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High-strength low-alloy (HSLA) steels have garnered significant attention owing to their widespread applications across various industries, with weldability being a particularly critical aspect. However, the impact toughness of the coarse-grained heat-affected zone (CGHAZ) remains a notable challenge under high-heat-input welding conditions. Despite existing research acknowledging the beneficial effects of micro-alloying elements on steel properties, there are still numerous uncertainties and controversies regarding the specific influence of these elements on the microstructure and impact toughness of the CGHAZ under specific welding conditions. To address this issue, this study presents a comprehensive review of the impact of common micro-alloying elements on the microstructure and toughness of the CGHAZ during high-heat-input welding. The results indicate that elements such as cerium, magnesium, titanium, vanadium, nitrogen, and boron significantly improve the toughness of the CGHAZ by promoting intragranular nucleation of acicular ferrite and inhibiting the coarsening of austenite grains. In contrast, the addition of elements such as aluminum and niobium adversely affect the toughness of the CGHAZ. These findings offer crucial theoretical guidance and experimental evidence for further optimizing the welding performance of HSLA steels and enhancing the impact toughness of the CGHAZ.

An attempt is made to cover the whole of the topic of biodegradable magnesium (Mg) alloys with a focus on the biocompatibility of the individual alloying elements, as well as shed light on the degradation characteristics, microstructure, and mechanical properties of most binary alloys. Some of the various work processes carried out by researchers to achieve the alloys and their surface modifications have been highlighted. Additionally, a brief look into the literature on magnesium composites as also been included towards the end, to provide a more complete picture of the topic. In most cases, the chronological order of events has not been particularly followed, and instead, this work is concentrated on compiling and presenting an update of the work carried out on the topic of biodegradable magnesium alloys from the recent literature available to us.

Strengthening Mg alloys with rare earth elements has been a research focus for several decades. To minimize the usage of rare earth elements while enhancing mechanical properties, we adopted the strategy of alloying with multiple rare earth elements, namely Gd, Y, Nd, and Sm. Additionally, to promote the precipitation of basal precipitate, Ag and Zn doping was also induced. Thus, we designed a new cast Mg-2Gd-2Y-2Nd-2Sm-1Ag-1Zn-0.5Zr (wt.%) alloy. The microstructure of the alloy and its relevance to mechanical properties in various heat treatment conditions were investigated. After undergoing a heat treatment process, the alloy demonstrated exceptional mechanical properties, with a yield strength of 228 MPa and an ultimate tensile strength of 330 MPa achieved through peak-aging for 72 h at 200 °C. The excellent tensile properties are due to the synergistic effect of basal γ″ precipitate and prismatic β′ precipitate. In its as-cast state, its primary mode of fracture is inter-granular, whereas in the solid-solution and peak-aging conditions, the predominant mode of fracture is a mixture of trans-granular and inter-granular fractures.

Inconel 738LC (IN738LC) is a nickel-based superalloy specially used in the hot section components of turbine engines. One of its main drawbacks relies on the cracking susceptibility when it is manufactured by laser powder bed fusion (LPBF). This paper analyzes the influence of minor alloying element concentration on cracking tendency of IN738LC superalloy manufactured by LPBF. For that objective, samples were manufactured using two powders, which presented different minor alloying elements concentration (Si, Zr and B). It was shown that the samples crack tendency was very different depending on the powder used for their manufacturing. In fact, the measured crack density value was 2.73 mm/mm2 for the samples manufactured with the powder with higher minor alloying elements concentration, while 0.25 mm/mm2 for the others. Additionally, a special emphasis has been put on elemental composition characterization in cracked grain boundaries in order to quantify possible Si or Zr enrichment. It has been also studied the differences of solidification ranges and grain structures between both samples as a consequence of different minor alloying elements concentration in order to analyze their effect on crack susceptibility. In this sense, Scheil-Gulliver simulation results have shown that samples with higher Si and Zr contents presented higher solidification range temperature. This fact, as well as an increase of the presence of high angle grain boundaries (HAGB), leaded to an increment in the crack formation during solidification. Therefore, in this research work, an understanding of the factors affecting crack phenomenon in the LPBF manufactured IN738LC was accomplished.

The necessity for biomedical components is increasing every year. However, Ti6Al4V, the most widely utilized titanium alloy for biomedical implants are very costly owing to the high price of V alloying element. Furthermore, both alloying elements Al and V, have adverse effects in human body which is not desirable. This review paper highlights significant findings on alloy design using low-cost alloying elements, their processing routes, and their relationship to microstructural, mechanical, and biological properties. Mo, Fe, Mn, Zr, and Cu were identified as low-cost alloying elements and fabrication of titanium alloys with these elements are usually carried out using arc melting, investment casting, powder metallurgy, additive manufacturing, diffusion couple, and thermomechanical processing. Several processing routes can be chosen to obtain optimum properties such as β-phase titanium alloy structure, low elastic modulus, and high strength. Alloy design, post-heat treatment process, and fatigue test for newly developed alloys are research that can be carried out in the future for the development of new titanium materials that are safe for human use and at a more affordable price.

