness than pure metal, combined that Gasar alloying process has its complex solidification behavior and microstructure, Gasar alloying become the main research field of lotus-type porous materials. More importantly, Gasar alloying can provide the reference for application development process in the future.Lotus-type porous Cu-1.3wt%Cr alloy were fabricated under different hydrogen pressure. The influence of hydrogen pressure on structure and microstructure of lotus-type porous Cu-Cr alloy was analyzed. Theoretical model of porosity was complement and the influence of the critical pressure of the gas to escape and of gases pore to form on pore was discusses. The results was shown that:the porosity of lotus-type porous Cu-Cr alloys was increased with hydrogen pressure increased; when the hydrogen pressure is greater than the critical pressure of gases pore to form the pore 0.07MPa, the lotus hole will form. In this time, porosity increased gradually with nucleation rate was increased. When the hydrogen pressure is greater than the critical pressure to escape 0.48MPa, the hydrogen would escape out and a lot of porosity decreased. Because of influence of hydrogen gas pressure and the nucleation rate, a decreasing pore diameter was determined by the increasing hydrogen pressure. The pore density increased first quickly back slowly with increasing hydrogen pressure. When the hydrogen pressure is greater than the critical pressure of the gas to escape, bigger morphology factor, smaller and narrower pores shape.Meanwhile, for the complex solidification behavior of lotus-type Cu-Cr alloy, the influence of the microstructure of Cu-1.3wt%Cr alloy on pore structure, including the primary phase, primary dendrite arm spacing and eutectic percentage, etc., were analyzed. The particularity existence of alloy microstructure were summed up. the effect of microstructure of pores on the pore structure was explains qualitatively. The results showed that:lotus-type porous Cu-1.3wt%Cr alloy morphology was divorced eutectic. Porosity of lotus-type porous Cu-1.3wt%Cr alloy was decreased and pore density of which increased as primary dendrite arm spacing decreases. Because it have a large amount of eutectic phase and primary a phase, the content, organization and morphology of lotus-type porous Cu-1.3wt%Cr alloy changes the porosity. Porosity was decreases as eutectic content was increases. Dendrite morphology of primary a phase hindered bubbles escape, it makes the porosity increases. Therefore, the porosity is determined by eutectic phase, solidification morphology and the hydrogen pressure.As a result of the air bubbles floating and containing hydrogen, the crystal nucleation and growth pattern is changed. So that the solidification structure of Cu-1.3wt%Cr alloy had three or more halo. This is because that grain growth direction occurred the migration along the cavity periphery solidification direction. When there are many grains closed to pore, so that grains grow more small and skewed. |
