Research

11 pages, 6997 KiB

Open AccessArticle

Silicon Poisoning and Effects of Tantalum on AlSi Alloys

by Maria Pammer, Johannes Pölzl and Jiehua Li

Metals 2023, 13(12), 1917; https://doi.org/10.3390/met13121917 - 21 Nov 2023

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Grain refinement in Al-Si alloys is crucial for enhancing material castability and mechanical properties. Industrial practice involves adding inoculants, composed of TiB₂ particles coated with metastable Al₃Ti via adsorption, to the melt. This introduces essential free titanium for metastable phase [...] Read more.

Grain refinement in Al-Si alloys is crucial for enhancing material castability and mechanical properties. Industrial practice involves adding inoculants, composed of TiB₂ particles coated with metastable Al₃Ti via adsorption, to the melt. This introduces essential free titanium for metastable phase formation and subsequent growth restriction. The superstoichiometric grain refiner Al-5Ti-1B, with 2.2 wt.% free titanium, is applied for this purpose. A peritectic reaction forms α-aluminium from this layer. However, when silicon content exceeds 3.5 wt.%, grain coarsening occurs due to silicon’s detrimental effect. This study quantified silicon poisoning in an Al-10Si alloy using stoichiometric and superstoichiometric grain refiners through ASTM-standardized TP1 tests. Adding 0.02 wt.% tantalum acted as an antidote to the τ₁ phase, resulting in a finer microstructure. This was attributed to the formation of a Ta-rich layer on TiB₂ particles, which causes α-aluminium formation via a peritectic reaction without generating ternary phases with Ti or Si. Correlating to the increasing particle size curves from the TP1 tests, phases were collected in the filter cake with the help of a PoDFA apparatus. These could be examined more closely on the SEM and identified as needle- or plate-shaped. By using an EDS unit, the phases found were assigned to the poisoning phase and further investigated. After the addition of tantalum, a solubility of tantalum could be detected in former poisoning phases. In combination with the gradients of the grain size, it can thus be assumed that tantalum is both an antidote for silicon poisoning in the Al-Si-Ti system and can itself have a grain-refining effect in this system. Full article

(This article belongs to the Special Issue Grain Refinement and Mechanical Properties of Cast Alloys)

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14 pages, 10202 KiB

Open AccessArticle

Liquid Metal Embrittlement Susceptibility of Hot Formed Zn-Al-Mg Coated Steel with Eutectic Coating Microstructure

by Yubo Yang, Yu Fu, Guangxin Wu, Hongliang Liu, Yu Chen, Qun Luo and Qian Li

Metals 2023, 13(9), 1523; https://doi.org/10.3390/met13091523 - 27 Aug 2023

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Abstract

Liquid metal embrittlement (LME) in Zn-based coating plates during hot stamping is an abnormal phenomenon where intimate contact between liquid Zn and a steel matrix results in the penetration of liquid Zn into the matrix, causing ruptures. In order to alleviate LME phenomenon, [...] Read more.

Liquid metal embrittlement (LME) in Zn-based coating plates during hot stamping is an abnormal phenomenon where intimate contact between liquid Zn and a steel matrix results in the penetration of liquid Zn into the matrix, causing ruptures. In order to alleviate LME phenomenon, this paper designed a series of eutectic Zn-Al-Mg coating alloys to improve the uniformity of the Zn element distribution in the coating during heat treatment and inhibit the reaction between Fe and Zn. The high temperature mechanical properties of the coated steels are determined using thermal simulation to calculate the relative reduction in fracture energy, which is used to evaluate the LME level of the different composition coatings. It is suggested that the Zn-4.5Al-3.0Mg coating shows the highest LME resistance at 920 °C. The microstructure of these Zn-Al-Mg coated steels is observed after austenitization at 850 °C~920 °C for 3 min, which shows that the uniformity of the microstructure after austenitizing is affected by the composition of the coating and the austenitizing temperature. The higher temperature benefits the homogenization of the coating and steel and inhibits LME. The findings of this study provide valuable insights for the development of ternary Zn based LME resistant coatings. Full article

