Special Issue "Microstructure, Mechanical Properties and Solidification Behavior of Metals and Alloys"

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: 31 July 2022 | Viewed by 1255

Special Issue Editor

Prof. Dr. Crystopher Cardoso de Brito
E-Mail Website
Guest Editor
São Paulo State University (UNESP), Campus of São João da Boa Vista, São João da Boa Vista 13876-750, SP, Brazil
Interests: casting; solidification

Special Issue Information

Dear Colleagues,

Solidification is one of the oldest processes for producing complex shapes for applications ranging from art to industry. It is a multidisciplinary field which is highly important when it comes to the comprehension of industrial processing involving molten alloys such as welding, continuous casting, powder metallurgy and foundry. Process limits are still present and need to be overcome. Many research groups have conducted valuable research regarding particular subjects, such as nucleation, macrostructure, structural transitions, as-cast microstructure, porosity, macrosegregation, metal/mold interface, interdendritic fluid flow, additive manufacturing and the mechanical and corrosion properties of as-cast metals. All these topics have been studied for decades following either experimental or modeling approaches, with remarkable complementary aspects between them. Nowadays, complementary research has been developed concerning the evaluation of experimental data from stationary and transient directionally solidified alloys. The knowledge of the physical phenomena occurring at microscopic and macroscopic scales, between liquid and solid phases, is fundamental for the control of the microstructure in all the solidification processes, from casting to welding. The comprehension of solidification remains essential for the development of various recently proposed processes. For example, additive manufacturing processes are still to be interpreted concerning how much the solidification thermal parameters can be used to design the solidification microstructure, as well as to solve quality problems.

Prof. Dr. Crystopher Cardoso de Brito
Guest Editor

Manuscript Submission Information

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Keywords

  • Dendritic and cellular growth
  • Microsegregation
  • Synchrotron X-ray radiography
  • Mechanical properties
  • Corrosion resistance
  • Aluminum alloys
  • Pb-free solder alloys
  • Solidification modeling
  • Rapid solidification
  • Alloy atomization
  • Wire arc additive manufacturing

Published Papers (3 papers)

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Research

Article
Hypereutectic Zn–Al Alloys: Microstructural Development under Unsteady-State Solidification Conditions, Eutectic Coupled Zone and Hardness
Metals 2022, 12(7), 1076; https://doi.org/10.3390/met12071076 - 23 Jun 2022
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Abstract
The present study investigates the effects of Al content and solidification thermal parameters on the microstructural development under transient heat flow conditions for two hypereutectic Zn–Al alloys: Zn-6wt.%Al and Zn-11wt.%Al. The alloys were directionally solidified and had experimental cooling profiles monitored permitting cooling [...] Read more.
The present study investigates the effects of Al content and solidification thermal parameters on the microstructural development under transient heat flow conditions for two hypereutectic Zn–Al alloys: Zn-6wt.%Al and Zn-11wt.%Al. The alloys were directionally solidified and had experimental cooling profiles monitored permitting cooling rates and growth rates to be determined along the length of the directionally solidified (DS) castings. The microstructure of the Zn-6wt.%Al alloy is shown to be formed by eutectic colonies, constituted by a eutectic mixture of (Zn) and (Al′) phases in the form of lamellae and the Zn-11wt.% Al alloy by the pro-eutectic (Al′) dendrites and the eutectic mixture in the interdendritic regions. Growth laws are experimentally determined relating eutectic and dendritic spacings to the growth rate and cooling rate. A diagram exhibiting the coupled zone of Zn–Al alloys as a function of cooling rate is proposed, which shows different microstructural morphologies influenced by composition and thermal parameters, that is, growth rate and the temperature gradient, synthesized by the cooling rate (Ṫ = G.V). The microhardness of both Zn-6wt.%Al and Zn-11wt.%Al alloys were shown not to depend on the length scale of the resulting microstructure. Full article
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Article
Assessing Microstructure Tensile Properties Relationships in Al-7Si-Mg Alloys via Multiple Regression
Metals 2022, 12(6), 1040; https://doi.org/10.3390/met12061040 - 17 Jun 2022
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Abstract
The development of Al-based alloys presumes a detailed understanding of the microstructure evolution during solidification since the as-solidified microstructure also has effects on the subsequent thermo-mechanical processing. In the present investigation Al-7wt.%Si-xMg (x = 0.5 and 1 wt.%) alloys are subjected to transient [...] Read more.
The development of Al-based alloys presumes a detailed understanding of the microstructure evolution during solidification since the as-solidified microstructure also has effects on the subsequent thermo-mechanical processing. In the present investigation Al-7wt.%Si-xMg (x = 0.5 and 1 wt.%) alloys are subjected to transient directional solidification with a view to characterizing the microstructure evolution, with special focus on both dendritic evolution and the inherent features of the Mg2Si and π-AlSiFeMg intermetallics. Experimental power-type functions relating the primary, secondary and tertiary interdendritic spacings to the solidification cooling rate and growth rate are developed. It is observed that the Mg content added to the Al-7wt.%Si alloy and the consequent increase in the Mg2Si fraction tends to increase the values of the primary dendritic spacing. However, this same behavior is not verified for the growth evolution of dendritic side branches. A multiple linear regression (MLR) analysis is developed permitting quantitative correlations for the prediction of tensile properties and hardness from microstructural parameters to be established. The increase in the Mg alloy content from 0.5 to 1 was shown to promote an increase in both the ultimate tensile strength (σu) and elongation. Full article
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Article
Evolution Behavior and Closure Mechanism of Porosity in Large Billet during the Reduction Pretreatment
Metals 2022, 12(4), 599; https://doi.org/10.3390/met12040599 - 30 Mar 2022
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Abstract
The reduction pretreatment process was proposed to be applied to large billets for the purpose of alleviating the center porosities and reducing the rolling ratio. This study focused on the evolution behavior and closure mechanism of porosity in a large billet during reduction [...] Read more.
The reduction pretreatment process was proposed to be applied to large billets for the purpose of alleviating the center porosities and reducing the rolling ratio. This study focused on the evolution behavior and closure mechanism of porosity in a large billet during reduction pretreatment. The porosities were characterized by ultrasonic scanning and 3D reconstruction. The results showed that the porosities near the surface of the billet were firstly closed during the reduction pretreatment. The reduction began to effectively act on the center of the billet at the deformation of 0.16. When the reduction amount increased to 0.20–0.22, both the pore number and the porosity degree at the center of the billet were the smallest. As the deformation exceeded 0.25, the porosities gathered at the center of the billet, which may have caused larger defects. A numerical model for the reduction pretreatment was established to analyze the evolution behavior of porosity. The simulation results showed that the position with the maximum of strain moved toward the center of the billet as the reduction amount increased. At the position where the deformation was 0.20, the deformation would readily occur at the center, and the center strain was almost twice as much as the surface strain. The upper and lower surfaces of porosity were compressed to the center of the porosity in the thickness direction. The two ends of porosity were not stretched in the rolling direction. The closure index indicated that the deformation penetrated into the center would accelerate the deformation of porosity. The cross-sectional area of the porosity gradually decreased with the increase in the hydrostatic integration, which indicated that the hydrostatic integration could be used to assess the closure degree of porosity during the reduction pretreatment process. Both the closure index and the hydrostatic integration proved the effective role of the reduction pretreatment in the alleviation of porosity. Full article
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