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| 1 | Effects of Rare Earth elements on microstructure evolution and mechanical properties of 718H pre-hardened mold steel显示文摘718 H Pre-ha rdened mold steels with diffe rent Rare Earth(RE) contents were prepared to investigate the influence of RE on microstructure evolution and mechanical properties through a series of experiments and theoretical analysis.The results indicated that the toal oxygen(T.O) content decreased from 15 ppm to 6 ppm with 0.022 wt% RE addition,which is attributed to the active chemical properties of RE elements.For test steels,RE additions of 0.012 wt% and 0.022 wt% were significantly effective for refining inclusions by eliminating 11.5% large-sized inclusions with diameter exceeding 10 μm compared with that of ORE steel.RE addition contributed to modify irregular MnS and Al2 O3 inclusions into ellipsoidal RE-inclusions(RE2 O,RES,RE2 O2 S and REAlO3).The purification of molten steel and the modification of inclusions by RE treatment have significant effects on improvement of the fatigue crack growth tests(FCG) inhibition ability and impact energy as well as the isotropy.However,excessive addition of RE elements(0.07 wt%)seriously reduced the impact energy,ultimate tensile strength and FCG inhibition ability due to rapidly increase of the volume fraction of large-sized inclusions.In addition to the inclusions formed by RE treatment,trace solid solution RE atoms improve the stability of undercooled austenite,resulting in the transformation region of bainite and perlite of 0.07 RE steel shifting to the bottom right and prolonging the incubation period compared with that of ORE steel. | Hanghang Liu Paixian Fu Hongwei Liu Yanfei Cao Chen Sun Ningyu Du Dianzhong Li | 2020 | Journal of Materials Science & Technology2020，47，15： | 11 |
| 2 | Effect of vanadium micro-alloying on the microstructure evolution and mechanical properties of 718H pre-hardened mold steel显示文摘The effects of different contents of vanadium(V)(0.1,0.2,and 0.3 wt%)on the microstructure evolution and mechanical properties of 718H steel were investigated.The precipitate was characterized by means of atom probe tomography(APT)and bright-field transmission electron microscopy(TEM).The increase in V content has great benefits for strength,but has an adverse effect on impact toughness.The strength increase can be attributed to the influence of V addition on dislocation density,misorientation gradient,and fine scale MC precipitates.Precipitation strengthening mainly contributes to the V-added steel by analyzing various strengthening mechanisms.However,fine scale MC precipitates can pin dislocation leading to a decrease in its mobility.A large number of immovable dislocations will increase the dislocation accumulation,internal stress and brittle cracking,resulting in a gradual decrease in impact toughness with the V addition.In addition,compared with V-free steel,the dissolved V content in austenite decreases the grain boundary energy and inhibits the diffusion of the C atoms,ultimately reducing the transformation range of pearlite(P). | Hanghang Liu Paixian Fu Hongwei Liu Chen Sun Ningyu Du Dianzhonga Li | 2019 | Journal of Materials Science & Technology2019，35，11： | 5 |
| 3 | miR-103-3p regulates the differentiation of bone marrow mesenchymal stem cells in myelodysplastic syndrome显示文摘The pathogenesis of myelodysplastic syndrome(MDS)may be related to the abnormal expression of microRNAs(miRNAs),which could influence the differentiation capacity of mesenchymal stem cells(MSCs)towards adipogenic and osteogenic lineages.In this study,exosomes from bone marrow plasma were successfully extracted and identified.Assessment of miR-103-3p expression in exosomes isolated from BM in 34 MDS patients and 10 controls revealed its 0.52-fold downregulation in patients with MDS compared with controls(NOR)and was downregulated 0.55-fold in MDS-MSCs compared with NOR-MSCs.Transfection of MDS-MSCs with the miR-103-3p mimic improved osteogenic differentiation and decreased adipogenic differentiation in vitro,while inhibition of miR-103-3p showed the opposite results in NOR-MSCs.Thus,the expression of miR-103-3p decreases in MDS BM plasma and MDS-MSCs,significantly impacting MDS-MSCs differentiation.The miR-103-3p mimics may boost MDS-MSCs osteogenic differentiation while weakening lipid differentiation,thereby providing possible target for the treatment of MDS pathogenesis. | NINGYU LI XIAOFANG CHEN SUXIA GENG PEILONG LAI LISI HUANG MINMING LI XIN HUANG CHENGXIN DENG YULIAN WANG JIANYU WENG XIN DU | 2023 | BIOCELL2023，47，1： | 0 |
| 4 | Limitations of the homogenization process of bulk martensitic mold steel-depending on the comprehensive manifestation of various strengthening显示文摘A homogenization treatment(1250 °C + 12 h) was carried out to minimize the micro-segregation of bulk 718H martensitic mold steel, as verified by advanced experimental characterization and kinetic model of diffusion. However, new research found that there are still limitations in the use of the homogenization process. The result indicates that the chemical heterogeneity can be significantly reduced after homogenization. The segregation ratio of Cr and Mo elements of sample decreased by 40.9% and 35.6% of the original level, respectively. Simultaneously, the test steel with higher strength and toughness is produced by controlling micro-segregation tempered from 540 °C to 650 °C. Importantly, it reveals that the impact energy is increased by up to 27.3%. The isotropy of impact energy in different directions can reach 0.89,resulting in an overall improvement in the isotropy. Toughness mainly depends on the orientation relationship between the crack propagation direction and the band segregation region. The chain carbides formed due to the decomposition of the micro-segregated region during tempering are considered the main source of cracks. The more evenly distributed the subsequent tempered carbides after homogenization, resulting in an increase in toughness. However, an abnormal phenomenon is found in which the yield strength after homogenization is lower than that of the untreated sample tempered at 700 °C. This result can be attributed to the combined influences of precipitation strengthening and fine grain strengthening by analyzing various strengthening mechanisms. The mutually restrictive strengthening effect leads to the limitations of the homogenization process of bulk martensitic mold steel. | Hanghang Liu Paixian Fu Hongwei Liu Chen Sun Ningyu Du Dianzhong Li | 2022 | Journal of Materials Science & Technology2022，，22： | 0 |
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