【作者】 李鹏；

【导师】 曹卓坤；

【作者基本信息】 东北大学 ， 冶金工程（专业学位）， 2020， 硕士

【摘要】 泡沫铝具有高比刚度、吸声、隔热、隔绝电磁、高阻尼等特性,广泛应用于建筑、汽车、国防工业等领域。泡沫铝的泡孔结构对于其力学性能和功能特性均有重要影响,改善泡沫铝孔径分布、控制气泡壁厚度等研究对于制备高性能泡沫铝材料具有重要意义。本文研究了发泡剂预处理、合金元素含量和环境压力对于粉末致密化发泡法制备泡沫铝发泡过程中的泡孔结构演化过程的影响,并研究了泡孔结构变化对其力学性能的影响规律,具体研究结果如下:(1)通过添加硅粉降低预制体熔点,并加入适量Mg粉改善氧化物与铝熔体的润湿性,可增强液态金属泡沫的稳定性,制得泡沫铝材料。确定了较优的Si添加量为1 1.7wt.%,Mg 添加量为 0.6wt.%。(2)研究了加热氧化处理对TiH2释氢行为的影响机理。结合DSC、XRD和SEM观察分析,发现经高温氧化后,TiH2颗粒表面发生氧化,热分解吸热峰由591℃升高至607℃。当发泡剂氧化处理温度为490℃,质量分数为1.0wt.%时,可制得孔结构均匀性较好的泡沫铝材料。(3)研究了压制压力和发泡温度等工艺参数对泡沫铝发泡行为的影响。维氏硬度测试结果表明,随着压制压力增加,预制体表面维氏硬度增大,且中心位置与边缘的维氏硬度差值减小。确定了预制体压制压力为400 MPa,加热温度710℃时,制得泡沫铝样品膨胀率可达到366%,泡孔结构较均匀。(4)研究了发泡腔内气体压力对泡沫铝膨胀过程的影响。结果表明,随着氩气气压的增加,泡沫铝膨胀速率和最大膨胀高度均出现下降。当发泡腔内压力从0.1MPa增大至0.5MPa时,泡沫铝的平均孔径由9.8 mm降低到2.9mm,气泡壁平均厚度由168.9μm 降低到 115.1 μm。(5)对不同孔结构的泡沫铝样品进行了准静态压缩试验。结果表明,粉末致密化发泡法制得的泡沫铝材料的应力—应变曲线有明显的应力软化阶段,且波动较大,表现为典型的脆性泡沫材料。当泡沫铝孔径减小、均匀化后,应力—应变曲线波动性变小,压缩强度由0.84 MPa增加到5.28 MPa。更多还原

【Abstract】 Foamed aluminum has high specific stiffness,sound absorption,heat insulation,electromagnetic insulation,high damping and other characteristics,widely used in construction,automotive,defense industry and other fields.The cellular structure of aluminum foam has an important influence on its mechanical properties and functional properties.It is important to improve the pore size distribution of aluminum foam and control the thickness of bubble wall.In this thesis,the effects of foaming agent pretreatment,alloy element content and ambient pressure on the evolution of cellular structure during the foaming process of aluminum foams prepared by powder densification were studied.The results are as follows:(1)The melting point of the preform is decreased by adding silicon powder,and the wettability of the oxide and aluminum melt is improved by adding proper amount of Mg powder and the stability of the liquid metal foam can be enhanced to prepare the foam aluminum material.The optimum Si addition was determined to be 11.7wt.%.The content of Mg was 0.6 wt.%.(2)The mechanism of the effect of heat oxidation on the hydrogen evolution behavior of TIH2 was studied.The results of DSC,XRD and SEM showed that the surface of TiH2 particles was oxidized at high temperature,and the thermal decomposition endothermic peak increased from 591℃ to 607℃.When the oxidation temperature of foaming agent is 490℃ and the mass fraction is 1.0 wt.%,a foamed aluminum material with good uniformity of pore structure can be prepared.(3)The effects of processing parameters such as pressing pressure and foaming temperature on the foaming behavior of aluminum foam were studied.The vickers hardness test results show that the vickers hardness on the surface of the preform increases with the increase of pressing pressure,and the vickers hardness difference between the center and the edge decreases.The expansion rate of aluminum foam samples can reach 366%when the preform pressure is 400 MPA and the heating temperature is 710℃.(4)The effect of gas pressure in the cavity on the expansion process of aluminum foam was studied.The results show that the expansion rate and the maximum expansion height of aluminum foam decrease with the increase of argon pressure.When the pressure in the foamed cavity increases from 0.1 MPa to 0.5 MPa,the average pore diameter of the foamed aluminum decreases from 9.8 mm to 2.9 mm,and the average thickness of the bubble wall decreases from 168.9μm to 115.1μm.(5)Quasi-static compression tests were carried out on aluminum foams with different pore structures.The results show that the stress-strain curve of the foamed aluminum prepared by powder densification-foaming method has obvious stress-softening stage and fluctuates greatly.When the pore size decreases and homogenizes,the stress-strain curve becomes less fluctuant and the compressive strength increases from 0.84 MPa to 5.28 MPa.更多还原