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Dynamic mechanical behavior and high...

Martin, Morgana.

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Dynamic mechanical behavior and high pressure phase stability of a zirconium-based bulk metallic glass and its composite with tungsten.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Dynamic mechanical behavior and high pressure phase stability of a zirconium-based bulk metallic glass and its composite with tungsten./
Author:	Martin, Morgana.
Description:	280 p.
Notes:	Adviser: Naresh N. Thadhani.
Contained By:	Dissertation Abstracts International69-04B.
Subject:	Engineering, Materials Science. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3308796
ISBN:	9780549570295

Dynamic mechanical behavior and high pressure phase stability of a zirconium-based bulk metallic glass and its composite with tungsten.
Martin, Morgana.

Dynamic mechanical behavior and high pressure phase stability of a zirconium-based bulk metallic glass and its composite with tungsten. - 280 p.

Adviser: Naresh N. Thadhani.

Thesis (Ph.D.)--Georgia Institute of Technology, 2008.

The research involved performing controlled impact experiments on BMG composites consisting of amorphous Zr57Nb5Cu 15:4Ni12:6Al10 (LM106 or Vitreloy106) with crystalline tungsten reinforcement particles. Monolithic LM106 was also examined to aid in the understanding of the composite. The mechanical behavior of the composite was investigated over a range of strain rates (10-3 s -1 to 106 s-1), stress states (compression, compression-shear, tension), and temperatures (RT to 600°C) to determine the dependence of mechanical properties and deformation and failure modes (i.e., homogeneous deformation vs. inhomogeneous shear banding) on these parameters. Mechanical testing in the quasi-static to intermediate strain-rate regimes was performed using an Instron, Drop Weight Tower, and Split Hopkinson Pressure Bar, respectively. High-strain-rate mechanical properties of the BMG-matrix composite and monolithic BMG were investigated using dynamic compression (reverse Taylor) and dynamic tension (spall) impact experiments performed using a gas gun instrumented with velocity interferometry and high-speed digital photography. These experiments provided information about dynamic strength and deformation modes, and allowed for validation of constitutive models via comparison of experimental and simulated transient deformation profiles and free surface velocity traces. Hugoniot equation of state measurements were performed on the monolithic BMG to investigate the high pressure phase stability of the glass and the possible implications of a high pressure phase transformation on mechanical properties. Specimens were recovered for post-impact microstructural and thermal analysis to gain information about the mechanisms of dynamic deformation and fracture, and to examine for possible shock-induced phase transformations of the amorphous phase.

ISBN: 9780549570295Subjects--Topical Terms:

