小孔径泡沫铝的制备及孔结构细化机理

Fabricating and cell structure refining mechanism of aluminum foam with fine cell structure

在常规熔体发泡法的基础上,采用加入0.5%(质量分数)Mg、添加1%形核剂和发泡剂,经(400℃,6h)+(475℃,1h)氧化预处理、搅拌发泡50s等措施,制备出平均孔径1.03mm、孔隙率75%、结构均匀的小孔径Al-9Si泡沫。孔径细化机理分析表明,Mg的作用在于降低铝熔体的表面张力,提高气泡稳定性;形核剂的作用在于增加气泡非均匀形核的核心;发泡剂氧化预处理可以推迟和延缓发泡剂的分解,提高发泡剂的分散均匀性;搅拌发泡的作用是在发泡剂剧烈分解的中段,通过搅拌搅碎气泡,减小平均孔径。

Based on the general melt foaming processing, A1-9Si foam with cell diameter of 1.03 mm, porosity of 75% and uniform cell structure was fabricated through adding alloying element 0.5%（mass fraction）Mg, adding 1% nuclear forming agent and pre-heating foaming agent by （400 ℃, 6 h）＋（ 475 ℃, 1 h）, stirring when foaming for 50 s. The cell structure refining mechanism sho＇;vs that adding Mg decreases the surface tension of the aluminum alloy melt and hence to increase the bubble stabilization. Adding nuclear forming agent increases the nuclei of heterogeneous nucleation. Adding pre-heating foaming agent postpones its decomposition, hence to increase the uniform of foaming agent dispersion. Stirring within the middle stage of foaming agent rapid decomposition breaks up big bobbles to fine bobbles, hence to reduce mean cell diameter.