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This study investigated the artificial aging process of TiB2/Al–5Cu composite, with a focus on the influence of TiB2 particles on the precipitation behavior of the composite. Additionally, a comparative analysis of the microhardness and tensile properties between the TiB2/Al–5Cu composite and the Al–5Cu alloy was conducted. X-ray Diffraction (XRD) analysis reveals that the TiB2/Al–5Cu composite consists of TiB2 and Al2Cu phases. The Scanning Electron Microscopy (SEM) imagery demonstrates a predominantly cellular crystal composition in the composite. Notably, as the aging time progresses, there's an initial increase followed by a subsequent decrease in the gray grain boundaries of the composite. Transmission Electron Microscopy (TEM) images uncover the presence of needle-like θ phase, TiB2, and dislocations within the TiB2/Al–5Cu composite. The incorporation of TiB2 particles has emerged as a pivotal factor in significantly curtailing the artificial aging duration. With the peak hardness aging time determined at a mere 8 h, the TiB2/Al–5Cu composite showcases substantially higher hardness levels compared to the Al–5Cu base alloy. Remarkably, the optimum aging time for achieving the best mechanical properties in the composites is reduced from 20 to 8 h. Directly comparing the TiB2/Al–5Cu composite to the Al–5Cu alloy under peak aging conditions, notable enhancements in both yield strength (22%) and tensile strength (41%) are observed. Additionally, a slight increase in elongation is observed in the TiB2/Al–5Cu composite. [ABSTRACT FROM AUTHOR]

Forming conditions and compositional changes of primary inclusions in molten steel have been studied due to the demand for high cleanliness of steels. MnS, a common inclusion in steel, does not form in molten steel, although it is observed in steel with oxide inclusions such as MnO, Al2O3 and SiO2. On the other hand, Mn and S are enriched in molten steel due to the segregation phenomenon during the solidification process which suggests that MnS form in molten steel during solidification. However, the precipitation behavior of MnS inclusions in molten steel due to the enrichment of Mn and S and the interaction between the primary inclusion and the molten steel is still unclear. In this work, a new experimental technique was developed and the precipitation behavior of MnS from molten steel onto solid Al2O3 was studied. Solid MnS precipitates were observed on the Al2O3 rod immersed in the sample with adding Al whereas precipitates containing MnO, A2O3 and MnS were observed on the Al2O3 rod in the sample without adding Al. Thermodynamic analysis revealed that Mn enriched in molten steel is oxidized to form MnAl2O4 when Al content is low and the MnAl2O4 reacts with S in molten iron to form molten MnO-Al2O3-MnS. MnS can precipitate from the molten MnO-Al2O3-MnS. On the other hand, Mn enriched in molten steel does not react with Al2O3 when Al content is high. Therefore, MnS can precipitate at the final period of solidification where Mn and S are significantly enriched in molten steel. [ABSTRACT FROM AUTHOR]

The influence mechanism of Boron (B) addition on the precipitation behavior of S32654 was systematically investigated in this work. The results indicated that B significantly inhibited the nucleation and growth of σ phase through its non-equilibrium grain boundary segregation (NGS) at 1000 °C. The segregation of B at grain boundary (GB) decreased GB energy and suppressed Cr and Mo segregation, thus reducing the nucleation sites of intergranular σ phase. B also segregated at vacancies and dislocations during its reverse diffusion process, reducing the nucleation sites of intragranular σ. Meanwhile, B markedly decreased the nucleation rate of σ phases. In addition, B inhibited the growth of σ phase through segregation at σ/γ interface. Under the combined inhibitory effects of B, the precipitation of σ phase was markedly suppressed. By comparation, the addition of B has little effect on the precipitation of Cr2N. B decreased the nucleation position but accelerated the nucleation rate. Under the joint action of these two opposing factors, the nucleation ability of Cr2N has not significantly changed. Additionally, the segregation tendency of B at Cr2N/γ interfaces was weak, leading to a little inhibition effect on the Cr2N growth. Therefore, the precipitation tendency of Cr2N in B-bearing and B-free steels was basically the same. [ABSTRACT FROM AUTHOR]

