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High-performance Load-bearing Alloys
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this thesis is to study advanced metallic alloys as load-bearing componentsfor engineering and biomedical applications. The investigations have been focusing onthe improvement of the properties and performance of existing materials as well assynthesizing and developing completely new materials. This thesis covers alloy design,microstructure characterizations, mechanical and electrochemical tests, together withevaluating the tribocorrosion performances under the combined action of wear andcorrosion. The thesis consists of three parts:In part one (paper I and II), two types of multicomponent Ti-Fe-Sn-Nb alloys weredeveloped showing superior mechanical properties with distinct microstructures. Firstlythe hypoeutectic alloy consisting of ductile dendrites and ultrafine eutectic presentedsuperior yield strength and enhanced ductility compared to those of bulk metallicglasses (BMGs). Secondly, the β-type alloys completely retaining of β-Ti phasedisplayed outstanding plasticity without sacrificing the high mechanical strength.In part two (paper III), a series of Ti-based glassy alloys containing no biological toxicelements e.g. Ni, Cu and Al, were designed by a novel method coupling thermodynamiccalculations and topological instability criterion. A self-consistent thermodynamicdatabase was constructed based on the CALPHAD (Calculation of Phase Diagrams)approach. The experimental verifications matched reasonably well with the theoreticalcalculation, suggesting this method provides an effective approach for glass formingpredictions.In part three (paper IV and V), the degradation mechanisms of the load-bearing Zrbased BMGs were evaluated under the effects of tribological wear and electrochemicalcorrosion. Comparatively the tribo-electrochemical performances of the surfacemodified (plasma nitriding or diamond-like carbon) conventional metallic biomaterialsi.e. medical grade pure Ti, stainless steel and CoCrMo alloys, were investigated in linewith that of the BMGs.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. , 44 p.
National Category
Materials Engineering
Research subject
Materials Science and Engineering
Identifiers
URN: urn:nbn:se:kth:diva-208641ISBN: 9789177294283 (print)OAI: oai:DiVA.org:kth-208641DiVA: diva2:1107623
Public defence
2017-06-08, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20170612

Available from: 2017-06-12 Created: 2017-06-09 Last updated: 2017-06-12Bibliographically approved
List of papers
1. Ti-Fe-Sn-Nb hypoeutectic alloys with superb yield strength and significant strain-hardening
Open this publication in new window or tab >>Ti-Fe-Sn-Nb hypoeutectic alloys with superb yield strength and significant strain-hardening
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2017 (English)In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 135, 59-62 p.Article in journal (Refereed) Published
Abstract [en]

In this letter new Ti-Fe-Sn-Nb hypoeutectic alloy comprised of primary dendritic β-Ti and ultrafine (β-Ti + TiFe) eutectic was developed showing superior mechanical properties. The as-cast Ti67Fe27Sn3Nb3 (at.%) alloy exhibited exceptionally high yield stress (2.18 GPa) comparable to that of bulk metallic glasses. Most importantly, the sample presented significant strain-hardening (320 MPa) and enhanced plasticity. The slip deformation and dislocation accumulation in the β-Ti dendrite contribute to the plasticity and the pronounced strain-hardening, whereas the high strength stems from the ultrafine (β-Ti + TiFe) eutectic structure as well as the solution hardening in the multicomponent system.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Materials Engineering
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-208528 (URN)10.1016/j.scriptamat.2017.03.033 (DOI)000402344900014 ()2-s2.0-85016418143 (ScopusID)
Note

QC 20170612

Available from: 2017-06-08 Created: 2017-06-08 Last updated: 2017-06-20Bibliographically approved
2. New Beta-type Ti-Fe-Sn-Nb alloys with superior mechanical strength
Open this publication in new window or tab >>New Beta-type Ti-Fe-Sn-Nb alloys with superior mechanical strength
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(English)In: Journal of Materials Science and Engineering: A, ISSN 2161-6213Article in journal (Refereed) Accepted
Abstract [en]

Multicomponent beta-type Ti-Fe-Sn-Nb alloys comprised of single bcc phase were developed showing excellent mechanical strength and superior plasticity, where the Ti80Fe14Sn3Nb3 alloy presented the highest yield stress (1.88 GPa) comparable to that of Ti-based nanocrystalline alloys. Moreover, a significant strain-hardening (520 MPa) was achieved along with the plastic deformation. 

