Article
Materials Science, Multidisciplinary
Xiaolong Xu, Cheng Tang, Hongfu Wang, Yukang An, Yuhong Zhao
Summary: The Cu-Ni alloys were undercooled by fluxing method, and the rapid solidification structure with different undercoolings were obtained. The grain refinement events occurred in the low and high undercooling range, respectively. The microstructure characteristics and evolution law were systematically studied. It was confirmed that the grain refinement under low undercooling was caused by dendrite remelting, while the grain refinement under high undercooling was caused by stress-induced recrystallization. The microhardness of the alloys decreased sharply near the critical undercooling.
JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY
(2022)
Article
Materials Science, Multidisciplinary
Jee Seok Choi, Moonwoo La, DongEung Kim, Kyeong-Hwan Choe, Soong-Keun Hyun, Moon-Jo Kim
Summary: The effect of electric current on the refinement of pure aluminum during solidification was investigated in this study. It was found that electric current can significantly alter the grain morphology and reduce grain size. The grain refinement is influenced by electrical conditions such as the intensity and duration of applied electric current, but under extreme conditions, the refining effect may disappear.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2021)
Article
Engineering, Manufacturing
Xinwei Li, Gan Li, Ming-Xing Zhang, Qiang Zhu
Summary: The study focused on the development and application of a hybrid grain refiner for high-strength aluminum alloys fabricated by LPBF. By adding a Ti/TiN hybrid grain refiner, ultrafine grains were achieved, significantly enhancing the mechanical properties of the aluminum alloys.
ADDITIVE MANUFACTURING
(2021)
Article
Materials Science, Multidisciplinary
Mahdieh Jahanbakhshi, Salman Nourouzi, Reza Naseri, Kourosh Esfandiari
Summary: This study investigates the simultaneous use of cooling slope and mechanical vibration during solidification to improve the microstructure of as-cast A356 aluminum alloy. The results show that by using both cooling slope and mechanical vibration, finer grains can be achieved compared to using these two procedures separately. In the experimental conditions of 20 Hz vibration frequency and 3 minutes duration, an average grain size of 50 μm and a shape factor of 0.66 were obtained, while the mechanical properties of the alloy were also enhanced.
METALS AND MATERIALS INTERNATIONAL
(2022)
Article
Materials Science, Multidisciplinary
Feng Gao, Zhongyun Fan
Summary: This study focuses on the competition among different types of solid particles during the solidification process of metallic materials. Numerical calculations using a solidification model reveal that the competition for nucleation is strongly influenced by the nucleation undercooling of the particles, while the competition for grain initiation is closely related to the sizes of the solid particles.
Article
Materials Science, Multidisciplinary
Nilam S. Barekar, Ivan Skalicky, Shihao Wang, Pavel Shurkin, Onuh Adole, N. Hari Babu, Martin Jarrett
Summary: This paper presents the first trial of using a novel Al-Ni-B grain refiner in the manufacturing of Al-Si wrought piston alloys. The results show that the addition of Nb-B inoculant leads to a refined as-cast structure and a more homogenous distribution of the solute. However, billet homogenization affects the precipitation and properties, and non-homogenized specimens perform better during machining and tensile testing.
Article
Materials Science, Multidisciplinary
O. Sitdikov, E. Avtokratova, M. Markushev
Summary: The study revealed that the grain refinement of Al-Mg-based alloy during multidirectional isothermal forging occurs through continuous dynamic recrystallization controlled by nanosized precipitates, resulting in the formation of (ultra) fine grain structure.
METALS AND MATERIALS INTERNATIONAL
(2021)
Article
Metallurgy & Metallurgical Engineering
Mehdi Malekan, Ahmad Bahmani
Summary: The study revealed that different cooling rates and grain refiner contents significantly influence the dendrite coherency point (DCP) of Al-Si-Mg alloy A357. Increasing the cooling rate and grain refiner content results in a greater solid fraction in which dendrite coherency occurs, as well as an increased difference between liquidus and coherency temperatures.
