The super combination of ultrahigh strength and good ductility is in high demand for the gear steels. Here we improved the mechanical properties of a micro-alloyed gear steel through the fabrication ...route composed of carburizing and re-quenching. The results showed that the different re-quenching temperatures significantly affect not only the sizes and morphologies of precipitates and martensite but also the ratio of low-angle grain boundaries to high-angle grain boundaries as well as dislocation densities. The maximum ultimate tensile strength up to 2420 MPa was obtained after re-quenching at 780 °C, while the steel re-quenched at 820 °C exhibited the highest yield strength of 1500 MPa despite of the decreased ultimate tensile strength of 2145 MPa. Especially, a good ductility of 8.5% was maintained in the carburized steel processed after 780 °C re-quenching. The spherically nanosized precipitates together with the high ratio of low-angle grain boundaries were beneficial for the simultaneously improved strength and ductility.
The micromechanical behavior of high-strength steels with multiple phases was characterized using the in situ high-energy X-ray diffraction technique. For the materials investigated, the {2
0
0} ...lattice strains of the constituent phases (ferrite, bainite and martensite) with similar crystal structures were determined by separating their overlapped diffraction peaks and then examining the respective changes in peak positions during deformation. Based on those experimental data, the anisotropic elastic and plastic properties of the steels were simulated using a self-consistent model for predicting the grain-to-grain and phase-to-phase interactions. The constitutive laws for describing the elastic and plastic behavior of each constituent phase were directly obtained by comparing the predicted lattice strain distributions with the measured ones. The transmission electron microscopy observations of the microstructure development verified the partitioning of plastic strains among different phases. The present investigations provide a fundamental understanding of the stress partitioning of soft and hard phases, and the different work-hardening rates of the multiphase steels.
Recently, high-entropy alloys (HEAs) in which the face-centered cubic (fcc) structure is dominant have attracted great attention due to their excellent ductility and good fracture toughness. However, ...the room-temperature yield strength of those alloys is usually low, which can not meet the demand of engineering applications. In addition, grain refinement in HEAs is limited, thus ultrahigh strength can not be achieved through grain boundary strengthening. In this study, a heavily N-doped (5 at.%) FeMnCoCr HEA with multiple heterostructures was prepared by the mechanical alloying (MA) method combined with spark plasma sintering (SPS). It consisted of recrystallized grains with the sizes ranging from submicron to micron and uniformly dispersed nano-scale nitrides and oxides. The N-doped alloy sintered at 900 °C exhibited a high compressive yield strength up to 1960 MPa at room temperature, which was ∼7.8 times stronger than that of the as-cast FeMnCoCr base alloy. In addition, under compression the soft and the hard domains within the inhomogeneous microstructures accommodated deformation with each other. This promoted continuous activation of dislocation slip and interactions between dislocations and stacking faults, leading to a satisfactory fracture strain of 21% and some work hardening ability for the alloy.
•The N-doped HEA fabricated by powder metallurgy shows an ultrahigh yield strength.•Good strength-ductility synergy is attributed to the multiple heterostructures.•The soft and the hard domains accommodate with each other during co-deformation.
Background
Tertiary lymphoid structure (TLS) plays an important role in antitumour immunity, largely reflecting the prognosis. However, its clinical implication in cutaneous squamous cell carcinoma ...(cSCC) remains unknown.
Objectives
To explore the features of TLS in cSCC and its association with clinicopathological characteristics.
Methods
Two independent RNA‐seq data of cSCC were used to investigate the tumour immune microenvironment, as well as TLS‐related chemokines and cytokines. The density and location of TLSs were assessed in a total of 82 cSCC patients, and the clinicopathologic association was examined.
Results
Bioinformatics analysis showed that a large amount of immune cell infiltration and significant up‐regulation of TLS‐related chemokines were observed in cSCC. Histologically, TLSs appeared as highly organized structures in 72 (87.8%) cases with different levels of density and maturation, among which 14 cases were in low‐density group and 58 cases were in high‐density group. Clinically, the presence of TLS was prominently associated with better degree of histopathological grades and higher level of sun exposure. Furthermore, the presence of intratumoral TLS was associated with lower lymphovascular invasion.
Conclusions
TLS is highly organized in cSCC, and the presence of TLS is a positive prognostic factor for cSCC, which will provide a theoretical basis for the future diagnostic and therapeutic value in cSCC.
With the continuous growth of the automation level, the production process is featured by multiple stages and process parameters. There is a huge sum of diverse data on automated production. With a ...low value density, these data come from heterogenous sources, and respond to lots of concurrent processing demands. It is necessary to simulate and optimize the production scheduling of the automated production system. Drawing on the existing research, this paper illustrates the process of multi-stage production scheduling of automated production, and simulates the automated production line on Plant Simulation. The flow of the simulation model was illustrated, the simulation objectives were specified, and the model hypotheses were detailed. From the angle of deterministic simulation modelling, a joint optimization model was established for the multi-stage production scheduling of automated production, and the production task assignment was improved for traditional pull scheduling model to meet the demand of dynamic collaborative demand for machines. The proposed model was proved effective through simulations.
