【作者】 吕学旺；

【导师】 邱克强； 任英磊；

【作者基本信息】 沈阳工业大学 ， 材料学， 2007， 硕士

【摘要】 利用NaCl颗粒作为预制型，采用渗流铸造方法制备了AZ91泡沫合金，样品孔隙之间具有良好的连通性。泡沫密度为0.724g/cm³，孔隙率为0.602。压缩实验结果表明AZ91镁合金泡沫材料的塑性变形能力明显高于铸态AZ91镁合金。在孔隙被压合的过程中，泡沫材料在低应力条件下发生剪切破坏。这一变形机制在金属泡沫材料中尚未见到报道。同时采用渗流铸造法分别制备了不同体积分数Fe丝和钢网增强的AZ91镁合金复合材料。用真空淬火炉迅速加热AZ91镁合金到700℃左右。保温60分钟，待AZ91合金完全熔化后，在2×10⁵Pa的Ar气作用下将AZ91镁合金溶液渗流到Fe丝中，并迅速淬入水中，经过快速淬火，形成所要求的试样。该工艺要求严格控制加热温度和保温时间才能取得良好的效果。通过光学显微镜和扫描电镜观察了复合材料的结构和压缩时的断口形貌，并将其与镁合金相对比。结果发现：复合材料的断裂强度较AZ91镁合金断裂强度明显提高，提高的幅度随着Fe丝和钢网体积分数的增加而增加。材料的破坏方式也受Fe丝和钢网数量的影响。采用真空铜模浇铸法制备了四种Mg-Cu-Nd系非晶合金。均可以形成直径为2mm的大块非晶合金。其中Mg₅₅Cu₃₅Nd₁₁大块非晶合金具有明显且较高的玻璃转变温度T_g（419K），高的晶化初始温度T_x（472K），宽的过冷液相区△T_x=T_x-T_g（53K），是非晶形成能力和热稳定性较高的合金。Mg₅₃Cu₃₇Nd₁₀室温压缩断裂强度（s_f）高达685MPa。采用铜模铸造法制备了直径2mm，3mm的Mg-Ni-Zn-Y系复合材料。经实验测试，由于快速凝固三种成分合金均具有部分非晶特征。断裂方式为脆性断裂。具有很高的断裂强度，在400MPa以上。组织照片显示部分非晶特征。更多还原

【Abstract】 The AZ91 magnesium alloy foam with a diameter of 9mm were fabricated by using vacuum melt infiltration and water quenching methods. NaCl salt was used as a placeholder in this investigation. The porosity and density were 0.602 and 0.724 g/cm³ respectively for the AZ91 magnesium foam. The pores were evenly distributed in the material. The plastic strain during compression for the AZ91 magnesium alloy foam is much higher than that of the as-cast AZ91 magnesium alloy fabricated by the same process. The fracture event occurred at low stress during the pores vanishing, which is the first evidence observed in metal foam materials during compression according to our knowledge.The AZ91 magnesium based composites reinforced by wire and steel web have been fabricated by melt infiltrating casting method. The volume fraction of wire and steel web are different. An optical microscopy and a scanning electronic microscopy were used to investigate the structure of the composite and the microscopic morphologies of the fracture surface. The compression results show that the yielding strength of the composites is higher than that of the AZ91 magnesium alloy,and the extent is increased with increase of the volume fraction of wire and steel web. In the same time, the volume fraction of wire and steel web also has large effect on the fracture modes of the composites.we studied the glass-forming ability of the Mg-Cu-Nd alloy system. It was found that three alloy could be cast into amorphous rods with a diameter of 3mm. The high and obvious observable glass transition temperature(Mg₅₅Cu₃₅Nd₁₁) T_g（419K）, remarkable supercooled liquid region△T_x=T_x-T_g（53K） of the amorphous rods, suggest that such a alloy is a good glass former and with high thermal stability. The fracture of Mg₅₃Cu₃₇Nd₁₀ alloy strengthσ_f at room temperature is 685MPa.Mg-Ni-Zn-Y alloys were prepared by copper mold casting. The microstructure and the mechanical properties of the alloys have been investigated. The results indicate that the compressive fracture strength of alloys is as high as 433MPa.更多还原