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Achieving Large-area Bulk Ultrafine Grained Cu via Submerged Multiple-pass Friction Stir Processing

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Journal of materials Science & Technology 2013年第12期29卷 1111-1115页

作者： P. Xue B.L. Xiao z.y. ma Shenyang National Laboratory for materials Science Institute of Metal Research Chinese Academy of Sciences 72 Wenhua Road Shenyang 110016 China

Large-area bulk ultrafine grained （UFG） pure Cu was successfully prepared by multiple-pass overlapping friction stir processing （FSP） under additional rapid cooling. Overlapping FSP did not exert a significant effect on the microstructure and mechanical properties of the FSP UFG Cu. Similar average grain size was achieved in the transitional zone （Tz） of the multiple-pass FSP sample compared to that in the nugget zone of the single-pass FSP sample, and the Tz exhibited a strong {111}（112） type A fiber shear texture, Very weak softening occurred in the Tz of the multiple-pass FSP UFG Cu, resulting in a relatively uniform hardness distribution throughout the whole processed zone. A high yield strength of - 310 MPa and a uniform elongation of - 13% were achieved in the bulk FSP UFG Cu. This study provides an effective strategy to prepare large-area bulk IUFG materials.

关键词： Friction stir processing Multiple-pass Ultrafine grains Microstructure Mechanical properties

High Strain Rate Superplasticity in a Micro-grained Al-Mg-Sc Alloy with Predominant High Angle Grain Boundaries

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Journal of materials Science & Technology 2012年第11期28卷 1025-1030页

作者： F. C. Liu z.y. ma F. C. zhang Shenyang National Laboratory for materials Science Institute of Metal Research Chinese Academy of SciencesShenyang 110016 China State Key Laboratory of Metastable materials Science and Technology Yanshan University Qinhuangdao 066004China

Friction stir processing （FSP） was applied to extruded AI-Mg-Sc alloy to produce fine-grained microstructure with a grain size of 2.2μm. Electron backscatter diffraction （EBSD） result showed that the grain boundary misorientation distribution was very close to a random grain assembly for randomly oriented cubes. Super- plastic investigations in the temperature range of 425-500 ℃ and strain rate range of 1x100^-2-1x10 s^-1 showed that a maximum elongation of 1500% was achieved at 475 ℃ and a high strain rate of 1x100^-2-1x10 s^-1. The FSP AI-Mg-Sc exhibited enhanced superplastic deformation kinetics compared to that predicted by the constitutive relationship for superplasticity in fine-grained aluminum alloys. The origin for enhanced superplas- tic deformation kinetics in the FSP alloy can be attributed to its high fraction of high angle grain boundaries （HAGBs）. The analyses of the superplastic data and scanning electron microscopy （SEM） examinations on the surfaces of deformed specimens indicated that grain boundary sliding is the main superplastic deformation mechanism for the FSP AI-Mg-Sc alloy.

关键词： Superplasticity Friction stir processing Aluminum Microstructure Friction stir welding

Effect of Rotation Rate on Microstructures and Mechanical Properties of FSW Mg-zn-y-zr Alloy Joints

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Journal of materials Science & Technology 2011年第12期27卷 1157-1164页

作者： G.M. Xie z.y. ma z.A. Luo P. Xue G.D. Wang The State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110819 China Shenyang National Laboratory for materials Science Institute of Metal Research Chinese Academy of SciencesShenyang 110016 China

Friction stir welding （FSW） of Mg-zn-y-zr plates with 6 mm in thickness was successfully carried out under a wide range of rotation rates of 600-1200 r/rain with a constant traverse speed of 100 mm/min. After FSW, the coarse grains in the parent material （PM） were changed into fine equiaxed recrystallized grains at the＇nugget zone （Nz）. Furthermore, the coarse Mg-zn-y particles （W-phase） were broken up and dispersed homogenously into the Mg matrix. With increasing rotation rates, the size of the W-phase particles at the Nz significantly decreased, but the recrystallized grain size tended to increase. The hardness values of the Nzs for all the FSW joints were higher than those of the PM, and the lowest hardness values were detected in the heat affected zone （HAz）. The fracture occurred in the thermo-mechanical affected zone （Tmaz） on the advancing side for all the FSW joints in the tensile test, due to the incompatibility of the plastic deformation between the Nz and Tmaz caused by remarkably different orientation of grains and W-phase particles. The strength of FEW ioint reaches 90% of that of its PM

关键词： Friction stir welding magnesium alloys Microstructure Mechanical property

Formability of friction stir processed low carbon steels used in shipbuilding

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Journal of materials Science & Technology 2018年第1期34卷 237-244页

作者： D.M. Sekban S.M. Akterer O. Saray z.y. ma G. Purcek Department of Naval Architecture and marine Engineering Karadeniz Technical University Trahzon Turkey Department of Autumotive Technology RecepTayyip Erdogan University Rize Turkey Department of Mechanical Engineering Bursa Technical University. Bursa Turkey Shenyang National Laboratory for materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China Department of Mechanical Engineering. Karadeniz Technical University Trabzon Turkey Engineering Faculty Giresun University Giresun Turkey

The stretch formability of a low carbon steel processed by friction stir processing （FSP） was studied under biaxial loading condition applied by a miniaturized Erichsen test. One-pass FSP decreased the ferritic grain size in the processed zone from 25 μm to about 3 μm, which also caused a remarkable increase in strength values without considerable decrease in formability under uniaxial loading. A coarse-grained （CG） sample before FSP reflected a moderate formability with an Erichsen index （EI） of 2.73 mm. FSP slightly decreased the stretch formability of the sample to 2.66 ram. However, FSP increased the required punch load （FEI） due to the increased strength by grain refinement. FSP reduced considerably the roughness of the free surface of the biaxial stretched samples with reduced orange peel effect. The average roughness value （Ra） decreased from 2.90 in the CG sample down to about 0.65 μm in fine-grained （FG） sample after FSP. It can be concluded that the FG microstructure in low carbon steels sheets or plates used generally in shipbuilding provides a good balance between strength and formability.

