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22 pages, 9430 KB

Open AccessArticle

Effect of Welding Speed on Microstructure and Properties of 7075-T6 Aluminum Alloy Pulsed MIG Welded Joints

by Zhongying Liu, Linjun Liu, Shuai Li and Sanming Du

Coatings 2026, 16(5), 605; https://doi.org/10.3390/coatings16050605 - 16 May 2026

Viewed by 155

Abstract

The objective of this study was to systematically investigate the effect of welding speed on the microstructure, mechanical properties, and corrosion behavior of 7075-T6 aluminum alloy similar joints. Pulsed metal inert gas (P-MIG) welding with ER5356 filler wire was employed as the methodology [...] Read more.

The objective of this study was to systematically investigate the effect of welding speed on the microstructure, mechanical properties, and corrosion behavior of 7075-T6 aluminum alloy similar joints. Pulsed metal inert gas (P-MIG) welding with ER5356 filler wire was employed as the methodology to fabricate the joints, with welding speed as the sole variable parameter (450, 500, 550, and 600 mm/min) while maintaining constant welding current and voltage. The key results showed that increasing welding speed refined the dendritic structure in the weld zone (WZ) and promoted a more uniform distribution of precipitates. The tensile strength first increased and then decreased, reaching a maximum of 257.7 MPa at 550 mm/min, with a corresponding elongation of 8.1%. The microhardness of the WZ increased from 91 HV_0.1 (450 mm/min) to 107.4 HV_0.1 (600 mm/min). Corrosion resistance, assessed via intergranular corrosion tests and electrochemical analysis, varied significantly with welding speed; optimal performance was obtained at 450 mm/min, while the poorest occurred at 550 mm/min due to variations in precipitate distribution and passive film stability. The conclusion is that an optimal welding speed of 550 mm/min achieves the best balance between mechanical strength and ductility by refining the microstructure, while the corrosion resistance is primarily governed by the electrochemical activity of grain boundary precipitates induced by the welding thermal cycle. Full article

(This article belongs to the Special Issue Advances in Alloy Surface Mechanics: The Effects of Coating Technologies on Performance)

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23 pages, 21431 KB

Open AccessArticle

Microstructure Evolution-Induced Mechanical Response in Welded Joints of 7075-T6 Aluminium Alloy Thin Sheets Subjected to Different Friction Stir Paths

by Jiajia Yang, Feifan Lv, Jie Liu, Xiaoping Xie, Qing Xu, Pengju Xu, Zenglei Ni, Yong Huang and Liang Huang

Coatings 2026, 16(2), 186; https://doi.org/10.3390/coatings16020186 - 2 Feb 2026

Viewed by 527

Abstract

As a solid-state joining technology, friction stir welding (FSW) exhibits significant advantages for joining aluminium alloys, including low heat input and minimal formation of intermetallic compounds, thereby enhancing joint quality and mitigating deformation. This study investigates the single-sided and double-sided FSW processes of [...] Read more.

As a solid-state joining technology, friction stir welding (FSW) exhibits significant advantages for joining aluminium alloys, including low heat input and minimal formation of intermetallic compounds, thereby enhancing joint quality and mitigating deformation. This study investigates the single-sided and double-sided FSW processes of 3 mm thick 7075-T6 aluminium alloy sheets, focusing on characterising the microstructure and mechanical properties of the joints. Experimental results show that at a rotational speed of 1500 rpm and a welding speed of 80 mm/min, the double-sided co-directional FSW joint achieves a tensile strength of 388 MPa and an elongation of 7.09%, significantly outperforming those of the other two welding paths. In the weld nugget zone (WNZ), continuous dynamic recrystallization (CDRX) occurs, generating uniformly refined equiaxed grains (average size: 1.10 μm) and facilitating the transformation of low-angle grain boundaries (LAGBs) to high-angle grain boundaries (HAGBs). Meanwhile, the strong rotated cube texture is remarkably weakened and replaced by random recrystallized brass textures with the lowest kernel average misorientation (KAM) value in the WNZ. In contrast, the thermo-mechanically affected zone (TMAZ) accumulates a high density of LAGBs due to welding-induced plastic deformation. Microhardness testing reveals a typical “W”-shaped distribution: WNZ hardness is relatively high but slightly lower than that of the base metal (BM), and the minimum hardness of the advancing side (AS) of the heat-affected zone (HAZ) is higher than that of the retreating side (RS). This study confirms that double-sided co-directional FSW crucially regulates microstructural evolution and improves the mechanical properties of 7075-T6 aluminium alloy joints, providing a viable process optimisation strategy for high-quality welding of thin-gauge sheets. Full article