(This article belongs to the Special Issue Grain Refinement and Mechanical Properties of Cast Alloys)

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15 pages, 3097 KiB

Open AccessArticle

Comparison of the Grain-Refining Efficiencies of Ti and LaB₆ Inoculants in Additively Manufactured 2024 Aluminum Alloy: The Important Role of Solutes

by Qiyang Tan, Yu Yin and Ming-Xing Zhang

Metals 2023, 13(8), 1490; https://doi.org/10.3390/met13081490 - 19 Aug 2023

Cited by 1 | Viewed by 1331

Abstract

The present work aims to boost our understanding of factors governing the grain-refining efficiency of inoculation treatments by comparing the grain-refining efficiencies of two inoculators: Ti nanoparticles and LaB₆ nanoparticles, in a 2024 Al alloy during additive manufacturing (AM). Experimental results obtained [...] Read more.

The present work aims to boost our understanding of factors governing the grain-refining efficiency of inoculation treatments by comparing the grain-refining efficiencies of two inoculators: Ti nanoparticles and LaB₆ nanoparticles, in a 2024 Al alloy during additive manufacturing (AM). Experimental results obtained by scanning electron microscopy show that the LaB₆ nanoparticle possessed almost no refining effect on the alloy, with the addition content ranging from 0.5 wt.% to 2 wt.%. Conversely, the Ti nanoparticle resulted in a more pronounced refinement and a fine, fully equiaxed microstructure at 1 wt.% Ti addition. Based on transmission electron microscopy analysis, the higher refining efficiency of Ti inoculation was ascribed to the incorporation of both Ti solute and the in situ-formed L1₂-Al₃Ti nucleation particles. The former significantly increased the overall undercooling ahead of the growing Al grain, which ensured the activation of heterogeneous nucleation on the L1₂-Al₃Ti nanoparticles, leading to grain refinement. This work highlights that despite the addition of nucleation particles, the incorporation of appropriate solutes to generate sufficient undercooling is the prerequisite for the activation of heterogenous nucleation in AM. Full article

(This article belongs to the Special Issue Grain Refinement and Mechanical Properties of Cast Alloys)

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13 pages, 12675 KiB

Open AccessArticle

The Effects of Post-Welding Heat Treatment on the Cryogenic Absorbed Energy of High Manganese Steel Weld Metal

by Seungho Baek, Minha Park, Je In Lee and Sung-Hwan Kim

Metals 2023, 13(6), 1126; https://doi.org/10.3390/met13061126 - 15 Jun 2023

Cited by 1 | Viewed by 1522

Abstract

In this study, a post-weld heat treatment (PWHT) was proposed at high temperatures of 600 °C, 750 °C, and 900 °C for 30 min to significantly improve the impact absorbed energy of high manganese steel weld metal. Electron backscatter diffraction (EBSD), electron probe [...] Read more.

In this study, a post-weld heat treatment (PWHT) was proposed at high temperatures of 600 °C, 750 °C, and 900 °C for 30 min to significantly improve the impact absorbed energy of high manganese steel weld metal. Electron backscatter diffraction (EBSD), electron probe microanalysis (EPMA), and high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) were employed to characterize the production and study the deformation mechanisms in the high manganese steel weld metal. The impact absorbed energy is divided into crack initiation energy and crack propagation energy, which are divided by the value of P_max. The cryogenic impact absorbed energy was 81 J. After PWHT at 600 °C, 750 °C, and 900 °C, it was 75 J, 69 J, and 88 J, respectively. The impact absorbed energies did not follow a proportional relationship with the PWHT temperatures. The increase in impact absorbed energy can be attributed to the narrowing of the dendritic region, which blocks the crack propagation path and efficiently prevents crack propagation. Conversely, the decrease in impact absorbed energy can be attributed to the presence of 100-nm-sized (Cr, Mn)₂₃C₆-type carbides at the grain boundaries, which facilitate crack propagation. Full article

