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Indentation behavior of highly confined elasto-plastic materials
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.ORCID iD: 0000-0001-5385-4796
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.ORCID iD: 0000-0002-4521-6089
KTH, Superseded Departments (pre-2005), Materials Science and Engineering.ORCID iD: 0000-0002-7656-9733
(English)In: Article in journal (Refereed) Accepted
Abstract [en]

The effect of geometric confinement is well-known from hardness measurements of thin films on stiff substrates and has been modeled both phenomenologically and using e.g. Finite Element Analysis. However, these models are mainly focused on a specific experiment or a certain material family. In the present work, Finite Element Analysis is used to gain a better understanding of the interplay between geometric constraints in various microstructures and a wide range of materials properties. It is shown that a very simple model can be used to replicate thin film hardness data where the film is softer than the substrate as well as how materials properties alter the indentation behavior of materials confined in one to three dimensions. It is shown that qualitative agreement with nanoindentation of the metallic binder phase in the complex 3D-microstructure of a cemented carbide is achieved using an axisymmetric “pill-box” model with classical plasticity. It is also shown that the effect of higher-order confinement can be described by the Korsunsky thin film hardness model by re-optimizing the fitting parameters. 

Keywords [en]
Nanoindentation; Hardness; Composite; Finite Element Analysis; Complex microstructure;
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-266817OAI: oai:DiVA.org:kth-266817DiVA, id: diva2:1388273
Note

QC 20200124

Available from: 2020-01-24 Created: 2020-01-24 Last updated: 2020-01-24Bibliographically approved
In thesis
1. Towards computational materials design and upscaling of alternative binder cemented carbides
Open this publication in new window or tab >>Towards computational materials design and upscaling of alternative binder cemented carbides
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Increasing demands on economic, social and environmental sustainability throughout society is putting pressure on the development of new and improved materials for resource efficiency, improved component life-time and substitution of toxic or rare elements. For the cemented carbide industry, as a major provider of tools for e.g. mining and metal cutting which are integral parts of many production chains, this may require complete or partial substitution of cobalt. Cobalt ore is primarily mined in conflict regions and cobalt powder has been shown to be carcinogenic upon inhalation. Substitution of this element could therefore have significant impact on several aspects of society. However, it is far from trivial to substitute this critical element in cemented carbide production. Nearly a century of materials and product development has made state-of-the-art cemented carbides with cobalt binder phase one of the most successful engineering materials. Over the years, accumulated investments throughout the supply chain has made these materials indispensable in industrial production. When envisioning cobalt substitution, it is therefore critical to generate new methods for accelerated materials development and standardised materials qualification. This will enable faster and more reliable development of new materials with the potential to substitute cobalt throughout the industry.

The present thesis is focused on the continued development of an integrated computational materials engineering framework for materials design as well as the development of quality control methods for alternative binder cemented carbides. The existing computational framework is here extended with a model for fracture toughness which allows for property trade-off between hardness and toughness. The extended framework is shown to replicate experimentally well-established property combinations and is thereby applicable for computational design of cemented carbides for specific applications. Furthermore, conventional quality control methods based on magnetic properties are evaluated and further developed for alternative binder cemented carbides. Combining these results on computational materials design and the steps towards standardised quality control has the potential to greatly accelerate future development of cemented carbides, both for cobalt substitution and for improved component life-time.

Abstract [sv]

Ökande krav på ekonomisk, social och miljömässig hållbarhet i samhället sätter press på utvecklingen av nya och förbättrade material för resurseffektivitet, ökad komponentlivslängd och substitution av toxiska ämnen. Inom hårdmetallindustrin, som producerar verktyg till exempelvis gruvbrytning och metallbearbetning vilket är centrala delar av många produktionskedjor, kan detta kräva total eller partiell substitution av kobolt. Koboltmineral utvinns huvudsakligen i konfliktregioner och koboltpulver har visats vara cancerogent vid inhalering. Koboltsubstitution kan därför ha betydande effekt på flera aspekter av samhället. Det är däremot långt ifrån trivialt att ersätta en så central komponent i hårdmetallproduktion. Närmare ett århundrande av material- och produktutveckling har gjort modern hårdmetall med kobolt som bindefas till ett av de mest framgångsrika materialen. Genom åren har ackumulerade investeringar genom hela leverantörskedjan gjort dessa material oumbärliga inom industriell produktion. I samband med visionen om koboltsubstituton är det därför kritsikt att generera nya metoder för accelererad materialutveckling och standardiserad materialkvalificering. Detta skulle medföra snabbare och mer tillförlitlig utveckling och introduktion av nya material med potential att ersätta kobolt genomgående i industrin. 

Den här avhandlingen fokuserar på fortsatt utvekling av ett beräkningsbaserat ramverk för materialdesign enligt konceptet ”Integrated Computational Materials Engineering” samt utvecklingen av metoder för kvalitetskontroll av hårdmetall med alternativa bindefaser. Den existerande beräkningsplattformen utvecklas vidare med en modell för brottseghet. Detta medför möjligheten att med hjälp av beräkningar göra avvägningar mellan hårdhet och seghet genom design av mikrostrukturen. Det utökade ramverket påvisas upprepa empiriskt väletablerade samband mellan mikrostruktur och mekansika egenskaper och kan därmed tillämpas för beräkningsbaserad materialdesign av hårdmetall för specifika tillämpningar. Utöver detta utvärderas tillämpbarheten av konventionella metoder för kvalitetskontroll, baserade på magnetiska egenskaper, för hårdmetall med alternativa bindefaser. En kombination av resultaten kring beräkningsbaserad materialdesign och stegen mot standardiserad kvalitetskontroll har potential att accelerera framtida utveckling av hårdmetall, både för koboltsubstitution och förbättrad materiallivslängd.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2020. p. 160
Series
TRITA-ITM-AVL ; 2020:5
National Category
Materials Engineering
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-266818 (URN)978-91-7873-433-7 (ISBN)
Public defence
2020-02-21, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2020-01-31 Created: 2020-01-24 Last updated: 2020-01-31Bibliographically approved

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