The hot forming-quenching integrated process (HFQ®) organically combines the deformation and heat treatment, which can improve the forming performance of aluminum alloy while ensuring the final strength of formed parts. Thermal deformation in HFQ® has a non-negligible influence on precipitation behavior in subsequent artificial aging treatment and affects the mechanical properties of the formed parts. In this study, the relationship between the precipitation behavior and thermal deformation ratios was investigated. Results indicated that the formation temperatures of η′ and η decreased with an increasing deformation ratio; however, the former decreased more than the latter. The activation energy of η′ precipitation decreased linearly with increasing deformation ratio. Additionally, the phase transition fraction of η′ increased with the deformation ratio, leading to shorter times required to reach equivalent phase transition fractions. Deformation accelerated the phase transition of η′, and greater deformation resulted in a shorter transition time. The aging time required for peak Vickers hardness decreased with increasing deformation ratio, reflecting the promotion of precipitated phase formation and transformation by introduced dislocations. Consequently, peak hardness and yield strength were achieved in shorter aging times. In terms of industrial applications, this discovery offers significant advantages for shortening the production cycle of the hot stamping process and reducing production costs. [ABSTRACT FROM AUTHOR]

The characteristic of primary carbides in industrial grade M35 high-speed steel was analyzed systematically using an association of scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), and energy dispersive spectrometer (ESD), and the precipitation behavior of various carbides was discussed by combining the thermodynamic calculation and the microsegregation model. The results indicate that the size of network carbides at the center area is larger than that at the edge area in the electroslag remelting (ESR) ingot. The area fraction and average width of carbides increase gradually with the increase of height, and the values located in the top are 6.79% and 4.83 μm, respectively. The lamellar M2C carbide, fishbone M6C carbide and blocky MC carbide compose the network structure, also there are several independently distributed cerebriform carbides. Compared to M6C carbide, the Mo/W ratio and the contents of V and C in M2C carbide are higher, and MC carbide is prominently characterized by the highest V content. Simultaneously, the precipitation of Fe-rich M6C carbide that occurs in the top is closely related to the low cooling rate besides the influence of alloying elements. The current reduction operation can genetically promote a reduction of 0.75% in the average area fraction and 0.04 μm in the average size of carbides in the forged steels, which is beneficial for reducing and homogenizing primary carbides in the ESR ingot.

A novel Mg-6.2Gd-4.2Sm-1.2Zn alloy with a superior strength-ductility combination was achieved by traditional extrusion process and aging. Based on the characteristics of substitutional solution among rare earth (RE) elements, the Sm substitute part Gd element change the morphology of the LPSO phase, and the volume fraction of the 14H-LPSO phase increases, leading to a finer size and more dispersed distribution. Meanwhile, the Sm addition reduces the level of GB segregation of Zn and Gd, which further affects the precipitation of nano-precipitates during aging. The results offer insight into determining the precipitation behavior of second phases via regulating solute GB segregation.

The microstructural evolution of Al-Zn-Mg-Cu alloy under different stress and aging temperature was studied using cold compression and heat treatment. The relationship between the process parameter and the microstructure of the material was analyzed by OM, EBSD, and TEM. The results showed that the grain size decreased and the recrystallization fraction increased with the increase of compression. Textures of ||X (cubic), //Y, Goss have higher intensity after solution treatment, but their intensity and proportion also decrease with the increase of compression. η' is the main precipitate in the alloy aged at 140 °C, while η is the main precipitate in the alloy aged at 160°C. Precipitation coarsening and grain refinement affect the microhardness of the alloy together.

