Metals and Materials International最新文献

This study aimed at developing a structural analysis method considering both acceleration and rotation of projectiles in gas gun tests to evaluate and improve their impact resistance during artillery firing. The 2- and 3-dimensional simulation results of deceleration and target penetration depth closely aligned with actual test results, providing an effective means to quantitatively assess the impact resistance of projectiles and analyze the influence of rotation on collision processes. While the projectile's deceleration slightly increased with rotational speed, rotational motion had minimal effect on deformation during most collision processes, maintaining stability and efficiently transferring energy. This indicates that high-speed rotation had an insignificant effect on deceleration and target penetration depth, and solid-state electronic equipment was largely unaffected by rotation. However, rotational deceleration increased with projectile velocity and rotation speed. For thermal batteries, thus, solid-state electrolytes should be used to prevent liquid leakage due to rotation. Additionally, shock-absorbing materials, sealing, and protective layers can be employed to mitigate vibration and shock. These findings suggest that simulations effectively complemented gas gun tests, providing an efficient method to evaluate projectile impact resistance.

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This study conducts an in-depth investigation into the oxidation mechanisms of the AlCrMoNbTi high-entropy alloy at 1000 °C and 1200 °C, using experimental and multiscale characterization techniques. At 1200 ℃, the alloy exhibited parabolic oxidation kinetics with an oxidation constant of 3.32 mg·cm^-2∙h^-1, which was a 57.4% improvement over similar Zr-containing high-entropy alloys. The protection performance can be attributed to the formation of stable CrNbO₄ and Nb₂O₅, along with Al₂O₃ filling. In contrast, at 1000 ℃, the oxide scale consists of a layered structure accompanied by Nb₂O₅ polymorphism and MoO₃ volatility, promoting oxidation kinetics from parabolic to linear and reducing oxidation resistance.

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In this work, the effects of cold rolling and T6 treatment on the microstructures, mechanical properties and corrosion resistance of hot-rolled Al-4Cu-xMg (x = 0, 0.25 and 0.5 wt%) alloy sheets were investigated. After cold rolling, the coarse deformed grains with high-density dislocations were preserved in the three alloys. In contrast, after the T6 treatment, fine equiaxed grains developed due to static recrystallization. The addition of Mg decreased the average grain size and triggered the formation of S’-Al₂CuMg. The increased amount of precipitate and the narrow precipitate-free zone were beneficial for increasing the mechanical strength. The mechanical strength slightly increased after cold rolling because only dislocations were introduced, whereas the mechanical strength significantly increased after T6 treatment because of the sharp refinement of grains and the static precipitation of second phases. The addition of Mg greatly optimized the corrosion resistance, which was mainly attributed to the composite oxides composed of Al₂O₃/Al(OH)₃-MgO. In contrast, the corrosion resistance decreased after cold rolling because high-density dislocations triggered localized corrosion. Moreover, the corrosion resistance decreased continuously after the T6 treatment because the massive amount of precipitates had negative effects on the corrosion resistance. Although the corrosion resistance slightly decreased, the mechanical strength was greatly optimized. Thus, a good balance between the mechanical strength and corrosion resistance was obtained for the Al-4Cu-0.5Mg alloy via cold rolling and T6 treatment.

Laser powder bed fusion (LPBF) is one of the most suitable processes in metal additive manufacturing (AM) due to its higher strength and better dimensional accuracy. LPBF has proven to build complicated components like heat exchangers, turbines, intake manifolds, and other aerospace components. These areas have a huge demand of ferrous materials (SS300 series) for better performance. SS316L has good corrosion resistance and better mechanical properties than other stainless steels like SS304. Therefore, SS316L demand has increased in the automobile, aerospace and health care sectors. A comprehensive review of the LPBF AM process on SS316L material was undertaken in the current study. The paper presents the physical, mechanical and microstructural properties of additively manufactured SS316L. The major problems that occur with the LPBF additive manufacturing process are surface roughness, residual stress and distortion also presented in this paper. The prediction of distortion and residual stresses are discussed for different AM process parameters and different simulation software. The effect of post-processing of AM parts is also discussed in detail. This review article will be very helpful for understanding the process parameters, testing methods, post-processing techniques and mechanical properties of LPBF-processed AM SS316L.

