Research And Development Of High Performance Amorphous Alloys Based On High-Throughput Method And Micro-Doping Effects

Amorphous alloys(also known as metallic glass)are a new type of young multicomponent alloys.Because of their long-range disordered and short-range ordered atomic structure,amorphous alloys show excellent mechanical properties such as high hardness,high strength,high specific strength and high elastic limit.For example,the strength of Hf-based amorphous alloy can be as high as 2.0 GPA,and the strength of Co-based amorphous alloy can be as high as 6.0 GPa.The free combination of huge metal element systems provides broad application prospects and potential value.However,the complexity brought by the diversity of elements also seriously hinders the design and development of amorphous alloy materials.The traditional method of amorphous alloy development is"Trial and error",so it is difficult to quickly develop amorphous alloys with excellent properties.In this thesis,amorphous alloys with excellent mechanical properties were selected in a huge composition space by micro doping and high throughput methods.Firstly,we adopt an accurate and efficient high-throughput method,which can overcome the obstacles of material preparation.This high-throughput method can quickly realize the parallel preparation of a series of samples and the high-throughput characterization of mechanical properties,so as to screen amorphous alloys with excellent mechanical properties in a short time and improve the development rate of amorphous alloys.Taking Zr-Ni-Cu-Al quaternary system as an example,in the less developed Zr Ni-based amorphous alloys,the composition gradient library was prepared by magnetron sputtering,the mechanical properties were screened by nano indentation,the alloy components with excellent mechanical properties were screened,and the macro mechanical properties were tested according to the screened components.It is verified that the high-throughput screening has sufficient reliability.The composition samples of Zr₄₂Ni₄₄Cu₁₂Al₂ alloy were selected in the composition gradient library by means of high-throughput screening method.They have the best comprehensive mechanical properties.Their hardness and tensile strength are 7.13GPa and 1383 MPa respectively,which are significantly better than the two comparative alloy compositions of Zr₄₅Ni₄₂Cu₁₁Al₂ and Zr₄₃Ni₄₁Cu₁₃Al₃.By changing the sputtering target and sputtering parameters,the component gradient library of more component systems could be prepared,the screening of mechanical properties of more component systems were completed and the development speed of amorphous alloys with excellent mechanical properties were improved,which is of great significance in component development.In addition,the effect of Ag addition on the glass forming ability and plasticity of Hf-Cu-Ni-Al amorphous alloy was studied by micro doping method.By adding Ag element with positive mixing heat with Cu and Ni,Hf₄₈Cu_29.25Ni_9.75Al₁₂Ag₁with glass forming ability of 5mm,compressive plasticity of 4%and compressive strength greater than 2300 Mpa was prepared bulk amorphous alloy.The results of transmission electron microscopy(TEM)and energy dispersive spectroscopy(EDS)show that the alloy has the characteristics of phase separation,there is an obvious Cu segregation region,and the content of the second phase decreases with the increase of Ag content.The results show that with the increase of Ag content,the yield strength decreases,and the compressive plasticity first increases and then decreases.