Nickel Aluminum Bronze (NAB) and Manganese Aluminum Bronze (MAB) are high-alloyed bronzes that are increasingly employed in several industrial sectors, mainly related to hostile environments due to their excellent properties against corrosion, cavitation, erosion and improved mechanical properties in relation to other copper-based alloys. These materials are very sensitive against thermal treatments due to a multiphase microstructure in as-cast condition. To contribute to the knowledge of the behavior of both alloys, the effect of thermal treatments on the corrosion behavior of NAB (CuAl10Fe5Ni5) and MAB (CuMn12Al8Fe4Ni2) was studied. As-cast material was subjected to various combinations of quenching and quenching and tempering at 850 °C and 600 °C. Corrosion testing was carried out using simulated sea and fresh water. The microstructures of the as-cast and heat-treated samples were characterized by metallography using two chemical agents with FeCl₃ and NH₄OH solutions and examination by optical and scanning electron microscopy. The major effect of thermal treatments on corrosion was found in influencing the amount and distribution of β-phase, which is prone to selective corrosion in both electrolytes. Full article

During vacuum carburizing, coarse reticulated carbides tend to precipitate along grain boundaries due to high-carbon-potential conditions. This phenomenon is often one of the main factors in the failure of conventional gear steels. In this paper, a novel solid-solution carburizing process was proposed to achieve nano-carbide formation in the surface of the carburizing layer, and the conventional carburizing process and material thermodynamic calculations were combined to study the carburized layer by changing the parameters of the carburizing process, and to optimize the microstructure and properties of the carburized layer. The results showed that the high carbon potential or the long-time boost carburizing process could easily cause the enrichment of many carbon atoms in the traditional carburization, thus forming a carbide network and decreasing the carburization efficiency. The minor increase in large-sized M₇C₃ carbides did not significantly improve the surface hardness and wear resistance. However, the presence of small and dispersed M₂C carbides was the main factor in improving the microhardness and mechanical properties. The novel solid-solution carburizing process could improve the carburizing efficiency and transform reticulated carbides into nano-dispersed M₂C carbides. The surface carbon content and microhardness of 1.07% and 875 HV, respectively, increased 17.7 and 2.4% compared to conventional carburizing processes at 1100 °C. On the other hand, the surface’s ultimate tensile strength was found to be 1900 MPa by mini-tensile testing, and the core had a good match of strength and toughness. It was concluded that the novel solid-solution carburizing process could dissolve the carbon network and thus effectively increase the surface carbon content, achieving fully nanosized carbide on the surface. Modifying the size, morphology, and distribution of the nano-M₂C carbides dispersed within the lath-martensite after tempering the test steel was found to be the main factor in improving the mechanical properties. Full article

A laboratory-scale procedure was developed to obtain lanthanum oxide from spent fluid catalytic cracking catalyst, commonly used in the heavy crude oil cracking process. Two different solids, consisting mainly of silica, alumina, and a certain amount of rare earth elements, were leached under several conditions to recover the rare earths. Nitric acid leaching lead to the highest recovery of lanthanum, reaching a recovery percentage greater than 95% when a 1.5 M concentration was used. Subsequently, liquid phases were subjected to a liquid–liquid extraction process using Cyanex 923 diluted in Solvesso 100, and the lanthanum was quantitatively extracted. Lanthanum was also quantitatively stripped using oxalic acid to obtain the corresponding lanthanum oxalates, as revealed by X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential thermal analysis (DTA), and Fourier transform infrared (FTIR) techniques. After thermal treatment at 1200 °C for 2 h, these solids yielded lanthanum oxide. Full article

The effects of solution treatment time on the morphology evolution of Si particles and the thermal conductivity and tensile properties of Sb-modified alloys were studied. The results show that the evolution of Si particles follows four mechanisms: spheroidization, necking and splitting of particles with large aspect ratios, fusion of spherical particles, and coarsening controlled by diffusion. The first three mechanisms mainly occur at the early stage of solution treatment. The addition of Sb does not change the evolution law of the Si particles, but it does change the contribution of various evolution mechanisms, including promoting spheroidization, fusion, and coalescence, as well as significantly reducing the coarsening rate, which makes the thermal modification of Sb-modified alloys more effective. The increase in thermal conductivity during solution treatment is related to the decrease of the anharmonicity of lattice vibration, lattice wave scattering, and electron scattering of Si particles. The 0.4 wt. % Sb-modified alloy exhibits excellent tensile strength and elongation under as-cast T4- and T6-heat-treated conditions, because the modification significantly reduces the stress concentration of the Si particles and delays the germination and propagation of microcracks. Full article

