Special Issue "Microstructure and Mechanical Properties of Casting Alloys"

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (31 March 2018)

Special Issue Editor

Guest Editor
Prof. Annalisa Pola

Department of Mechanical and Industrial Engineering, University of Brescia, via Branze 38, 25123 Brescia (Italy)
Website | E-Mail
Interests: microstructural characterization; nonferrous alloys (Al, Zn, Ti, etc.); wear, cavitation and corrosion resistance; numerical simulation of foundry processes; rheology of metals and alloys; processing of foundry alloys; semisolid processing; spray quenching processing and simulation

Special Issue Information

Dear Colleagues,

As is well-known, foundry processes allow the obtaining of complex near net shape parts, characterized by high performance and good appearance. The properties of castings depend on different factors, as the alloy type, the use of corrective elements, the treatment of the liquid metal, the design of the mould, the process parameters, as well as heat treatment and finishing operations. Each one affects the microstructure of the component and, therefore, the final in-service properties.

The aims of this Special Issue are to present recent research and developments on casting alloys, molten metal and post processing treatments, characterization methods, and prediction models, with a particular focus on the correlation between microstructure and performance.

Hence, the different aspects related to the advances in the design, characterization and evaluation of the properties of casting alloys, based on experimental, analytical and computer simulation methods are welcomed in this Special Issue.

Prof. Annalisa Pola
Guest Editor

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1200 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Ferrous casting alloys
  • Nonferrous casting alloys
  • Solidification
  • Microstructure
  • Defects
  • Mechanical properties
  • Simulation and modelling

Published Papers (7 papers)