National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-208639 (URN)
Note

QC 20170612

Available from: 2017-06-09 Created: 2017-06-09 Last updated: 2017-06-12Bibliographically approved
3. Glass forming range of the Ti-Fe-Si amorphous alloys: An effective materials-design approach coupling CALPHAD and topological instability criterion
Open this publication in new window or tab >>Glass forming range of the Ti-Fe-Si amorphous alloys: An effective materials-design approach coupling CALPHAD and topological instability criterion
2016 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 120, no 20, 205106Article in journal (Refereed) Published
Abstract [en]

A method of composition design for metallic glasses was proposed by using the Calculation of Phase Diagrams (CALPHAD) with the assistance of the topological instability criterion. This methodology was demonstrated in the quick and effective searching of glass-forming regions for Ti-Fe-Si and Ti-Zr-Fe-Si alloys containing no biologically toxic elements, e.g., Ni and Cu. In addition, the Ti-Fe-Si system may promote the glass formation owing to the existence of a deep eutectic at the Ti-rich corner. A self-consistent thermodynamic database was constructed based on the CALPHAD approach. The liquidus projection, isothermal sections, and the enthalpy of mixing were calculated by using the database. On the basis of these calculations coupling with the topological instability "lambda lambda criterion," the potential glass-forming alloy compositions in a narrow region were suggested for experimental validation. Thereafter, the isothermal sections of the Ti-Zr-Fe-Si quaternary system were calculated at certain contents of Zr. The designed alloys were prepared by arc-melting and followed by melt-spinning to the ribbon shape. The experimental verifications matched reasonably well with the theoretical calculations. This work offers new insights for predicting glass-forming alloys based on thermodynamic arguments; it shall be of benefit for the exploration of new metallic glasses.

Place, publisher, year, edition, pages
AIP Publishing, 2016
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-199758 (URN)10.1063/1.4968585 (DOI)000390231700022 ()2-s2.0-85000893966 (ScopusID)
Note

QC 20170120

Available from: 2017-01-20 Created: 2017-01-16 Last updated: 2017-06-09Bibliographically approved
4. Degradation of Zr-based bulk metallic glasses used in load-bearing implants: A tribocorrosion appraisal
Open this publication in new window or tab >>Degradation of Zr-based bulk metallic glasses used in load-bearing implants: A tribocorrosion appraisal
2016 (English)In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 60, 56-67 p.Article in journal (Refereed) Published
Abstract [en]

Owing to the amorphous structure, Bulk Metallic Glasses (BMGs) have been demonstrating attractive properties for potential biomedical applications. In the present work, the degradation mechanisms of Zr-based BMGs with nominal compositions Zr55Cu30Ni5Al10 and Zr65Cu18Ni7Al10 as potential load-bearing implant material were investigated in a tribocorrosion environment. The composition-dependent micro-mechanical and tribological properties of the two BMGs were evaluated prior to the tribocorrosion tests. The sample Zr65-BMG with a higher Zr content exhibited increased plasticity but relatively reduced wear resistance during the ball-on-disc tests. Both BMGs experienced abrasive wear after the dry wear test under the load of 2N. The cross-sectional subsurface structure of the wear track was examined by Focused Ion Beam (FIB). The electrochemical properties of the BMGs in simulated body fluid were evaluated by means of potentiodynamic polarization and X-ray Photoelectron Spectroscopy (XPS). The spontaneous passivation of Zr-based BMGs in Phosphate Buffer Saline solution was mainly attributed to the highly concentrated zirconium cation (Zr4+) in the passive film. The tribocorrosion performance of the BMGs was investigated using a reciprocating tribometer equipped with an electrochemical cell. The more passive nature of the Zr65-BMG had consequently a negative influence on its tribocorrosion resistance, which induced the wear-accelerated corrosion and eventually speeded-up the degradation process. It has been revealed the galvanic coupling was established between the depassivated wear track and the surrounding passive area, which is the main degradation mechanism for the passive Zr65-BMG subjected to the tribocorrosion environment.

