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This research paper explores the impact of rotational speed on precipitate behaviour and mechanical properties of naturally aged FSW dissimilar joints. The outcome of this work showed that the rotational speed affects the mechanical behaviour of naturally aged FSW joints due to variations in microstructure. Severe plastic deformation resulted in the formation of fine equiaxed grains in the stir zone (SZ). The grain size increased from SZ to heat-affected zone (HAZ) on AS and RS due to uneven heat input and deformation. The grain size and extent of precipitate coarsening increased with rotational speed. Intermetallic particles were observed in the form of MgZn2, Cu5Zn8, and Al2CuMg, resulting in enhanced SZ microhardness. The lowest hardness was observed at the TMAZ/HAZ interface towards AS owing to the coagulation of the Al2Cu phase. Peak microhardness of 183.8 Hv was found in the SZ of the joints at 900 rpm. The ultimate tensile strength was reduced from 288 ± 12.3 MPa to 242 ± 9.8 MPa with increased rotational speed from 900 to 1120 rpm. The lowest microhardness zone was the fracture location for both welds during the tensile test. [ABSTRACT FROM AUTHOR]

The microstructure and impact toughness evolution of G115 steel after long-term (ranging from 500 h to 10,000 h) aging at 700 °C were investigated in this study. The results showed that the microstructure of the G115 steel evolved from a finer-grained matrix with minor precipitates to a coarse-grained matrix with more precipitate with aging time, presenting a decrease in the local deformation degree in the matrix. The impact toughness of the steel decreased with aging time, presenting the largest decline at the initial aging times. The decrease in impact toughness was attributed to the coarsening of precipitates (M23C6 and Laves phase) in the steel matrix. The stable impact toughness during the whole aging process (from 500 h to 10,000 h) should be related to the comprehensive effects, including the precipitation of the Laves phase, the increase in high-angle grain boundaries, and the softening of the metal matrix. [ABSTRACT FROM AUTHOR]

This study investigated the mineralogical and chemical characteristics of ochreous precipitates and mine water samples from abandoned Upper Carboniferous hard coal mines in an extensive former mining area in western Germany. Mine water characteristics have been monitored and assessed using a multi-methodological approach. Thirteen mine water discharge locations were sampled for hydrochemical analysis, with a total of 46 water samples seasonally collected in the whole study area for stable isotopic analyses. Mineralogical composition of 13 ochreous precipitates was identified by a combination of powder X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FE-SEM/EDS). Results showed that abandoned mine drainage was characterized by circumneutral pH, Eh values ranging from 163 to 269 mV, relatively low concentrations of Fe and Mn, and was dominated by HCO3− > SO42− > Cl− > NO3− and Na+ > Ca2+ > Mg2+ > K+. Goethite and ferrihydrite were the dominant precipitated Fe minerals, with traces of quartz, dolomite, and clay minerals. Some metal and metalloid elements (Mn, Al, Si, and Ti) were found in the ochreous sediments. The role of bacteria in the formation of secondary minerals was assessed with the detection of Leptothrix ochracea. The δ18O and δ2H values of mine water plotted on and close to the GMWL and LMWLs indicated local derivation from meteoric water and represented the annual mean precipitation isotopic composition. Results might help to develop strategies for the management of water resources, contaminated mine water, and public health. [ABSTRACT FROM AUTHOR]

This study aims to investigate the combined effect of Sc micro-alloying and applying low-frequency electromagnetic casting (LFEC) on precipitation behavior, mechanical and corrosion properties of 7A36 aluminum alloy. The results indicate that when compared to the T6 state, the two-stage over-aging (T73) treatment causes the transformation of the grain interior η′ phases into coarser η′ and η phases and leads to a more distinct appearance of precipitate free zone (PFZ). The addition of Sc results in the discontinuous and coarser formation of grain boundary precipitates (GBPs), and the Al3(Sc, Zr) phase particles contributes to the increased strength of 7A36 aluminum alloy. LFEC promotes the finer second phase and a finer distribution of grain interior precipitates, and dislocation movement bypasses a shorter distance and less energy is consumed, thus strength is decreased slightly. Meanwhile, the wider PFZ and the greater distribution spacing of the coarse GBPs contribute to a smaller intergranular fracture tendency, that's improve elongation of T6 and T73 alloys by 56.4% and 22.5% respectively, and contribute to improve corrosion resistance by blocking of intergranular corrosion channels. Based on the precipitation evolution, the synergy mechanism of Sc micro-alloying and LFEC processing is put forward in this paper. [ABSTRACT FROM AUTHOR]

In the present research work, creep strength enhanced ferritic/martensitic P91 steel was subjected to varying normalizing (950–1150 °C) and tempering temperature (730–800 °C). The varying normalizing and tempering temperature effect on microstructure evolution (precipitate size and their distribution and grain size) and microhardness were performed. The heat treatment consequences on microstructure evolution revealed an increase in grain size, and decrease in fraction area of precipitates, with increase in normalizing temperature. The grain size was found to be decreased with increase in tempering temperature while fraction area of precipitates and precipitate diameter increased. For microstructure characterization, optical microscope and field emission scanning electron microscope were utilized. The microhardness was found to be increased with increase in normalizing temperature while it decreased with increase in tempering temperature. [ABSTRACT FROM AUTHOR]

