Investigation of Pre-Yielding Inelastic Deformation Mechanisms for the Development of Metallic Glassess with Superior Mechanical Properties

After the dedication of substantial research efforts to the study of metallic glasses (MGs) for over 50 years, the scientific community is now reaching the threshold of exploiting a variety of methods for alloy design and further broadening the applications of MGs into many industrial and engineering disciplines. However, critical issues still remain with regard to the basic mechanisms governing the processes of damage initiation and evolution in MGs during their pre-yielding deformation stage. Such a stage is characterized by apparent elasticity; however, it is also strongly connected to the confined inelastic motion of atomistic defects, such as free-volume zones. Despite the appearance of overall elastic deformation, the ‘undetectable’ and confined inelasticity may engender materials failure on the accumulative basis. For instance, the fatigue failure below the yield strength of a MG alloy is a well-known phenomenon that has not been well understood at the present time. As such, the revelation and study of such a subcritical inelastic deformation process is challenging but also of great value to today’s MG research. The outcome of the related research not only enables a deeper understanding of how catastrophic defects are initiated in an amorphous structure, but also provides the useful guidelines for materials scientists to search for the favorable structural/chemical features that an MG alloy should possess in order to frustrate such a defect initiation process and thus attain better plasticity.In the proposed research, we will team up with the research groups from three different countries or areas to tackle the above-mentioned issue. By combining our strengths in nano/micromechanics with alloy design and the state-of-art neutron-based structural characterization technique, we will extend the ultrafast cyclic microcompression approach, which we have developed recently for the study of the properties of free-volume zones, into the area directed towards stress-induced structural relaxation and irreversible damage in MGs at varying temperatures. The research outcome, as can be correlated with alloy compositions, is expected to provide new insights into the development of MG alloys with superior mechanical properties.