INTERNATIONAL JOURNAL OF CAST METALS RESEARCH
(2021)
Article
Materials Science, Multidisciplinary
Jianyue Zhang, Guanyu Zhou, Bin Jiang, Alan Luo, Xuzhe Zhao, Aitao Tang, Fusheng Pan
Summary: The novel grain refinement method using a CaMgSn intermetallic phase was found to effectively reduce the average grain size in AZ31 magnesium alloy, improving microhardness and compressive yield strength. The added CaMgSn particles acted as heterogeneous nucleation sites in the grain interiors, contributing to the refinement of microstructure and mechanical properties of Mg-Al-based alloys.
Article
Chemistry, Physical
Fei Guo, Haipeng Dong, Weijiu Huang, Xusheng Yang, Li Hu, Mengdi Li, Luyao Jiang
Summary: The solid solution treated AA 2099 alloy was rolled with a total reduction of 80% at both room and cryogenic temperature. Nanocrystalline grain structure was observed only in the cryogenic temperature rolled sample, related to shear banding behavior. Shear banding behavior was greatly promoted by cryogenic temperature rolling and had a strong influence on mechanical homogeneity of rolled samples.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Chemistry, Physical
Xinghui Han, Wenyi Chen, Xuan Hu, Lin Hua, Fang Chai
Summary: This paper investigates the grain refinement mechanisms of 5A06 aluminum alloy sheets during cold rotary forging (CRF). The study finds that the grains go through a clear refinement from 25.1 μm to 11.8 μm during the CRF process. The grain refinement mechanism can be categorized into two modes: the activation of grains with small Schmid factors (SF) through multi-slip systems and the activation of grains with large SF primarily through a single slip system.
Article
Materials Science, Multidisciplinary
T. J. Chen, X. K. Yang, H. Xue, G. L. Bi, X. Z. Zhang, R. G. Guan
Summary: In this study, a controlled diffusion solidification (CDS) process with simultaneous mixing of two precursor melts was proposed. The effects of mixing rate on the microstructure were studied through simulation and experiments. The results showed that increasing the mixing rate can improve the blending result and achieve a microstructure with small nondendritic or spheroidal grains.
JOURNAL OF MATERIALS SCIENCE
(2022)
Article
Materials Science, Multidisciplinary
A. M. Aziz, M. Z. Omar, Z. Sajuri
Summary: Alloys exposed to elevated temperatures often experience a decrease in mechanical properties, leading to material failure. Thixoforming, as an alternative metal processing method, can enhance mechanical properties by reducing defects. This study compared the tensile strength of thixoformed A319 with that of conventionally cast alloy, finding a 30% increase in ultimate tensile strength for thixoformed samples under elevated temperatures.
METALS AND MATERIALS INTERNATIONAL
(2021)
Review
Materials Science, Multidisciplinary
Nagasivamuni Balasubramani, Jeffrey Venezuela, David StJohn, Gui Wang, Matthew Dargusch
Summary: It has been found that refining the as-solidified alloy structure can improve structural properties and reduce solidification defects. External field melt processing and solidification studies have provided effective methods for refining the structure and exploring the mechanisms. The origin of fine grains may be attributed to heterogeneous nucleation, fragmentation of dendrites and grains, and separation from the melt and mold wall under vibration or agitation. This review critically compares the current understanding of these grain refinement mechanisms.
JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY
(2023)
Article
Materials Science, Multidisciplinary
Xing Zhu, Zhiguang Zhu, Tingting Liu, Wenhe Liao, Yulei Du, Huiliang Wei
Summary: In this study, highly dense and crack-free AA2024 samples were successfully additively manufactured by inoculation treatment of Zr-based metallic glass powders. The grain refinement in the LPBF-fabricated AA2024 alloy was achieved by the formation of Al3Zr particles, acting as heterogeneous nucleation sites. The complete routes for columnar-equiaxed transition were revealed by tailoring the concentration of nucleation particles and solidification conditions, leading to the formation of bimodal grain size distribution consisting of ultrafine grains and coarser grains.
JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY
(2023)
Article
Materials Science, Multidisciplinary
Mehdi Malekan, Reza Rashidi, Saeed G. Shabestari
Article
Materials Science, Multidisciplinary
F. Yavari, S. G. Shabestari
METALLURGICAL AND MATERIALS TRANSACTIONS B-PROCESS METALLURGY AND MATERIALS PROCESSING SCIENCE
(2020)
Article
Metallurgy & Metallurgical Engineering
Mohsen Abdi, Saeed G. Shabestari
Summary: The addition of magnesium accelerates the response to ageing treatments of aluminum-silicon-copper alloys, increasing hardness and strength. Two-stage solution heat treatment can achieve higher mechanical properties.
TRANSACTIONS OF NONFERROUS METALS SOCIETY OF CHINA
(2021)
Article
Materials Science, Multidisciplinary
Katayoun Mohammadi, Mehdi Divandari, Saeed G. Shabestari
Summary: The study investigated the electroplating of ionic Cu on polymeric foam substrates with different pore sizes, showing that reducing foam pore size leads to decreased coating rates. Pulsed current electroplating resulted in smoother Cu coatings compared to direct current electroplating, with SEM images revealing flower-shaped precipitations and the nucleation and grain growth process. A physical model based on limiting diffusion current (LDC) was used to describe the precipitation mechanism.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2021)
Article
Materials Science, Ceramics
Mehdi Malekan, Reza Rashidi, Saeed G. Shabestari, Juergen Eckert
Summary: In this study, the effect of different yttrium doping levels on the glass-forming ability of copper-zirconium-aluminum-based metallic glasses was investigated from thermodynamic and kinetic perspectives. The amorphous structure of the alloys was confirmed using various techniques, and the correlation between the forming ability and thermodynamics/kinetics factors was established through the analysis of thermal characteristics. The results showed that 2% yttrium doping significantly improved the glass-forming ability of the metallic glasses. Yttrium enhances the forming ability by promoting a more densely packed atomic configuration and scavenging oxygen as an undesirable element.
JOURNAL OF NON-CRYSTALLINE SOLIDS
(2022)
Article
Materials Science, Multidisciplinary
S. G. Shabestari, M. Abdi, S. Naghdali
Summary: The study investigated the effects of thixoforming and precipitation hardening heat treatment on the microstructure and mechanical properties of Al-10.5Si-3Cu-0.2Mg alloy produced by the SIMA process. Thixoforming and precipitation hardening significantly improved the mechanical properties of the alloy, demonstrating an effective method for achieving a specific microstructure with excellent castability and high mechanical properties.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2021)
Article
Metallurgy & Metallurgical Engineering
S. Ashkvary, S. G. Shabestari, F. Yavari
Summary: The formation, size, and morphology of Mg2Si intermetallics in Al-Mg2Si in situ composites significantly influence the mechanical properties of the alloy. Cooling rate during solidification has a direct impact on the microstructure and characteristics of the reinforcement particles. This study investigated the effect of different cooling rates on the microstructure and solidification parameters of Al-20%Mg2Si in situ composite using cooling curve thermal analysis technique. The results showed that increasing the cooling rate resulted in higher nucleation temperature of primary Mg2Si, binary eutectic, and ternary eutectic, while decreasing the growth temperature of the eutectic reactions. Furthermore, the Mg2Si reinforcement particles changed from coarse dendritic to fine polygonal shape, accompanied by decreased size and increased density.
INTERNATIONAL JOURNAL OF METALCASTING
(2023)
Article
Thermodynamics
S. G. Shabestari, A. Gholizadeh, S. Naghdali
Summary: This study investigates the effects of Al-5Ti-1B and Zr grain refiners on the solidification transformations and dendrite coherency point (DCP) of Al-6Mg alloy. The results show that Al-5Ti-1B is more effective in refining the grain size and reducing casting defects compared to Zr.
THERMOCHIMICA ACTA
(2022)
Article
Metallurgy & Metallurgical Engineering
M. Honarmand, M. Salehi, S. G. Shabestari, H. Saghafian
Summary: In this study, gas induced semi-solid (GISS) process was used for semi-solid processing of A380 aluminum alloy. The effects of argon inert gas flow rate, starting temperature, and duration of gas purging as key GISS parameters, as well as modification with Sr, on the structural refinements, hardness, and impact strength of GISS alloys were investigated. The results showed that the morphology and size of primary alpha(A1) in the alloy can be changed from coarse dendritic to fine globular structure by adjusting the pouring temperature and adding Sr. The optimized GISS sample obtained from Sr modified alloy with gas purging starting at 610 degrees C exhibited fine grains and a high level of globularity, resulting in significantly increased impact strength and hardness.
