Volume 23 Issue 7 - March 22, 2013 PDF
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INVESTIGATION OF THE RELATIONSHIP BETWEEN PRIMARY AND SECONDARY SHEAR BANDS INDUCED BY INDENTATION IN BULK METALLIC GLASSES
Kuan-Wei Chen1 and Jen-Fin Lin1,2,*
1 Department of Mechanical Engineering, National Cheng Kung University
2 Center for Micro/Nano Science and Technology, National Cheng Kung University
 
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Bulk metallic glass (BMG) materials have good mechanical properties, such as hardness, and some have superior corrosion resistance. With high glass-forming ability, good castability, and good printability, bulk glassy alloys have been applied to the fields in which conventional crystalline alloys cannot be used [Inoue et al., 2008]. However, the poor ductility and formation of shear bands induced by highly-localized inhomogeneous deformation limit BMGs applications [Johnson, 2002]. Plastic deformation in BMG is accompanied by the primary shear bands (PSB) and the secondary shear bands (SSB). In the present study, PSB and SSB circles obtained from microindentations of Zr-based BMG (Zr53Cu30Ni9Al8) are used to establish an analytical model. Using the force balance for an arbitrary PSB annulus, the spacing of a shear band can be expressed as a linear function of its inner radius. The radius ratio of any two adjacent PSB circles is approximately a constant value. Observations of the experiment results of shear band circles of BMG confirmed that the radius ratio of any two adjacent PSB circles is approximately a constant value (C). Furthermore, SSB circles are found forming on two sides of their corresponding PSB circles. The mathematical expression for a pair of SSB circles is determined by using the orthogonal behavior that arises at the intersection points. The angle of a pair of SSB circles is 90°. The radius of an SSB circles is times as large as the radius of its corresponding PSB circle. Furthermore, the proposed model can be employed to evaluate the ratio of the deformation zone to the contact radius induced by an indentation in BMG.
Fig.1 Mechanical diagram of an indenter and the primary and secondary shear bands created at a given indentation depth.
Fig.2 Schematic diagram of primary and secondary shear bands morphology induced by an indentation.
Fig.3 Geometries of a primary shear band and its two secondary shear bands.
Fig.4 SEM micrograph of the bonded interface of the Zr53Cu30Ni9Al8 BMG material after an indentation was applied.

REFERENCES:
  1. A. Inoue, X.M. Wang, W. Zhang, 2008, “Developments and applications of bulk metallic glasses”, Rev. Adv. Mater. Sci. 18, 1-9.
  2. W.L. Johnson, 2002, “Bulk amorphous metal – an emerging engineering material”, JOM 54, 40–43.
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