In this paper, the effects of two solid solution processes, single-stage solid solution (SHT) and two-stage solid solution (S-SHT), on the precipitated phases and corrosion behavior of Al-Cu-Mg-Ag in wire arc additive manufacturing were investigated. It is found that S-SHT is a composite solid solution with relatively small pore coarsening and narrower grain boundary precipitation-free zone, which provides better mechanical properties and corrosion resistance than SHT. SHT is little affected at the aging temperature, and the precipitated phases are lath-like θ′ and Ω phases. The aging precipitation phases of S-SHT are significantly affected by the aging temperature. S-SHT165 precipitated phase is mainly fine θ′ phase, while S-SHT185 precipitated phase is mainly lath-like Ω phase. [ABSTRACT FROM AUTHOR]

This paper investigated the effect of cooling rate after solution heat treatment and pre-aging at 303K after cooling on aging behavior of Al-- 6 mass%Zn--0.75 mass%Mg alloy to elucidate the aging behaviors and strengthening mechanism throughout aging heat treatment in the case of low cooling rate, such as furnace cooling, followed by solution heat treatment. Regardless the absence of pre-aging, the maximum hardness obtained in the materials with furnace cooling after solution treatment was almost the same as that of water-cooled and pre-aged materials during the same aging time. The result of microstructure observations using transmission electron microscope show that fine precipitates consisting of η phase have been formed in all peak-aged materials. [ABSTRACT FROM AUTHOR]

The evolution of the microstructural and mechanical properties of alloy 617B during long-term service on a key-component test platform at 700 °C was systematically investigated. The precipitation behavior and size changes of the M23C6 and γ′ phases were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that carbide M23C6 precipitated in the form of discontinuous particles, plates, or needles at grain boundaries and within grains, while the γ′ phase had a spherical shape and was distributed in a dispersed manner. With prolonged service time, both the M23C6 and γ′ phases gradually coarsened. After 24,000 h of service, the yield strength, tensile strength, and Brinell hardness of alloy 617B significantly increased; however, the impact toughness decreased, accompanied by intergranular embrittlement. The increase in precipitate volume fraction and its contribution to the strength of the alloy were evaluated by a precipitation strengthening model. The coarsening of M23C6 was identified as the main cause of embrittlement. The findings of this study provide important experimental data and theoretical support for the stability of 617B alloys under long-term high-temperature service conditions. [ABSTRACT FROM AUTHOR]

The precipitation behavior of a novel Ni-Fe-based superalloy developed for advanced ultra-supercritical (A-USC) coal-fired power plant applications during high-temperature aging treatment was investigated. The results showed that the major precipitates in the novel alloy were randomly distributed MC carbides, M23C6 carbides at grain boundaries, and the γ′-Ni3 (Al, Ti) phase in grain interiors after aging. MC remained relatively stable during both short-term and long-term aging. M23C6 quickly precipitated and exhibited a discrete distribution at grain boundaries during short-term aging, and partly developed into continuous films during long-term aging. After uniform precipitation, the shape of γ′ remained spherical, and the size kept increasing with aging time according to the Lifshitz–Slyozov–Wagner (LSW) model. The hardness of the novel alloy was mainly associated with the precipitation behavior of γ′; as γ′ gradually precipitated, the hardness steadily increased; after complete precipitation, as the size of γ′ increased, the hardness first increased and then decreased, reaching the peak hardness when the average radius of γ′ achieved the critical size. In addition, the novel alloy exhibited abnormal coarsening behavior at grain boundaries during both short-term and long-term aging. The coarsened grain boundaries were actually precipitate-free zones (PFZs) and the coarsened and elongated rod-like particles inside were identified as γ′ precipitates. The mechanism of strain-induced grain boundary migration and the discontinuous coarsening reaction is proposed for the formation of PFZs. Furthermore, PFZs were considered to be potential crack sources during the creep rupture test, leading to earlier failure of the material. [ABSTRACT FROM AUTHOR]