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Research

Open AccessArticle Mo Addition to the A354 (Al–Si–Cu–Mg) Casting Alloy: Effects on Microstructure and Mechanical Properties at Room and High Temperature
Metals 2018, 8(6), 393; https://doi.org/10.3390/met8060393
Received: 1 March 2018 / Revised: 18 May 2018 / Accepted: 25 May 2018 / Published: 29 May 2018
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Abstract
Cast aluminum alloys are widely used in the automotive field for the production of complex engine parts. However, the mechanical properties of heat-treatable alloys (e.g., Al–Si–Mg or Al–Si–Cu–Mg) are negatively affected by prolonged exposure to temperatures higher than about 200 °C. To date,
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Cast aluminum alloys are widely used in the automotive field for the production of complex engine parts. However, the mechanical properties of heat-treatable alloys (e.g., Al–Si–Mg or Al–Si–Cu–Mg) are negatively affected by prolonged exposure to temperatures higher than about 200 °C. To date, several researchers have proposed the addition of alloying elements, such as Sc or Hf, for enhancing the high temperature behavior of cast Al alloys, while Mo has not been widely investigated. The present study aimed to assess the effects of Mo addition on microstructure, mechanical properties, and thermal stability of the A354 alloy. Samples of A354 alloy with different amount of Mo (in the range 0.1 to 0.8 wt %) were produced. The casting conditions and heat treatment parameters were optimized by means of optical and scanning electron microscopy, thermal analysis and hardness tests. Tensile tests highlighted that Mo induces a moderate increase of yield strength at room temperature (about 10%), but no appreciable improvement in the performance of the alloy at 250 °C was observed. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties of Casting Alloys)
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Open AccessArticle Effect of Microstructures on Working Properties of Nickel-Manganese-Copper Cast Iron
Metals 2018, 8(5), 341; https://doi.org/10.3390/met8050341
Received: 12 April 2018 / Revised: 7 May 2018 / Accepted: 7 May 2018 / Published: 11 May 2018
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Abstract
In the paper, the effects, on basic usable properties (abrasive wear and corrosion resistance), of solidification (acc. to the stable and non-stable equilibrium system) and transformations occurring in the matrix during the cooling of castings of Ni-Mn-Cu cast iron were determined. Abrasive wear
[...] Read more.
In the paper, the effects, on basic usable properties (abrasive wear and corrosion resistance), of solidification (acc. to the stable and non-stable equilibrium system) and transformations occurring in the matrix during the cooling of castings of Ni-Mn-Cu cast iron were determined. Abrasive wear resistance was mainly determined by the types and arrangements of high-carbon phases (indicated by eutectic saturation degree), and the kinds of matrices (indicated by the nickel equivalent value, calculated from chemical composition). The highest abrasive wear resistance was found for white cast iron, with the highest degree of austenite to martensite transformation occurring in its matrix. Irrespective of solidification, a decrease of the equivalent value below a limit value resulted in increased austenite transformation, and thus, to a significant rise in hardness and abrasive wear resistance for the castings. At the same time, corrosion resistance of the alloy was slightly reduced. The examinations showed that corrosion resistance of Ni-Mn-Cu cast iron is, too a much lesser degree, decided by the means of solidification of the castings, rather than transformations occurring in the matrix, as controlled by nickel equivalent value (especially elements with high electrochemical potential). Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties of Casting Alloys)
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Open AccessArticle Room Temperature Mechanical Properties of A356 Alloy with Ni Additions from 0.5 Wt to 2 Wt %
Metals 2018, 8(4), 224; https://doi.org/10.3390/met8040224
Received: 6 February 2018 / Revised: 6 March 2018 / Accepted: 26 March 2018 / Published: 29 March 2018
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Abstract
In recent years, the influence of Ni on high-temperature mechanical properties of casting Al alloys has been extensively examined in the literature. In the present study, room temperature mechanical properties of an A356 alloy with Ni additions from 0.5 to 2 wt %
[...] Read more.
In recent years, the influence of Ni on high-temperature mechanical properties of casting Al alloys has been extensively examined in the literature. In the present study, room temperature mechanical properties of an A356 alloy with Ni additions from 0.5 to 2 wt % were investigated. The role of Ni-based compounds and eutectic Si particles in reinforcing the Al matrix was studied with image analysis and was then related to tensile properties and microhardness. In the as-cast condition, the formation of the 3D network is not sufficient to determine an increase of mechanical properties of the alloys since fracture propagates by cleavage through eutectic Si particles and Ni aluminides or by the debonding of brittle phases from the aluminum matrix. After T6 heat treatment the increasing amount of Ni aluminides, due to further addition of Ni to the alloy, together with their brittle behavior, leads to a decrease of yield strength, ultimate tensile strength, and Vickers microhardness. Despite the fact that Ni addition up to 2 wt % hinders spheroidization of eutectic Si particles during T6 heat treatment, it also promotes the formation of a higher number of brittle Ni-based compounds that easily promote fracture propagation. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties of Casting Alloys)
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Open AccessArticle Compound Formation and Microstructure of As-Cast High Entropy Aluminums
Metals 2018, 8(3), 167; https://doi.org/10.3390/met8030167
Received: 8 February 2018 / Revised: 2 March 2018 / Accepted: 6 March 2018 / Published: 9 March 2018
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Abstract
The aim of this work is to study the microstructure of four high entropy alloys (HEAs) produced by large scale vacuum die casting. Al40Cu15Mn5Ni5Si20Zn15, Al45Cu15Mn5Fe
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The aim of this work is to study the microstructure of four high entropy alloys (HEAs) produced by large scale vacuum die casting. Al40Cu15Mn5Ni5Si20Zn15, Al45Cu15Mn5Fe5Si5Ti5Zn20, Al35Cu5Fe5Mn5Si30V10Zr10, and Al50Ca5Cu5Ni10Si20Ti10 alloys formed a mixture of different structures, containing intermetallic compound (IC) and solid solution (SS) phases. The phases observed in the casting alloys were compared with the equilibrium phases predicted by Thermo-Calc. The measured densities varied from 3.33 g/cm−3 to 5.07 g/cm−3 and microhardness from 437 Hv to 887 Hv. Thus, the microhardness and estimated strength/density ratios are significantly higher than other lightweight high entropy alloys (LWHEAs). Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties of Casting Alloys)
