Structural Quality and Its Effects on the Performance of Light Alloy Castings

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Metal Casting, Forming and Heat Treatment".

Deadline for manuscript submissions: 30 September 2024 | Viewed by 9894

Special Issue Editors

School of Engineering and Technology, Jacksonville University, Jacksonville, FL 32211, USA
Interests: production of high quality castings; solidification of aluminium alloys; aluminium castings; quench sensitivity of aluminium alloys
Special Issues, Collections and Topics in MDPI journals
Department of Materials and Manufacturing, School of Engineering, Jönköping University, 55111 Jönköping, Sweden
Interests: casting; aluminium; magnesium; heat treatment; mechanical behavior; fatigue; process microstructure performance; additive manufacturing
Special Issues, Collections and Topics in MDPI journals
Institute of Structural Durability and Railway Technology, Graz University of Technology, 8010 Graz, Austria
Interests: fatigue design; technological aspects; high- and low-cycle fatigue assessment; structural durability; fracture behavior
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Cast materials are used in most of our products, ranging from simple household appliances to advanced products such as cars, lorries and aircraft. In all these applications, cast materials offer a unique combination of function and performance.

Increasing requirements for lighter, stiffer and stronger materials with increasing requirements for thermal transport properties and corrosion resistance are moving boundaries for material performance further. Aspects critical to delivering improved performance are the alloy content and the microstructure, especially in light weight alloys.

Accordingly, this Special Issue of “Structural Quality and Its Effects on the Performance of Light Alloy Castings” is intended to review and to present the cutting edge state-of-the-art developments in the production of high quality light alloy castings that can meet the ever-increasing performance requirements in today’s applications. The latest developments in the assessment of structural quality will be highlighted. Finally, the effect of processing and structure on the performance of light alloy castings as well as the applicability of traditional and modern approaches for fatigue design will be addressed.

Prof. Dr. Murat Tiryakioglu
Prof. Dr. Anders E. W. Jarfors
Prof. Dr. Martin Leitner
Guest Editors

Manuscript Submission Information

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Keywords

  • pores
  • bifilms
  • inclusions
  • stress concentration
  • oxide films
  • porosity
  • fracture
  • premature failure
  • performance potential

Published Papers (6 papers)

