Development of ultrahigh strength bulk metallic glasses

It is always desirable to develop bulk metal materials with extremely mechanical properties. Ultrahigh strength bulk metallic glass (BMG) is a kind of advanced metallic material with extremely high strength (above 4 GPa), high thermal stability (the glass transition temperature: normally above 800 K), and high hardness (normally above 12 GPa). A typical system of the ultrahigh strength BMG is Co-Ta-B alloy with a fracture strength of above 6 GPa, which is the highest value in the fracture strengths for all kinds of bulk metallic materials (including crystalline and amorphous ones) that we have known so far. In this paper, the compositions, thermal properties, elastic constants, and mechanical properties for all of the reported ultrahigh strength BMGs are summarized. The research progress of these BMGs is also introduced. The correlations among the characteristic temperature, elastic constants, hardness and mechanical properties are built, and the natures of chemical bonding for the ultrahigh strength and high hardness of these BMGs are revealed. The results relating to the structure and physical properties of this kind of ultrahigh strength BMG are significant for potential applications in advanced manufacture, super-durable components and machining.