Interior Of Sample Research Articles

Abstract 2479: Preclinical assessment of imaging agents for identification of fucosyl-GM1 expression in vivo

Abstract Background: Fucosyl-GM1 (FucGM1) is a monosialoganglioside highly expressed in 50%-70% of small cell lung cancer (SCLC) cells, supporting it as a potential biomarker. BMS-986012 is a nonfucosylated, first-in-class, fully human immunoglobulin G1 monoclonal antibody that binds to FucGM1 with high affinity and specificity. Understanding how FucGM1+ tumor expression correlates with response to BMS-986012 may improve patient selection and therapeutic efficacy. Objective: Evaluate ability of imaging agents built on BMS-986012 to detect tumor FucGM1 expression. Methods: BMS-986012 was labeled with a near-infrared fluorophore. Binding to human H520 (FucGM1−) and DMS79 (FucGM1+) xenografts was assessed in vivo via optical imaging. BMS-986012 was labeled with deferoxamine and radiolabeled to produce 89Zr-BMS-986279, which was evaluated in vitro with H520 and DMS79 cells. Tracer distribution and tumor accumulation was assessed by positron emission tomography (PET) imaging in mice bearing bilateral H520 and DMS79 xenografts and analyzed with ex vivo autoradiography (ARG). Results: Optical imaging with fluorescent BMS-986012 showed statistically significant accumulation in DMS79 vs H520 tumors at all time points (P<.05), beginning 6 hours post administration and reaching a 3:1 maximum uptake ratio. Maximum tumor to background signal was measured at 96 hours (final imaging time point). Total radiolabeled 89Zr-BMS-986279 binding to intact DMS79 cells was ≈15-fold higher than to H520 control cells in vitro and was almost completely blocked by coincubation with a 1000-fold excess of BMS-986012. In vivo, longitudinal PET imaging of 89Zr-BMS-986279 showed significantly higher tracer accumulation in FucGM1+ DMS79 xenografts vs H520 tumors (P<.001). The difference in tracer uptake between tumor models increased with time and was highest (≈2-fold) approximately 8 days post injection. PET signal decreased over time in both FucGM1− H520 xenografts and background muscle tissues, consistent with slow accumulation of specific binding and clearance from background common with antibody-based tracers. Ex vivo ARG studies confirmed in vivo PET results and indicated that 89Zr-BMS-986279 can be used to assess FucGM1 expression throughout the tumor volume, with signal found in the periphery and interior of tumor samples. Conclusions: In vitro cell binding, in vivo fluorescence and PET imaging, and ex vivo ARG studies demonstrated that 89Zr-BMS-986279 was sensitive and specific for detecting FucGM1 expression in tumor cells. Specificity to the intended target in animal disease models coupled with kinetics typical of antibody-based tracers further support the utility of 89Zr-BMS-986279 as a potential FucGM1 imaging agent. A phase 2 study is evaluating safety and efficacy of BMS-986012 combined with carboplatin, etoposide, or nivolumab in patients with newly diagnosed extensive-stage SCLC (NCT04702880). Citation Format: R. Adam Smith, Erin L. Cole, Andrea Olga Shorts, Thomas Petrone, Joonyoung Kim, Daniel Cohen, Paul Morin, Samuel J. Bonacorsi, Patrick L. Chow. Preclinical assessment of imaging agents for identification of fucosyl-GM1 expression in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2479.

Hydrogen concentration-induced stresses in an environmental TEM

The hydrogen-enhanced localized plasticity (HELP) mechanism is a leading candidate among proposed hydrogen embrittlement (HE) mechanisms. Transmission electron microscopy (TEM) measurements of an increased dislocation mobility on exposure to hydrogen have provided the most direct evidence for the HELP mechanism. However, it has been hypothesized that the observed dislocation behavior is not a consequence of the interaction between hydrogen atoms and dislocations but a systematic error due to the nature of in situ TEM. Specifically, the electron beam in TEM microscopes can dissociate hydrogen, leading to a hydrogen fugacity much greater than the applied pressure. Such high fugacity will generate a large concentration gradient between the surface and interior of a TEM sample. It has been proposed that the observed dislocation mobility is due only to stresses arising from this concentration gradient rather than an effect of the interaction with hydrogen. Here we calculate the expected stresses for H/Fe and H/Ni systems fugacities expected in an in situ TEM. We show the stresses to be an order of magnitude too low to impact dislocation mobility in the H/Fe system, and that the concentration gradient-induced stresses dissipate quickly in both H/Fe and H/Ni systems---well before observation by TEM would occur.

