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Use of spherical indentation technique for measurement of property variations of γTiAl

Published online by Cambridge University Press:  24 November 2011

Alfred Cornec ,
Mohammad Rizviul Kabir  and
Norbert Huber
Alfred Cornec*
Affiliation:
Division of Materials Mechanics, Institute of Materials Research, Helmholtz-Zentrum Geesthacht, 21502 Geesthacht, Germany
Mohammad Rizviul Kabir
Affiliation:
Institute of Materials Research, German Aerospace Center (DLR), 51147 Köln, Germany
Norbert Huber
Affiliation:
Division of Materials Mechanics, Institute of Materials Research, Helmholtz-Zentrum Geesthacht, 21502 Geesthacht, Germany
*
a)Address all correspondence to this author. e-mail: alfred.cornec@hzg.de
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Abstract

Novel lightweight intermetallic titanium aluminides, so-called γTiAl, provide good strength and creep resistance up to 700 °C. Their stress–strain behavior at room temperature is however strongly confined in elongation due to their low ductility. For studying the stress–strain behavior of γTiAl, the viscoplastic mechanical properties are determined using spherical indentation testing. The identification problem is solved on the continuum level by neural network analysis, which is based on a unified viscoplasticity model. The identified material parameters are validated by comparing the predicted stress–strain behavior with conventional compression tests at different deformation velocities. It was found that the average response of the indentation tests is in good agreement with the compression tests of round bars. Using a spherical indenter tip of R = 0.2 mm, a small volume is tested, offering possibilities for investigation of local property variations due to processing. The experimental indentation curves exhibited wide hysteresis loops, revealing the existence of pure kinematic hardening. Since tensile fracture strength for γTiAl is very low, microcracking occurred during loading as well as during unloading, significantly contributing to the unloading compliance.

Keywords

Stress/strain relationshipMicrostructureSimulation
Type
Articles
Information
Journal of Materials Research , Volume 27 , Issue 1: Focus Issue: Instrumented Indentation , 14 January 2012 , pp. 378 - 388
Copyright
Copyright © Materials Research Society 2011

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