Nonoriented electrical steel for new energy vehicles should have high strength and excellent magnetic properties simultaneously. However, it is challenging to optimize mechanical and magnetic properties simultaneously during nonoriented electrical steel processing. This article prepares nonoriented electrical steel with high strength and excellent magnetic properties by Cu–Ni alloying, and the evolution of properties of Cu–Ni‐alloyed nonoriented electrical steel during aging and underlining mechanisms is studied. The optimal strength is achieved when aging for 10 min with a yield strength of 773 MPa, where the magnetic induction intensity (B50) is 1.66 T, and the iron loss (P1.0/400) is 18.07 W Kg−1. The optimal strength is attributed to the Cu–Ni recombination, which induces a rapid precipitation of numerous small‐sized Cu‐rich phases within a short period. Besides, the main strengthening mechanisms of the small‐size Cu‐rich phases are modulus strengthening and ordered strengthening. Furthermore, the small‐size Cu‐rich phases with B2 and body‐centered cubic structure in the earlier aging period do not deteriorate the magnetic properties of the steel. Nevertheless, in the late aging period, due to the coarsening of the precipitated Cu‐rich phase with face‐centered cubic structure and the abnormal growth of some grains, the eddy current loss increases, leading to worsen magnetic properties. [ABSTRACT FROM AUTHOR]

Nickel-based superalloys have been widely used in the aerospace industry, and regulating the reinforcing phases is the key to improving the high-temperature strength of the alloy. In this study, a series of aging treatments (650 °C, 750 °C, 850 °C and 950 °C for 8 h) were designed to study different thermal deformation behaviors and microstructure evolutions for a novel nickel-based superalloy. Among the aged samples, the 950 °C aged sample achieved the peak stress of ~323 MPa during the thermal deformation and the highest microhardness of ~315 HV after thermal compression, which were the greatest differences compared to before deformation. In addition, the grains of the 950 °C sample exhibit deformed fibrous shapes, and the grain orientation is isotropic, while the other samples exhibited isotropy. In the 850 °C and 950 °C high-temperature aging samples, the γ′ precipitate (about 20 nm in size) is gradually precipitated, which inhibits the movement of dislocation in the grain during compression, thus inhibiting the occurrence of dynamic recrystallization and improving the high-temperature mechanical properties of the alloy. [ABSTRACT FROM AUTHOR]

For nickel (Ni) superalloys, including Inconel 738, electrochemical machining (ECM) is commonly used. However, the mechanisms behind ECM surface flattening and improved surface quality have not been fully elucidated, and the relationship between corrosion and ECM is weakly established without microstructural correlation. To bridge this knowledge gap, we have systematically investigated the electrochemical dissolution behavior of wrought Inconel 738 superalloy in the selected NaNO3 solution and narrowed down the optimal ECM parameters (i.e., 12 V, 0.8 mm/min, and 0.8 MPa). The results show that the precipitates and secondary phases of the Inconel 738 superalloy dominate the final surface quality and the ECM efficiency. Importantly, we have confirmed that a core–shell precipitate phase with shell-layer Ti and Mo enrichment remains on the surface even after the 12 V ECM, limiting the final roughness. This novel finding clarifies why the morphology differs under two representative conditions (i.e., anodic dissolution at 1.3 V, 1500 s and optimal ECM with 12 V, 0.8 mm/min, and 0.8 MPa), and how the core–shell precipitates evolve during the non-equilibrium 12-V ECM condition leads to a totally different flattening process. This ECM analysis method, with solid electrochemical theory and detailed microstructural investigation, reveals the microstructure-dependent ECM flattening mechanisms at precipitate scale and demonstrates how the microstructures influence the ECM processing quality. This novel finding plays a guiding role in improving the quality of ECM processing, shows great value for various industrial applications, and helps strategically break the current surface roughness limit. [ABSTRACT FROM AUTHOR]

High-strength Al alloys of the 7xxx series are promising candidates for further light-weighting of car bodies. However, they are difficult to process by extrusion: complex geometries in particular pose a major challenge due to high extrusion pressures and tool wear. In addition to process optimization, alloy chemistries can be tailored for properties such as good extrudability or high strength. In this work, several experimental alloys based on EN AW 7108A were investigated with respect to the contents of the main alloying elements Zn and Mg, as well as heat treatment (e.g., homogenization), to achieve good extrudability and favourable mechanical properties. The experimental alloys were initially extruded on a small-scale extrusion press and evaluated with regards to their warm formability, microstructure, extrudability, and mechanical properties in T5 temper. Alloy compositions with Mg contents

The cold rolling and intermediate annealing process, along with the incorporation of rare earth elements, play an important role in the microstructure, texture, and inhibitors of oriented silicon steel. Currently, there is limited research on the impact of rare earth yttrium on texture evolution during the cold rolling and intermediate annealing processes. Therefore, the effects of different cold rolling deformations and intermediate annealing temperatures on the microstructure and texture of Y bearing oriented silicon steel have been studied. The experimental results demonstrate that the average grain size of the intermediate annealed plate progressively decreases with increasing the cold rolling deformation. This is because the high cold rolling deformation brings more additional dislocations and distortions, consequently enhancing the driving force for recrystallization. Observing the microstructure with various cold rolling deformation, the results show that the annealed plate with a 72 % reduction rate exhibited the highest Goss texture percentage of 4.83 %. This is because the cold-rolled sheet with a reduction rate of 72 % exhibits an abundance of Goss oriented substructures. These substructures quickly dominate the {111} deformed matrix during the initial recrystallization, and promote grains nucleation and growth. As the annealing temperature increases, the driving force for the growth of recrystallized grains also increases, leading to a gradual increase in grain size. The plate annealed at 940 °C exhibits the highest percentage (4.83 %) of Goss texture. The addition of rare earth Y can lead to an increase in grain size in the intermediate annealed plate and facilitate the formation of {411} texture. This is advantageous for the abnormal growth of Goss texture. The results demonstrate that a cold rolling deformation rate of 72 % and an intermediate annealing temperature of 940 °C are good for promoting abnormal growth of Goss orientation. The study results on precipitation kinetics suggests that the grain boundary nucleation of AlN and dislocation nucleation of MnS are the most effective way of nucleation. The precipitates in oriented silicon steel without Y are Al2O3 and MnS, while those in the samples with Y are AlN, YS, and YOxSy. The addition of rare earth Y leads to a reduction in both the density and size of precipitates. Moreover, With the increase of annealing temperature, the size of precipitates decreases and the amount of precipitates increases. Additionally, the addition of Y makes the steel more clean, meanwhile, the pinning effect of inclusions on grain boundaries is weakened. Therefore, the grain size of the steel with Y is larger.