(This article belongs to the Special Issue Advances in Alloy Surface Mechanics: The Effects of Coating Technologies on Performance)

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12 pages, 7889 KB

Open AccessArticle

Growth Process and Formation Mechanism of Oxide Films for FSX-414 Alloy: Comparing External Surface and Narrow Crevice During Long-Term Oxidation at 900 °C

by Junjie Wu, Changlin Yang, Fan Zhao, Yi Zeng, Jianping Lai, Jiaxin Yu, Yingbo Guan, Zhenhuan Gao and Xiufang Gong

Coatings 2026, 16(1), 128; https://doi.org/10.3390/coatings16010128 - 19 Jan 2026

Viewed by 671

Abstract

Welding repair of cracks in FSX-414 cobalt-based alloy, used in high-temperature components, poses significant challenges due to the presence of surface oxide films within the cracks. By comparing the formation of oxide films on the external surface and inside the narrow crevice of [...] Read more.

Welding repair of cracks in FSX-414 cobalt-based alloy, used in high-temperature components, poses significant challenges due to the presence of surface oxide films within the cracks. By comparing the formation of oxide films on the external surface and inside the narrow crevice of FSX-414 alloys preserved at 900 °C for up to 1000 h, we found that the oxide film growth rate on the external surface was slightly larger than that inside the narrow crevice, and the latter slowed down after 672 h. Additionally, the oxide films on both surfaces were mainly composed of O and Cr elements, providing excellent protection to the underlying metal and resulting in minimal internal oxidation. A compositional transition region formed between the oxide film and the base metal. The width of the transition region decreased with heating duration and was narrower in the external surface sample, leading to a steeper composition gradient between the oxide film and the inner metal. With prolonged exposure, increasing numbers of “pores” rich in W and O appeared near the oxide films, creating channels that connect the oxide layer with the internal metal and accelerate material degradation. “Pores” extended deeper into the metal within the narrow crevice compared to those on the surface. Prior to welding repair, channels composed of W and O near the oxide films must be cleaned along with the oxide layer itself, and the removal of oxide from narrow cracks poses greater difficulty. Full article

(This article belongs to the Special Issue Advances in Alloy Surface Mechanics: The Effects of Coating Technologies on Performance)

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17 pages, 8049 KB

Open AccessFeature PaperArticle

Effect of Welding Current on Microstructure and Mechanical and Corrosion Properties of 7075/7075 Pulsed MIG Welded Joints

by Tong Wu, Yaqiang Wang, Linjun Liu, Shuai Li and Hongfeng Liu

Coatings 2025, 15(12), 1437; https://doi.org/10.3390/coatings15121437 - 6 Dec 2025

Cited by 1 | Viewed by 630

Abstract

This study investigates the effects of welding current on the microstructure, mechanical properties, and corrosion behavior of 7075/7075 pulsed metal inert gas (P-MIG) welded joints. Welding experiments were conducted at currents of 190 A, 200 A, and 210 A using ER5356 filler wire, [...] Read more.

