氢化钛预氧化处理和发泡温度对Al-7Si闭孔泡沫铝泡孔结构的影响

Effect of pre-oxidation treatment of TiH 2 and foaming temperature on cell structure of Al-7Si closed-cell aluminum foams

采用粉末冶金快速发泡法制备Al-7Si闭孔泡沫铝,研究使用高导热发泡模具后制备工艺参数对泡沫铝膨胀率、孔隙率、泡孔个数与孔径的影响。结果表明:在450-550℃时对氢化钛预氧化处理1 h可细化颗粒尺寸,提高氢化钛开始分解温度和最大分解速率温度。过度预氧化处理会导致氢化钛释气量下降,获得的试样膨胀率较低。发泡温度的提高有助于提高泡沫铝膨胀率和泡孔个数,对孔隙率和平均孔径影响较小,但温度过高会使得试样顶部低圆度裂纹状泡孔分布范围增加。发泡模具的使用有助于约束膨胀方向,提高冷却过程中孔径均匀程度。粉末冶金快速发泡法可获得均匀泡孔结构泡沫铝。采用450℃预处理90 min的氢化钛作为发泡剂,发泡温度为720℃,发泡时间为160 s时可获得孔隙率为78.1%,孔径为(2.29±0.8)mm,并具有最优泡孔结构的泡沫铝材料。

A powder metallurgy rapid foaming method was used to prepare Al-7Si closed-cell aluminum foam,and the influence of the preparation process parameters on the expansion rate,porosity,cell number and pore diameter of the aluminum foam after using high thermal conductivity foaming mold was studied.The results show that the TiH 2 which is pre-oxidation treated isothermally at 450-500℃for 1 h can refine the particle size,increase the onset decomposition temperature and the peak hydrogen release temperature of TiH 2.Excessive pre-oxidation treatment of TiH 2 reduces the gas released and expansion rate of aluminum foam.The increase of foaming temperature is beneficial to increase the expansion rate and the number of cells,and has little effect on the porosity and average pore size,but too high temperature can increase the distribution range of low-circularity crack-like cells on the top of the sample.The foaming mold can constrain the direction of expansion and improve the uniformity of the pore size during the cooling process.The powder metallurgy rapid foaming method can obtain aluminum foams with uniform cell structure.The aluminum foams can be obtained with the porosity of 78.1%,the pore diameter of(2.29±0.8)mm and the optimal structure,when TiH 2 pretreated at 450℃for 90 min and foaming temperature at 720℃for 160 s.