Ni-WC composite coating was prepared on Q235 steel substrate by plasma transfer arc (PTA) with welding current ranging from 70 A to 85 A. The results show that the dissolution behaviour of WC particles and the elemental diffusion at the interface promoted by the increased welding current promote the formation and evolution of precipitates, including M 7 (B, C) 3 and M 6 C. The increased current reduced the volume fraction of WC particles in the coating, but increased that of the precipitates. At welding currents of 75 A and 80 A, dendritic-like M 7 (B, C) 3 presented a regular distribution at the bottom of the coating. At a welding current of 80 A, M 6 C phase began to form at the bottom of the coating. When the welding current reached 85 A, the dendritic structure was broken, and the M 6 C phase aggregated and grew. The Ni-WC coating had visible delamination. WC particles at the upper part of the coating dissolved more severely compared to those at the middle and bottom of the coating. Ni 3 Si compound was formed at the upper and middle of the coating, and it had a crystal orientation relationship of [011] Ni3Si ∥[011] γ-Ni , (11-1) Ni3Si ∥(11-1) γ-Ni , (−200) Ni3Si ∥(-200) γ-Ni , (-11-1) Ni3Si 1.3° from (-11-1) γ-Ni with γ-Ni. The average hardness of the coating decreased slightly due to the dissolution of WC, but the hardness at the interface increased, showing an improved bonding of the interface. The newly formed high hardness precipitates can share the load coming from the friction paired ball, thus reducing CoF and wear loss of the coating. [ABSTRACT FROM AUTHOR]

In this investigation, a high-strength Mg-12Gd-1.0Er-0.5Zr (wt.%) alloy sheet was produced by hot extrusion (HE) and subsequent hard-plate rolling (HPR) at different temperatures. The results indicate that the microstructures of these final-rolled sheets are inhomogeneous, mainly including coarse deformed grains and dynamic recrystallized (DRXed) grains, and the volume fraction of these coarse deformed grains increases as the rolling temperature increases. Thus, more DRXed grains can be found in R-385 °C sheet, resulting in a smaller average grain size and weaker basal texture, while the biggest grains and the highest strong basal texture are present in R-450 °C sheet. Amounts of dynamic precipitation of β phases which are mainly determined by the rolling temperature are present in these sheets, and its precipitation can consume the content of Gd solutes in the matrix. As a result, the lowest number density of β phase in R-450 °C sheet is beneficial to modify the age hardening response. Thus, the R-450 °C sheet displays the best age hardening response because of a severe traditional precipitation of β' (more) and βΗ /βΜ (less) precipitates, resulting in a sharp improvement in strength, i.e. ultimate tensile strength (UTS) of ∼ 518 ± 17 MPa and yield strength (YS) of ∼ 438±18 MPa. However, the elongation (EL) of this sheet reduces greatly, and its value is ∼ 2.7 ± 0.3%. By contrasting, the EL of the peak-aging R-385 °C sheet keeps better, changing from ∼ 4.9 ± 1.2% to ∼ 4.8 ± 1.4% due to a novel dislocation-induced chain-like precipitate which is helpful to keep good balance between strength and ductility.

In-situ electron irradiation and aging are applied to introduce high-density precipitates in an Mg-10Gd-3Y-1Zn-0.5Zr (GWZ1031K, wt.%) alloy to improve the hardness. The results show that the hardness of the Mg alloy after irradiation for 10 h and aging for 9 h at 250 °C is 1.64 GPa, which is approximately 64% higher than that of the samples before being treated. It is mainly attributed to γ′ precipitates on the basal plane after irradiation and the high-density nanoscale β′ precipitates on the prismatic plane after aging, which should be closely related to the irradiation-induced homogenous clusters. The latter plays a key role in precipitation hardening. This result paves a way to improve the mechanical properties of metallic materials by tailoring the precipitation through irradiation and aging.

Al–Zn–Mg–Cu alloy additive manufacturing components were fabricated by cold metal transfer advance (CMT-A) and metal inert-gas welding (MIG). The results indicate that the CMT-A as-deposited sample has fine grains with small-sized η'-strengthened precipitates and supersaturated solid solution, and the hardness is increased by 16.1% compared to the MIG as-deposited sample, and its peak aging hardness increased by 36.8% compared to the MIG. It indicates that CMT-A can directly produce Al–Zn–Mg–Cu products that have the potential to achieve high strength without the need for re-solutionizing.

The effect of cooling rate and Nb addition on the phase transformation, microstructures, and mechanical properties of thermomechanically controlled hot-rolled low-carbon CrNiMnMoB ultrahigh-strength steel were studied. The aspects impeding Nb's benefits on hardenability, phase transformation, and mechanical properties were investigated. The hot rolling process was simulated, and a continuous cooling transformation diagram was constructed for the studied steels. Microstructures were analysed using laser scanning confocal microscopy and field emission scanning electron microscopy, with the latter also used for in-depth investigations of the non-metallic inclusions. Transmission electron microscopy was employed to investigate the precipitate characteristics. The concentrations of Nb in the solution and precipitates were quantified for the martensitic and granular bainitic structures. The effect of Nb in solution on phase transformation and strengthening is diminished, and the hardness is reduced by Nb precipitation at an early processing stage. Decreasing the cooling rate promotes the formation of granular bainitic structures rather than martensite. After being subjected to hot rolling followed by water quenching and air cooling, the microstructures are autotempered martensite and fully granular bainite, respectively. Various non-metallic inclusions, including Al2O3, MnS, and Al2O3–MnS, MnS·BN, Al2O3·BN and MnS·Al2O3·BN were observed. The number density and area fraction of non-metallic inclusions in the Nb-containing steel and the air-cooled samples are higher than those observed in the Nb-free and water-quenched samples. Adding 0.04 wt% of Nb slightly increased the strength, but the toughness properties dropped, mainly due to the higher number density and area fraction of non-metallic inclusions and primary large precipitates.