This study investigates the effects of welding current on the microstructure, mechanical properties, and corrosion behavior of 7075/7075 pulsed metal inert gas (P-MIG) welded joints. Welding experiments were conducted at currents of 190 A, 200 A, and 210 A using ER5356 filler wire, with the joints analyzed through optical microscopy (OM), scanning electron microscopy (SEM/EDS), and tensile and hardness testing, as well as intergranular and electrochemical corrosion evaluations. The results reveal that increasing welding current alters the solidification dynamics and precipitation behavior in the WZ. At 190 A, refined and uniformly distributed dendrites were obtained, whereas at 210 A, grains coarsened and elemental segregation was more pronounced. The weld hardness exhibited a trend of first increasing and then slightly decreasing with increasing welding current, with a maximum value of 99.5 HV0.1 obtained at 200 A. Similarly, the tensile strength improved with increasing welding current, reaching 257.7 MPa with 8% elongation at 210 A. Corrosion resistance exhibited a non-monotonic trend, with the best performance observed at 200 A, as indicated by the shallowest intergranular corrosion depth, the most positive open-circuit potential, and the highest charge transfer resistance in electrochemical impedance spectroscopy. The findings demonstrate that welding current is a critical parameter controlling the balance between microstructural refinement, mechanical strengthening, and corrosion resistance, and that 200 A represents the optimal condition under the investigated parameters. These insights provide theoretical guidance and experimental evidence for process optimization in the welding of high-strength aluminum alloys. Full article

(This article belongs to the Special Issue Advances in Alloy Surface Mechanics: The Effects of Coating Technologies on Performance)

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21 pages, 8896 KB

Open AccessArticle

Structural and Phase Characteristics and Properties of Multilayer Cr/CrN Coatings Obtained by Magnetron Sputtering

by Nazerke Muktanova, Bauyrzhan Rakhadilov, Erasyl Naimankumaruly and Aisulu Kalitova

Coatings 2025, 15(12), 1375; https://doi.org/10.3390/coatings15121375 - 24 Nov 2025

Cited by 1 | Viewed by 924

Abstract

Multilayer Cr/CrN coatings with two-, four-, and six-layer architectures were deposited on E110 zirconium alloy substrates by reactive magnetron sputtering. The effect of layer number on structure, phase composition, and performance was systematically investigated. XRD revealed that the coatings consisted mainly of CrN [...] Read more.

Multilayer Cr/CrN coatings with two-, four-, and six-layer architectures were deposited on E110 zirconium alloy substrates by reactive magnetron sputtering. The effect of layer number on structure, phase composition, and performance was systematically investigated. XRD revealed that the coatings consisted mainly of CrN and Cr phases, with an increase in the CrN fraction and texture intensity as the number of layers increased. Cross-sectional SEM and EDS analyses confirmed the formation of dense multilayer structures with clear Cr/CrN interfaces and strong adhesion to the substrate. Nanoindentation showed a progressive increase in hardness and Young’s modulus from 2.59 ± 0.09 GPa and 97 ± 2 GPa (two-layer) to 5.0 ± 0.27 GPa and 110 ± 4 GPa (six-layer), respectively. Tribological and scratch tests demonstrated that the 6-layer coating exhibited the lowest wear rate and highest adhesion strength (Lc ≈ 20.5 N). Full article

(This article belongs to the Special Issue Advances in Alloy Surface Mechanics: The Effects of Coating Technologies on Performance)

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Review

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24 pages, 4914 KB

Open AccessReview

Recent Advances in Magnetocaloric Effect of High-Entropy Alloys

by Xiaoli Zhang, Ziwei Guo, Fulong Zhang and Yanzhou Li

Coatings 2025, 15(12), 1425; https://doi.org/10.3390/coatings15121425 - 4 Dec 2025

Cited by 2 | Viewed by 2401

Abstract

High-entropy alloys (HEAs), as a novel class of materials, have attracted widespread attention in the field of materials science due to their unique multi-element high-concentration mixing design. Recent research has found that this alloy mixing strategy not only exhibits excellent performance in structural [...] Read more.

