Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Mechanical Properties of Transition Metal Alloys from First-Principles Theory
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of the thesis is to investigate the alloying effect on the mechanical properties of random alloys using the all-electron exact muffin-tin orbitals methodin combination with the coherent-potential approximation. The second-order elastic constants describe the mechanical properties of materials in the small deformation region, where the stress-strain relations arelinear. Beyond the small elastic region, the mechanical properties of dislocation-free solids are described by the ideal strength.

The elastic constants and ideal tensile strengths have been investigated as a function of Cr and Ti for the body centered cubic V-based random solidsolution. Alloys along the equi-composition region are found to exhibit the largest shear and Young’s modulus as a result of the opposite alloying effectsobtained for the two cubic shear elastic constants C' and C44.Classical solid-solution hardening (SSH) model predicts larger hardening effect in V-Ti thanin V-Cr alloy. By considering a phenomenological expression for the ductile-brittle transition temperature (DBTT) in terms of Peierls stress and SSH, itis shown that the present theoretical results can account for the variations of DBTT with composition. Under uniaxial [001] tensile loading, the ideal tensilestrength of V is 12.4 GPa and the lattice fails by shear. Assuming isotropic Poisson contraction, the ideal tensile strength are 36.4 and 52.0 GPa for V inthe [111] and [110] directions, respectively. For the V-based alloys, Cr increases and Ti decreases the ideal tensile strength in all principal directions. Addingthe same concentration of Cr and Ti to V leads to ternary alloys with similar ideal tensile strength values as that of pure V. The alloying effects on the idealtensile strength are explained using the electronic band structure.

The ideal tensile strengths of bcc ferromagnetic Fe-based random alloys have been calculated as a function of compositions. The ideal tensile strength of Fe in the [001] direction is calculated to be 12. 6GPa,in agreement with the available data. For the Fe-based alloys, we predict that V, Cr, and Co increase the ideal tensile strength, while Al and Ni decrease it. Manganese yields a weak non-monotonous alloying behavior. We show that the limited use of the previouslyestablished ideal tensile strengths model based on structural energy differences in the case of Fe-bases alloys is attributed to the effect of magnetism. We find that upon tension all the investigated solutes strongly alter the magneticresponse of the Fe host from the unsaturated towards a stronger ferromagnetic behavior.

Place, publisher, year, edition, pages
KTH: KTH Royal Institute of Technology, 2014. , viii, 58 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-142666ISBN: 978-91-7595-037-2 (print)OAI: oai:DiVA.org:kth-142666DiVA: diva2:704122
Presentation
2014-04-08, Sal N111,Hall 1, Brinellvägen 23, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20140312

Available from: 2014-03-12 Created: 2014-03-11 Last updated: 2014-03-12Bibliographically approved
List of papers
1. Elastic properties of vanadium-based alloys from first-principles theory
Open this publication in new window or tab >>Elastic properties of vanadium-based alloys from first-principles theory
Show others...
2012 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 86, no 1, 014105- p.Article in journal (Refereed) Published
Abstract [en]

The effect of Cr and Ti on the fundamental mechanical properties of V-Cr-Ti alloys has been investigated using the all-electron exact muffin-tin orbitals method in combination with the coherent-potential approximation. The static lattice constant and elastic parameters have been calculated for the body-centered-cubic V1-x-yCrxTiy (0 <= x,y <= 0.1) random solid solution as a function of composition. Our theoretical predictions are in good agreement with the available experimental data. Alloys along the equicomposition region are found to exhibit the largest shear and Young's modulus as a result of the opposite alloying effects obtained for the two cubic shear elastic constants. The classical solid-solution hardening (SSH) model predicts larger strengthening effect in V1-yTiy than in V1-xCrx. By considering a phenomenological expression for the ductile-brittle transition temperature (DBTT) in terms of Peierls stress and SSH, it is shown that the present theoretical results can account for the variations of DBTT with composition.