(This article belongs to the Special Issue Grain Refinement and Mechanical Properties of Cast Alloys)

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16 pages, 6856 KiB

Open AccessFeature PaperArticle

Effect of Ca and P on the Size and Morphology of Eutectic Mg₂Si in High-Purity Al-Mg-Si Alloys

by Muhammad Zarif, Ivo Spacil, Thomas Pabel, Peter Schumacher and Jiehua Li

Metals 2023, 13(4), 784; https://doi.org/10.3390/met13040784 - 17 Apr 2023

Cited by 3 | Viewed by 1085

Abstract

Controlling the size and morphology of primary and eutectic Mg₂Si phase via modification and refinement (i.e., Ca and P addition) in Al-Mg₂Si-based alloys containing higher percentages of Si and Mg is of great necessity to ensure their high performance. [...] Read more.

Controlling the size and morphology of primary and eutectic Mg₂Si phase via modification and refinement (i.e., Ca and P addition) in Al-Mg₂Si-based alloys containing higher percentages of Si and Mg is of great necessity to ensure their high performance. The present investigation is mainly aimed to elucidate the effect of Ca and P on the nucleation and growth pattern of eutectic Mg₂Si in high-purity Al-13.1 wt.% Mg₂Si near-eutectic alloys with and without the additions of P and Ca. It was found that purity levels of raw starting materials exert a significant influence on the size and morphology of the near-binary eutectic Al-Mg₂Si. The presence of P suppresses the precipitation of ternary eutectic Al-Mg₂Si-Si. The presence of low levels of Ca promotes the faceted growth of Mg₂Si, while at sufficiently higher levels of Ca, Al₂Si₂Ca intermetallic is formed and the morphology of the Mg₂Si phase is changed from fibers/or globules to blocks or plates. The current investigation is of great importance for the further development of high-performance Al-Mg₂Si-based cast alloys. Full article

(This article belongs to the Special Issue Grain Refinement and Mechanical Properties of Cast Alloys)

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13 pages, 5558 KiB

Open AccessArticle

Effects of Cr Addition on the Precipitation and Properties of Cryo-Rolled CuNiSi Alloys

by Wei Wang, Zongning Chen, Enyu Guo, Siruo Zhang, Huijun Kang and Tongmin Wang

Metals 2023, 13(4), 758; https://doi.org/10.3390/met13040758 - 13 Apr 2023

Cited by 5 | Viewed by 1048

Abstract

CuNiSi alloys are widely used for lead frames and connectors due to the combination of high strength and high electrical conductivity. In this work, the microstructures, properties and precipitation behaviors of cryo-rolled CuNiSi alloys with different Cr additions were investigated. The results show [...] Read more.

CuNiSi alloys are widely used for lead frames and connectors due to the combination of high strength and high electrical conductivity. In this work, the microstructures, properties and precipitation behaviors of cryo-rolled CuNiSi alloys with different Cr additions were investigated. The results show that the microstructures of cryo-rolled CuNiSi alloys are mainly composed of nano-sized deformation twins. During aging, discontinuous precipitation gradually takes the place of continuous precipitation with the onset of recrystallization. The addition of chromium reacts to form Cr₃Si particles and facilitates the formation of lamellar structures in the cryo-rolled states of CuNiSi alloys. Moreover, both the recrystallization and the discontinuous precipitation of cryo-rolled CuNiSi alloys are hindered by the addition of Cr elements. As a result, the mechanical strength of cryo-rolled CuNiSi alloys after aging can be maintained. The best combination of properties obtained in the CuNiSi-0.15Cr alloy is 761 MPa, 6.1% and 48.4% IACS in ultimate strength, elongation and electrical conductivity, respectively. Full article

