Research

15 pages, 6545 KiB

Open AccessArticle

Investigation of Multi-Factor Stress Corrosion Cracking Failure of Safe-End Feedwater Lines of Submarine Power System

by Chenlong Ji, Zhongliang Zheng, Ziming Qin and Hao Xue

Materials 2024, 17(6), 1381; https://doi.org/10.3390/ma17061381 - 18 Mar 2024

Viewed by 389

The corrosion process under the complex safe-end feedwater line conditions was investigated via experimental lab testing and numerical simulation. The corrosion of safe-end feedwater lines was controlled through the combination of galvanic corrosion, residual stress, and flow velocity. Firstly, galvanic corrosion occurred once [...] Read more.

The corrosion process under the complex safe-end feedwater line conditions was investigated via experimental lab testing and numerical simulation. The corrosion of safe-end feedwater lines was controlled through the combination of galvanic corrosion, residual stress, and flow velocity. Firstly, galvanic corrosion occurred once the 20 steel was welded with 316L stainless steel. The pitting corrosion could be observed on the 20 steel side of the weld joint. Secondly, a vortex flow was detected around the welding bump and within the pits. The growth of the pits was accelerated in both the vertical and horizontal directions. Finally, under the residual stress condition, the stress intensity factor (K) at the bottom of the pits was easier to reach than the critical stress intensity factor (K_ISCC). Then, pitting was transformed into stress corrosion cracking which then propagated along the weld line. Therefore, the critical factor inducing the failure of safe-end feedwater lines was the combined action of galvanic corrosion, residual stress, and flow velocity. Full article

(This article belongs to the Special Issue Synthesis, Applications and Characterization of Advanced Precious Metal Materials)

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12 pages, 6540 KiB

Open AccessArticle

Realization of Large Low-Stress Elastocaloric Effect in TiZrNbAl Alloy

by Bang-He Lv, Hua-You Xiang, Shang Gao, Yan-Xin Guo, Jin-Han Yang, Nai-Fu Zou, Xiaoli Zhao, Zongbin Li, Bo Yang, Nan Jia, Hai-Le Yan and Liang Zuo

Materials 2024, 17(4), 885; https://doi.org/10.3390/ma17040885 - 14 Feb 2024

Viewed by 759

Abstract

Seeking novel high-performance elastocaloric materials with low critical stress plays a crucial role in advancing the development of elastocaloric refrigeration technology. Here, as a first attempt, the elastocaloric effect of TiZrNbAl shape memory alloy at both room temperature and finite temperatures ranging from [...] Read more.

Seeking novel high-performance elastocaloric materials with low critical stress plays a crucial role in advancing the development of elastocaloric refrigeration technology. Here, as a first attempt, the elastocaloric effect of TiZrNbAl shape memory alloy at both room temperature and finite temperatures ranging from 245 K to 405 K, is studied systematically. Composition optimization shows that Ti-19Zr-14Nb-1Al (at.%), possessing excellent room-temperature superelasticity with a critical stress of around 100 MPa and a small stress hysteresis of around 70 MPa and outstanding fracture resistance with a compressive strain of 20% and stress of 1.7 GPa, demonstrates a substantial advantage as an elastocaloric refrigerant. At room temperature, a large adiabatic temperature change (

Δ T_{ad}

) of −6.7 K is detected, which is comparable to the highest value reported in the Ti-based alloys. A high elastocaloric cyclic stability, with almost no degradation of

Δ T_{ad}

after 4000 cycles, is observed. Furthermore, the sizeable elastocaloric effect can be steadily expanded from 255 K to 395 K with a temperature window of as large as 140 K. A maximum

Δ T_{ad}

of −7.9 K appears at 355 K. The present work demonstrates a promising potential of TiZrNbAl as a low critical stress and low hysteresis elastocaloric refrigerant. Full article

(This article belongs to the Special Issue Synthesis, Applications and Characterization of Advanced Precious Metal Materials)