Al-Mg alloys are characterized by permanent solid solution hardening and can additionally be work-hardened. The high mechanical properties of Al-Mg alloys with above-standard Mg content obtained after plastic deformation processes decrease over time. The addition of minor alloying elements like Er or Zr is an alternative method to improve the durability of mechanical properties and increase the strength of Al-Mg alloys due to densely and evenly distributed dispersoids being formed. In this paper, Al-Mg alloys with above-standard Mg content (7 wt.%) and Zr and Er micro-alloying elements and their influence on the microstructure and durability of the mechanical properties were examined. The cast ingots of AlMg7 alloys were characterized by a smooth surface without cracks. The plastic deformation process in a static compression test resulted in an about 60 HBW increase in the Brinell hardness of all the deformed alloys relative to casting. It was revealed that the addition of Er and Zr significantly improved the mechanical properties and durability of the mechanical properties of the Al-Mg after annealing. The addition of Er or Zr slightly restrained the decrease in the Brinell hardness after annealing but did not inhibit it.

The effect of solution treatment on the microstructure and stress-rupture property of a Ni 3 Al-based single-crystal superalloy was investigated. The solution treatment temperature is lower or higher than the dissolution temperature of γ/γ′ eutectic phase ( T eut ) which has a significant effect on the microstructure. When it is slightly below the T eut , the γ/γ′ eutectic coarsened and aggregated to form a large petal-like shape. This process caused non-γ′-phase forming elements to diffuse to the ID region, and the γ/γ′ eutectic phase acted as an obstacle hindering the diffusion of these elements, exacerbating the segregation degree of these elements. On the contrary, the γ/γ′ eutectic phases were eliminated, and the segregation degree of alloying elements reduced when the temperature was higher than T eut . Besides, the deformation inhomogeneity due to the differences in γ′ particle size in ID and dendritic core area for the former regime, γ/γ′ eutectic phase as a weak position decreased the stress-rupture life at 1100 °C/137 MPa. However, the stress-rupture life is nearly twice times that of former when the sample is treated with the later regime, and it is greater than VKNA-25 alloy. This study guides the design of solution heat treatment for Ni 3 Al-based single-crystal superalloys.

The influence of alloying element Mg on Na and Sr modifying Al-7Si hypoeutectic alloys was investigated. The residual content of Na and the morphology of modified eutectic silicon were characterized. It was found that the alloying element Mg had an enhanced effect on the uptake of sodium in the Al-7Si hypoeutectic alloy modified by the Na-contained modifier. Moreover, the morphology of eutectic silicon of the modified Al-7Si alloys was significantly different from that of Al-7Si-0.4Mg alloys in the present research. When the addition of the modifier is enough, both modifiers could entirely modify the eutectic silicon phase of Al-7Si alloys, while incompletely modified eutectic silicon was observed in both Na-modified and Sr-modified Al-7Si-0.4Mg alloy. It was observed that there was an adhering relationship between the partially modified eutectic silicon with Mg-rich phases. According to the results, it can be proposed that the addition of Mg will affect the solidification behavior of alloys, thereby, leading to the incomplete modification of eutectic silicon phases.

Due to their high strength, high toughness, and corrosion resistance, high-strength aluminum alloys have attracted great scientific and technological attention in the fields of aerospace, navigation, high-speed railways, and automobiles. However, the fracture toughness and impact toughness of high-strength aluminum alloys decrease when their strength increases. In order to solve the above contradiction, there are currently three main control strategies: adjusting the alloying elements, developing new heat treatment processes, and using different deformation methods. This paper first analyzes the existing problems in the preparation of high-strength aluminum alloys, summarizes the strengthening and toughening mechanisms in high-strength aluminum alloys, and analyzes the feasibility of matching high-strength aluminum alloys in strength and toughness. Then, this paper summarizes the research progress towards adjusting the technology of high-strength aluminum alloys based on theoretical analysis and experimental verification, including the adjustment of process parameters and the resulting mechanical properties, as well as new ideas for research on high-strength aluminum alloys. Finally, the main unsolved problems, challenges, and future research directions for the strengthening and toughening of high-strength aluminum alloys are systematically emphasized. It is expected that this work could provide feasible new ideas for the development of high-strength and high-toughness aluminum alloys with high reliability and long service life.

Al-Bi-Ga alloy is a good sacrificial anode material, but research on its electrochemical performance in seawater, freshwater, and soil is limited. This article focuses on Al-Bi-Ga-Pb-In and Al-Bi-Ga-Sn-In alloys. The working potential, current efficiency, and corrosion morphology of aluminum alloys under constant current conditions were studied through electrochemical performance testing, microstructure observation, and composition detection. The influence of alloy elements (Bi, Ga, Pb) on the electrochemical performance of aluminum alloys was analyzed. The results indicate that the dissolution morphology of Al-Bi-Ga-Sn-In is better than that of Al-Bi-Ga-Pb-In, and the distribution of Bi element in Al-Bi-Ga-Sn-In is more extensive. The destruction of the oxide film on the surface of aluminum alloy is more uniform, exhibiting better dissolution morphology; As the Bi content increases, the corrosion rate shows a trend of first increasing, then decreasing, and then increasing. The current efficiency first decreases and then increases, usually stopping and rebounding around 4.5%; Ga can increase the corrosion rate and reduce the surface impedance value; When the Ga content is greater than 0.10%, the corrosion rate significantly increases; As the Ga content increases, the current efficiency first decreases and then increases, then stops decreasing and rebounds around 0.2%.