TRANSACTIONS OF NONFERROUS METALS SOCIETY OF CHINA
(2022)
Article
Materials Science, Multidisciplinary
Mohammad Hosein Abbasi, Saeed G. Shabestari, Rouhollah Tavakoli
Summary: This research used molecular dynamics simulation method to study the atomic scale local structures in (Zr0.5Cu0.5)(100-x)Alx (x = 0,2,4,6,8,10,12) bulk metallic glass. The study found that Cu-centered and Al-centered icosahedra were the most frequent and experienced the most changes during the glass transition process, and they had the greatest effect on the Glass-Forming Ability (GFA) enhancement. The stability and mobility of the Cu-FI structure were higher compared to the Al-FI and other local structures, and its trend as a function of chemical composition explained the optimal GFA achieved in the 8% Al composition.
MATERIALS TODAY COMMUNICATIONS
(2022)
Article
Materials Science, Ceramics
M. Salehi, S. G. Shabestari
Summary: The properties of Al-Cu-Y based alloys containing La and Co atoms were studied, exhibiting thermal stability and increased hardness at 618 K. The hardness of the alloy increased after primary crystallization and decreased slightly after the second crystallization reaction.
JOURNAL OF NON-CRYSTALLINE SOLIDS
(2022)
Article
Materials Science, Multidisciplinary
M. Faraji, S. G. Shabestari, S. H. Razavi
Summary: This study investigates the influence of time and heating rate on the stabilization of AA5083 aluminum sheets. By using appropriate heating rate and stabilizing time, it was found that the mechanical properties were improved, fine-grained structure was achieved, and the corrosion resistance of the alloy was also suitable.
JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE
(2023)
Article
Materials Science, Multidisciplinary
Y. Najafi, S. G. Shabestari
Summary: Small and uniform globular grains can be produced by introducing inert gas bubbles into the melt in a semi-solid process. The effects of argon gas bubbling on the microstructure and mechanical properties of AZ91 magnesium alloy have been investigated. The gas flow rate was found to significantly influence the microstructure. Image analysis showed that inert gas bubbling treatment could result in fine and spherical semi-solid slurry. Under the optimal conditions of 4 L min(-1) gas flow rate, 610°C gas purging temperature, and 10 s duration of gas injection, the primary α-Mg particles had a mean diameter of 58.4 μm and a mean shape factor of 0.75. By performing inert gas bubbling under the optimum condition, the yield strength, ultimate strength, and elongation of the AZ91 alloy were improved by 17%, 25%, and 190%, respectively, compared to conventional casting. The improvement in mechanical properties was attributed to the spheroidizing and refinement of primary α-Mg, reduction of gas porosity, and good distribution of eutectic phases during solidification.
Article
Materials Science, Ceramics
Saeedeh Naghdali, Saeed G. Shabestari, Hassan Saghafian, Parthiban Ramasamy, Florian Spieckermann, Zhuo Chen, Zaoli Zhang, Juergen Eckert
Summary: Through the use of DSC, SEM, TEM, and XRD, we have discovered hierarchical transformations during the crystallization of Mg66Zn29Ca5 metallic glass ribbons. The activation energies for the crystallization process were calculated using different thermodynamic models. Our findings indicate the formation of short-range order patterns in Mg66Zn29Ca5 metallic glass and the impact of heating rate on crystallization and growth process. The phase transformations during annealing were also studied, revealing the formation and consumption of various metastable phases.
JOURNAL OF NON-CRYSTALLINE SOLIDS
(2023)
Article
Materials Science, Multidisciplinary
H. Momeni, S. G. Shabestari, S. H. Razavi
IRANIAN JOURNAL OF MATERIALS SCIENCE AND ENGINEERING
(2020)