Keyword
Cubic Transition-Metals, V-Cr Alloys, Mechanical-Properties, Fusion Applications, Temperature-Dependence, Structural Material, Internal-Friction, V-4cr-4ti, Ti, Constants
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-100159 (URN)10.1103/PhysRevB.86.014105 (DOI)000306308100002 ()2-s2.0-84863661838 (Scopus ID)
Funder
Swedish Research CouncilEU, European Research Council
Note

QC 20140312

Available from: 2012-08-06 Created: 2012-08-06 Last updated: 2017-12-07Bibliographically approved
2. Ideal strength of random alloys from first principles
Open this publication in new window or tab >>Ideal strength of random alloys from first principles
Show others...
2013 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 87, no 21, 214203- p.Article in journal (Refereed) Published
Abstract [en]

The all-electron exact muffin-tin orbitals method in combination with the coherent-potential approximation was employed to investigate the ideal tensile strengths of elemental V and Mo solids, and V-and Mo-based random solid solutions. Under uniaxial [001] tensile loading, the ideal tensile strength of V is 11.6 GPa and the lattice fails by shear. Assuming isotropic Poisson contraction, the ideal tensile strengths are 26.7 and 37.6 GPa for V in the [111] and [110] directions, respectively. The ideal strength of Mo is 26.7 GPa in the [001] direction and decreases when a few percent of Tc is introduced in Mo. For the V-based alloys, Cr increases and Ti decreases the ideal tensile strength in all principal directions. Adding the same concentration of Cr and Ti to V leads to ternary alloys with similar ideal strength values as that of pure V. The alloying effects on the ideal strength are explained using the electronic band structure.

Place, publisher, year, edition, pages
American Physical Society, 2013
Keyword
Vanadium-Base Alloys, Theoretical Tensile-Strength, Cubic Transition-Metals, Ab-Initio Calculations, Mechanical-Properties, Elastic-Constants, Temperature-Dependence, Fusion Applications, Bcc Metals, Stability
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-124722 (URN)10.1103/PhysRevB.87.214203 (DOI)000321060500002 ()2-s2.0-84879725158 (Scopus ID)
Funder
Swedish Research CouncilEU, European Research Council
Note

QC 20130730

Available from: 2013-07-30 Created: 2013-07-29 Last updated: 2017-12-06Bibliographically approved
3. Ieal tensile strength of ferromagnetic Fe-based alloys from first-principles theory
Open this publication in new window or tab >>Ieal tensile strength of ferromagnetic Fe-based alloys from first-principles theory
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-142685 (URN)
Note

QS 2014

Available from: 2014-03-12 Created: 2014-03-12 Last updated: 2014-03-12Bibliographically approved
4. Anomalous ideal tensile strength of ferromagnetic Fe and Fe-rich alloys
Open this publication in new window or tab >>Anomalous ideal tensile strength of ferromagnetic Fe and Fe-rich alloys
Show others...
2014 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 90, no 2Article in journal (Refereed) Published
Abstract [en]

Within the same failure mode, iron has the lowest ideal tensile strength among the transition metals crystallizing in the body-centered cubic structure. Here, we demonstrate that this anomalously low strength of Fe originates partly from magnetism and is reflected in unexpected alloying effects in dilute Fe(M) (M = Al, V, Cr, Mn, Co, Ni) binaries. We employ the structural energy difference and the magnetic pressure to disentangle the magnetic effect on the ideal tensile strength from the chemical effect. We find that the investigated solutes strongly alter the magnetic response of the Fe host from the weak towards a stronger ferromagnetic behavior, which is explained based on single-particle band energies.

National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-142686 (URN)10.1103/PhysRevB.90.024201 (DOI)000345446400001 ()2-s2.0-84903839928 (Scopus ID)
Note

Updated from manuscript to article in journal. Previous title: Anomalous ideal tensile strength of ferromagnetic Fe.

QC 20150126

Available from: 2014-03-12 Created: 2014-03-12 Last updated: 2017-12-05Bibliographically approved

Open Access in DiVA

Xiaoqing_Li_thesis(1205 kB)351 downloads
File information
File name FULLTEXT01.pdfFile size 1205 kBChecksum SHA-512
d61936b3f5df7081861f17038b8608cf03998b829be9e1d6ffebf969e79a136b296495b3cbebc7e8d2a9fdf7c79bf363e20b3312463554f6e8eaf94e5dd74b6d
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Li, Xiaoqing
By organisation
Applied Material Physics
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar
Total: 351 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 319 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf