Phase Change Properties And Mechanical Properties Of Mg-based Metallic Glass Films

We successfully fabricated Mg-Cu-Y metallic glass films (MGFs) by magnetron sputtering method. The amorphous nature makes them have abnormal high hardness, and their relative physical properties could be changed radically after crystallization. This thesis startes from the engineering application of Mg-based MGF based on phase change storage application and structural coating application for wear resistance and corrosion resistance, and then does a series of studies.Mg-based MGFs with different elements proportion can be fabricated by controlling Ar pressure in the sputtering process. The resistivity and reflectivity can be changed after crystallization. It reveals that Mg5gCu29Y13MGF fabricated by0.5Pa Ar pressure sputtering has the largest resistivity contrast of36.4%and reflectivity contrast of10%. Thus, Mg58Cu29Y13MGF is a potential material for phase change storage application.Further study shows that Mg58Cu29Y13MGF appears phase separation phenomenon above Tg. The activation energy for nucleation is greatly decreased in the Mg-enriched area, which help increase the nucleation rate above Tx.This Mg58Cu29Y13MGF with fast phase change property has significant application value in phase change storage.The wear and corrosion resistances of the traditional Mg alloy can be improved by deposition Mg-based MGF. Furthermore, surface mechanical attrition treatment (SMAT) on the Mg alloy can introduce hardening layer on the surface of Mg alloy, which could decrease the hardness mismatch between the film and substrate. The adhesion between the film and substrate could also be increased as a result of better diffusion property of the sample surface after SMAT. The decrease of the hardness mismatch and increased adhesion make the Mg-based MGF deposited SMATed Mg alloy has excellent wear and impact resistances under high load.The Mg-based MGF on the SMATed Mg alloy can effectively suppress the cracks propagation in the tensile test, which makes the tensile plasticity of the Mg alloy has a big increase.We have verified the nanoscale heterogeneity structure of Mg-based MGF by several experimental methods. In order to reduce this structure, we applied low rate deposition, appropriate substrate heating and substrate bias voltage in the sputtering process, and then fabricate a ultra-hard Mg-based MGF. The hardness of MGF is increased from5.18GPa to6.25GPa. This ultra-hard MGF has significant application value in fabricating ultra-fast phase change storage.When crystalline Mg alloy is chosen as substrate, Mg-based MGF with granular structure can be fabricated, which is attributed to the homogeneity deposition. The size of the amorphous particle can be decreased from several micrometers to the particle disappear by increasing the negative bias voltage in the sputtering process. Furthermore, the Mg-based metallic nanoglass with particle diameter of～25nm can be fabricated by choosing SMATed Mg alloy as substrate. This nanoglass has significant application value in hydrophobic and catalytic research.