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Open AccessFeature PaperArticle A Microstructural Evaluation of Friction Stir Welded 7075 Aluminum Rolled Plate Heat Treated to the Semi-Solid State
Metals 2018, 8(1), 41; https://doi.org/10.3390/met8010041
Received: 5 December 2017 / Revised: 3 January 2018 / Accepted: 5 January 2018 / Published: 9 January 2018
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Abstract
Two rolled plates of 7075 aluminum alloy were used as starting material. The plates were welded using a simultaneous double-sided friction stir welding (FSW) process. One way of obtaining feedstock materials for Semi-solid processing or thixoforming is via deformation routes followed by partial
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Two rolled plates of 7075 aluminum alloy were used as starting material. The plates were welded using a simultaneous double-sided friction stir welding (FSW) process. One way of obtaining feedstock materials for Semi-solid processing or thixoforming is via deformation routes followed by partial melting in the semi-solid state. As both the base plate materials and the friction weld area have undergone extensive deformation specimens were subjected to a post welding heat-treatment in the semi-solid range at a temperature of 628 °C, for 3 min in order to observe the induced microstructural changes. A comparison between the microstructural evolution and mechanical properties of friction stir welded plates was performed before and after the heat-treatment in the Base Metal (BM), the Heat Affected Zone (HAZ), the Thermomechanically Affected Zone (TMAZ) and the Nugget Zone (NZ) using optical microscopy, Scanning Electron microscopy (SEM) and Vickers hardness tests. The results revealed that an extremely fine-grained structure, obtained in the NZ after FSW, resulted in a rise of hardness from the BM to the NZ. Furthermore, post welding heat-treatment in the semi-solid state gave rise to a consistent morphology throughout the material which was similar to microstructures obtained by the thixoforming process. Moreover, a drop of hardness was observed after heat treatment in all regions as compared to that in the welded microstructure. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties of Casting Alloys)
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Open AccessArticle Modeling and Simulation of the Gray-to-White Transition during Solidification of a Hypereutectic Gray Cast Iron: Application to a Stub-to-Carbon Connection Used in Smelting Processes
Metals 2017, 7(12), 549; https://doi.org/10.3390/met7120549
Received: 22 September 2017 / Revised: 25 November 2017 / Accepted: 1 December 2017 / Published: 7 December 2017
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Abstract
This work reports on experimental and numerical results of the gray-to-white transition (GWT) during solidification of a hypereutectic gray cast iron (GCI) in a casting test using a stub-to-carbon (STC) connection assembly. Since in this process non-uniform cooling rates are produced, the mechanical
[...] Read more.
This work reports on experimental and numerical results of the gray-to-white transition (GWT) during solidification of a hypereutectic gray cast iron (GCI) in a casting test using a stub-to-carbon (STC) connection assembly. Since in this process non-uniform cooling rates are produced, the mechanical properties are expected to spatially vary due to the development of different microstructures along the thimble. The twin aims of this work were to (1) experimentally validate the GWT prediction capabilities of the microstructural model proposed earlier by the authors in the rodding process of a hypereutectic GCI-STC, and (2) estimate, from the numerically obtained microstructure and ultimate tensile strength (UTS), the local hardness of the alloy after the numerical predictions of the microstructure were experimentally validated. To this end, the final microstructure at different points of the thimble and the hardness profile along its radial direction were measured for validation purposes. Moreover, this rodding process was simulated using an extension of a thermal microstructural model previously developed by the authors and the GWT was superimposed on that simulation. The computed results encompass cooling curves, the evolution of gray and white fractions, eutectic radii and densities and, in addition, the hardness profile. A detailed discussion of the experimental and numerical results is presented. Finally, the computed GWT was found to adequately reproduce the experimental data. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties of Casting Alloys)
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Open AccessArticle Secondary Solidification Behavior of A356 Aluminum Alloy Prepared by the Self-Inoculation Method
Metals 2017, 7(7), 233; https://doi.org/10.3390/met7070233
Received: 25 May 2017 / Revised: 17 June 2017 / Accepted: 19 June 2017 / Published: 26 June 2017
Cited by 1 | PDF Full-text (12318 KB) | HTML Full-text | XML Full-text
Abstract
Semisolid slurry of A356 aluminum alloy was prepared by Self-Inoculation Method, and the secondary solidification behavior during rheo-diecasting forming process was researched. The results indicate that the component with non-dendritic and uniformly distributed microstructures can be produced by Rheo-Diecasting (RDC) process (combining Self-inoculation
[...] Read more.
Semisolid slurry of A356 aluminum alloy was prepared by Self-Inoculation Method, and the secondary solidification behavior during rheo-diecasting forming process was researched. The results indicate that the component with non-dendritic and uniformly distributed microstructures can be produced by Rheo-Diecasting (RDC) process (combining Self-inoculation Method (SIM) with High Pressure Die Casting (HPDC)). The isothermal holding time of the slurry has large effect on primary particles, but has little effect on secondary particles. Growth rate of the primary particles in the isothermal holding process conforms to the dynamic equation of Dt3 − D03 = Kt. The suitable holding time for rheo-diecasting of A356 aluminum alloy is 3 min. During filling process, the nucleation occurs throughout the entire remaining liquid, and nuclei grow stably into globular particles with the limited grain size of 6.5μm firstly, then both α1 and α2 particles appear unstable growth phenomenon due to the existence of constitutional undercooling. The average particle sizes and shape factors of both α1 and α2 are decreasing with the increase of filling distance due to different cooling rate in different positions. The growth rate of the eutectic in RDC is 4 times faster than HPDC, which is mainly due to the limitation of α2 particles in RDC process. The average eutectic spacings are decreasing with the increase of filling distance. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties of Casting Alloys)
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