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Research

10 pages, 3122 KiB  
Article
The Impact of the Minimum Ductility Requirement in Automotive Castings on the Carbon Dioxide Footprint throughout the Useful Life of an Electric Car
Metals 2023, 13(3), 513; https://doi.org/10.3390/met13030513 - 03 Mar 2023
Viewed by 1181
Abstract
There is a trend in the automotive producers to require that foundries use more secondary aluminum alloy ingots to reduce the CO2 footprint of car production. The merits of this trend have been investigated in this study. Results have shown that requiring [...] Read more.
There is a trend in the automotive producers to require that foundries use more secondary aluminum alloy ingots to reduce the CO2 footprint of car production. The merits of this trend have been investigated in this study. Results have shown that requiring the use of more secondary ingots while simultaneously reducing the elongation requirement of aluminum alloy die castings is counterproductive, i.e., increases the CO2 footprint of the car over its useful life by not taking advantage of the weight reduction possible. It is recommended that (i) foundries improve their melt handling capabilities to reduce and minimize the entrainment damage made to the melt in the melting and casting process chain, and (ii) automobile producers reduce the weight of die castings by increasing requirements on elongation, to secure a reduced CO2-footprint in the designs, materials usage and life-cycle of cars. Full article
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18 pages, 7132 KiB  
Article
Fatigue Failure in Engineered Components and How It Can Be Eliminated: Case Studies on the Influence of Bifilms
Metals 2022, 12(8), 1320; https://doi.org/10.3390/met12081320 - 06 Aug 2022
Cited by 7 | Viewed by 2180
Abstract
The fatigue of engineered components involves more than the fatigue of metals as studied in laboratories. The miniscule laboratory test pieces cannot represent the pre-existing macroscopic crack defects in real engineering components. This brief study illustrates five examples in which major cracks are [...] Read more.
The fatigue of engineered components involves more than the fatigue of metals as studied in laboratories. The miniscule laboratory test pieces cannot represent the pre-existing macroscopic crack defects in real engineering components. This brief study illustrates five examples in which major cracks are pre-existing as a result of the presence of bifilm defects. The pre-existing defects account for up to 90 per cent of the failure of so-called fatigue failure. The presence of pre-existing bifilm defects is of overwhelming importance. It is, with regret, suggested that the attempts at the elimination of so-called fatigue failures by only studying fatigue is misguided. The so-called fatigue failures of engineering components can be understood and addressed by realizing the major contributions of bifilms. Full article
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11 pages, 3205 KiB  
Article
Evaluation of Microstructure and Mechanical Properties of a Ti10Mo8Nb Alloy for Biomedical Applications
Metals 2022, 12(7), 1065; https://doi.org/10.3390/met12071065 - 21 Jun 2022
Cited by 5 | Viewed by 1358
Abstract
The growth of the elderly population is urging for more suitable biomaterials to allow the performance of better surgical and implant procedures and accelerate the patient’s healing because the elderly are more vulnerable to orthopedic and dental problems. β-phase Ti alloys can improve [...] Read more.
The growth of the elderly population is urging for more suitable biomaterials to allow the performance of better surgical and implant procedures and accelerate the patient’s healing because the elderly are more vulnerable to orthopedic and dental problems. β-phase Ti alloys can improve the mechanical properties of implants by reducing their elastic modulus and, consequently, the effects of stress shielding within bones. Therefore, the objective of this article is to study a novel ternary β-phase alloy of Ti10Mo8Nb produced by an electric arc furnace and rotary forge. The microstructure and mechanical properties of the Ti10Mo8Nb alloy were investigated in order to evaluate its suitability for biomedical applications and compare its characteristics with those present in Ti-alloys commerced or widely researched for prosthetic purposes. A tensile test, Vickers microhardness test, use of microstructure of optical microscopy for examination of microstructure, X-ray diffraction and hemolysis analysis were carried out. Thus, the Ti10Mo8Nb alloy showed suitable properties for biomedical applications, as well as having the potential to reduce the possibility to occur stress shielding after prosthetic implantations, especially for orthopedics and dentistry. Full article
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21 pages, 5536 KiB  
Article
Fatigue Crack Initiation on Semi-Solid Al–7Si–Mg Castings
Metals 2022, 12(7), 1061; https://doi.org/10.3390/met12071061 - 21 Jun 2022
Cited by 3 | Viewed by 1493
Abstract
Four-point bending fatigue tests were performed on semi-solid Al–7Si–Mg castings with varying magnesium contents and heat treatment conditions. Additionally, the effect of anodising on the fatigue resistance of semi-solid Al–7Si–Mg castings was evaluated. Fracture surface and microstructure analysis showed that fatigue crack initiation [...] Read more.
Four-point bending fatigue tests were performed on semi-solid Al–7Si–Mg castings with varying magnesium contents and heat treatment conditions. Additionally, the effect of anodising on the fatigue resistance of semi-solid Al–7Si–Mg castings was evaluated. Fracture surface and microstructure analysis showed that fatigue crack initiation occurred mainly at the periphery of regions of positive macrosegregation at the casting surface, resulting most likely from exudation. The microstructure of these macrosegregation regions was mostly eutectic and was frequently found surrounded by a layer of oxides. This layer of oxides promoted weak bonding between the macrosegregation region and the surrounding material and acted as a crack initiation site. In this study, primary α-Al globule agglomerates at the casting surface and surrounded by a layer of oxides also promoted fatigue crack initiation. Fatigue resistance of semi-solid Al–7Si–Mg castings in the T5 and T6 conditions increased with the increase in the magnesium content of the alloy from 0.3 to 0.45 wt.% due to the higher precipitation hardening response. However, the increase in the magnesium content from 0.45 to 0.6 wt.% resulted in a slight decrease in the fatigue resistance. The oxide layer formed during anodising had no significant effect on the fatigue resistance of the semi-solid Al–7Si–Mg castings in this study due to the dominant effect of the macrosegregation regions on fatigue crack initiation. Full article
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22 pages, 18914 KiB  
Article
A Probabilistic Fatigue Strength Assessment in AlSi-Cast Material by a Layer-Based Approach
Metals 2022, 12(5), 784; https://doi.org/10.3390/met12050784 - 30 Apr 2022
Cited by 6 | Viewed by 1889
Abstract
An advanced lightweight design in cast aluminium alloys features complexly shaped geometries with strongly varying local casting process conditions. This affects the local microstructure in terms of porosity grade and secondary dendrite arm spacing distribution. Moreover, complex service loads imply changing local load [...] Read more.
An advanced lightweight design in cast aluminium alloys features complexly shaped geometries with strongly varying local casting process conditions. This affects the local microstructure in terms of porosity grade and secondary dendrite arm spacing distribution. Moreover, complex service loads imply changing local load stress vectors within these components, evoking a wide range of highly stressed volumes within different microstructural properties per load sequence. To superimpose the effects of bulk and surface fatigue strength in relation to the operating load sequence for the aluminium alloy EN AC 46200, a layer-based fatigue assessment concept is applied in this paper considering a non-homogeneous distribution of defects within the investigated samples. The bulk fatigue property is now obtained by a probabilistic evaluation of computed tomography results per investigated layer. Moreover, the effect of clustering defects of computed tomography is studied according to recommendations from the literature, leading to a significant impact in sponge-like porosity layers. The highly stressed volume fatigue model is applied to computed tomography results. The validation procedure leads to a scattering of mean fatigue life from −2.6% to 12.9% for the investigated layers, inheriting strongly varying local casting process conditions. Full article
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15 pages, 8156 KiB  
Article
Microstructure and Mechanical Properties of Ultrafine Quaternary Al-Cu-Si-Mg Eutectic Alloy
Metals 2022, 12(1), 7; https://doi.org/10.3390/met12010007 - 21 Dec 2021
Cited by 5 | Viewed by 2617
Abstract
The microstructure evolution and mechanical properties of quaternary Al-Cu-Si-Mg eutectic alloy prepared via arc melting and suction casting were studied. This alloy exhibits a single endothermic DSC peak with a melting temperature of 509 °C upon heating, suggesting a eutectic reaction. The cast [...] Read more.
The microstructure evolution and mechanical properties of quaternary Al-Cu-Si-Mg eutectic alloy prepared via arc melting and suction casting were studied. This alloy exhibits a single endothermic DSC peak with a melting temperature of 509 °C upon heating, suggesting a eutectic reaction. The cast alloy microstructure consisted of four phases, α-Al, Al2Cu (θ), Si and Al4Cu2Mg8Si7 (Q), in the eutectic cells and also in the nano-scale anomalous eutectic in the intercellular regions. The eutectic cells show different morphologies in different parts of the sample. Well-defined orientation relationships between the α-Al, Al2Cu, and Q phases were found in the eutectic cell centres, while decoupled growth of Q phase occurred at the cell boundaries. The bimodal microstructure exhibits excellent compressive mechanical properties, including a yield strength of 835 ± 35 MPa, a fracture strength of ~1 GPa and a compressive fracture strain of 4.7 ± 1.1%. The high strength is attributed to a combination of a refined eutectic structure and strengthening from multiple hard phases. Full article
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