He2+ irradiation induced microstructure evolution in sub-surface layer of the coarse-grained tungsten accessed by synchrotron GIXRD and GISAXS

In this study the microstructure evolution in sub-surface layer of the coarse-grained W after irradiation of 400 keV He2+ at different fluences and temperatures was assessed by synchrotron grazing incident X-ray diffraction (GIXRD) and grazing-incidence small-angle X-ray scattering (GISAXS). The splitting of GIXRD peaks obtained at different incident angles indicates that the un-irradiated coarse-grained W exhibits a compression strain state in the near surface and the He ions irradiation results in a lattice swelling which is more severe at higher irradiation temperature and fluence. The GISAXS results combined with the TEM analysis indicate that after irradiation at room temperature, uniformly distributed high density dislocation loops with an average radius of about 3.7 nm were formed due to the extrusion of He-V clusters. After irradiation at 400 °C, high density He bubbles with radii between 1 and 3 nm were formed in the sample interior, while large blisters appeared near the surface. This work provides a reference for the study of irradiation damage in the sub-surface layer of W alloys via synchrotron GIXRD and GISAXS.

Preparation and Strength Formation Mechanism of Calcined Oyster Shell, Red Mud, Slag, and Iron Tailing Composite Cemented Paste Backfill.

The use of bulk solid-waste iron tailing (IOT), red mud (RM), and oyster shells to prepare cemented paste backfill (CPB) can effectively solve the ecological problems caused by industrial solid waste storage and improve the utilization rate of such materials. In this study, a new type of CPB was prepared by partially replacing slag with RM, with calcined oyster shell (COS) as the alkaline activator and IOT as aggregate. The central composite design (CCD) method was used to design experiments to predict the effects of the COS dosage, RM substitution rate, solid mass, and aggregate–binder ratio using 28-dUCS, slump, and the cost of CPB. In this way, a regression model was established. The quantum genetic algorithm (QGA) was used to optimize the regression model, and X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscope (SEM), and energy dispersive spectroscopy (EDS) microscopic tests are performed on CPB samples of different ages with the optimal mix ratio. The results showed that COS is a highly active alkaline substance that provides an alkaline environment for polymerization reactions. In the alkaline medium, the hematite and goethite in RM and quartz in IOT gradually dissolved and participated in the process of polymerization. The main polymerization products of the CPB samples are calcium–silicate–hydrogel (C–S–H), calcium–aluminosilicate–hydrogel (C–A–S–H), and aluminosilicate crystals such as quartz, albite, and foshagite. These products are intertwined and filled in the internal pores of the CPB, enabling the pore contents to decrease and the interiors of the CPB samples to gradually connect into a whole. In this way, the compressive strength is increased.

Valorization of turmeric (Curcuma longa L.) rhizome: Effect of different drying methods on antioxidant capacity and physical properties

Turmeric has high commercial demand internationally, owing to its high nutrient and medical value. In this research, turmeric samples were subjected to several drying methods viz. infrared freeze drying (IRFD), freeze drying (FD), and pulse-spouted microwave-assisted freeze-drying (PSMFD). Over the range of operating conditions employed in this study, IRFD of infrared radiation was showed to shorten the drying time by 21.27% relative to FD, while the retention valves of ascorbic acid, curcumin, total phenols, and total flavonoids remains at 75.61%, 94.06%, 69.00%, and 80.09%, respectively over the range of experimental parameters. IRFD significantly (P < 0.05) reduced 25.19% of the energy consumption in comparison with FD. Furthermore, the interior of IRFD samples exhibited a honeycomb porous structure, and increased hardness, lower shrinkage, apparent density compared to PSMFD. Additionally, IRFD also performed better than PSMFD and FD under vacuum freezing conditions.

