强力错距旋压Al-Zn-Mg-Cu(7075)合金管材的显微组织与力学性能

采用强力错距旋压技术在400℃(HS)和室温(RTS)条件下制备7075铝合金管材,并对其成形过程中的显微组织演变和力学性能变化进行研究。结果表明:经过旋压变形后,7075铝合金管材的晶粒明显细化,并且在400℃下厚度减薄60%和70%(HS-60%和HS-70%)的管材组织以变形组织为主,而厚度减薄85%(HS-85%)的管材组织以再结晶组织为主。此外,HS-85%管材由于动态再结晶和异常晶粒长大的出现,形成了具有弱立方织构的双峰晶粒组织。随着400℃下厚度减薄率从0%增加到85%,管材的屈服强度(YS)和极限抗拉强度(UTS)先增加后降低,而伸长率则先降低后增加。室温厚度减薄85%(RTS-85%)的管材的UTS和YS分别为613.5和567.9 MPa,与HS-85%管材相比,分别提高了33.7%和57.4%,但其伸长率仅为7.3%。

Fatigue limit assessment of a 6061 aluminum alloy based on infrared thermography and steady ratcheting effect

To quickly predict the fatigue limit of 6061 aluminum alloy,two assessment methods based on the temperature evolution and the steady ratcheting strain difference under cyclic loading,respectively,were proposed.The temperature evolutions during static and cyclic loadings were both measured by infrared thermography.Fatigue tests show that the temperature evolution was closely related to the cyclic loading,and the cyclic loading range can be divided into three sections according to the regular of temperature evolution in different section.The mechanism of temperature evolution under different cyclic loadings was also analyzed due to the thermoelastic,viscous,and thermoplastic effects.Additionally,ratcheting strain under cyclic loading was also measured,and the results show that the evolution of the ratcheting strain under cyclic loading above the fatigue limit undergone three stages:the first increasing stage,the second steady state,and the final abrupt increase stage.The fatigue limit of the 6061 aluminum alloy was quickly estimated based on transition point of linear fitting of temperature increase and the steady value of ratcheting strain difference.Besides,it is feasible and quick of the two methods by the proof of the traditional S-N curve.

Eye metastasis in lung adenocarcinoma mimicking anterior scleritis:A case report

BACKGROUND The eye is a rare site for lung cancer metastasis. Indeed, ocular metastasis is one of the greatest challenges to quality of life in a cancer patient. Here we present a patient with lung adenocarcinoma and ocular metastasis.CASE SUMMARY The patient was a 70-year-old man diagnosed with lung adenocarcinoma who developed eye metastasis mimicking anterior scleritis. Brain magnetic resonance imaging showed an abnormal signal in the right eye. Based on next generation sequencing of the surgical specimen, the patient was shown to have a KRAS point mutation(p.G12D).CONCLUSION Multidiscipline expertise collaboration is needed to make the early diagnosis and determine the prompt treatment in patients. We hope to increase the awareness of the possibility of lung cancer metastasizing to the eye.

Understanding micro-diffusion bonding from the fabrication of B_4C/Ni composites

A Ni-B_4C macroscopic diffusion welding couple and a Ni-15 wt% B_4C composite fabricated by spark plasma sintering(SPS) were used to understand the micro-scale diffusion bonding between metals and ceramics. In the Ni-B_4C macroscopic diffusion welding couple a perfect diffusion welding joint was achieved. In the Ni-15 wt% B_4C sample, microstructure analyses demonstrated that loose structures occurred around the B_4C particles. Energy dispersive X-ray spectroscopy analyses revealed that during the SPS process, the process of diffusion bonding between Ni and B_4C particles can be divided into three stages. By employing a nano-indentation test, the room-temperature fracture toughness of the Ni matrix was found to be higher than that of the interface. The micro-diffusion bonding between Ni and B_4C particles is quite different from the Ni-B_4C reaction couple.

Molecular Dynamics Simulations and Experimental Investigations of Atomic Diffusion Behavior at Bonding Interface in an Explosively Welded Al/Mg Alloy Composite Plate