In sequel to our previous study (Mater. Sci. Eng. A, 769 (2020) 138,471), we elucidate here the determining role of alloying with Ti and tempering effect on tensile and creep properties in low ...activation martensitic steel (LAM) and compare with the coarse-grained (CG) LAM steel. When the tempering temperature was decreased from 760 °C to 730 °C, while maintaining time constant at 30 min, grain size and MX carbide density was constant at ~7.0 ± 0.5 μm and (8.20 ± 0.05) × 1024 m−3 in 0.1 Ti LAM steels, compared to ~20.0 ± 0.5 μm and (3.20 ± 0.05) × 1024 m−3 in Ti-free CG LAM steel. However, the thickness of martensitic lath decreased from 450 ± 10 nm to 370 ± 10 nm and the density of M23C6 carbides increased from (4.30 ± 0.05) × 1019 m−3 to (1.10 ± 0.05) × 1020 m−3, which were 320 ± 10 nm and (6.05 ± 0.05) × 1019 m−3 in CG LAM steel. Yield strength (σy) increased with the decrease of tempering temperature. At room temperature, σy of 0.1 Ti LAM steels increased from 660 ± 10 MPa to 700 ± 10 MPa, accompanied by no apparent decrease in elongation (25 ± 1% to 24 ± 1%). In CG LAM steel, σy was 570 MPa and elongation was 23%. Creep life at 600 °C/170 MPa increased from 145 ± 5 h to 190 ± 5 h with the decrease of tempering temperature from 760 °C to 730 °C, while it was 120 h for CG LAM steel. Furthermore, σy increased with the decrease of subgrain size and the increase of M23C6 density. At 600 °C/170 MPa, the coarsening of martensitic lath and the decrease of M23C6 carbide density reduced the strength, leading to crack initiation in the vicinity of large M23C6 carbides and fracture. The mechanisms involving differences in the mechanical behavior are discussed.
The static recrystallization and MX precipitation of a low activation martensitic (LAM) steel processed by different compression temperatures were studied. The result shows that at an identical ...duration of 200 s, the static recrystallization degree of steel decreases continuously from 96% to 62% and 25 % with decreasing compression temperature from 1050℃ to 950℃ and 850℃, respectively. Analysis shows that, with the decrease of compression temperature, the reduced recrystallization rate is mainly due to the decrease of temperature and the increase of nano precipitation content. After solution treatment, the sizes of grains, subgrains and the MX carbides decrease in the LAM steel with the decrease of compression temperature. After 1050 ℃ compression, the average size of grains, subgrains and MX carbides are 7 μm, 220 nm and 15 nm, respectively. However, in the 850 ℃ case, the corresponding size significantly decreases to 4.5 μm, 175 nm and 10 nm, respectively, which is mainly due to the lower recrystallization degree and the increase of nano precipitation content in the steel after compression. With the decrease of the compression temperature from 1050 ℃ to 950 ℃ and 850 ℃, the hardness of LAM steel after solid solution treatment increases from 4.0 GPa to 4.2 GPa and 4.5 GPa, mainly resulting from the refinement of grains, subgrains and MX carbides.
Dislocation behavior in laminated metallic composites (LMCs) plays a pivotal role in strength and ductility of bulk materials. Here, we studied evolutions of geometrically necessary dislocations ...(GNDs) and statistically stored dislocations (SSDs) as well as their effects on strain hardening in the uniaxially deformed Ti/Nb LMCs fabricated by accumulative roll bonding plus the subsequent annealing. By combining in-situ neutron diffraction and ex-situ electron backscattered diffraction (EBSD) techniques, for the first time, we quantitatively reveal that dislocation evolutions in the laminates are independent of initial layer thickness within the micron scale. As the applied strain reaches the uniform elongation stage, GND density in Ti increases remarkably by an order of magnitude in all laminates, while that in Nb almost remains unchanged. Besides, the total dislocation density in Ti develops rapidly with deformation, whereas the SSD density does not increase monotonically. In Nb, both total dislocation density and SSD density increase significantly below 0.02 true strain, and gradually saturate in the late stage of strain hardening. During the whole plastic deformation, Nb bears more stress and dominates the global hardening because of the significant development of SSDs in this metal. Importantly, the strengthening induced by heterophase interfaces is more significant in the softer Ti in which GNDs are extensively activated, and SSDs only marginally contribute to the heterophase interface strengthening. These findings provide insights into the exploration of deformation mechanisms in materials with laminated and gradient structures, and also guide the development of LMCs with advanced mechanical properties.
We prepared aluminum-doped zinc oxide (ZnO:Al, AZO) films by a sol–gel method and investigated the effect of doping on the electrical properties of AZO films in the Al doping concentration range of ...0.5–3.0 at.%. The negative effect of Al dopants on the carrier mobility counteracted their positive effect on the carrier concentration and the resistivity of the films remained almost constant at the optimum Al doping level of 0.5 at.%. Moreover, the doping efficiency of Al dopant decreased with increasing doping level and the maximum efficiency was not higher than 50% even at the optimum doping concentration. The microstructure and chemical composition of the films were examined by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy to elucidate the mechanism behind the low doping efficiency of Al dopant in the sol–gel-derived AZO films. The reason was attributed to the passivation of the dopant in two forms, defect complex
n
Al
Zn
–
V
Zn
originating from the dopant–defect reaction in the ZnO grains and aluminum oxide phase segregating at the ZnO grain boundaries.
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