Cold rolling is one of the feasible and effective methods for regulating the microstructure and enhancing the mechanical properties of metallic materials. However, the cold rolling of particulate-reinforced aluminum matrix composites has been rarely studied comprehensively and systematically due to their limited plasticity. In this study, in-situ TiB2/2219Al matrix composites with a comparable ductility to 2219Al matrix were prepared and subjected to T3 treatment, which includes solution treatment, cold rolling, and natural ageing, with varying degrees of rolling reduction. The effects of cold rolling on the dislocation multiplication, grain and texture evolution, precipitation behavior, and mechanical properties were comprehensively investigated and discussed. The results reveal that both total dislocation density and geometrically necessary dislocation density increase with increasing rolling reduction. The average grain size progressively decreases under the joint influence of gradual growth of large grains and increase of small grains. Besides, rolling deformation changes the ageing behavior of composites, resulting in a decrease in precipitation temperature for both θ″ and θ′ phases. Under a large deformation, these phases precipitate at room temperature. Moreover, the types and proportions of textures undergoes a distinct evolution during deformation, with S, Copper and Brass textures being predominantly observed in the composite subjected to a 60% rolling reduction. Additionally, the increase in deformation results in an enhanced hardness and strength at both room temperature and 373 K. However, the strength initially increases but subsequently decreases at 573 K, and the composite with a 20% rolling reduction exhibits the highest strength at 573 K. [ABSTRACT FROM AUTHOR]

A cost-effective, high-performance Mg-2.0Zn-1.5Mn alloy was fabricated using closed forging extrusion (CFE). The results reveal that CFE can promote a dynamic recrystallization (DRX) ratio and enhance the residual dislocation density in deformed grains and subgrains. Grain refinement is achieved through multiple DRX mechanisms, particle-stimulated nucleation, and pinning effects. In addition, the basal texture and precipitation behavior are significantly influenced by pre-forging in CFE. Finally, grain refinement and substantial residual dislocations result in a good combination of strength and plasticity, with the ultimate tensile strength of 400 MPa and elongation of 22.1%, respectively. A novel strategy for regulating the bimodal grain structure is proposed to guide the optimization of the mechanical performance of rare-earth free Mg alloys.

In response to the growing demand for high-performance magnesium alloys in the aerospace and transportation industries, researchers conducted a study on the AZ80 magnesium alloy. The primary objective was to achieve a nanocrystalline structure in the alloy through severe plastic deformation using low-strain multi-directional compression at room temperature. Subsequently, an aging treatment was performed to induce the transformation of the structure into a stable state. The study aimed to investigate the morphology and mode of the second phase precipitation in the magnesium alloy after undergoing severe plastic deformation. The research findings revealed that the application of multi-directional and multi-pass compression during room temperature deformation of the magnesium alloy effectively prevented instability and fracture. Moreover, this process facilitated the accumulation of larger true strain. As the number of compression passes increased, deformation twins became increasingly denser, particularly in the intersecting areas. Consequently, ultrafine high-angle grain structures were preferentially formed in these regions. Furthermore, the number of fine-grained areas gradually increased with each deformation pass. After ΣΔε 5.12, the grain size was refined to a range of 100–200 nm. Additionally, the aging treatment following severe plastic deformation brought about a significant change in the traditional lamellar precipitation mode of the second phase Mg17Al12 in the magnesium alloy. Instead, spherical precipitation occurred.

In this study, Cu–9Ni–6Sn-xCr alloys (x = 0, 0.3, 0.6, or 1.0) were designed and prepared. The influence of Cr content on the microstructure, the precipitation behavior, and the mechanical properties of the alloys was systematically investigated. The results show that the Cu–9Ni–6Sn-0.6Cr alloy exhibits outstanding mechanical properties and higher level electrical conductivity after aging at 400 °C for 8 h: The peak-aged hardness reaches 323.6 ± 8.4 HV, with a tensile strength of 876.4 MPa and an electrical conductivity of 12.59 ± 0.33% IACS. These excellent comprehensive properties of Cu–9Ni–6Sn-0.6Cr alloy are attribute to the refinement effect and the precipitation of DO22 phase within the Cu matrix grains. Further analysis reveals that the addition of an appropriate amount of Cr refines the microstructure of the alloy and promotes the precipitation of the DO22 phase. At the same time, Cr also suppresses the precipitation of the DO3 phase at grain boundaries, achieving an excellent combination of plasticity, electrical conductivity, and strength. This work suggests that the potential application prospects of Cr in the multi-component design of Cu–Ni–Sn alloy, and the addition of 0.6 wt% Cr can achieve good strengthening effects and provide outstanding comprehensive performance for Cu–Ni–Sn alloys.

