A Study of the Crystallization and Amorphization Mechanisms of Metallic Glasses under Ion Bombardment
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The recent development of metallic glasses has led to a growth in study and innovation of the unique material properties these systems have to offer. In general, metallic glasses offer high yield strength, great corrosion resistance and high elasticity. These properties, along with the ease of part creation through plastic forming, make it a desirable material for several different industry applications. For the nuclear industry in particular, metallic glasses are being researched as coatings for reactor vessels as well as coatings for fuel cladding for long term storage. However, metallic glasses do have drawbacks. Metallic glasses are defined by their amorphous structure, and as such have an undesirable brittle failure mode. The amorphous structure is also a meta-stable structure and under several stimuli including high heat, pressure shocks, irradiation and plastic deformation can cause crystallization within the metallic glass. This crystallization does allow for some improvement in ductility but reduces strength and corrosion resistance. The nuclear environment will subject metallic glass to all of the aforementioned stimuli. It is therefore important to know under what conditions crystallization will occur and the mechanism behind the phase change in order for this material to be effectively implemented. While crystallization under high heat and plastic deformation has been studied extensively, crystallization from irradiation is an understudied field. This behavior is difficult to describe and quantify due to its nuanced and unintuitive nature. This body of work is aimed at more completely understanding the crystallization and re-amorphization mechanisms in metallic glass due to ion bombardment. Thin film samples and bulk ribbon samples were both subjected to a variety of ion bombardment conditions. It was found that direct crystallization in thin film samples can be induced from irradiation induced excess free volume, while it can recover to an amorphous state from rapid damage cascade quenching. In bulk studies, it was found that the beam cannot induce direct crystallization, but can make a metallic glass amorphous after it has been crystallized. These findings will help determine the proper operation envelope for this material, so it can be used effectively in engineering applications.
Price, Lloyd Milton (2016). A Study of the Crystallization and Amorphization Mechanisms of Metallic Glasses under Ion Bombardment. Doctoral dissertation, Texas A & M University. Available electronically from