Powder bed fusion (PBF), along with subsequent heat treatment, plays a crucial role in enhancing the impact toughness of FeCoNiCrMo0.2 high-entropy alloys (HEAs) and expanding their potential applications in field for high-speed deformation. In this study, the dynamic-mechanical properties and microstructure of the as-built PBF–FeCoNiCrMo0.2 HEAs and quenched PBF–FeCoNiCrMo0.2 HEAs heated at 600–750 °C for 8 h were investigated. As the heating temperature increases, the columnar grains and cellular structures undergo coarsening and the dislocation density gradually decreases. Moreover, higher heating temperatures facilitate the precipitation of Mo-rich second phases. This occurrence can be primarily attributed to the segregation of Mo at the boundaries of the as-built specimens. Consequently, in the quenched specimens, the μ phases are predominantly distributed along the boundaries of the cellular structures. In the quenched Q700 specimen (heated at 700 °C for 8h), the size and volume fraction of the μ phases are measured to be 63.4 nm and 3.59%, respectively. Additionally, under the same condition, the Q700 specimens also exhibited a relatively slight increase in the size of the cellular structures. The impact energy absorption, dynamic yield strength, and dynamic compressive strength of the Q700 quenched specimens were found to be 210.1 MJ/m3, 1066 MPa, and 1649 MPa at a strain rate of 1840 s−1. These values represent a dramatic improvement of 38.1%, 52.7%, and 14.7% higher in comparison to those of the as-built specimens. Under impact deformation, the presence of the μ phases plays a significant role in impeding the movement of dislocations by acting as a pinning agent for the boundaries of the cellular structures, thereby enhancing the strength. Simultaneously, the cellular structures were significantly elongated to form the deformation bands and to coordinate the impact deformation, leading to good impact energy absorption. In combination, the synergistic strengthening and toughening effect of the μ phases and the elongated cellular structures contribute to a remarkable improvement in the impact toughness of the PBF-HEAs.

Abstract Microstructures and mechanical properties of Mg-12Gd-0.8Zn-0.4Zr (GZ1208K, wt.%) alloy under different treatments (as-cast: signed as nonHIP-GZ1208K, hot isostatic pressing (HIP): signed as HIP-GZ1208K) were characterized. Based on microstructure characterization, two prismatic precipitates, β′ and β1 precipitates, and one basal precipitate, γ′ precipitate, formed in both of nonHIP-GZ1208K and HIP-GZ1208K alloy. According to analysis, the area number density and the size of β′ precipitate could be adjusted through HIP treatment. The area number density of β′ precipitate increased after HIP treatment when aged at 32 h, and the size of β′ precipitate refined in both of the HIP-GZ1208K alloy aged at 8 h and 32 h. Except the influence of HIP treatment on microstructures, the ultimate tensile strength (UTS) and elongation of nonHIP-GZ1208K alloy also improved after HIP treatment. The UTS of the GZ1208K alloy aged at 8 h increased from 348 MPa (nonHIP-) to 371 MPa (HIP-) and the elongation increased from 2.6% to 4.7%. The density of the nonHIP-GZ1208K alloy increased after HIP treatment, that is to say the casting defects could be eliminated and the compactness of microstructures could be increased under the high pressure of HIP treatment.

Achieving ultra-high strength without sacrificing too much ductility is the focus of attention in nanostructured materials. Here, the strengthening mechanism and property enhancement of surface-mechanically treated 17-4PH stainless steel (SS17-4PH) were investigated. Our findings show that a grain refinement and elongated lath-like martensitic grain (~ 50 nm thick) could be produced after surface treatment. The grain size remains in the nanoscale, and random crystallographic orientations with the presence of nanocrystallites characterize the nanocrystalline grains formed on the treated sample. This contributes to the property enhancement with a yield strength of about 901 MPa and a reduced elongation to failure of about 17%. The atom probe tomography (APT) characterization unveiled the emergence of high-density precipitate (Cu-rich) at the material surface, with a number density of about 2.6255 × 1024 m−3 and an average radius of 2.22 nm. Besides, the dislocation activities caused by SMAT result in the gradual breakdown of precipitates into smaller sizes and final dissolution in the matrix, increasing the number of nucleation sites and leading to more grain refinement processes. The grain boundary, dislocation densities, and the Cu-rich precipitate greatly influence the strengthening mechanism of surface-treated SS17-4PH. [ABSTRACT FROM AUTHOR]

Mine permitting requires an analysis of reasonably foreseeable impacts. In pit lake models, precipitates may be invoked to reduce dissolved aqueous concentrations, and thereby perceived groundwater impacts in the event of a throughflow pit lake after mine closure. The phases selected by modelers are generally based on geochemical theory rather than empirical data, and in this context, a review of available information is helpful. The mineralogy of Spanish, German, Czechian, Australian, and USA acidic pit lakes includes schwertmannite, jarosite, alunite, amorphous ferric oxyhydroxide (AFH), ferrihydrite, goethite, hydrobasaluminite, gibbsite, amorphous iron and aluminum oxyhydroxysulfates, gypsum, barite, and clays (kaolinite, dickite, halloysite, and smectite). Conversely, alkaline pit lakes exhibit distinct inorganic precipitation of calcite, ikaite, gaylussite, and siderite entraining metal removal from solutions at pH > 7 with biogenic iron oxyhydroxides and carbonates. Microbial activity facilitates the formation and transformation of metal sulfide precipitates predominantly in alkaline pit lakes but also in acidic water bodies. Therefore, predictive pit lake studies should focus on selecting authigenic precipitates on an empirical basis where possible, or if observed in corresponding environments in the case of permitting a new pit lake, taking into consideration kinetic barriers to mineral precipitation. This study characterized amorphous iron, aluminum, and calcium precipitate with entrained arsenic, manganese, and zinc floc from the previously acidic, now alkaline Lone Tree pit lake. The formerly acidic Liberty pit lake generated primarily gypsum and AFH, while the basic former Cortez pit lake sediment comprised calcite with solid solution Ba, Cd, Mg, Mn, and Zn. [ABSTRACT FROM AUTHOR]