A novel Mg-Nd-Sm-Zn-Zr alloy with promising age-strengthening effects has been successfully developed to meet the urgent needs of lightweight in the aerospace industry. The precipitation behavior and elastic properties of the nano-precipitates in the alloy have been revealed using transmission electron microscopy and first-principles calculation. The Guinier-Preston (GP) zones, lamellar γ′ precipitates, and granular β′ precipitates formed in the α-Mg matrix after aging at 190 °C for 3 h (under-aging stage). Notably, the alloy reached the peak-aging stage and achieved an excellent ultimate tensile strength of 266 MPa after aging for 18 h. These precipitates further transformed into the lamellar β′ and β1 precipitates, and the enclosed nano-strengthening structure was constructed by γ′, β′ and β1 precipitates. The precipitation sequence of the aged alloy was determined as the supersaturated solid solution (SSSS) → GP zones → β′/γ′ → β1. First-principles calculations and 3D visualization approach demonstrated that the addition of mixed light RE elements can effectively improve the elastic modulus and reduce the elastic anisotropy of β′ nano-precipitates. The Young's modulus (E), shear modulus (G), and anisotropy index (AU) of β′-Mg7(Nd,Sm) precipitates were 48.38 MPa, 18.79 MPa and 2.29, respectively. This study provides a theoretical and experimental basis for further research and development of novel high-performance Mg-light RE alloys.

The cast Al–3Li–2Cu-0.15Zr alloy is a promising material due to its high strength-to-weight ratio and stiffness. In this work, the Sn addition and heat treatment were employed to regulate its microstructure and mechanical properties. The results indicate that Sn exists in the matrix as Sn solute atoms and Sn-rich particles including Li5Sn2, Li13Sn5, Li7Sn2, and Li22Sn5. The number of these particles increases as the Sn content rises. The addition of Sn significantly enhances the grain refinement, reducing the average grain size to 50.2 μm when 0.3 wt% Sn is incorporated. During the aging process, the δ′ and δ'/β′ precipitates gradually grow and coarsen, while the T1 and θ′ precipitates nucleate and grow. Some δ′ precipitates attach to the board of θ′ to form sandwich-like phases, such as δ'/θ'/δ'. The addition of Sn promotes the nucleation of θ′ and T1 precipitates. This is achieved by leveraging the Sn-rich particles as nucleation sites and utilizing Sn solute atoms to decrease the interface energy between these precipitates and α-Al. Moreover, the addition of Sn with a high vacancy binding energy and the reduction of aging temperature can effectively decrease the diffusion rate of Li atoms and vacancies, thereby inhibiting the broadening of the δ′-PFZ. After a suitable heat treatment, the Sn-modified Al–Li alloy exhibits a microstructure characterized by fine and equiaxed grain, fine and uniform δ′ precipitates, and a narrow δ′-PFZ, contributing to excellent mechanical properties of the alloy. Significantly, the underlying mechanisms behind the aforementioned observations were discussed analytically.

The hot forming-quenching integrated process (HFQ®) organically combines the deformation and heat treatment, which can improve the forming performance of aluminum alloy while ensuring the final strength of formed parts. Thermal deformation in HFQ® has a non-negligible influence on precipitation behavior in subsequent artificial aging treatment and affects the mechanical properties of the formed parts. In this study, the relationship between the precipitation behavior and thermal deformation ratios was investigated. Results indicated that the formation temperatures of η′ and η decreased with an increasing deformation ratio; however, the former decreased more than the latter. The activation energy of η′ precipitation decreased linearly with increasing deformation ratio. Additionally, the phase transition fraction of η′ increased with the deformation ratio, leading to shorter times required to reach equivalent phase transition fractions. Deformation accelerated the phase transition of η′, and greater deformation resulted in a shorter transition time. The aging time required for peak Vickers hardness decreased with increasing deformation ratio, reflecting the promotion of precipitated phase formation and transformation by introduced dislocations. Consequently, peak hardness and yield strength were achieved in shorter aging times. In terms of industrial applications, this discovery offers significant advantages for shortening the production cycle of the hot stamping process and reducing production costs.