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18 pages, 9010 KiB

Open AccessArticle

Microstructural Heterogeneity and Property Variations in Cast and Vacuum Hot-Pressed CoCrPtB Alloy

by Yan Li, Weiming Guan, Ming Wen, Junmei Guo, Ze Chen and Chuanjun Wang

Materials 2024, 17(3), 544; https://doi.org/10.3390/ma17030544 - 23 Jan 2024

Viewed by 422

Abstract

Limited research has been undertaken regarding the homogeneity of CoCrPtB alloy billets. A CoCrPtB alloy was processed through casting and vacuum hot pressing. This investigation delved into the interconnection between the secondary dendrite arm spacing (SDAS) in the as-hot-pressed samples and their corresponding [...] Read more.

Limited research has been undertaken regarding the homogeneity of CoCrPtB alloy billets. A CoCrPtB alloy was processed through casting and vacuum hot pressing. This investigation delved into the interconnection between the secondary dendrite arm spacing (SDAS) in the as-hot-pressed samples and their corresponding attributes, specifically Vickers hardness and magnetic properties. Systematic sampling was conducted on the cross-sectional layer and longitudinal surface. Upon examination of the cross-sectional layer proximate to the uppermost region of the hot casting, a discernible parabolic trend was observed for the SDAS that exhibited a gradual increment from the peripheral regions toward the central area along the width. Simultaneously, the fraction of the dendrite phase displayed a consistent linear decline, attaining its peak value at the central portion of the billet. Conversely, on the longitudinal surface, SDAS and the fraction of the dendrite phase remained fairly uniform within the same column sampling regions. However, a notable divergence was identified in the central section, characterized by an augmented SDAS and diminished dendrite phase content. This inherent microstructural inhomogeneity within the CoCrPtB alloy engendered discernible disparities in material properties. Full article

(This article belongs to the Special Issue Synthesis, Applications and Characterization of Advanced Precious Metal Materials)

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13 pages, 2138 KiB

Open AccessArticle

The Effect of d¹⁰ Precious Elements on Structural, Magnetic and Elastic Properties of MnPt Alloy: A First-Principles Study

by Ramogohlo Diale, Phuti Ngoepe, Hasani Chauke, Joseph Moema and Maje Phasha

Materials 2024, 17(3), 541; https://doi.org/10.3390/ma17030541 - 23 Jan 2024

Viewed by 464

Abstract

MnPt’s exceptional stability and extremely high Néel temperature have generated a lot of interest in data storage applications. Previously, it was reported experimentally that the MnPt alloy shows ferromagnetic (FM) behavior at room temperature. In this study, the effects of partial substitution of [...] Read more.

MnPt’s exceptional stability and extremely high Néel temperature have generated a lot of interest in data storage applications. Previously, it was reported experimentally that the MnPt alloy shows ferromagnetic (FM) behavior at room temperature. In this study, the effects of partial substitution of Pt with Pd, Au, and Ag on magnetic properties is investigated using density functional theory. The stability of Mn₅₀Pt_50−xM_x (M = Pd, Au, Ag, x = 6.25, 12.5, 18.75) alloys was assessed by determining their thermodynamic, magnetic, and mechanical properties. The calculated lattice constants of Mn₅₀Pt₅₀ agree well with available theoretical results. The Mn₅₀Pt_50−xM_x alloys’ formability was assessed by measuring the thermodynamic stability using the heat of formation. It was found that B2 Mn₅₀Pt_50−xPd_x alloys (0 ≤ x ≤ 18.75) are thermodynamically stable due to the negative heat of formation close to that of a pristine MnPt alloy. Based on the elasticity results, the B2 Mn₅₀Pt_50−xPd_x is most likely to undergo martensitic transformation for the entire considered composition range. From the calculated values of the Poisson′s ratio, it is shown that an increase in Pd, Ag, and Au effectively improves the ductility of the B2 Mn₅₀Pt_50−xM_x compounds. It was revealed that ferromagnetism is maintained with Pd addition but significantly reduced in the case of Au and Ag. Thus, this work showed that density functional theory can be exploited to propose new possible compositions for future magnets in spintronic applications. Full article

