Diffusion Of Hydrogen In Molten Aluminum And Detection Of Compactness Of Molten Aluminum

In this paper,the influence of the diffusion process of hydrogen in the aluminum liquid on the formation of the pores is investigated by using the solute redistribution theory.Using pure aluminum and ZL105 alloy with different crystallization temperature range,the influence of different crystallization temperature range on the density of aluminum liquid was analyzed.By changing the technics parameters,the influence of technics parameters on the testing of the density of aluminum liquid is analyzed.Analysis of the influence of equivalent density detection method on the density measurement of aluminum liquid.Research results show:When hydrogen diffuses in the molten aluminum,the redistribution of solutes occurs.Meanwhile,for the alloy with a wide temperature range occurs constitutional supercooling such as ZL105.The dendritic skeleton is rapidly formed in the constitutional supercooling zone,and the gas separate out is trapped in the dendritic skeleton to form pores.By changing the surface solidification pressure of aluminum liquid,found that the gas pressure smaller on the surface of the solidified surface,hydrogen is more easily nucleated in the aluminum liquid,and the gas content of the aluminum liquid is increased.As for pure aluminum that no crystallization temperature range follow the planar solidification way,there is a large error in the quantitative determination of gas content in alloy by density method,but it can be qualitatively analyzed in the aluminum liquid during the solidification process of samples by the hydrogen evolution.ZL105 alloy aluminum liquid with a wider crystallization temperature range has a larger supercooling zone,the gas separate from the liquid is retained inside the sample.It can be used to quantitatively evaluate the gas content in the aluminum alloy liquid by measuring the density of the sample.However,because there are few bubbles in the negative pressure state,the gas content of the aluminum alloy liquid can not be analyzed by the method of observing solidification process.When the amount of aluminum liquid casting is more,the crystallization latent heat of aluminum liquid release is more,the solidification speed of aluminum liquid is slower,the v value of solidification rate in Tiller formula is smaller,the supersaturation concentration area is greater,the gas content in aluminum liquid is more.The calculation shows that the thicker the crucible wall is,the larger the storage capacity is,the faster the solidification rate of molten aluminum is,the larger the V value of solidification rate is,the supersaturation concentration zone of the Tiller formula is smaller,the gas content in the aluminum solution is less.It is calculated that the equivalent density can intuitively reflect the gas content in the aluminum liquid.Under different decompression pressure,the density value of solidified sample is not very different,but the equivalent density value is much different.The less gas content in aluminum liquid,the smaller the equivalent density,the better the aluminum liquid.The numerical change of equivalent density detection method is more obvious than density detection method,that the equivalent density value can not only accurate liquid aluminum containing gas reaction in liquid aluminum,also make changes in the gas content is more obvious,more reflects the gas containing aluminum liquid.