How to improve the strength, plasticity and electrical conductivity of metal materials at the same time and reduce the constraints between performances has always been a research difficulty in the field of metal materials. Recently, the Chinese research team has developed a new method that can simultaneously improve the strength and plasticity of nanostructured metal materials. This new structural design can also be effectively extended to other metal systems.
In the application process of metal, whether it is strength or plasticity, if it does not meet the requirements, it may cause accidents, such as: the bridge is easy to break, the shock absorption function of the car is greatly reduced, and precision instruments such as computers and mobile phones are prone to crashes and cards. pause.
Nano metal film is one of the main component materials of microelectronic devices and microelectromechanical systems in mobile phone chips and computer CPUs. It designs and prepares high-strength and high-plasticity nanometals, and establishes new theories and methods of micro-nanomaterial performance variation. It is information , Electronics, and nanotechnology.
How to break through this grain size limit, further refine the microstructure, and continue to improve the strength of the metal material while improving its structural stability is a major scientific problem facing the research of nano-metal materials today.
Studies have shown that increasing the deformation rate and deformation gradient during plastic deformation can effectively increase the dislocation proliferation and storage dislocation density, thereby promoting the grain refinement process. To this end, the Luke research group used surface mechanical milling to achieve high-speed shear plastic deformation on the surface of the pure nickel rod. This plastic deformation can obtain large strain, high strain rate and high strain gradient at the outermost surface of the material. As the depth from the surface increases, the strain, strain rate and strain gradient decrease gradually, forming a microstructure with a gradient distribution.
The thickness of the nanometer layer is the essential reason for the ultra-high hardness, and the high thermal stability is due to the straight small-angle grain boundaries and strong deformation texture. This new type of ultra-hard ultra-high stability metal nanostructure is expected to be applied in engineering materials to provide its wear resistance and fatigue performance.
Due to continuous breakthroughs in ultra-deep sub-micron processing technology, electronic components have continued to be miniaturized, gradually realizing miniaturization and intelligentization of mobile phones and computers. As an important material in the new generation of microelectronic devices, copper's characteristic scale is also reduced to below 10 nanometers, which results in significant changes in its mechanical properties that will affect the performance and working life of microelectronic microdevices.
The research team took nano metal copper as the research object, and used DC magnetron sputtering technology to introduce an ultra-thin metal tantalum layer in the copper metal film, the size of which was almost equal to the thickness of the grain boundary, that is, it played a role similar to "artificial grain boundary" . By adjusting the spacing of the tantalum layer, two layered metal composite films with gradient grains and equal-sized grains were obtained. It was found that the yield strength and uniform plastic strain of the metal composite film reached 1 GPa and 70% respectively . "
In the end, the team worked with other institutions to successfully design nanostructured metal materials with both high strength and high plasticity. This new structural design can also be effectively extended to other metal systems, and it also opens up new ideas for the design and preparation of high-performance nanometals.