In this article, the effects of Ce (0–120 ppm) on inclusions and precipitates in industrially produced CO2/H2S‐resistant 10Cr5MoVCe special oil well pipe steel and the microscopic behavior of Ce solid solution in steel were systematically studied by scanning electron microscopy, transmission electron microscopy, electrolysis separation of nonaqueous mixed solutions, and first‐principles calculations. After adding Ce to 10Cr5MoV steel the inclusions changed from chain‐like Al2O3 inclusions to polygonal Ce–O–S–Al–Ca complex inclusions and spheroidal Ce2O3, CeAlO3, Ce2O2S, and CeS inclusions. When the total Ce content was 25–120 ppm, the solid solution Ce content was maintained at about 20% of the total Ce content. The Ce had no significant influences on the types of chromium carbide precipitates, and the chromium carbide precipitates of all tested steels were Cr23C7 and Cr7C3. However, with the increase of Ce, the content of Cr23C7 and Cr7C3 precipitates decreased slightly, from 1.27% without Ce to 1.18% when Ce was 120 ppm. The first‐principles calculation results show that there was strong interaction between Fe, Ce, and Cr. Ce enhanced the interaction force between the Fe and Cr atoms, and improved the stability of the system, which facilitated the solid solution of Cr in the Fe–Cr system. [ABSTRACT FROM AUTHOR]

• The high rolling temperature would impede the DRX occurrence for these final-rolled sheets. • The reduction of the volume fraction of this β phases led to the highest peak-aging hardness in R-450 °C sheet. • The precipitate chains in R-385 °C + A sheets were beneficial for strength and elongation. • The traditional precipitation characteristic in R-450 °C + A sheet was bad for elongation but good for strength. • The peak-aging R-450 °C sheet showed the highest strength, i.e. UTS of 518±17 MPa and YS of 438±18 MPa. In this investigation, a high-strength Mg-12Gd-1.0Er-0.5Zr (wt.%) alloy sheet was produced by hot extrusion (HE) and subsequent hard-plate rolling (HPR) at different temperatures. The results indicate that the microstructures of these final-rolled sheets are inhomogeneous, mainly including coarse deformed grains and dynamic recrystallized (DRXed) grains, and the volume fraction of these coarse deformed grains increases as the rolling temperature increases. Thus, more DRXed grains can be found in R-385 °C sheet, resulting in a smaller average grain size and weaker basal texture, while the biggest grains and the highest strong basal texture are present in R-450 °C sheet. Amounts of dynamic precipitation of β phases which are mainly determined by the rolling temperature are present in these sheets, and its precipitation can consume the content of Gd solutes in the matrix. As a result, the lowest number density of β phase in R-450 °C sheet is beneficial to modify the age hardening response. Thus, the R-450 °C sheet displays the best age hardening response because of a severe traditional precipitation of β' (more) and β Η / β Μ (less) precipitates, resulting in a sharp improvement in strength, i.e. ultimate tensile strength (UTS) of ∼ 518 ± 17 MPa and yield strength (YS) of ∼ 438±18 MPa. However, the elongation (EL) of this sheet reduces greatly, and its value is ∼ 2.7 ± 0.3%. By contrasting, the EL of the peak-aging R-385 °C sheet keeps better, changing from ∼ 4.9 ± 1.2% to ∼ 4.8 ± 1.4% due to a novel dislocation-induced chain-like precipitate which is helpful to keep good balance between strength and ductility. [ABSTRACT FROM AUTHOR]

Influence of different levels of silicon under a variety of thermal treatment is investigated on the thermophysical behaviour of Al-Si-Cu-Mg automotive alloys. Conventional cast alloys are subjected to T6 heat treatment for age hardening. Hardness values, thermal conductivity along with microstructural observation under different heattreated conditions are well thought-out to comprehend the ageing performance and the precipitation behaviour of the alloys. From these investigational results it is indicated that two successive hardening peaks take place in the aged alloys. Ageing sequence consists of different phases like a supersaturated solid solution, GP zones, intermediate β", intermetallic β', equilibrium β and the Q phase but GP zones and the metastable phases are most likely responsible for these ageing peaks. Thermal conductivity decreases for these precipitates formation during ageing and increases for relieving the internal stress, dissolution of metastable phase and coarsening the precipitation of the alloys. Adding up of Si to the alloy showed earlier ageing peaks with higher intensities intended for its increasing properties of heterogeneous nucleation and diffusion kinetics. After ageing around at 200°C for four hours the alloys offer the height hardness. Microstructural study reveals that eutectic silicon makes the grain boundary coarsen and beyond the eutectic composition the star-shaped blocky primary Si is formed. Subsequent to ageing at 350oC for one hour the alloys reach completely recrystallized state. [ABSTRACT FROM AUTHOR]

In-situ electron irradiation and aging are applied to introduce high-density precipitates in an Mg-10Gd-3Y-1Zn-0.5Zr (GWZ1031K, wt.%) alloy to improve the hardness. The results show that the hardness of the Mg alloy after irradiation for 10 h and aging for 9 h at 250 °C is 1.64 GPa, which is approximately 64% higher than that of the samples before being treated. It is mainly attributed to γ′ precipitates on the basal plane after irradiation and the high-density nanoscale β′ precipitates on the prismatic plane after aging, which should be closely related to the irradiation-induced homogenous clusters. The latter plays a key role in precipitation hardening. This result paves a way to improve the mechanical properties of metallic materials by tailoring the precipitation through irradiation and aging. [ABSTRACT FROM AUTHOR]