Cu–Cr–Ti alloy was successfully prepared by vacuum melting, solution treatment at 960 °C for 1 h, 80 % cold rolling and aging at 500 °C for 1 h. The effect of Ti content on the microstructure was characterized by Scanning electron microscope (SEM) and Transmission electron microscope (TEM). Their tensile strength, electrical conductivity, thermal stability, wear resistance and arc erosion resistance were also measured. The results showed that Ti can form the Ti0.77S phase with S, which can prevent the occurrence of sulfur embrittlement. And Ti can segregate around the Cr precipitates, hindering their growth. Therefore, the tensile strength, hardness, high temperature softening resistance, wear resistance and arc erosion resistance improved with the increase of Ti content. But the electrical conductivity decreased sharply since Ti was mainly solidly dissolved in the matrix. What's more, the electrical conductivity decreased sharply and other properties did not improve when the content increased from 0.066 wt% to 0.098 wt%, that is, the comprehensive performance was the best when the Ti content was 0.066 wt%. The tensile strength was 551 MPa, electrical conductivity was 78.3%IACS and the friction coefficient was 0.33. This work provides effective ideas for preparing copper alloys with desired properties.

Impact toughness is essential for evaluating the mechanical properties of ship hull steels. This study focused on understanding the embrittlement mechanism of NiAl precipitation-strengthened HSLA steels by integrating advanced characterization and atomic-scale calculations. The factors causing the deterioration of the impact toughness of NiAl precipitation-strengthened steels, which have been contentious, were identified. The embrittlement mechanism and crack propagation mode were revealed using first-principles calculations and 3D impact fracture morphology, respectively. The results suggested that the numerous homogeneous NiAl nanoparticles within the bcc-Fe matrix reduced the impact toughness of the HSLA steels. As the precipitate interparticle spacing (L) decreased, the impact toughness decreased until it attained a critical value (∼27 nm). This is interpreted effectively by the calculations indicating that the shear modulus (75 GPa) and fracture energy (4.5 J/m2) of the NiAl phase, particularly the NiAlMn phase (46 GPa, 4 J/m2), are significantly lower than those of bcc-Fe (83 GPa, 5 J/m2). This induces the fracture of nanoparticles under rapid impact loading, which functions as numerous crack initiations before plastic deformation of the matrix. The small L achieved after peak-hardening aging can result in the interconnection of these crack sources and cause instantaneous cleavage fractures, similar to brittle materials.

A new Cu-1.5Ni-0.7Co-0.7Si-0.3Fe-0.1Mg alloy with low cobalt content was designed. Multi-stage thermo-mechanical treatment (MTT) was used to produce the high-performance alloy with hardness of 286 HV, yield strength of 858 MPa, tensile strength of 910 MPa and electrical conductivity of 45.4 % IACS. The addition of 0.3 wt% Fe element dissolved in (Ni,Co)2Si resulted in the formation of the orthorhombic δ-(Ni,Co,Fe)2Si. During MTT, the δ-(Ni,Co,Fe)2Si, (Ni,Co)2Si, β-Ni3Si, and Fe2Si precipitated successively near the deformation microstructure. Transmission electron microscope observations indicated that the δ-(Ni,Co,Fe)2Si precipitates showed disc-like and rod-like shapes at different orientations, respectively. A new resource-saving, high-strength and medium-conductivity Cu-Ni-Co-Si-Fe-Mg alloy was prepared by replacing an equal amount of Co element with 0.3 wt% Fe element, reducing the amount of scarce metal Co in the alloy.