The onset of morphological instabilities along a solidifying interface has a tendency to influence the microstructural characteristics of cast alloys. In the present study, the initiation as well as the mechanism of microstructural pattern formation is investigated by a quantitative phase-field approach. For energetically isotropic interfaces, we show that the presence of grain boundary grooves promotes the initiation of morphological instabilities, and with progressive solidification, they subsequently amplify into tip-splitting microstructures. We also demonstrate that the grain boundary groove shape influences the amplification of the ridge-shaped instability near the pit region. The structural transition of tip splitting to dendritic microstructures is showcased through the effect of interfacial anisotropy. In addition, the prediction of the tip-splitting position is discussed through an analytical criterion, wherein the sign of the surface Laplacian of interfacial curvature dictates the formation of crest and trough positions in a tip-splitting pattern. In complete agreement with the sharp-interface theory, our phase-field simulations validate the analytically obtained tip-splitting position and suggest that the two tips evolve symmetrically on either side of the hindered concave region. Furthermore, the role of lattice anisotropy on the tip-splitting phenomenon is also discussed in detail. Full article

Alloys based on magnesium are of considerable scientific interest as they have very attractive mechanical and biological properties that could be used to manufacture biodegradable materials for medical applications. Mechanical alloying is a very suitable process to obtain alloys that are normally hard to produce as it allows for solid-state diffusion via highly energetic milling, producing fine powders. Powders obtained by this method can be sintered into nearly net-shape products, moreover, their phase and chemical composition can be specifically tailored. This work aims to investigate the effect of milling time on the density, microstructure, phase composition, and mechanical properties of Mg-Zn-Ca-Pr powders processed by high energy mechanical alloying (HEMA) and consolidated by spark plasma sintering (SPS). Thus, the results of XRD phase analysis, particle size distribution (granulometry), density, mechanical properties, SEM investigation of mechanically alloyed and sintered Mg-Zn-Ca-Pr alloy are presented in this manuscript. The obtained results illustrate how mechanical alloying can be used to produce amorphous and crystalline materials, which can be sintered and demonstrates how the milling time impacts their microstructure, phase composition, and resulting mechanical properties. Full article

The influence of various Ag contents on the microstructure, mechanical properties, and corrosion behavior of extruded Al-4.0Cu-1.1Li-0.4Mg-xAg-0.2Mn-0.2Zr (x = 0.4 and 0.9, wt.%) alloys was investigated. The alloy with 0.9 Ag content contains higher number density of slender T1 (Al₂CuLi) precipitates along with some θ’ (Al₂Cu) phases in the matrix than the alloy with 0.4 Ag content, which is associated with a more rapid hardening response and higher mechanical properties and corrosion resistance, particularly for aging at 130 °C. When aging at high temperatures (above 160 °C), the increase of Ag content mitigates hardness loss by preventing the T1 precipitates from coarsening, and makes the alloy decorate more coarse precipitates at grain boundaries, which leads to the fracture morphology mainly occupied by intergranular fracture. Furthermore, due to the simultaneous promotion of T1 precipitates at grain boundaries and in grain interiors, the 0.9 Ag-containing Al-Cu-Li-Mg-Ag alloy has almost no improvement in corrosion resistance. Full article

The effects of different Ce content on the microstructure and corrosion resistance of Al-5Mg-3Zn-1Cu alloy in metal mold gravity casting were studied in this paper. The microstructure of the alloy was characterized by scanning electron microscope (SEM) and X-Ray diffractometer (XRD). The corrosivity of all alloys in 3.5 wt.%NaCl solution was studied by electrochemical and immersion corrosion techniques. The results show that the microstructure of the alloy is mainly composed of α-Al, T phase, and Al₂Cu phase. Ce can refine the organization of the alloy, but when the addition of Ce is higher than 0.25 wt.%, a massive Ce-rich phase appears in the alloy. The results of a potential polarization test show that the corrosion potential of the alloy increases obviously from −1.253 V to −1.193 V with the increase in Ce content in the alloy. Full article