The effect of 0.2%Cr addition on the structure, phase composition, and mechanical properties of the novel cast and wrought Al-2.5Zn-2.5Mg-2.5Cu-0.2Zr-Er(Y) alloys were investigated in detail. Chromium is distributed between primary crystals (5.7–6.8%) of the intermetallic phase and the aluminum solid solution (0.2%) (Al). The primary crystals contain for the main part Cr, Ti, Er(Y). The experimental phase composition is in good correlation with the thermodynamic computation data. The micron-sized solidification origin phases (Al8Cu4Er(or Y) and Mg2Si) and supersaturated (Al) with nano-sized Al3(Zr,Ti) and E (Al18Mg3Cr2) precipitates are presented in the microstructure of the novel alloys after solution treatment. The nucleation of η (MgZn2) (0.5%), S (Al2CuMg) (0.4%), and T (Al,Zn,Mg,Cu) (8.8%) phase precipitates at 180 °C, providing the achievement of a maximum hardness of 135 HV in the Al2.5Zn2.5Mg2.5CuYCr alloy. The corrosion potential of the novel alloy is similar to the Ecor of the referenced alloy, but the corrosion current density (0.68–0.98 µA/sm2) is still significantly lower due to the formation of E (Al18Mg3Cr2) precipitates and S phase precipitates of the aging origin, in addition to the T phase. The formation of E (Al18Mg3Cr2) precipitates under the solution treatment provides a lower proportion of recrystallized grains (2.5–5% vs. 22.4–25.1%) and higher hardness (110 HV vs. 85–95 HV) in the Cr-rich alloys compared to the referenced alloys. Solution treated, hot and cold rolled, recrystallized, water quenched and aged at 210 °C alloys demonstrate an excellent microstructure stability and tensile properties: YS = 299–300 MPa, UTS = 406–414 MPa, and El. = 9–12.3%. [ABSTRACT FROM AUTHOR]

Microstructures and mechanical properties of Mg-12Gd-0.8Zn-0.4Zr (GZ1208K, wt.%) alloy under different treatments (as-cast: signed as nonHIP-GZ1208K, hot isostatic pressing (HIP): signed as HIP-GZ1208K) were characterized. Based on microstructure characterization, two prismatic precipitates, β′ and β1 precipitates, and one basal precipitate, γ′ precipitate, formed in both of nonHIP-GZ1208K and HIP-GZ1208K alloy. According to analysis, the area number density and the size of β′ precipitate could be adjusted through HIP treatment. The area number density of β′ precipitate increased after HIP treatment when aged at 32 h, and the size of β′ precipitate refined in both of the HIP-GZ1208K alloy aged at 8 h and 32 h. Except the influence of HIP treatment on microstructures, the ultimate tensile strength (UTS) and elongation of nonHIP-GZ1208K alloy also improved after HIP treatment. The UTS of the GZ1208K alloy aged at 8 h increased from 348 MPa (nonHIP-) to 371 MPa (HIP-) and the elongation increased from 2.6% to 4.7%. The density of the nonHIP-GZ1208K alloy increased after HIP treatment, that is to say the casting defects could be eliminated and the compactness of microstructures could be increased under the high pressure of HIP treatment. [ABSTRACT FROM AUTHOR]

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The effect of different compression creep parameters on the creep behavior and microstructure of Al-x%Li-0.1%Sc alloy was studied. The Al-Li-Sc alloy with Li content of 1, 3 and 5% and Sc content of 0.1% was subjected to creep compression treatment for 24 h at 155, 175, 245, 285 and 325 °C. It is found that when the effective temperature and time are the same, the higher the content of Li in the sample, the more and finer the equiaxed grains, and the higher the microhardness of the corresponding sample. Additionally, it can be found that the alloys have different texture densities and the phenomenon of Al3Li and Al3 (Sc, Li) precipitates pinning dislocations at different temperature result in different properties with different Li contents under different creep parameters. [ABSTRACT FROM AUTHOR]

The effect of acid-soluble aluminum content on precipitates and magnetic properties of grain oriented silicon steel was researched by optical microscopy and zeiss ultra 55 Scanning Electron Microscope (SEM) technique respectively. The results show that the number of precipitates increases with the increase of acid-soluble aluminum content, and the size of precipitates is relatively large after hot rolling. Under the low hot rolling temperature, the number of precipitates in the samples is large and the size is small, moreover, the grain size of the primary recrystallized grain is small. The matching of process parameters under different production process lines is the key to obtain good magnetic performance. The effect of nitriding on magnetic properties of the samples is related to the acidsoluble aluminum content of the samples. Too much acid-soluble aluminum can deteriorate the magnetic properties. [ABSTRACT FROM AUTHOR]

2205 Duplex Stainless Steel (DSS) is extensively utilized in various structural components due to its exceptional strength and corrosion resistance. However, for complex structural parts that are challenging to process using conventional methods, Selective Laser Melting (SLM) technology offers a viable solution by enabling layer-by-layer solidification. The rapid cooling rates during the forming process effectively suppress the precipitation of detrimental brittle phases like σ, while concurrently promoting a high proportion of ferrite phases within the structure upon cooling to room temperature. This paper investigates the microstructure and properties of 2205 DSS fabricated via SLM. A notable observation was the presence of abundant precipitates along the ferrite grain boundaries. Characterization through Energy-Dispersive X-ray Spectroscopy (EDS) and Transmission Electron Microscopy (TEM) confirmed the presence of χ-phase and nanoscale closely packed hexagonal Cr2N-phase precipitates. The high fault density and precipitates induced by the SLM process significantly enhanced the sample's strength, resulting in a remarkable tensile strength of 1301.69 ± 19.6 MPa and yield strength of 781.2 ± 12.2 MPa. Subsequent cooling via solid solution water treatment at 1050°C yielded a biphase structure with an austenite content of 54.7% and ferrite content of 45 %. The tensile strength decreased to 815.61 ± 16.4 MPa, and the yield strength decreased to 443.245 ± 7.5 MPa, while the elongation increased significantly from 19.03 ± 1.2% to 46.53 ± 0.7%. These findings demonstrate that the material achieved performance levels comparable to forging and hot rolling processes.