Laser powder bed fusion (LPBF) AlSi10Mg alloy exhibits high susceptibility to hydrogen porosity during fusion welding, and the mechanical properties of the welded joint are significantly reduced compared to the base metal (BM). In this study, LPBF AlSi10Mg alloy was welded using laser metal deposition (LMD) process, followed by direct aging (DA) heat treatment at 160 °C for 6 h. The porosity characteristics, microstructure, and mechanical properties of the welded joints were investigated, along with an in-depth analysis of the pore formation mechanism and the strengthening mechanism induced by DA heat treatment. The results show that the increase in the number of weld passes can significantly reduce both the hydrogen pore diameter and porosity in the weld metal (WM). The porosity concentration is notably higher at the inter-pass region. After DA heat treatment, the proportion of spherical and short rod-like Si phases in the WM increased, and the connectivity of eutectic Si networks also improved. Additionally, DA heat treatment reduces kernel average misorientation and geometric necessary dislocations, decreases low-angle grain boundaries proportion, and slightly increases grain size. Schmid factor analysis confirms reduced slip system activation, improving crack resistance via strengthening from nano-Si precipitates. DA heat treatment enhanced the average hardness of the welded joints, with the maximum average hardness reaching 111.04 HV. The tensile strength of the joint reached 293.6 MPa, with an elongation of 1.7%. The enhancement of mechanical properties is attributed to the precipitation strengthening of silicon elements following DA heat treatment.

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The introduction of powder bed fusion (PBF) is crucial for advancing the next-generation automotive industry. However, the PBF faces challenges such as size constraints and difficulties in mass production, necessitating effective welding methods to integrate PBF-produced components with conventionally manufactured counterparts. Among various welding methods, integrating resistance spot welding in the assembly of PBFed products with conventionally fabricated ones may address the inherent PBF challenges. But, our findings revealed that during the resistance spot welding of PBF-fabricated stainless steel (STS) 316L, excessive heat generation caused weld expulsion at relatively low welding current. This expulsion reduced the effective weld volume, resulting in significant degradation in weld strength. To understand the root cause of this phenomenon, this study investigated the origin of the excessive heat and its impact on weldability when connecting the PBFed parts to CRed counterparts. The results show that welding PBF-produced STS 316L to CR-produced STS 316L generated significant heat due to the high surface roughness and unique microstructure of the PBF material. These factors led to weld expulsion and decreased weldability. However, by analyzing these thermal characteristics, we optimized welding parameters and enhanced mechanical properties. Ultimately, we demonstrate that PBF-produced components can be effectively welded to traditionally manufactured parts, providing crucial insights for improving the integration of PBF components in the automotive industry.

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Grain boundaries (GBs) are essential in defining the mechanical characteristics and behavior of any polycrystalline material. Their presence has been known to impact the various properties of the materials, including mechanical, thermal, electrical, and optical properties. Interestingly, specific GBs are known to form special faceted structures wherein they adopt a series of distinct planar segments or facets. The presence of faceted GBs has been linked with the anisotropic nature of GB free energies with respect to their inclination, introducing distinct characteristics that significantly influence the overall performance and functionality of materials. Moreover, the formation of faceted GBs increases the total boundary area due to the creation of additional facets. However, as these facets are more energetically favorable, the formation of these faceted GBs leads to a reduction in the overall GB energy. Further, their migration behavior contrasts significantly with that of non-faceted GBs. Understanding the nature of faceted GBs is crucial since they have been closely associated with phenomena such as abnormal grain growth, GB migration, wetting, and diffusion, all of which can result in significant variations in the material’s mechanical, electrical, and thermal properties. In this extensive review article, we have discussed in depth the alteration in the material’s performance incorporated with faceted GBs. Both the experimental and simulation-based investigations have been critically examined and reported to present an informed perspective on recent advancements in this field. Key findings revealed how the faceted GBs contribute to the unique stress responses and alter the energy of the structure, underscoring their role in altering material performance. Finally, we have highlighted prospective research avenues that could help in deepening our understanding of faceted GBs and their impact on material properties.

Graphical Abstract

Vaporization of alloying elements during laser welding adversely affects weld metal composition and properties. The high-temperature molten pool affect alloying element vaporization and weld metal composition change. In this study, the laser mirror welding technology is utilized to minimize heat input and decrease element evaporation within the weld, thereby reducing welding deformation. Numerical simulations and experimental validations were employed to reveal the intrinsic relationship between heat distribution and elemental evaporation in the weld zone. The theory of element evaporation and the temperature field are quantitatively researched. To obtain the temperature variation trends and establish the element burn-off models in various regions. The results show that laser mirror welding significantly reduces the evaporation of alloying elements compared to conventional laser welding. Within a 0.5 mm × 0.5 mm × 0.5 mm representative volume, the maximum mass losses of aluminum, copper, and lithium were quantified as 1.34 × 10⁻³ g, 6.4 × 10⁻⁵ g, and 1.25 × 10⁻⁵ g, respectively, in the weld center above the joint, the evaporation mass of copper exhibited a negative value, suggesting that the inward diffusion of copper into this region exceeded its evaporation rate. Furthermore, at both the upper and lower extremities of the weld center, the evaporation rate of lithium was significantly reduced, reaching only 40% of its peak value. This innovative welding approach substantially reducing elemental loss in aluminum-lithium alloy joints, establishing a highly promising avenue for subsequent scientific exploration and industrial application.