In this study, 6061 aluminum alloy and AZ31 B magnesium alloy composite plate was fabricated through explosive welding. Molecular dynamics（MD） simulations were conducted to investigate atomic diffusion behavior at bonding interface in the AI/Mg composite plate. Corresponding experiments were conducted to validate the simulation results. The results show that diffusion coefficient of Mg atom is larger than that of A1 atom and the difference between these two coefficients becomes smaller with increasing collision velocity. The diffusion coefficient was found to depend on collision velocity and angle. It increases linearly with collision velocity when the collision angle is maintained constant at 10° and decreases linearly with collision angle when the collision velocity is maintained constantly at 440 m/s. Based on our MD simulation results and Fick＇s second law, a mathematical formula to calculate the thickness of diffusion layer was proposed and its validity was verified by relevant experiments. Transmission electron microscopy and energy-dispersive system were also used to investigate the atomic diffusion behavior at the bonding interface in the explosively welded 6061/AZ31B composite plate. The results show that there were obvious Al and Mg atom diffusion at the bonding interface,and the diffusion of magnesium atoms from magnesium alloy plate to aluminum alloy plate occurs much faster than the diffusion of aluminum atoms to the magnesium alloy plate. These findings from the current study can help to optimize the explosive welding process.

Microstructure,fracture behavior,in vitro corrosion resistance,and cytotoxicity of Zn-Mg/Mg-Zn-HAp laminated composites produced by spark plasma sintering

Ideal biodegradable materials exhibit suitable degradation rates and sufficient mechanical properties for their specific application.With these parameters in mind,Zn-Mg/Mg-Zn-hydroxyapatite(HAp) laminated composites were designed and fabricated by spark plasma sintering.This paper describes the structure,mechanical properties,in vitro corrosion resistance,and cytotoxicity of the Zn-Mg/Mg-Zn-HAp laminated composites.The compressive strength and elastic moduli of the laminated composites matched that of cortical bone and could effectively reduce the stress shielding effect as an implant with good biomechanical compatibility.Analysis of the fracture path and morphology after fracture toughness tests indicated that the Zn-Mg/Mg-Zn-HAp laminated composites exhibited significant capacity to prevent crack propagation,improving the fracture toughness.In vitro degradation experiments showed that the design of the laminated structure can provide a gradient degradation rate for the material.Furthermore,the laminated composites exhibited excellent biocompatibility and are promising candidates for orthopedic implants.

Inducing and isolation of antibacterial peptides from oriental fruit fly, Bactrocera dorsalis Hendel

One antibacterial activity fraction from an immunized dipteran insect, Bactrocera dorsalis, was isolated and purified by prepurification, ion-exchange chromatography, gel filtration chromatography and reverse-phase high performance liquid chromatography （HPLC）. The final purified fraction was checked on the Smart system HPLC and was judged as a pure fraction. The results of physical and biological analysis revealed that this fraction is heat stable and showed strong activities against Gram-positive bacterial growth. It possesses antibicrobial peptide properties and is worth further investigation.

Microstructure and Dynamic Compression Properties of PM Al6061/B_4C Composite

Aluminum 6061 matrix composite reinforced by 35 wt% B4 C particle was fabricated by power metallurgy method. Then, the as-deformed composite was tested by quasi-static（0.001 s-1） and dynamic（760-1150 s-1） compression experiments. The Johnson-Cook plasticity model was employed to model the flow behavior. The damage mechanism of composite was analyzed through the microstructure observations. The results showed that the B4 C particles exhibited uniform distribution and no deleterious reaction product Al4C3 was found in the composite. Al6061/B4 C composite showed high yield strength, moderate strain rate sensitivity and strain hardening under the dynamic loading, and a constitutive model under dynamic compression was established based on Johnson-Cook model, and accorded well with experimental results. The microstructure damage was dominated by particle fracture and interface debonding, and the dislocation was observed in the composite at a higher strain rate.

Effect of Nb addition on microstructure and mechanical properties of 25CrNiMoV(DZ2)steel for high-speed railway axles

The microstructure,precipitates and properties of 25CrNiMoV(DZ2)steel for high-speed railway axles with different Nb contents were investigated by means of optical microscopy,scanning electron microscopy,electron back-scattering diffraction,transmission electron microscopy and physicochemical phase analysis.The results show that the grain size of the original austenite of the test steels decreases from 20.5 to 14.2 and 10.8μm after adding 0.026 and 0.039 wt.%Nb to a 25CrNiMoV steel,respectively.Moreover,the block width of the tempered martensite in the test steels is refined from 1.91 to 1.72 and 1.60µm,respectively.MC-type precipitates in 25CrNiMoV steel are mainly VC,while(Nb,V)C gradually precipitates when Nb is microalloyed,and the amount of precipitates increases with increasing Nb content.Through strengthening mechanism analysis,it is found that grain refinement strengthening is the primary way to increase the strength.The improvement in the yield strength with increasing Nb content is attributed to a significant increase in precipitation strengthening,grain refinement strengthening and dislocation strengthening.