To address the limited wear resistance attributed to the insufficient initial mechanical properties observed in high manganese steel (HM) wear behavior, we introduced nitrogen (N) to modulate precipitation behavior, thereby elevating material mechanical properties and wear resistance, and this was further enhanced through aging treatments. Due to the nitrogen addition, the precipitates transformed from MC to M(C, N), concurrently triggering a substantial increase and refinement in precipitates. As a result, nitrogenous high manganese steel (NHM) exhibited improved strength, toughness, and work-hardening capacity. The enhancements amounted to 67–77 MPa in yield strength and 5.3–9.3 % in elongation, with these improvements becoming more pronounced after extending the aging treatment. Under impact abrasive wear conditions, the NHM demonstrated the development of a stable work-hardened layer. The NHM hardened layer rapidly reached a depth of 4–6 mm, effectively resisting abrasive embedding and suppressing matrix abrasion. This transitioned the primary wear mechanisms from cutting and plowing to plastic deformation and micro-spalling. Additionally, NHM's great uniformity and toughness-plasticity played a crucial role in preventing the initiation and propagation of fatigue cracks and fatigue sheds.

Achievement of ultra-high yield strength of above 400 MPa for rare-earth-free magnesium (Mg) alloys is quite difficult via traditional thermal-mechanical processing. In this study, Mg–6Al–4Sn–1Zn alloy (ATZ641) sheet with the yield strength of 410 MPa, ultimate tensile strength of 442 MPa, and elongation of 5.1 %, was fabricated by combining extrusion and high-speed rolling (HSR). The results showed significant refinement in the grains of high-speed rolled ATZ641 alloy due to dynamic recrystallization (DRX) effectively promoted by particle-stimulated nucleation (PSN) of pre-existing relatively coarse Mg17Al12 precipitates uniformly distributed along grain boundaries, formed during extrusion prior to HSR. Meanwhile, the Mg17Al12 nano-precipitates with high number density, mainly due to dynamic precipitation during HSR and submicron Mg2Sn precipitates formed during both extrusion and HSR, suppress DRX and thus promote the formation of a certain amount of subgrains via particle pinning. The excellent mechanical properties are mainly attributed to fine-grain strengthening, high density residual dislocations and presence of numerous hybrid particles such as bimodal size (micron and nanometer) Mg17Al12 precipitates and submicron Mg2Sn precipitates as well as a large amount of subgrains. This study offers an important notion for developing rare-earth-free Mg alloys with ultra-high strength.

Si-containing ferritic/martensitic (F/M) steels are ideal candidate structural materials for the lead-cooled fast reactors on account of their good mechanical properties, corrosion resistance and irradiation resistance. In order to figure out the optimal Si content and the effect of Si-content on the microstructure and mechanical behavior of 9Cr–F/M steels, F/M steels with different Si addition of 0, 0.36, 0.68, and 0.93 % (wt.%) were prepared. It is found that with increasing Si content, both the room temperature ultimate tensile strength and the total elongation of the F/M steels are enhanced, but the yield strength has a little change. At elevated temperatures (500 and 800 °C), the steels containing 0.68 % and 0.93 % Si show better comprehensive tensile properties. The addition of Si is overall beneficial to the impact toughness. Si addition also refines the prior austenite grains and the martensitic structure units (packets, blocks and laths). When the Si content exceeds 0.68 %, δ-ferrite is formed in the steels. No adverse effect from the δ-ferrite was found on the tensile properties. As the Si content increases, the MX precipitates are refined and their area fraction is reduced. However, the area fraction of the Cr-rich carbide precipitates increases with the increase of Si content. For the steels containing 0 % and 0.36 % Si, the Cr-rich precipitates are mainly M23C6, while for the steels with 0.68 % and 0.93 % Si, the Cr-rich precipitates are mainly M7C3.

Preset twins in Mg-5Gd-3Y-0.5Zr (GW53K) alloy, the effects of preset twins on the aging precipitates and mechanical properties of GW53K alloy were thoroughly investigated. The results showed that the preset twin boundaries provided nucleation locations for the aging precipitates and promoted the aging precipitation behavior of GW53K alloy. High density of lath-like twins increased the strength of the alloy. Lattice distortions were generated around twin boundaries, which impeded dislocation slip and produced stress concentration, so that the solute atoms Gd and Y easily clustered there to form precipitates. Precipitates could form ''barriers'' with twin boundaries and increased the ability of twin boundaries to block dislocation slip and the movement of twins, which further improved the strength of the alloy. However, the presence of twins accelerated the fracture process of GW53K alloy and reduced plasticity.

