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Influence of Microstructural Inhomogeneity on Fracture Behaviour in SSM-HPDC Al-Si-Cu-Fe Component with Low Si Content
Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.ORCID iD: 0000-0001-6755-2123
Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.ORCID iD: 0000-0002-0101-0062
Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
2015 (English)In: Solid State Phenomena, ISSN 1012-0394, E-ISSN 1662-9779, Vol. 217-218, 67-74 p.Article in journal (Refereed) Published
Abstract [en]

In the current paper, a low-Si aluminium alloy (1.4-2.4% Si) was used to fabricate acomplex shape telecom component using Semi-Solid High-Pressure Die Cast (SSM-HPDC),process. Microstructure and fracture characteristics were investigated. The cast material exhibitedmicrostructural inhomogeneity, in particular macrosegregation in the form of liquid surfacesegregation bands in addition to sub-surface pore bands and gross centre porosity. Tensilespecimens were taken from the cast components. Elongation and microstructural inhomogeneitywere investigated and correlated. Fracture surfaces of the tensile specimen were examined underscanning electron microscope (SEM). The study showed that both near surface liquid segregationbands and subsurface porosity strongly affected the fracture behaviour. Dominant for loss ofductility was gross centre porosity. The centre porosity was found to be a combination of trappedgas and insufficient, irregular feeding patterns.

Place, publisher, year, edition, pages
Switzerland: Trans Tech Publications Inc., 2015. Vol. 217-218, 67-74 p.
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:hj:diva-24393DOI: 10.4028/www.scientific.net/SSP.217-218.67Scopus ID: 2-s2.0-84914151681OAI: oai:DiVA.org:hj-24393DiVA: diva2:739774
Projects
RheoCom
Funder
Knowledge Foundation
Available from: 2014-08-21 Created: 2014-08-21 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Rheocasting of Aluminium Alloys: Slurry Formation, Microstructure, and Properties
Open this publication in new window or tab >>Rheocasting of Aluminium Alloys: Slurry Formation, Microstructure, and Properties
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Innovative materials with novel properties are in great demand for use in the criticalcomponents of emerging technologies, which promise to be more cost-effective and energyefficient.A controversial issue with regard to manufacturing complex industrial products isto develop advanced materials with optimised manufacturability in addition to the requiredmechanical and physical properties. The objective of this research study was to develop andoffer new solutions in material-processing-related issues in the field of mechanical andelectrical engineering. This was achieved by investigating the new opportunities affordedby a recently developed rheocasting method, RheoMetalTM process, with the goal of comingto an understanding of the critical factors for effective manufacturing process.

A study of the evolution of microstructure at different stages of the rheocasting process,demonstrated the influence of multistage solidification on the microstructural characteristicsof the rheocast components. The microstructural investigation onquench slurry showed itconsists of the solute-lean coarse globular α-Al particles with uniform distribution ofalloying elements, suspended in the solute-rich liquid matrix. Such inhomogeneous slurryin the sleeve seems to play a critical role in the inhomogeneity of final microstructure. Inthe rheocast component, the separation of the liquid and solid parts of slurry during fillinginfluenced on the microstructural inhomogeneity.

The relationship between the microstructural characteristics and properties of the rheocastcomponents was investigated. The study on the fracture surfaces of the tensile-testedspecimens showed that the mechanical properties strongly affected by microstructuralinhomogeneity, in particular macrosegregation in the form of near surface liquid segregationbands and subsurface porosity. The thermal conductivity measurement showed variation ofthis property throughout the rheocast component due to variations in the ratio of solute-leanglobular α-Al particles and fine solute α-Al particles. The result showed silicon in solidsolution have a strong influence (negative) on thermal conductivity and precipitation ofsilicon by heat treatment process increase the thermal conductivity.

Place, publisher, year, edition, pages
Jönköping: Jönköping University, School of Engineering, 2015. 50 p.
Series
JTH Dissertation Series, 6
Keyword
SSM Casting, aluminium alloy, RheoMetalTM process, microstructure, physical and mechanical properties
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-26297 (URN)978-91-87289-07-1 (ISBN)
Presentation
2015-04-24, E1405, Tekniska Högskolan, Högskolan i Jönköping, Jönköping, 14:36 (English)
Opponent
Supervisors
Projects
RheoCom
Funder
Knowledge Foundation, 20100203
Available from: 2015-04-08 Created: 2015-03-30 Last updated: 2016-08-12Bibliographically approved
2. Rheocasting of aluminium alloys: Process and components characteristics
Open this publication in new window or tab >>Rheocasting of aluminium alloys: Process and components characteristics
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Semi-Solid Metal (SSM) casting is a promising technology offering an opportunity to manufacture net-shape, complex geometry metal components in a single operation. However, the absence of foundry guidelines and limited design data for SSM casting makes it challenging to predict the performance of both process and components. The objective of this research was to develop and offer new solutions to material processing-related issues in the electronics industry. By investigating the opportunities afforded by the recently developed RheoMetalTM rheocasting process, a better understanding of the critical factors needed for an effective manufacturing process and optimised component characteristics was achieved.

A study of the evolution of microstructure at different stages of the RheoMetalTM process demonstrated the influence of multistage solidification on the microstructural characteristics of the rheocast components. The microstructure of a slurry consists of the solute-lean and coarse globular α-Al particles with a uniform distribution of alloying elements, suspended in the liquid matrix. Additional solute-rich α-Al particles were identified as being a consequence of discrete nucleation events taking place after the initial slurry production. In the final components, macrosegregation was observed in the form of variations in the ratio of solute-lean coarse globular α-Al particles and solute-rich fine α-Al particles in both longitudinal and transverse directions.

The relation between microstructural characteristics and material properties was established by determination of the local properties of a rheocast component. The fracture of a rheocast telecom component was strongly affected by microstructural inhomogeneity. In particular, macrosegregation in the form of liquid surface segregation bands and sub-surface pore bands strongly affected the fracture behaviour. Thermal conductivity measurements revealed that regions of the component with a high amount of solute-lean globular α-Al particles showed higher thermal conductivity. The effect of the local variation in thermal conductivity on the thermal performance of a large rheocast heatsink was evaluated by simulation. The results clearly show the importance of considering material inhomogeneity when creating a robust component design.

Place, publisher, year, edition, pages
Jönköping: Jönköping University, School of Engineering, 2016. 45 p.
Keyword
Rheocasting, aluminium alloy, RheoMetal(TM) process, microstructural characteristics, component properties and performance, robust design process
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-31428 (URN)978-91-87289-16-3 (ISBN)
Public defence
2016-09-23, E1405, School of Engineering, Jönköping, 10:00 (English)
Opponent
Supervisors
Funder
Knowledge Foundation
Available from: 2016-08-22 Created: 2016-08-22 Last updated: 2016-08-22Bibliographically approved

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