镁基金属玻璃膜的相变特性和机械性能研究

发布时间：2018-06-03 06:01

本文选题：金属玻璃膜 + 相变特性　；参考：《华中科技大学》2015年博士论文

【摘要】：Mg-基金属玻璃材料在其非晶态具有异常高的硬度,晶化后的物理特性则会发生根本性的改变。本文以Mg-基金属玻璃膜的工程应用为未来目标,研究了其相变特性和机械性能。本文首先通过磁控溅射方法成功制备出了Mg-Cu-Y金属玻璃膜。磁控溅射中使用不同的溅射氩气压可制备出元素比例不同的Mg-基金属玻璃膜。其晶化后电阻率和反射率会发生变化。经研究对比发现,0.5Pa氩气压溅射沉积的Mg58Cu29Y13金属玻璃膜在非晶态和晶态间有最大的电阻率差异(36.4%)和反射率差异,因此其有潜力成为相变存储器的记录层。进一步研究发现,Mg58Cu29Y13金属玻璃膜在玻璃转变温度以上会发生相分离现象,富Mg区的产生使得形核激活能大大降低,在晶化温度以上的形核速率得到了大大提升。这种Mg58Cu29Y13金属玻璃膜具有的高速相变特性对于相变存储器应用有重要意义。在传统Mg合金上沉积Mg-基金属玻璃膜可以提高Mg合金的耐磨和耐腐蚀特性。对Mg合金进行机械研磨处理(SMAT)可以在Mg合金的表面引入硬化层,从而减弱金属玻璃膜与基体硬度不匹配的程度,并且由于基底表面扩散活性的提升,金属玻璃膜与基底的吸附能力会得到增强。硬度不匹配程度的减弱与吸附能力的增强使得这种沉积Mg-基金属玻璃膜的SMAT处理的Mg合金具有抗高载荷磨损及冲击特性。在拉伸实验中,沉积在SMAT处理的Mg合金表面的Mg-基金属玻璃膜还可以有效抑制裂纹的扩展,从而使Mg合金的拉伸塑性得到大大提升。论文对Mg-基金属玻璃膜的纳米级异质性结构进行了验证。为减少金属玻璃膜中的这种异质结构,我们在磁控溅射过程中采用低速沉积、基片适当加热并同时施加基片负偏压的方法制备出了超硬的Mg-基金属玻璃膜,使其硬度从5.18GPa提升至6.25GPa。由于超硬金属玻璃膜中纳米级异质结构的较少,从TTT相图分析还可看出其还具备超快晶化特性。因此,这种超硬金属玻璃膜对其机械应用及制备超快相变存储器有重要意义。当采用晶态Mg合金做衬底时,可制备出具有颗粒状结构的Mg-基金属玻璃膜,主要原因是由于同质沉积的结果。通过提高磁控溅射过程中的基片负偏压,可以使颗粒的尺寸由几微米减小直至观察不到颗粒。使用SMAT处理的Mg合金作为基底,还可制备出颗粒尺寸为～25nm的Mg-基金属纳米玻璃。这种纳米玻璃在疏水性及催化特性研究方面有重要意义。
[Abstract]:Mg-based metallic glass materials have extremely high hardness in amorphous state, and the physical properties of Mg-based metallic glass materials after crystallization will be fundamentally changed. In this paper, the phase transformation and mechanical properties of Mg- based metallic glass film are studied. In this paper, Mg-Cu-Y metallic glass films were successfully prepared by magnetron sputtering. Mg-based metallic glass films with different proportion of elements can be prepared by using different sputtering argon pressure in magnetron sputtering. The resistivity and reflectivity will change after crystallization. It is found that the Mg58Cu29Y13 metallic glass films deposited by ar pressure sputtering at 0.5 Pa have the greatest difference in resistivity and reflectivity between amorphous and crystalline states, so they have the potential to be the recording layer of phase change memory. It is further found that phase separation occurs in the Mg58Cu29Y13 metallic glass film above the glass transition temperature, and the nucleation activation energy decreases greatly due to the formation of Mg-rich region, and the nucleation rate above the crystallization temperature is greatly increased. The high-speed phase change characteristics of the Mg58Cu29Y13 metallic glass film are of great significance for the application of phase change memory. The wear resistance and corrosion resistance of mg alloy can be improved by deposition of mg-base metallic glass film on traditional mg alloy. Mechanical grinding of mg alloy can introduce hardening layer on the surface of mg alloy, thus reducing the mismatch between metallic glass film and substrate hardness, and because of the enhancement of diffusion activity on the substrate surface, The adsorption ability of the metallic glass film to the substrate will be enhanced. Due to the weakening of hardness mismatch and the enhancement of adsorption ability, the mg alloy treated with SMAT deposited by Mg-based metallic glass film has the characteristics of high load wear and impact resistance. In the tensile test, the Mg-based metallic glass film deposited on the surface of mg alloy treated with SMAT can also effectively inhibit the crack growth, thus greatly improving the tensile plasticity of mg alloy. The nanoscale heterogeneity of Mg- based metallic glass films was verified in this paper. In order to reduce the heterogeneity in metallic glass films, superhard Mg-based metallic glass films were prepared by magnetron sputtering with the method of low speed deposition, proper heating of the substrate and negative bias of the substrate at the same time. The hardness was raised from 5.18GPa to 6.25GPa. Because there are few nanoscale heterostructures in the superhard metal glass film, it can be seen from the TTT phase diagram that it also has ultrafast crystallization characteristics. Therefore, this kind of superhard metallic glass film is of great significance for mechanical application and preparation of ultrafast phase change memory. When the crystalline mg alloy is used as the substrate, the Mg-based metallic glass film with granular structure can be prepared, which is mainly due to the result of homogeneous deposition. By increasing the negative bias of the substrate during the magnetron sputtering process, the particle size can be reduced from several microns until the particles can not be observed. Using mg alloy treated with SMAT as substrate, Mg-based metallic nanocrystalline glass with particle size of 25 nm can also be prepared. This kind of nanocrystalline glass is of great significance in hydrophobicity and catalytic properties.
【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG139.8

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