Interface History on Strain Field Evolution in Epoxy Resins

To determine if full-strain measurements are sufficient in measuring interfacial phenomena in additively manufactured thermosets, we devised a testing method to examine the effect of interface history (i.e., time between interface formation and original material deposition) on localized mechanical properties. Interfaces were formed in diglycidyl ether of bisphenol A (DGEBA)/diethylenetriamine (DETA) epoxy resins with various DETA concentrations. Times to the gel point and full cure were assessed by rheology and Fourier transform infrared spectroscopy (FTIR) for each composition. From here, dogbone samples were fabricated with an interface formed at either the gel point or at full cure for each composition. Key findings show that tensile strength and Young’s modulus deteriorate globally with the presence of an interface regardless of the history or initiator (DETA) concentration. Samples with an interface demonstrate high strain regions near the interface prior to fracture. Micro X-ray computed tomography revealed high density regions at the interface that increased in number with both cure times and initiator concentrations. FTIR revealed that the interface demonstrated a higher cure completion than the sample interior, resulting in a stiffer epoxy localized at the interface versus the bulk. These findings were confirmed by atomic force microscopy modulus mapping at the interface. Finally, computational modeling of epoxy in uniaxial tension with an increasing number of stiff inclusions demonstrated that inclusion contents correlated with increased, localized stress concentrations. These findings will aid in the understanding of fracture phenomenon in additively manufactured thermosets and point to digital image correlation as a useful tool in epoxy interface detection.

Three dimensional visualization of simulations of liquids and solids

Visualization in three dimensions is invaluable for understanding the nature of condensed and fluid systems, but it is not always easy. In nature it is hard to view sample interiors, but on computers it is possible. We describe and contrast two opposite approaches - “smoke” visualization for viewing interiors of liquid samples and interactive WebGL for solids and molecules. Both are extensions of earlier Technion Computational Physics group projects and complement and are interoperable with the recent SimPhoNy Fp7 project. They require only desktop hardware and software accessible to students. Examples and standalone instructions for both are presented, starting with sample creation and concluding with image galleries.

Phase Evolution and Thermal Expansion Behavior of a γ′ Precipitated Ni-Based Superalloy by Synchrotron X-Ray Diffraction

The phase evolution and thermal expansion behavior in superalloy during heating play an essential role in controlling the size and distribution of precipitates, as well as optimizing thermomechanical properties. Synchrotron X-ray diffraction is able to go through the interior of sample and can be carried out with in situ environment, and thus, it can obtain more statistics information in real time comparing with traditional methods, such as electron and optical microscopies. In this study, in situ heating synchrotron X-ray diffraction was carried out to study the phase evolution in a typical γ′ phase precipitation strengthened Ni-based superalloy, Waspaloy, from 29 to 1050 °C. The γ′, γ, M23C6 and MC phases, including their lattice parameters, misfits, dissolution behavior and thermal expansion coefficients, were mainly investigated. The γ′ phase and M23C6 carbides appeared obvious dissolution during heating and re-precipitated when the temperature dropped to room temperature. Combining with the microscopy results, we can indicate that the dissolution of M23C6 leads to the growth of grain and γ′ phase cannot be completely dissolved for the short holding time above the solution temperature. Besides, the coefficients of thermal expansions of all the phases are calculated and fitted as polynomials.

Effect of surface burnishing process with different strain paths on the copper microstructure

