Combinatorial high throughput synthesis of high entropy alloys

148 Pages·2016·29.51 MB·English

by  Laura Asensio Dominguez

Combinatorial high throughput
synthesis of high entropy alloys
Laura Asensio Dominguez
Department of Materials Science and Engineering
University of Sheffield
This dissertation is submitted for the degree of
Doctor of Philosophy
September 2016

Amisabuelos:
ManuelAsensioMartíndeLucía,
MaríaDomínguezSánchez,
PascasiaArévaloMorenoyPascualDomínguezArévalo

Declaration
I hereby declare that except where specific reference is made to the work of others, the
contents of this dissertation are original and have not been submitted in whole or in part
forconsiderationforanyotherdegreeorqualificationinthis,oranyotheruniversity. This
dissertation is my own work and contains nothing which is the outcome of work done in
collaboration with others, except as specified in the text and Acknowledgements. This
dissertationcontainsfewerthan65,000wordsincludingappendices,bibliography,footnotes,
tablesandequationsandhasfewerthan150figures.
LauraAsensioDominguez
September2016

Acknowledgements
Firstly,IwouldliketoexpressmysinceregratitudetomysupervisorsDr. RussellGoodall
and Prof. Iain Todd for the continuous support of my PhD study and related research, for
theirpatience,motivation,andimmenseknowledge. Theirguidance,sometimeslookingat
differentdirections,helpedmenotonlyduringtheresearchstagesbutalsoonthewritingof
thisthesis.
I would also like to thank to all and each members of Accelerated Metallurgy for their
constructivecomments,subjectivepointsofviewandtheirethicvalues.
Mysincerethanks alsogoestoallthe membersformingMercuryCentre,where mostofthe
experimentalpartofthisprojecthasbeencarriedout,andwithoutthem,thisthesiswouldnot
havebeen possible. Particularly, Akemi, James, Fatos, Amit andMeurig for theircomments
andadviceswhichhavehelpedinshapethisthesis.
I thank to all my colleagues Navid, Zhao, Chris, Everth and especially to Lampros for
thesupport andstimulating discussions, forthe dayswehave beenworking togetheruntil
lateandforallthefunwehadinthelast3years.
Last but not the least, I would like to thank to all my family for supporting me spiritu-
allythroughoutwritingthisthesisandmylifeingeneral.

Abstract
ThisPhDthesisisapartoftheAcceleratedMetallurgy(AccMet)projectfundedunderthe
Seventh Framework Programme. AccMet’s aims consists on the delivery of an integrated
pilot-scale facilityfor the combinatorialsynthesis and testingof those unexplored material.
The contributionof this thesisto AccMet has beenexpanded in 3years while focused inthe
understanding and development of a methodology suitable for the combinatorial synthesis of
novelmaterials,andparticularlyofHighEntropyAlloys(HEAs). Thesenovelmaterialsare
composedofmultipleelementsatnearequiatomiclevelswiththecapacityofformingsimple
crystalline phases such as bcc and fcc instead of the expected intermetallic compounds as
wellastheirexcellentcombinationofstructuralandfunctionalpropertiescomparedtothe
traditionalmaterials.
A mathematical technique known as Principal Component Analysis has been used here
to identify patterns within a set of metallic systems forming a wide range of crystalline
structures. Thistechniquewouldnotonlyspeedupthecompositionaldesignstagebutalso
contributetothedevelopmentofavirtuallibrarycontainingalltheexploredsystems.
Mercury Centre has been an important key during the synthesis of HEAs where Spark
PlasmaSintering (SPS)and Electron BeamMelting (EBM)have beensuccessfullyapplied
forthedevelopmentofthethesis.
The final combination of the design stage, production and characterisation of HEAs de-
velopedinthisthesiswouldresultinanadvancestechniquesuitablenotonlyforthesynthesis
ofnovelHEAs,butalsoforthediscoveryofotherunexploredsystems.