Font Size: a A A

Micro-mechanical Properties Of Bulk Metallic Glasses And Metallic Glass Based Composites

Posted on:2006-12-13Degree:DoctorType:Dissertation
Country:ChinaCandidate:W H LiFull Text:PDF
GTID:1101360185488034Subject:Materials science
Abstract/Summary:PDF Full Text Request
Bulk metallic glasses (BMGs) have attracted a great attention on fundamental science and practical applications due to their promising mechanical properties. However, in the area of structural applications, they are often limited by the lack of any significant plastic deformation at room temperature. Extensive effort have been devoted to the study of the plastic deformation mechanism and the to the finding of new method for improving the ductility in BMGs. Some BMGs show prominent ductility in constrained loading modes (e.g., compression or bending), while more BMG systems are quite brittle showing nearly zero plasticity during macroscopic mechanical measurements. Thus, the understanding of the plastic deformation mechanism is limited by lack of valuable information. In this thesis, we systematically studied the plastic deformation behavior in various BMG systems using depth-sensing nanoindentation and microindentation in microscopic scale, combined with uniaxial compression in macroscopic scale. The serrated flow feature at different loading condition in various systems was characterized by nanoindentation measurements, and the plastic deformation behavior was correlated with the shear band pattern underneath the indent after indentation. Moreover, the effect of structural relaxation and partial crystallization on the plastic deformation behavior in two BMG systems is investigated for understanding the microscopic deformation mechanism in BMG based composites. In addition, the creep behavior and its mechanism in the BMGs with quite low glass transition temperature were also studied using nanoindentation. Some of the main results and conclusions are listed following:1. Seven typical BMGs, Ce65Al10Ni10Cu10Nb)5, Mg65Cu25Gd10, Pd43Ni10Cu27P20, Cu60Zr20Hf10Ti10, Pt57.5Cu14.7Ni5.3P22.5, Ni60Nb37Sn3 and Fe43Cr16Mo16C15B10 differing strongly in mechanical and thermal properties have been prepared by copper casting method.2. Serrated flow is observed in Mg-, Pd-, Zr, and Cu-based BMGs during nanoindentation, where rapid loading rate suppresses and slower loading rate...
Keywords/Search Tags:bulk amorphous alloy, shear band, serrated flow, nanoindentation, creep
PDF Full Text Request
Related items