The single strain path (SSP) and the reciprocating strain path (RSP) machining are performed on the sample surface with a multi-ball surface burnishing tool to study the effect of different deformation modes on the microstructure. The samples are characterized mechanically and metallographically via a microhardness tester, an optical microscope, and a backscattered scanning electron microscope. The effect of the two strain paths on the plastic strain in the material is explored by developing a numerical simulation model. The characterization and simulation results show that the deformation layer thicknesses are 79 μm, 208 μm, and 290 μm for the SSP treated samples and 108 μm, 191 μm, and 305 μm for the SSP models at penetration depths Dp of 30 μm, 60 μm, and 90 μm, and meantime, 195 μm, 249 μm and, 390 μm for the RSP treated samples and 146 μm, 248 μm, and 396 μm for the RSP models. Moreover, the RSP treated samples are harder than the SSP treated samples at the same penetration depth Dp, attributed to the smaller grain size and longer total length of grain boundaries of the RSP treated samples. The simulation results show that the RSP machining, with the assistance of the Bauschinger effect, further increases the strain degree and the machining influence depth in the sample compared with the SSP machining. The RSP machining disintegrates the dislocation cells in collaboration with the Bausinger effect, which causes the shielding effect of long-range stress to be significantly reduced, further transferring machining stress to the sample interior. It is the main reason why the RSP machining leads to deeper affecting depth. Furthermore, the grain boundaries in the fine-grain layer of the RSP and SSP treated samples are mainly dominated by high angle grain boundaries, supplemented by low angle grain boundaries, with a smaller percentage of twin boundaries, while in the coarse-grain layer are mainly twin boundaries, supplemented by high angle grain boundaries, with a smaller percentage of low angle grain boundaries. The micro-textures of the samples machined by the two strain paths are minor differences, but the grains in the subsurface layers produced different grain rotations.

PRODUCTION AND QUALITY CHARACTERIZATION OF SOYMILK ENRICHED BREAD

Soybean (Glycine max) is a valuable food crop which consists of various nutrients associated with health benefits. Large spectrums of phytochemicals having potential biological properties are associated with soybean. Soybean has 36% protein, 19 % oil, 35% carbohydrates and 5 % minerals. The USA, Brazil and Argentina are the world largest soybean producing countries. During current study soybean variety was evaluated for physicochemical composition to explore potential for utilization in bakery products. The soybean seed was subjected for soymilk production which was used as functional ingredients for the preparation of soy bread. The prepared products were analyzed for its physicchemical analysis. The sensorial responses of products were checked by authentic 9 point hedonic scale for the boost of soymilk on industrial scale. The bread was arranged by three different concentrations of soybean which were 10%, 20% and 30%. Other constituent that were used in soy bread making were flour, sugar, oil, eggs, salt, baking powder, baking soda and water. The four treatments T0, T1, T2 and T3 were prepared with different soymilk concentration. Treatments were placed to sensory assessment and prepared products were stored for 0, 2, 4 and 6 days at room temperature. The sensory appraisal was observed by the panel of judges to use interior and exterior uniqueness of special soy bread samples. The internals uniqueness was consisted of color, taste, texture, appearance and mouth feel overall acceptability. Treatment T1 and T2 was found to be best among the other treatments and got the maximum score 8.15±0.03 and 7.98±0.03 at T1 and T2, respectively.

PRODUCTION AND QUALITY CHARACTERIZATION OF SOYMILK ENRICHED BREAD

Soybean (Glycine max) is a valuable food crop which consists of various nutrients associated with health benefits. Large spectrums of phytochemicals having potential biological properties are associated with soybean. Soybean has 36% protein, 19 % oil, 35% carbohydrates and 5 % minerals. The USA, Brazil and Argentina are the world largest soybean producing countries. During current study soybean variety was evaluated for physicochemical composition to explore potential for utilization in bakery products. The soybean seed was subjected for soymilk production which was used as functional ingredients for the preparation of soy bread. The prepared products were analyzed for its physicchemical analysis. The sensorial responses of products were checked by authentic 9 point hedonic scale for the boost of soymilk on industrial scale. The bread was arranged by three different concentrations of soybean which were 10%, 20% and 30%. Other constituent that were used in soy bread making were flour, sugar, oil, eggs, salt, baking powder, baking soda and water. The four treatments T0, T1, T2 and T3 were prepared with different soymilk concentration. Treatments were placed to sensory assessment and prepared products were stored for 0, 2, 4 and 6 days at room temperature. The sensory appraisal was observed by the panel of judges to use interior and exterior uniqueness of special soy bread samples. The internals uniqueness was consisted of color, taste, texture, appearance and mouth feel overall acceptability. Treatment T1 and T2 was found to be best among the other treatments and got the maximum score 8.15±0.03 and 7.98±0.03 at T1 and T2, respectively.