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An important aspect of energy conservation and emission reduction in automotive industry is to improve the combustion efficiency of gasoline. The full combustion of gasoline will inevitably cause an increase in exhaust temperature. The coarsening and dissolution behavior of precipitates in steel will lead to a decrease in its high-temperature mechanical properties when the engine is used for a long time in such an alternating heating and cooling environment. In order to obtain ferritic stainless steel with good high-temperature resistance, this paper is based on 444 ferritic stainless steel and attempts to partially replace Mo element with W element to obtain Laves phase containing W, Mo, and Nb with more stable high-temperature performance. A simulated cyclic high-temperature annealing process up to 1050 °C was designed to investigate the precipitation behavior in this modified ferritic stainless steel. The results show that using W to replace Mo in 444 ferritic stainless steel can refine the grains of ferritic stainless steel. It can not only provide better solid solution strengthening at elevated temperature, but also stabilize the Laves phase and provide precipitation strengthening. The reason is that the W elements can change the composition of the Laves phase in ferritic stainless steels and precipitate Fe2(Nb, W) with high thermal stability to provide stable precipitation strengthening during long-term alternating annealing. The W-rich Laves phase is prone to precipitation at grain boundaries, effectively pinning grain boundaries and preventing microcracks from propagating along grain boundaries during service, thereby improving the service life of the steel.

The effects of the aging process on the κ-carbide precipitation behavior and thus on the mechanical properties of an Fe-30.5Mn–8Al-1.0C lightweight austenitic steel were experimentally studied. The morphology of intragranular κ-carbide precipitation evolved from spherical to cuboidal and then to rectangular with increasing aging temperature and time, and intergranular κ-carbides precipitate in the high-temperature-aged steels and exhibit lath-like and lamellar morphologies. For steels with intragranular κ-carbide precipitation, the yield strength becomes significantly improved with the persisting aging owing to the enhanced dislocation shearing strengthening via κ-carbide growth, and the increase in yield strength exceeded the contribution of work hardening. Intergranular precipitation in higher-temperature-aged steel has a negative effect on the strength and ductility; it partly counteracts the strength increase due to intragranular precipitation. In summary, the studied steel aged at 550 °C for 1–2 h exhibited a better strength–ductility match.

Rebar is an extremely important building material. The cooling rate and the presence of niobium (Nb) element are key factors influencing the overall performance of rebars. In this work, the high-strength rebar’s microstructure, precipitated phase, and mechanical properties were characterized using scanning electron microscopy, transmission electron microscopy, HVS-1000 hardness tester, and MTS810 universal tensile testing machine. The results showed that a shift in cooling rate from 0.3 to 3°C·s−1 resulted in noticeable changes in the microstructures of rebars, particularly between Nb-free and Nb-containing variants. In the case of Nb-containing rebars, there was an increase of 8.26% in the proportion of pearlite, along with a decrease of 10.63 μm in the average grain size of ferrite. Furthermore, the lamellar spacing of pearlite experienced a decrease of 0.0495 μm, the proportion of low-angle grain boundaries saw an increment of 4.13%, and the size of the precipitated phase (Nb, Ti, V) C reduced by 18.9 nm. These changes collectively led to a significant increase in hardness (98.56 HV), yield strength (179.02 MPa), and ultimate strength (199.43 MPa). The resultant fracture morphology manifested as a dimple pattern.

In order to investigate the effect of boron on the precipitation behavior of β phase in Al-Mn-Mg-B alloy used as a material for cask baskets, 1.00 © 104 hours aging treatment was carried out focusing on the temperature history in the cask as in the previous report, and the Timetemperature-precipitation diagram and Supersaturation-diffusion length-precipitation diagram were evaluated using the change tendency of the specific resistance obtained. In the Al-Mn-Mg-B alloy, although grain refinement by AlB2 was confirmed, the effect of boron addition on the precipitation rate of β phase was hardly recognized. That is to say, it was confirmed that the grain boundary and the interface between B compounds and matrix phase hardly contributed as nucleation sites of β phase. In conclusion, it is considered that the reduction of the solid solution Mg content in the Al-Mn-Mg-B alloy does not occur even after 60 years if the Mg content is 1.0 mass% as in the Al-Mn-Mg alloy. [ABSTRACT FROM AUTHOR]