1017759
Engineering, Materials Science.

Dynamic mechanical behavior and high pressure phase stability of a zirconium-based bulk metallic glass and its composite with tungsten.
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005 20110524
008 110524s2008 eng d
020 $a 9780549570295
035 $a (UMI)AAI3308796
035 $a AAI3308796
040 $a UMI $c UMI
100 1 $a Martin, Morgana. $3 1270911
245 1 0 $a Dynamic mechanical behavior and high pressure phase stability of a zirconium-based bulk metallic glass and its composite with tungsten.
300 $a 280 p.
500 $a Adviser: Naresh N. Thadhani.
500 $a Source: Dissertation Abstracts International, Volume: 69-04, Section: B, page: 2569.
502 $a Thesis (Ph.D.)--Georgia Institute of Technology, 2008.
520 $a The research involved performing controlled impact experiments on BMG composites consisting of amorphous Zr57Nb5Cu 15:4Ni12:6Al10 (LM106 or Vitreloy106) with crystalline tungsten reinforcement particles. Monolithic LM106 was also examined to aid in the understanding of the composite. The mechanical behavior of the composite was investigated over a range of strain rates (10-3 s -1 to 106 s-1), stress states (compression, compression-shear, tension), and temperatures (RT to 600°C) to determine the dependence of mechanical properties and deformation and failure modes (i.e., homogeneous deformation vs. inhomogeneous shear banding) on these parameters. Mechanical testing in the quasi-static to intermediate strain-rate regimes was performed using an Instron, Drop Weight Tower, and Split Hopkinson Pressure Bar, respectively. High-strain-rate mechanical properties of the BMG-matrix composite and monolithic BMG were investigated using dynamic compression (reverse Taylor) and dynamic tension (spall) impact experiments performed using a gas gun instrumented with velocity interferometry and high-speed digital photography. These experiments provided information about dynamic strength and deformation modes, and allowed for validation of constitutive models via comparison of experimental and simulated transient deformation profiles and free surface velocity traces. Hugoniot equation of state measurements were performed on the monolithic BMG to investigate the high pressure phase stability of the glass and the possible implications of a high pressure phase transformation on mechanical properties. Specimens were recovered for post-impact microstructural and thermal analysis to gain information about the mechanisms of dynamic deformation and fracture, and to examine for possible shock-induced phase transformations of the amorphous phase.
520 $a For the composite, mechanical testing revealed positive strain-rate sensitivity of its yield stress and negative strain-rate sensitivity of its failure stress over the range of strain rates evaluated, and work-hardening decreased as strain-rate increased. Its deformation mode was found to transition from heterogeneous deformation below the glass transition temperature (of the BMG), to homogeneous deformation between the glass transition and crystallization temperatures, and then back to heterogeneous deformation behavior above the crystallization temperature. The composite exhibited a large susceptibility to shear failure, as evidenced by much decreased strain-to-failure in biaxial (compression-shear) specimens as compared to that in uniaxial (compression) specimens. Failure took place primarily in the glass matrix and at the tungsten particle interfaces at all strain rates. Overall, the deformation and failure behavior of the composite is dominated by that of tungsten, but characteristics of BMG deformation and failure are evident, especially between the glass transition and crystallization temperatures, and at extremely high strain rates.
520 $a For the monolithic BMG, fracture surfaces became increasingly more disorganized as strain rate increased, with evidence of melting due to temperature rise during fracture. The deformation and elastic-plastic wave propagation and interaction response based on measured free surface velocity traces of the monolithic glass were quite well described by the pressure-hardening Drucker-Prager model. Likewise, the deformation response of the composite was described reasonably well considering a rule of mixtures combination of properties of the BMG and W. High-pressure equation of state experiments provided evidence of transition to a mixed phase region (at &sim;26 GPa) and then to a high-pressure phase (at &sim;67 GPa) with a bulk modulus of 288 GPa, 144% higher than that of the bulk modulus of the ambient pressure. Specimens obtained from recovery experiments did not reveal any crystallization, indicating that any crystallites that may have formed were too small and too few to detect. Alternatively, the transformation could be reversible or polyamorphic.
520 $a Mechanical testing performed on the BMG and composite over eleven orders of magnitude revealed a transition in the effect of strain-rate sensitivity at strain rates exceeding 104 s-1. The yield and failure stresses of LM106 and the failure stress of W increased drastically as a function of strain rate above this transition point. The strengthening of the BMG above 104 s-1 is attributed to the transition to a higher modulus phase. The toughening of the BMG above 10 4 s-1 is attributed to effects of energy dissipation associated with the high-pressure phase transition. (Abstract shortened by UMI.)
590 $a School code: 0078.
650 4 $a Engineering, Materials Science. $3 1017759
650 4 $a Engineering, Mechanical. $3 783786
650 4 $a Engineering, Metallurgy. $3 1023648
690 $a 0548
690 $a 0743
690 $a 0794
710 2 0 $a Georgia Institute of Technology. $3 696730
773 0 $t Dissertation Abstracts International $g 69-04B.
790 $a 0078
790 1 0 $a Thadhani, Naresh N., $e advisor
791 $a Ph.D.
792 $a 2008
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3308796