Effect of nonuniform sintering on mechanical and thermal properties of silica-based ceramic cores

During sintering of the silica-based ceramic core of turbine blades, a phenomenon called “nonuniform sintering” occurs that negatively affects the thermal and mechanical properties of the core. Standard samples of silica-based core were prepared by an injection molding method and sintered with alumina backfilling powder with different sodium contents. The effect of sodium content on the nonuniform sintering of silica-based cores and the thermal and mechanical properties was evaluated. Results show that the sintering level and the content of α-cristobalite in the surface layer are significantly higher than that of the sample interior. A considerable number of microcracks are found in the surface layer due to the β to α-phase transition of cristobalite. As the sodium content in the alumina powder decreases, the level of the nonuniform sintering and the amount of crystallized cristobalite in the surface layer decrease, which is beneficial to the thermal expansion and flexural strength at ambient temperature. The flexural strength and thermal deformation at high temperature are improved by reducing the surface cracks, but deteriorated with the decrease of the cristobalite crystallization when the surface cracks are macroscopically invisible.

Depth-dependent decomposition and property of large magnetostriction Fe-Ga alloys

Introducing dispersive and coherent nanoprecipitates by early-stage decomposition has been recognized as a promising strategy to achieve super-functional properties, such as the large and sensitive magnetostriction in Fe-Ga alloys. Considering that the diffusion-controlled decomposition is very sensitive to material position, where the atomic diffusion rate can be several orders faster at material surface than that at material interior, it is necessary to investigate how the transformation depth affects the microstructure and the macroscopic property. Here, we investigated the depth-dependent phase transformation and magnetostriction of isothermally-aged Fe75Ga25 alloy, which evolves a diffusion-controlled phase transformation from metastable body-centered-cubic (BCC) to equilibrium face-centered-cubic (FCC) intermediated by face-centered-tetragonal (FCT) phase. X-ray diffraction (XRD) and Transmission electron microscop (TEM) results revealed that from the surface to the interior, both volume fraction and size of the FCC phase gradually decrease, together with the gradual structure transformation from FCC to FCT. When compared with the solution-treated state prior to aging, ordering of the BCC matrix also happens at the sample interior. The gradual changes in precipitates’ structure and morphology result in the gradual magnetostriction enhancement from the material surface to the interior since the FCC phase has negative magnetostriction constant, being opposite to that of the BCC matrix. Our work not only reveals that the over-transformed surface layer of the bulk Fe-Ga material should be removed for fabricating large-magnetostriction materials but also suggests that the depth-dependent microstructure should be carefully controlled when applying the precipitation strategy to develop high-performance materials.

Organic Material Distribution in Mars-Analog Volcanic Rocks, as Determined with Ultraviolet Laser-Induced Fluorescence Spectroscopy.

Understanding the distribution of trace organic material in a rocky environment is a key to constraining the material requirements for sustaining microbial life. We used an ultraviolet laser-induced fluorescence (LIF) spectroscopy instrument to characterize the distribution of organic biosignatures in basalts collected from two Mars-analog environments. We correlated the fluorescence results with alteration-related sample properties. These samples exhibit a range of alteration conditions found in the volcanic environments of Hawai'i Volcanoes National Park, Hawai'i (HI), and Craters of the Moon National Monument, Idaho (ID), including fumarolic systems. LIF mapping of the sample surfaces and interiors showed a heterogeneous distribution of areas of highly fluorescent material (point[s]-of-interest [POIs])-with fluorescence characteristics indicative of organic material. Results suggest that POIs are associated with secondary alteration mineral deposits in the rock's vesicles, including zeolites and calcite. Scanning electron microscopy with electron-dispersive X-ray spectroscopy was used to characterize the mineralogy present at POIs and support the evidence of carbon-bearing material. Overall, samples collected proximate to active or relict meteoric fumaroles from Hawai'i were shown to contain evidence for organic deposits. This suggests that these minerals are measurable spectroscopic targets that may be used to inform sample-site selection for astrobiology research.

