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Ultra-high strength steel (UHSS) pipes find widespread application in the automotive industry. To address the challenges associated with forming complex structural parts from UHSS pipes, the three-dimensional free thermal bending (3D-FTB) technology for UHSS pipes based on a robotic arm and a bending roller mold was firstly developed. A finite element simulation prediction model for accurately describing the forming process is established and discussed. In this paper, the thermal-mechanical coupling model of the material is established by Gleeble thermal tensile test and modified Arrhenius model. The effects of parameters such as current frequency, current density, axial feed rate, and quenching conditions on forming temperature and microstructure transformation are thoroughly investigated via finite element simulation analysis. The mechanical properties and potential defects of the pipe fittings after forming are analyzed and validated experimentally. The results demonstrate that the finite element simulation and analysis method based on the thermal-force coupling model of the BR1500HS UHSS pipe can accurately predict the forming process parameters. The optimal process conditions are identified as follows: current frequency of 55 kHz, current density of 650 A/mm2, and feed rate of 8 mm/s. Under these parameters, the austenite transformation rate of the pipe fittings reaches an impressive 98 % and the maximum tensile strength reaches 1540 MPa. Lastly, the overall wall thickness distortion rate of the formed pipe remains below 0.2 % and the bending rebound angle exhibits an average reduction of over 80 % compared to that under room temperature conditions.

Optical microscope, X-ray diffractometer, scanning electron microscope and energy dispersive spectrometer were used to study the microstructure, phase growth morphology and phase composition of free solidified Mg-Sn eutectic in-situ composites at different solidification stages.The crystal growth mechanism of Mg-Sn eutectic in-situ composite and the effect of cooling rate on the microstructure of the alloy were investigated.The results show that the solidification structure of Mg-Sn hypoeutectic alloy is hexagonal rose-like primary α-Mg phase and eutectic Mg/Mg2Sn lamellar mixed structure. The solidification structure of Mg-Sn hypereutectic alloy is a mixed structure of angular primary Mg2Sn intermetallic compound phase and eutectic Mg/Mg2Sn lamellar structure.With the increase of Sn content, the quantity of primary α-Mg phase decreased and the content of eutectic phase increased. With the increase of cooling rate, the microstructure of the alloy is obviously refined.The α-Mg primary phase is a non-faceted phase, and the primary Mg2Sn intermetallic compound phase is a faceted phase.

Graphene has become one of the ideal reinforcers for aluminum matrix composites due to its unique structural characteristics and excellent properties. This paper mainly introduces the preparation technology of three categories of graphene-reinforced aluminum matrix composites, including the liquid forming method, powder forming method and composite processing technology, and so on. Base on analyzing the principle of different types of preparation technology, combined with four strengthening mechanisms of graphene-reinforced aluminum matrix composites, the development trend of graphene reinforced aluminum matrix composites is prospected, including the basic theoretical research, the breakthrough of preparation technology and large-scale industrial application of composites.

Background: Metformin has pleiotropic effects beyond glucose reduction, including tumor inhibition and immune regulation. It enhanced the anti-tumor effects of programmed cell death protein 1 (PD-1) inhibitors in serine/threonine kinase 11 (STK11) mutant non-small cell lung cancer (NSCLC) through an axis inhibition protein 1 (AXIN1)-dependent manner. However, the alterations of tumor metabolism and metabolites upon metformin administration remain unclear. Methods: We performed untargeted metabolomics using liquid chromatography (LC)-mass spectrometry (MS)/MS system and conducted cell experiments to verify the results of bioinformatics analysis. Results: According to the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database, most metabolites were annotated into metabolism, including nucleotide metabolism. Next, the differentially expressed metabolites in H460 (refers to H460 cells), H460_met (refers to metformin-treated H460 cells), and H460_KO_met (refers to metformin-treated Axin1-/- H460 cells) were distributed into six clusters based on expression patterns. The clusters with a reversed expression pattern upon metformin treatment were selected for further analysis. We screened out metabolic pathways through KEGG pathway enrichment analysis and found that multiple nucleotide metabolites enriched in this pathway were upregulated. Furthermore, these metabolites enhanced the cytotoxicity of activated T cells on H460 cells in vitro and can activate the stimulator of the interferon genes (STING) pathway independently of AXIN1. Conclusion: Relying on AXIN1, metformin upregulated multiple nucleotide metabolites which promoted STING signaling and the killing of activated T cells in STK11 mutant NSCLC, indicating a potential immunotherapeutic strategy for STK11 mutant NSCLC. [ABSTRACT FROM AUTHOR]