High-entropy alloys (HEAs), as a novel class of materials, have attracted widespread attention in the field of materials science due to their unique multi-element high-concentration mixing design. Recent research has found that this alloy mixing strategy not only exhibits excellent performance in structural properties but also shows potential in functional materials. This review summarizes the progress of research on HEAs in the magnetocaloric effect (MCE) area, first introducing the basic principles of MCE and the related concepts of HEAs. It then summarizes the research progress of rare-earth HEAs, non-rare-earth HEAs, and rare-earth-transition metal composite HEAs in MCE. Finally, this review outlines future research directions for HEAs in the MCE field, laying the groundwork for further applications of HEAs in the magnetocaloric field. Full article

(This article belongs to the Special Issue Advances in Alloy Surface Mechanics: The Effects of Coating Technologies on Performance)

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19 pages, 2172 KB

Open AccessReview

Preparation and Classification of Coatings by High-Energy Ball Milling: A Review

by Zhanfeng Qi, Hengye Zhang, Xiuli Guo and Le Geng

Coatings 2025, 15(11), 1343; https://doi.org/10.3390/coatings15111343 - 19 Nov 2025

Cited by 4 | Viewed by 1910

Abstract

High-energy ball milling (HEBM) offers a pathway for the green preparation of multifunctional coatings. However, existing research lacks systematic frameworks addressing the interplay of HEBM process parameters, elemental screening criteria, and coating classification systems. This study establishes a comprehensive “elemental screening–process synergy–classification and [...] Read more.

High-energy ball milling (HEBM) offers a pathway for the green preparation of multifunctional coatings. However, existing research lacks systematic frameworks addressing the interplay of HEBM process parameters, elemental screening criteria, and coating classification systems. This study establishes a comprehensive “elemental screening–process synergy–classification and prediction” framework for HEBM coatings. Key contributions include establishing a two-tier screening criterion based on non-radioactivity/low-toxicity and functionality for coating elements; revealing the synergistic effects of key process parameters; proposing a dual-dimensional coating classification system based on composition and function; and constructing a quantitative database encompassing 11 key performance indicators. This work provides theoretical foundations and data-driven guidance for the precise design and selection of high-performance HEBM coatings. Full article

(This article belongs to the Special Issue Advances in Alloy Surface Mechanics: The Effects of Coating Technologies on Performance)

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24 pages, 3803 KB

Open AccessEditor’s ChoiceReview

Review of Preparation and Key Functional Properties of Micro-Arc Oxidation Coatings on Various Metal Substrates

by Ningning Li, Huiyi Wang, Qiuzhen Liu, Zhenjie Hao, Da Xu, Xi Chen, Datian Cui, Lei Xu and Yaya Feng

Coatings 2025, 15(10), 1201; https://doi.org/10.3390/coatings15101201 - 12 Oct 2025

Cited by 36 | Viewed by 3714

Abstract

Micro-arc oxidation (MAO) technology demonstrates remarkable advantages in fabricating ceramic coatings on lightweight alloys. For aluminum alloys, MAO rapidly forms dense, pore-free ceramic layers within minutes, significantly enhancing corrosion and wear resistance at low processing costs. In magnesium alloys, optimized electrolyte compositions and [...] Read more.

Micro-arc oxidation (MAO) technology demonstrates remarkable advantages in fabricating ceramic coatings on lightweight alloys. For aluminum alloys, MAO rapidly forms dense, pore-free ceramic layers within minutes, significantly enhancing corrosion and wear resistance at low processing costs. In magnesium alloys, optimized electrolyte compositions and process parameters enable composite coatings with a combination of high hardness and self-lubrication properties, while post-treatments like laser melting or corrosion inhibitors extend salt spray corrosion resistance. Titanium alloys benefit from MAO coatings with exceptional interfacial bonding strength and mechanical performance, making them ideal for biomedical implants and aerospace components. Notably, dense ceramic oxide films grown in situ via MAO on high-entropy alloys (HEAs) triple surface hardness and enhance wear/corrosion resistance. However, MAO applications on steel require pretreatments like aluminizing, thermal spraying, or ion plating. Current challenges include coating uniformity control, efficiency for complex geometries, and long-term stability. Future research focuses on multifunctional coatings (self-healing, antibacterial) and eco-friendly electrolyte systems to expand engineering applications. Full article

(This article belongs to the Special Issue Advances in Alloy Surface Mechanics: The Effects of Coating Technologies on Performance)

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