Damage and failure mechanism of concentric perforated granite under static pressure after alternating action of high temperature and water at different temperatures

In this study, concentric perforated granite alternately treated with high temperature and water at different temperatures was evaluated based on the engineering environment of surrounding rock in the deep geothermal well energy storage area. The damage and failure mechanism of concentric perforated granite under radial load was studied using a combination of mechanical test, theoretical analysis, and numerical simulation. The results revealed that the inner bore diameter, high treatment temperature, soaking water temperature, and alternating times between cold and heat could weaken the resistance of concentric perforated granite to radial load, but the influence of the deformation pattern on the rock sample was relatively slight. The load–displacement curve during the loading process exhibited the following sections: initial upper concave, short straight line, slowly ascending platform, approximately straight line, short upper convex curve, and post-peak cliff descending sections. Based on the theory of biological population growth, the damage variables of the concentric perforated granite were defined, and the analysis revealed that the internal damage of the rock sample experienced a slow-growth deceleration to a critical state. The numerical simulation results of the shape of the broken rock block and the strain on the side of the rock sample were combined. It was found that two concentration zones of vertical tensile-stress effect were formed inside the rock sample under the action of radial load, which led to the germination of tensile microcracks in the interior of the rock sample and resulted in macroscopic failure. In addition, the tensile microcracks were generated inside the concentric perforated granite. First, they propagated from the inner wall of the rock sample in the loading direction and then, along the outer wall in the vertical loading direction. Then, the microcracks spread and penetrated the outer and inner walls of the rock sample to form the macroscopic fracture surface.

A green and efficient acid system for carbonate reservoir stimulation

Matrix acidizing is a well stimulation method that is applied to enhance productivity. The success of a stimulation job depends mainly on the efficiency of the acid systems that are employed. This study investigated a new and efficient acid system that is biodegradable, not corrosive, and safe to handle. The system efficiency was compared to that of HCl and chelating agents. Acid coreflooding has been applied to chalk, dolomite, and limestone carbonate rock samples to measure the efficiency in terms of injected pore volume to breakthrough (PVBT). The rock samples were characterized in terms of porosity, permeability, composition using X-ray diffraction (XRD), and pore distribution using nuclear magnetic resonance (NMR). The effluent was collected at different times and analyzed using induced coupled plasma (ICP). Medical computed tomography (MCT) was used to visualize the interior of the rock samples after acidizing. The new acid system was more efficient in terms of acid spending than straight HCl acid and chelating agents in Indiana limestone. At the optimum injection rate, chelating agents had an optimum PVBT value of about 15 compared to 0.85 for plain HCl acid. Using the new acid system resulted in an optimum PVBT value of only 0.41, which is less than half of HCl acid. A numerical wormhole simulator was implemented to match the experimental PVBT and assess the reactivity of the acid system.

Mechanical characteristics and freeze–thaw damage mechanisms of mode-I cracked sandstone from the Three Gorges Reservoir region under different chemical solutions

In consideration of the actual environment of the cold region, a test scheme of freeze–thaw (FT) cycles was adopted to explore the mechanical characteristics of sandstone with mode-I cracks under the three-point bending, tensile, and compressive compression tests. And to explore the chemical and freeze–thaw (FT) damage mechanisms, variations in the ion concentration of solutions and the microstructures of sandstone are observed and analyzed under the FT cycle. Experimental results show that the sandstone has a marked tendency to weaken after repeated FT cycles. The pH and chemical composition of chemical solutions had different effects on the deterioration degree from FT in sandstone. From the combined effects of the chemical corrosion and the FT cycles, the ion concentration that was dissoluted from a chemical solution had a clear, cumulative time periodicity. The surface of the sandstone sample was found to exhibit variable degrees of degradation after the combined effects of chemical solutions and FT cycles, and with an increasing number of FT cycles, the degradation degree in the surface microstructure of the sandstone gradually increased. Meanwhile, the interior of sandstone samples was clearly degraded. Specifically, the size of mineral particles was reduced, their edges and corners gradually disappeared or became smooth, the surface roughness of the mineral was found to decrease, and its structure became loose.