A novel Al-Mg-Si aluminum alloy with the addition of the micro-alloying element Er and Zr that was promptly quenched after extrusion has been studied. The solid solution and aging treatment of the novel alloy are studied by observing the microstructure, mechanical properties, and strengthening mechanism. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques are employed to examine the changes in the microstructure resulting from various solid solution treatments and aging treatments. The best strengthening effect can be achieved when the solubility of the MgSi phase and precipitate β″ (Mg2Si phase) is at their maximum. The addition of Er and Zr elements promotes the precipitation of the β″ phase and makes the b″ phase more finely dispersed. The aging strengthening of alloys is a comprehensive effect of the dislocation cutting mechanism and bypass mechanism, the joint effect of diffusion strengthening of Al3(Er,Zr) particles and the addition of Er and Zr elements promoting the precipitation strengthening of β″ phases. In this paper, by adding Er and Zr elements and exploring the optimal heat treatment system, the yield strength of the alloy reaches 437 MPa and the tensile strength reaches 453 MPa after solid solution treatment at 565 °C/30 min and aging at 175 °C/10 h. [ABSTRACT FROM AUTHOR]

Microstructure evolution, phase development and mechanical property of AZ80 alloy cup with various processing temperatures (573 K, 613 K, 653 K) and rotating revolutions (N = 0, 5, 50, 100) during rotating backward extrusion (RBE) were explored. The study founded that reducing deformation temperature or increasing revolution could promote the grain refinement and DRX proportion. And the sample deformed at the condition of 573 K and N = 100 exhibited the best grain refinement effect (grain size was 2.5 μm, DRX ratio was up to 99.01%). The bulk eutectic phase existed at all deformation temperatures, while the dynamic precipitation was only precipitated at temperature of 573 K and 613 K. Increasing the deformation temperature or revolution could reduce the proportion of the second phase. And an increase in revolution or a reduction of temperature would reduce the average size of second phase, due to the phase could be broken by large strain and resolved with elevated temperature. Moreover, increasing the revolution and deformation temperature could promote the texture weakening, which would be contributed to the occurrence of new recrystallization grains with random orientation and the activation of non-basal slip system. The mechanical property of microhardness was significantly improved with rotating revolution increasing and deformation temperature decreasing. Supported by the grain refinement and dispersion strengthening, the sample deformed at condition of 573 K and N = 100 achieved maximum hardness values of 96.3 HV. [ABSTRACT FROM AUTHOR]

Compared to conventional martensitic wear‐resistant steels of the same hardness, high‐titanium wear‐resistant steels with in situ TiC particles can significantly improve wear resistance. However, micron‐sized TiC particles will decrease the toughness of high‐titanium wear‐resistant steels. Here, in order to improve wear resistance without reducing impact toughness, we incorporate 0.0025% cerium elements into high‐titanium wear‐resistant steels. Compared with no cerium steel, the steel containing cerium is demonstrating comparable mechanical properties, with the yield strength of 1283 MPa and impact toughness of 35.6 J, and the wear performance of the steel containing cerium is 1.78 times that of the steel with no cerium. The results show that with the addition of cerium the effective grain size of the steel decreases, and yield strength and toughness increase. The addition of cerium can form intermetallic compounds of Ce2O2S, which are used as heterogeneous nuclear particles in TiC to form rare earth composite particles calculated by the 2D mismatch theoretical model of Bramfitt. As the average spacing of the reinforcing phase particles in the steel decreases, the effective grain size of the steel decreases, and the number of reinforcing phase particles increases, the wear resistance of the steel with the addition of cerium is optimized. [ABSTRACT FROM AUTHOR]

The influence of carbide precipitation on the mechanical properties of hot work tool steels was investigated in this study. Compared to the commercial H13 hot work tool steel, the KMoW and RW steels containing W exhibited a reduced high-temperature softening and an enhanced thermal fatigue resistance during long-term aging. These improvements can be attributed to the increased structural and chemical stability of V-rich MC carbides. The increased (W + Mo)/(V + Fe) atomic ratios at MC metallic sites increased their coherency as well as reduced the driving force required for the precipitation of Cr-rich carbides. These findings suggest that the addition of W effectively improves the heat-checking resistance and mechanical properties of hot work tool steels.