(This article belongs to the Special Issue Synthesis, Applications and Characterization of Advanced Precious Metal Materials)

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16 pages, 3619 KiB

Open AccessArticle

Effect of Silver Powder Microstructure on the Performance of Silver Powder and Front-Side Solar Silver Paste

by Xianglei Yu, Hu Sun, Zhuo Qian, Weichao Li, Wei Li, Fuchun Huang, Junpeng Li and Guoyou Gan

Materials 2024, 17(2), 445; https://doi.org/10.3390/ma17020445 - 17 Jan 2024

Cited by 1 | Viewed by 767

Abstract

Silver powder, as the primary component of solar silver paste, significantly influences various aspects of the paste’s performance, including printing, sintering, and conductivity. This study reveals that, beyond the shape and size of the silver powders, their microstructure is a critical factor influencing [...] Read more.

Silver powder, as the primary component of solar silver paste, significantly influences various aspects of the paste’s performance, including printing, sintering, and conductivity. This study reveals that, beyond the shape and size of the silver powders, their microstructure is a critical factor influencing the performance of both silver powders and silver pastes in solar cell applications. The growth process leads to the formation of either polycrystalline aggregated silver powder or crystal growth silver powder. Analyzing the performance characteristics of these different microstructures provides guidance for selecting silver powders for silver pastes at different sintering temperatures. Polycrystalline aggregated silver powder exhibits higher sintering activity, with a sintering initiation temperature around 450 °C. The resulting silver paste, sintered at 750 °C, demonstrates a low sheet resistance of 2.92 mΩ/sq and high adhesion of 2.13 N. This silver powder is suitable for formulating silver pastes with lower sintering temperatures. The solar cell electrode grid lines have a high aspect ratio of 0.37, showing poor uniformity. However, due to the high sintering activity of the silver powder, the glass layer dissolves and deposits more silver, resulting in excellent conductivity, a low contact resistance of the silver electrode, a low series resistance of the solar cell of 1.23 mΩ, and a high photoelectric conversion efficiency of 23.16%. Crystal growth silver powder exhibits the highest tap density of 5.52 g/cm³. The corresponding silver paste shows improved densification upon sintering, especially at 840 °C, yielding a sheet resistance of 2.56 mΩ/sq and adhesion of 3.05 N. This silver powder is suitable for formulating silver pastes with higher sintering temperatures. The solar cell electrode grid lines are uniform with the highest aspect ratio of 0.40, resulting in a smaller shading area, a high fill factor of 81.59%, and a slightly higher photoelectric conversion efficiency of 23.17% compared to the polycrystalline aggregated silver powder. Full article

(This article belongs to the Special Issue Synthesis, Applications and Characterization of Advanced Precious Metal Materials)

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11 pages, 5280 KiB

Open AccessArticle

Hot-Pressing Deformation Yields Fine-Grained, Highly Dense and (002) Textured Ru Targets

by Shaohong Liu, Fengshuo Xu, Limin Zhou, Hao Cui, Manmen Liu, Ming Wen, Chuanjun Wang, Wei Wang, Song Li and Xudong Sun

Materials 2023, 16(20), 6621; https://doi.org/10.3390/ma16206621 - 10 Oct 2023

Viewed by 668

Abstract

Ruthenium (Ru) is a refractory metal that has applications in the semiconductor industry as a sputtering target material. However, conventional powder metallurgy methods cannot produce dense and fine-grained Ru targets with preferred orientation. Here, we present a novel method of hot-pressing deformation to [...] Read more.