Bending Fatigue Behaviour and Fatigue Endurance Limit Prediction of 20Cr2Ni4A Gear Steel after the Ultrasonic Surface Rolling Process.

To study the effect of the surface properties on the bending fatigue performance of heavy-duty gear steel, the authors of this paper used the ultrasonic surface rolling process (USRP) to strengthen 20Cr2Ni4A carburized gear steel. USRP is a novel technique in which the ultrasonic technology is incorporated into the concept of conventional deep rolling. In this study, we illustrated how the surface properties and cross-section mechanical property influence the three-point bending fatigue life of the samples before and after USRP treatment. At the same time, the predicted failure probability-stress-number of cycles (P-S-N) curve was drawn, and the fatigue fracture was analysed. The results show that the fatigue limit increased from 651.36 MPa to 918.88 MPa after USRP treatment. The fatigue source is mainly from the sample interior or surface scratches, and the fatigue performance is positively correlated with the results of the material surface roughness, surface residual stress and surface hardness. At the same time, combined with the change in the phase structure, dislocation structure, residual stress and hardness of the cross section of the material, it is found that the USRP process turns the steel into a gradient material with five layers. Finally, the coupling mechanism between the ultrasonic surface strengthening deformation layer and the carburized layer of 20Cr2Ni4A carburized gear steel is presented, and the grain structure distribution diagram of the section of the 20Cr2Ni4A model after surface strengthening treatment was simulated. The mechanism that influenced the fatigue performance after USRP treatment is explained from the perspectives of the surface and cross section of the samples.

A Comparative Study of Acicular Ferrite Transformation Behavior between Surface and Interior in a Low C–Mn Steel by HT-LSCM

In this study, the acicular ferrite transformation behavior of a Ti–Ca deoxidized low carbon steel was studied using a high-temperature laser scanning confocal microscopy (HT-LSCM). The in situ observation of the transformation behavior on the sample surface with different cooling rates was achieved by HT-LSCM. The microstructure between the surface and interior of the HT-LSCM sample was compared. The results showed that Ti–Ca oxide particles were effective sites for acicular ferrite (AF) nucleation. The start transformation temperature at grain boundaries and intragranular particles decreased with an increase in cooling rate, but the AF nucleation rate increased and the surface microstructure was more interlocked. The sample surface microstructure obtained at 3 °C/s was dominated by ferrite side plates, while the ferrite nucleating sites transferred from grain boundaries to intragranular particles when the cooling rate was 15 °C/s. Moreover, it was interesting that the microstructure and microhardness of the sample surface and interior were different. The AF dominating microstructure, obtained in the sample interior, was much finer than the sample surface, and the microhardness of the sample surface was much lower than the sample interior. The combined factors led to a coarse size of AF on the sample surface. AF formed at a higher temperature resulted in the coarse size. The available particles for AF nucleation on the sample surface were quite limited, such that hard impingement between AF plates was much weaker than that in the sample interior. In addition, the transformation stress in austenite on the sample surface could be largely released, which contributed to a coarser AF plate size. The coarse grain size, low dislocation concentration and low carbon content led to lower hardness on the sample surface.

Improved superelastic stability of NiTi shape memory alloys through surface nano-crystallization followed by low temperature aging treatment

In this work, we proposed a process to improve the functional stability of Ni-rich NiTi alloys, which combines surface nano-crystallization by means of ultrasonic shot peening and subsequent low-temperature (523 K) aging treatment. The as-annealed coarse-grained NiTi plates were fist subjected to ultrasonic shot peening, which generates nano-grains at the surface region, and introduces dislocation networks in the interior of the NiTi sample. Both the grain boundaries and the dislocations could serve as the heterogenous nucleation sites for Ni4Ti3 nanoprecipitates during subsequent low-temperature aging treatment. Therefore, with the presence of nano-grains and dislocation networks, a homogeneous distribution of Ni4Ti3 nanoprecipitates in the sample is expected, which will strengthen largely the NiTi matrix and resist the plastic activities during the repetitive martensitic transformation. As a result, the improved stability during cyclic superelastic loading is achieved.