Syndecan 4-c-ros oncogene 1 fusion as a mechanism of acquired resistance in epidermal growth factor receptor mutant lung adenocarcinoma

To the Editor:A 37-year-old Chinese woman,a nonsmoker,presented with adenocarcinoma of the left lung(stage IV)[Figure 1A],malignant pleural effusion,and multiple bone metastases in December 2014.Deoxyribonucleic acid sequencing of the tumor biopsy revealed an epidermal growth factor receptor(EGFR)exon 19 deletion,and treatment with gefitinib was consequently initiated in December 2014.There were no treatmentrelated side effects except for a grade 1 rash,and stable disease was achieved.Unfortunately,the patient did not experience long-term benefits and developed disease progression after only two months.A follow-up examination showed that extracranial disease and a small intracranial lesion had developed gradually.The patient then received whole-brain radiotherapy(30 Gy in ten fractions)and four cycles of single-agent pemetrexed in April 2015.Stable disease was achieved,which coincided with an improvement in the patient’s cough,shortness of breath,and general condition.The chemotherapy course was changed to two cycles of pemetrexed combined with cisplatin.A partial response(PR)was achieved,and the patient was treated with 14 cycles of pemetrexed alone as maintenance chemotherapy.The follow-up evaluations showed the patient’s condition to be stable;however,the patient’s disease progressed after 23 months.A computed tomography(CT)scan in March 2017 revealed that both the lung lesion and the malignant pleural effusion had increased in size[Figure 1B].The subsequent biopsy specimen was subjected to next-generation sequencing(NGS)and a Syndecan 4-c-ros oncogene 1(SDC4-ROS1)rearrangement was detected[Figure 1C].The patient then received crizotinib in April 2017,and a PR was achieved[Figure 1D].A CT scan done in August 2018 indicated the progression of the primary lesion in the left lung and malignant pleural effusion.However,the growth of the remaining lesions remained stable.

Corrosion Behavior of B_4C/6061Al Neutron Absorber Composite in Different H_3BO_3 Concentration Solutions

In this study, electrochemical corrosion tests, full-soak corrosion tests and associated microstructure analysis were conducted to investigate the corrosion behaviors of B4C/6061Al neutron absorber composites（NACs） manufactured by powder metallurgy method in solutions having different boric acid（H3BO3） concentrations（500, 2500 and 10,000 ppm）. In electrochemical corrosion tests, B4C/6061Al NACs demonstrate the highest（short-term） corrosion resistance in the 2500 ppm H3BO3 solution. While for full-soak corrosion tests, the B4C/6061Al NACs show the highest（long-term） corrosion resistance in the 500 ppm H3BO3 solution. This difference is found to be mainly due to the formation of different surface morphologies during these two different corrosion tests. As noticed, a layer of Al（OH）3was formed on the composite surface during full-soak corrosion tests, but it cannot be found in the electrochemical corrosion tests. The full-soak corrosion mechanism of the B4C/6061Al NACs in the H3BO3 solution is found to be primarily determined by the dynamic balance between the formation and dissolution rates of the oxide film, which is mainly controlled by the density of H~＋ ions in the solution.

Microstructure Evolution and Nanomechanical Behavior of Micro-Area in Molten Pool of Selective Laser Melting(CoCrNi)_(82)Al_(9)Ti_(9)High-Entropy Alloy

In this work,the phase evolution mechanism and nanomechanical properties of(CoCrNi))(82)Al_(9)Ti_(9)high-entropy alloy(HEA)prepared by selective laser melting(SLM)in the molten pool were studied.This HEA contains multiple primary elements and undergoes high-temperature gradient and rapid cooling during SLM.This leads to significant inhomogeneity of nano-scale microstructure characteristics and instability of properties.After optimizing process parameters,the microstructure evolution at the optimal parameter volume energy density of 440 J/mm^(3)was studied.A phase transition from BCC to FCC occurred in the melt micro-zone.Remelting the micro-area of the melt pool results in a temperature rise and the combustion-induced loss of Al elements.Moreover,the Ni element content increases significantly outside the melt pool.This process enhances the phase stability of FCC and facilitates phase transitions.Additionally,rapid cooling leads to the formation of distinctive ultrafine equiaxial crystals inside the melt pool,accompanied by the generation of intracrystalline needle-like nano-scale phases.Outside the melt pool,the accumulation of energy results in the formation of coarse dendrites.Therefore,the nano-hardness inside the molten pool is remarkably high at 11.79 GPa,while the outside the molten pool is reduced to 9.58 GPa.And the fracture toughness outside the melt pool also decreased.Comparing with inside the melt pool,the residual stress outside the melt pool changed from compressive to tensile stress and decreased from 603.28 to 322.84 MPa.