Ruthenium (Ru) is a refractory metal that has applications in the semiconductor industry as a sputtering target material. However, conventional powder metallurgy methods cannot produce dense and fine-grained Ru targets with preferred orientation. Here, we present a novel method of hot-pressing deformation to fabricate Ru targets with high relative density (98.8%), small grain size (~4.4 μm) and strong (002) texture. We demonstrate that applying pressures of 30–40 MPa at 1400 °C transforms cylindrical Ru samples into disk-shaped targets with nearly full densification in the central region. We also show that the hardness and the (002)/(101) peak intensity ratio of the targets increase with the pressure, indicating enhanced mechanical and crystallographic properties. Our study reveals the mechanisms of densification and texture formation of Ru targets by hot-pressing deformation. Full article

(This article belongs to the Special Issue Synthesis, Applications and Characterization of Advanced Precious Metal Materials)

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17 pages, 7649 KiB

Open AccessArticle

Hot Deformation Behavior and Processing Maps of Pure Copper during Isothermal Compression

by Tiantian Chen, Ming Wen, Hao Cui, Junmei Guo and Chuanjun Wang

Materials 2023, 16(11), 3939; https://doi.org/10.3390/ma16113939 - 24 May 2023

Viewed by 921

Abstract

In this study, pure copper’s hot deformation behavior was studied through isothermal compression tests at deformation temperatures of 350~750 °C with strain rates of 0.01~5 s⁻¹ on a Gleeble-3500 isothermal simulator. Metallographic observation and microhardness measurement were carried out of the hot [...] Read more.

In this study, pure copper’s hot deformation behavior was studied through isothermal compression tests at deformation temperatures of 350~750 °C with strain rates of 0.01~5 s⁻¹ on a Gleeble-3500 isothermal simulator. Metallographic observation and microhardness measurement were carried out of the hot compressed specimens. By analyzing the true stress–strain curves of pure copper under various deformation conditions during the hot deformation process, the constitutive equation was established based on the strain-compensated Arrhenius model. On the basis of the dynamic material model proposed by Prasad, the hot-processing maps were acquired under different strains. Meanwhile, the effect of deformation temperature and strain rate on the microstructure characteristics was studied by observing the hot-compressed microstructure. The results demonstrate that the flow stress of pure copper has positive strain rate sensitivity and negative temperature correlation. The average hardness value of pure copper has no obvious change trend with the strain rate. The flow stress can be predicted with excellent accuracy via the Arrhenius model based on strain compensation. The suitable deforming process parameters for pure copper were determined to be at a deformation temperature range of 700~750 °C and strain rate range of 0.1~1 s⁻¹. Full article

(This article belongs to the Special Issue Synthesis, Applications and Characterization of Advanced Precious Metal Materials)

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10 pages, 3279 KiB

Open AccessArticle

Achieving High Strength and High Conductivity of Cu-6 wt%Ag Sheets by Controlling the Aging Cooling Rate

by Zhongyuan Zhang, Yadong Ru, Tingting Zuo, Jiangli Xue, Yue Wu, Zhaoshun Gao, Yongsheng Liu and Liye Xiao

Materials 2023, 16(10), 3632; https://doi.org/10.3390/ma16103632 - 10 May 2023

Cited by 2 | Viewed by 1118

Abstract

In this paper, Cu-6 wt%Ag alloy sheets were prepared using vacuum induction melting, heat treatment, and cold working rolling. We investigated the influence of the aging cooling rate on the microstructure and properties of Cu-6 wt%Ag alloy sheets. By reducing the cooling rate [...] Read more.

In this paper, Cu-6 wt%Ag alloy sheets were prepared using vacuum induction melting, heat treatment, and cold working rolling. We investigated the influence of the aging cooling rate on the microstructure and properties of Cu-6 wt%Ag alloy sheets. By reducing the cooling rate of the aging treatment, the mechanical properties of the cold-rolled Cu-6 wt%Ag alloy sheets were improved. The cold-rolled Cu-6 wt%Ag alloy sheet achieves a tensile strength of 1003 MPa and an electrical conductivity of 75% IACS (International Annealing Copper Standard), which is superior to the alloy fabricated with other methods. SEM characterization shows that the change in properties of the Cu-6 wt%Ag alloy sheets with the same deformation is due to a precipitation of the nano-Ag phase. The high-performance Cu-Ag sheets are expected to be used as Bitter disks for water-cooled high-field magnets. Full article

(This article belongs to the Special Issue Synthesis, Applications and Characterization of Advanced Precious Metal Materials)

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