Adding an appropriate amount of Er element to Al-Zn-In alloys can improve the electrochemical performance of Al alloys; it is convenient to study the electrochemical behavior of the alloy in the rest of our work. However, Er segregation in solid solutions which reduced the comprehensive properties of alloys was difficult to reduce and there was no report on the homogenization of Al-Zn-In alloys. We found that the ultra-high temperature treatment (UHTT) can obviously reduce Er segregation. To explore the better homogenization treatment and the microstructure evolution of Al-5Zn-0.03In-1Er alloy after UHTT, we carried out a series of heat treatments on the alloy and characterized the microstructure of the alloy by optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy spectrum analysis (EDS) and transmission electron microscopy (TEM). The results showed that the main element Er of the Al-Zn-In-Er was largely enriched in grain boundaries after UHTT; the distribution Zn and In was almost unchanged. The as-cast Al-Zn-In-Er alloy consisted mainly of α(Al) solid solution and Al₃Er phase. As the temperature of UHTT increased and the treatment time prolonged, the precipitated phase dissolved into the matrix, and there were dispersed Al₃Er particles in the crystal. The proper UHTT for reducing the interdendritic segregation of the alloy was 615 °C × 32 h, which was properly consistent with the results of the evolution of the statistical amount of interdendritic phase, the line scanning analysis and the microhardness. Moreover, the microhardness of the alloy after treatment of 615 °C × 32 h was obviously higher than that of the as-cast alloy because of the anchoring effect of Al₃Er nanoparticles on the movement of dislocations. Full article

The existing knowledge about the effect of neutron irradiation on the mechanical properties of reactor pressure vessel steels under reactor service conditions relies to a large extent on accelerated irradiations realized by exposing steel samples to a higher neutron flux. A deep understanding of flux effects is, therefore, vital for gaining service-relevant insight into the mechanical property degradation. The existing studies on flux effects often suffer from incomplete descriptions of the irradiation-induced microstructure. Our study aims to give a detailed picture of irradiation-induced nanofeatures by applying complementary methods using atom probe tomography, positron annihilation, small-angle neutron scattering and transmission electron microscopy. The characteristics of the irradiation-induced nanofeatures and the dominant factors responsible for the observed increase of Vickers hardness are identified. Microstructural changes due to high flux conditions are smaller nm-sized solute atom clusters with almost the same volume fraction and a higher concentration of vacancies and sub-nm vacancy clusters compared to low flux conditions. The results rationalize why pronounced flux effects on the nanofeatures, in particular on solute atom clusters, only give rise to small or moderate flux effects on hardening. Full article

Tungsten (W) is considered to be the most promising plasma-facing material in fusion reactors. During their service, severe irradiation conditions create plenty of point defects in W, which can significantly degrade their performance. In this work, we first employ the molecular static simulations to investigate the interaction between a 1/2[111] dislocation loop and a vacancy-type defect including a vacancy, di-vacancy, and vacancy cluster in W. The distributions of the binding energies of a 1/2[111] interstitial and vacancy dislocation loop to a vacancy along different directions at 0 K are obtained, which are validated by using the elasticity theory. The calculated distributions of the binding energies of a 1/2[111] interstitial dislocation loop to a di-vacancy and a vacancy cluster, showing a similar behavior to the case of a vacancy. Furthermore, we use the molecular dynamics simulation to study the effect of a vacancy cluster on the mobility of the 1/2[111] interstitial dislocation loop. The interaction is closely related to the temperature and their relative positions. A vacancy cluster can attract the 1/2[111] interstitial dislocation loop and pin it at low temperatures. At high temperatures, the 1/2[111] interstitial dislocation loop can move randomly. These results will help us to understand the essence of the interaction behaviors between the dislocation loop and a vacancy-type defect and provide necessary parameters for mesoscopic scale simulations. Full article