(This article belongs to the Special Issue Grain Refinement and Mechanical Properties of Cast Alloys)

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12 pages, 9132 KiB

Open AccessArticle

Predicting the Quality of Grain Refiners from Electrical Resistance Measurements of Aluminum

by Maja Vončina, Irena Paulin, Jožef Medved and Mitja Petrič

Metals 2023, 13(4), 717; https://doi.org/10.3390/met13040717 - 06 Apr 2023

Cited by 1 | Viewed by 1171

Abstract

The objective of grain refining is to reduce the size of the primary solidified crystal grains in aluminum alloys, thereby eliminating large columnar grains. Excellent grain refining results can be achieved only when the grain refining agent is of excellent quality, i.e., the [...] Read more.

The objective of grain refining is to reduce the size of the primary solidified crystal grains in aluminum alloys, thereby eliminating large columnar grains. Excellent grain refining results can be achieved only when the grain refining agent is of excellent quality, i.e., the number of Al₃Ti and TiB₂ particles must be appropriate, the shape and size distribution of the particles must be suitable, the Ti/B ratio must be appropriate, and so on. To evaluate the quality of grain refiners, the electric resistivity was measured on four different grain refiners. The obtained results were supported by differential scanning calorimetry analyses and microstructure analyses. It was found that the quality of a grain refiner can be assessed by measurements of electrical resistance. The lowest electrical resistivity was measured for grain refiner B (Al-3Ti-1B), which had the lowest impurity content and the most suitable number and size distribution of TiB₂ and Al₃Ti particles, as well as the most optimal Ti/B ratio, namely, 3.6. A larger number and size of TiB₂ and Al₃Ti particles, as well as elements such as Fe and Si, and also inclusions, which were also confirmed by DSC analyses, cause a higher electrical resistivity due to a stronger scattering of electrons through the matrix. Full article

(This article belongs to the Special Issue Grain Refinement and Mechanical Properties of Cast Alloys)

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11 pages, 5592 KiB

Open AccessArticle

Two-Phase Flow Coordination Characteristics of H62 Brass Alloy Prepared by Up-Drawing Continuous Casting

by Bing Li, Qianqian Fu, Rongzhou Yu, Zikai Lin, Jun Wang, Xue Wang, Renguo Guan and Jiehua Li

Metals 2023, 13(3), 599; https://doi.org/10.3390/met13030599 - 15 Mar 2023

Viewed by 1209

Abstract

In this study, the two-phase flow coordination characteristics between α and β phases of H62 brass made by up-drawing continuous casting are investigated based on the upsetting process. An in situ and new research method for two-phase flow is put forward, and the [...] Read more.

In this study, the two-phase flow coordination characteristics between α and β phases of H62 brass made by up-drawing continuous casting are investigated based on the upsetting process. An in situ and new research method for two-phase flow is put forward, and the two-phase flow and grain refinement characteristics are observed under different deformation conditions. The results show that α phase flows fast under 400 °C, β phase is pulled and overridden by α phase under this temperature. When the temperature increases to 500 °C, which is higher than β phase transition temperature, the flow velocity of β phase increases, and the deformation of β phase is found to bulge. The flow of β phase is more sensitive to low deformation rates than α phase. The deformation amount has a more significant impact on β phase than α phase, and the deformation of β phase promotes the grain fragmentation and refinement of α phase accompanied by huge β phase bulging obviously. Under the conditions of high temperature, low deformation rate, and large deformation amount, both phase α and β of up-drawing continuous casting brass alloy are broken and the grains are refined. Based on the two-phase flow characteristic, numerical simulation is used to obtain the optimal continuous extrusion parameters of the H-shaped wire of up-drawing continuous casting H62 brass. Then, the optimized complex cross-section wire is prepared by continuous extrusion experiment. This research aims to provide guidance for the complex processing of two-phase alloys. Full article

(This article belongs to the Special Issue Grain Refinement and Mechanical Properties of Cast Alloys)

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