The effect of sigma-phase precipitation on plastic anisotropy of the equiatomic CoCrFeMnNi high-entropy alloy was investigated. Annealing at 700 °C after cold-rolling leads to the formation of the Cr-rich σ phase with a fraction of 2.7%. It is experimentally found that the planar anisotropy (∆r = −0.16) of the CoCrFeMnNi alloy annealed at 700 °C is two times lower than that of the alloy annealed at 800 °C (∆r = −0.35). This observation was further supported by measuring the earing profile of cup specimens after the deep drawing process. The plastic strain ratio, normal anisotropy, and planar anisotropy were also predicted using the visco-plastic self-consistent model. The results indirectly indicated that the reduction of plastic anisotropy in alloy annealed at 700 °C can be attributed to the formation of the σ phase. [ABSTRACT FROM AUTHOR]

Al-based foams have drawn increasing attention from industry due to their integration of structure and functional properties. However, large-sized Al-based foams still cannot be homogeneously strengthened by long-time aging due to their low thermal conductivity. In this study, we proposed an age-hardening approach that was applied in large-sized Al-0.16Sc-0.17Zr (wt.%) foams via micro-alloying with Zr and Ti compared with Al-0.21Sc foams; it not only achieved homogeneous strength by long-term aging but also reduced the cost of the alloy by substituting Zr and Ti for the more expensive Sc content. The results show that the Al3(Sc, Zr, Ti) phase with a core–shell structure as a crucial precipitation strengthening phase by micro-alloying with Zr and Ti was less prone to coarsening after a prolonged aging heat treatment. Therefore, the yielding strength of Al-Sc foam micro-alloying with Zr and Ti remained almost unchanged after a maximum aging time of 1440 h due to less coarsening precipitate, which is consistent with the results of mechanical experiments. These findings provide a new way for the heat treatment strengthening of large-sized Al-based foams, thus promoting their industrial applications. [ABSTRACT FROM AUTHOR]

The wastewater treatment industry could benefit from new technologies for the removal and recovery of phosphorus (P). The CalPrex precipitation reactor has the potential to recover P in a readily land-applicable form by treating organic acid digestate with calcium hydroxide to produce brushite. Using data from a pilot-scale reactor at the local Nine Springs Wastewater Treatment Plant in Madison, WI, we modified the plant's BioWin configuration using BioWin 6.2 to model the CalPrex technology and estimate performance under a variety of conditions. We produced dose/response curves for a range of possible lime dosages to estimate the impact of reagent dosage on the quantity and composition of precipitate produced by the CalPrex reactor and characterize the effects on downstream anaerobic digester performance. CalPrex was found to capture 46% of the plant's influent P, reducing nuisance struvite precipitates by 57% and biosolid sludge production by 14%. The CalPrex module was also tested in two predesigned plant configurations in the BioWin cabinet with the intention of testing applicability to other configurations and searching for the impacts of CalPrex on treatment train performance. This is the first work simulating a full-scale implementation of CalPrex and the first to model interactions of CalPrex with other treatment processes. [ABSTRACT FROM AUTHOR]

Copyright of Iron Steel Vanadium Titanium is the property of Iron Steel Vanadium Titanium Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Iron Steel Vanadium Titanium is the property of Iron Steel Vanadium Titanium Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Mg alloys with excellent high-temperature mechanical properties are urgently desired to meet the design requirements of new-generation aircraft. Herein, novel cast Mg-10Gd-2Y-0.4Zn-0.2Ca-0.5Zr-xAg alloys were designed and prepared according to the advantages of multi-component alloying. The SEM and XRD results revealed that the as-cast microstructures contained α-Mg grains, β, and Zr-containing phase. As Ag rose from 0 wt.% to 2.0 wt.%, the grain size was refined from 40.7 μm to 33.5 μm, and the β phase significantly increased. The TEM observations revealed that the nano-scaled γ′ phase could be induced to precipitate in the α-Mg matrix by the addition of Ag. The stacking sequence of lamellar γ′ phases is ABCA. The multiple strengthening phases, including β phase, γ′ phases, and Zr-containing particles, were effectively tailored through alloying and synergistically enhanced the mechanical properties. The ultimate tensile strength increased from 154.0 ± 3.5 MPa to 231.0 ± 4.0 MPa at 548 K when Ag was added from 0 to 2.0 wt.%. Compared to the Ag-free alloy, the as-cast alloy containing 2.0 wt.% Ag exhibited a minor reduction in ultimate tensile strength (7.0 ± 4.0 MPa) from 498 K to 548 K. The excellent high-temperature performance of the newly developed Mg-RE-Ag alloy has great value in promoting the use of Mg alloys in aviation industries. [ABSTRACT FROM AUTHOR]

In the aluminum industry, forming is an important process step that introduces dislocations in the material. To investigate the effect of dislocation retention after ageing on 6xxx-series alloys, a non-heat-treatable 5005 alloy was selected to measure the change in mechanical properties due to dislocation annihilation during dynamic recovery. However, the isothermal ageing treatment led to an unexpected and significant increase in mechanical properties after deformation. Increases in yield strength of 120% and tensile strength of 50% compared with the as-received material were achieved. However, this caused a significant decrease in elongation properties. The deformation start temperature did not have any impact on the final mechanical properties. TEM analysis attributed the increase in mechanical properties to an increased precipitation and dislocation density compared with the undeformed reference material. The precipitates are located along dislocation lines, showing that the solute elements are preferentially segregating to dislocations and precipitating. The precipitates were typical for the Al–Mg–Si(–Cu) system; therefore, the low amounts of Si and, to a lesser extent, Cu were responsible for the precipitation hardening in the 5005 alloy. [ABSTRACT FROM AUTHOR]

To improve the surface quality for aluminum alloy 6061(Al6061) in ultra-precision machining, we investigated the factors affecting the surface finish in single point diamond turning (SPDT) by studying influence of the precipitates generation of Al6061 on surface integrity and surface roughness. Based on the Johnson-Mehl-Avrami solid phase transformation kinetics equation, theoretical and experimental studies were conducted to build the relationship between the aging condition and the type, size and number of the precipitates for Al6061. Diamond cutting experiments were conducted to machine Al6061 samples under different aging conditions. The experimental results show that, the protruding on the chip surface is mainly Mg2Si and the scratches on the machined surface mostly come from the iron-containing phase (α-, β-AlFeSi). Moreover, the generated Mg2Si and α-, β-AlFeSi affect the surface integrity and the diamond turned surface roughness. Especially, the achieved surface roughness in SPDT is consistent with the variation of the number of AlFeSi and Mg2Si with the medium size (more than 1 µm and less than 2 µm) in Al6061. [ABSTRACT FROM AUTHOR]