Study of serrated flow and plastic deformation in metallic glasses through instrumented indentation

The plastic deformation behavior and serrated flow in seven bulk metallic glass (BMG) systems were investigated through instrumented indentation. These materials include Ce65Al10Ni10Cu10Nb5, Mg65Cu25Gd10, Pd43Ni10Cu27P20, Cu60Zr20Hf10Ti10, Pt57.5Cu14.7Ni5.3P22.5, Ni60Nb37Sn3 and Fe43Cr16Mo16C15B10 BMGs, which show a glass transition temperature (Tg) ranging from 360 to 908 K at a heating rate of 0.33 K/s. Remarkable difference in deformation behavior was found among these BMGs in the load–depth curves during nanoindentation. Prominent serrations are observed in Mg-, Pt- and Pd-based BMGs with medium Tg during the loading process, whereas no distinct serrated flow was found in Ce-, Ni- and Fe-based BMGs with quite low or high Tg. The subsurface plastic deformation regions after indentation were investigated using depth-sensing microindentation to characterize the shear band feature developed in various BMG systems. The size of the shear band upset is found to be larger in the alloys with lower Tg. The effect of Tg on the operation of shear bands and the serrated flow behavior in various BMG systems were discussed.