Place, publisher, year, edition, pages
Elsevier, 2016
Keyword
Bulk metallic glasses, Degradation, Tribocorrosion, Wear, Aluminum, Glass, Ion beams, Medical applications, Nickel, Wear of materials, Wear resistance, X ray photoelectron spectroscopy, Biomedical applications, Bulk metallic glass, Phosphate buffer salines, Reciprocating tribometer, Spontaneous passivation, Subsurface structures, Tribo-corrosion, Zr based bulk metallic glass, Metallic glass, biomaterial, metal, phosphate buffered saline, unclassified drug, zirconium, Article, body fluid, corrosion, electrochemistry, film, implant, mechanical stress, plasticity, potentiodynamic polarization, priority journal, procedures, surface property, Young modulus
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-186919 (URN)10.1016/j.jmbbm.2015.12.024 (DOI)000378969100006 ()2-s2.0-84954529193 (ScopusID)
Note

QC 20160526

Available from: 2016-05-26 Created: 2016-05-16 Last updated: 2017-06-09Bibliographically approved
5. Tribocorrosion studies of metallic biomaterials: The effect of plasma nitriding and DLC surface modifications
Open this publication in new window or tab >>Tribocorrosion studies of metallic biomaterials: The effect of plasma nitriding and DLC surface modifications
2016 (English)In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 63, 100-114 p.Article in journal (Refereed) Published
Abstract [en]

The medical grade pure titanium, stainless steel and CoCrMo alloy have been utilized as biomaterials for load-bearing orthopedic prosthesis. The conventional surgery metals suffer from a combined effect of wear and corrosion once they are implanted, which may significantly accelerate the material degradation process. In this work, the tribocorrosion performance of the metallic biomaterials with different surface modifications was studied in the simulated body fluid for the purpose of investigating the effect of the surface treatments on the tribocorrosion performance and eventually finding the most suitable implantation materials. The metals were subjected to surface modifications by plasma nitriding in different treatment temperatures or physical vapor deposition (PVD) to produce diamond-like carbon (DLC) coating, respectively. The dry wear and tribocorrosion properties of the samples were evaluated by using a reciprocating ball-on-disc tribometer equipped with an electrochemical cell. Prior to the tribocorrosion tests, their electrochemical behavior was measured by the potentiodynamic polarization in phosphate buffer saline (PBS) solution at room temperature. Both stainless steel and CoCrMo after low temperature nitriding kept their passive nature by forming an expanded austenite phase. The DLC coated samples presented the low anodic corrosion current due to the chemical inertness of the carbon layer. During the tribocorrosion tests at open circuit potential, the untreated and low temperature nitrided samples exhibited significant potential drop towards the cathodic direction, which was a result of the worn out of the passive film. Galvanic coupling was established between the depassivated (worn) area and the still passive (unworn) area, making the materials suffered from wear-accelerated corrosion. The DLC coating performed as a solid lubricant in both dry wear and tribocorrosion tests, and the resulting wear after the tests was almost negligible.

Place, publisher, year, edition, pages
Elsevier, 2016
Keyword
Tribocorrosion, Metallic biomaterials, Plasma nitriding, Diamond-like carbon (DLC)
National Category
Tribology
Identifiers
urn:nbn:se:kth:diva-193796 (URN)10.1016/j.jmbbm.2016.06.014 (DOI)000382270000011 ()27348147 (PubMedID)2-s2.0-84975450580 (ScopusID)
Note

QC 20161019

Available from: 2016-10-19 Created: 2016-10-11 Last updated: 2017-06-09Bibliographically approved

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