关键词： Friction stir processing Low carbon shipbuilding steel Formability Microstructure Mechanical properties

Constitutive equation and model validation for a 31 vol.% B_4Cp/6061Al composite during hot compression

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Journal of materials Science & Technology 2018年第10期34卷 1730-1738页

作者： L. zhou C. Cui Q.z. Wang C. Li B.L. Xiao z.y. ma Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China School of Electromechanical and Vehicle Engineering Yantai University Yantai 264005 China School of Mechanical Engineering Shenyang Ligong University Shenyang 110159 China Nuclear and Radiation Safety Center Ministry of Environmental Protection Beijing 100082 China

An accurate constitutive equation is essential to understanding the flow behavior of B4C/A1 compos-ites during the hot deformation. However, the constitutive equations developed previously in literature are generally for low strain rate deformation. In the present work, we modified the general consti-tutive equation and take the high strain rate correction into account. The constitutive equation for a 31 vol.% B4Cp/6061AI composite was constructed based on the flow stresses measured during isothermal hot compression at temperatures ranging from 375 to 525 ℃ and strain rates from 0.01 to 10 s^-1. The experimental flow stresses were corrected by considering temperature-dependent Arrhenius factor. The modified equation was then verified by using DEFORM-3D finite element analysis to simulate the exper-imental hot compression process. The results show that the modified equation successfully predicts flow stress, load-displacement, and the temperature rise. This helps to optimize the hot deformation process, and to obtain desirable properties, such as reduced porosity and homogenous particle distribution in B4C/AI composites.

关键词： Composites B4C/AI Constitutive equation Hot compression Finite element simulation

Finite Element Prediction of the Thermal Conductivity of GNP/Al Composites

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Acta Metallurgica Sinica(English Letters) 2022年第5期35卷 825-838页

作者： X.S.yang L.zhou K.y.Liu z.y.Liu Q.z.Wang B.L.Xiao z.y.ma School of Electromechanical and Automotive Engineering Yantai UniversityYantai264005China Shi-Changxu Innovation Center for Advanced materials Institute of Metal ResearchChinese Academy of SciencesShenyang110016China

A 3 D multi-scale finite element model was developed to predict the effective thermal conductivity of graphene nanoplatelet(GNP)/Al *** factors influencing the effective thermal conductivity of the GNP/Al composites were investigated,including the orientation,shape,aspect ratio,configuration and volume fraction of *** results show that GNPs shape has a little influence on the thermal conductivity of GNP/Al composites,and composites with elliptic GNPs have the highest thermal *** addition,with increasing the aspect ratio of GNPs,the thermal conductivity of GNP/Al composites increases and finally tends to be *** GNPs configuration strongly influences the thermal conductivity of GNP/Al composites,and the thermal conductivity of the composites with layered GNPs is the highest among the five *** effective thermal conductivity is sensitive to volume fraction of ***,when the volume fraction of layered GNPs reaches 1.54%,the thermal conductivity of GNP/Al composites is as high as 400 W/m *** findings of this study could provide a good theoretical basis for designing high thermal conductivity GNP/Al composites.

关键词： Multi-scale finite element model Thermal conductivity GNP/Al composites Shape Aspect ratio Configuration

Microstructural evolution of aluminum alloy during friction stir welding under different tool rotation rates and cooling conditions

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Journal of materials Science & Technology 2019年第6期35卷 972-981页

作者： X.H. zeng P. Xue L.H. Wu D.R. Ni B.L. Xiao K.S. Wang z.y. ma Shenyang National Laboratory for materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China University of Chinese Academy of Sciences Beijing 100049 China School of Metallurgical Engineering Xi'an University of Architecture and Technology Xi'an 710055 China

The microstructural evolution during friction stir welding(FSW) has long been studied only using one single welding parameter. Conclusions were usually made based on the final microstructure observation and hence were one-sided. In this study, we used the "take-action" technique to freeze the microstructure of an Al-Mg-Si alloy during FSW, and then systematically investigated the microstructures along the material flow path under different tool rotation rates and cooling conditions. A universal characteristic of the microstructural evolution including four stages was identified, i.e. dynamic recovery(DRV), dislocation multiplication, new grain formation and grain growth. However, the dynamic recrystallization(DRX)mechanisms in FSW depended on the welding condition. For the air cooling condition, the DRX mechanisms were related to continuous DRX associated with subgrain rotation and geometric DRX at high and low rotation rates, respectively. Under the water cooling condition, we found a new DRX mechanism associated with the progressive lattice rotation resulting from the pinning of the second-phase *** on the analyses of the influencing factors of grain refinement, it was clearly demonstrated that the delay of DRV and DRX was the efficient method to refine the grains during FSW. Besides, ultra-high strain rate and a short duration at high temperatures were the key factors to produce an ultrafine-grained material.

关键词： Aluminum alloys Grain refinement Dynamic recrystallization Severe plastic deformation Friction stir welding

LOW CyCLE FATIGUE BEHAVIOR OF Az91HP ALLOy IN AS HIGHP RESSURE DIE CASTING

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Acta Metallurgica Sinica(English Letters) 2000年第4期13卷 961-966页

作者： Liu, z. Xu, y.y. Wang, z.G. Wang, y. Liu, z.y. Inst of Metal Research Chinese Acad of Sciences Shenyang China

Fully reversed total strain-controlled low-cycle fatigue tests were conducted at room temperature in air to study the fatigue behavior of Az91HP magnesium alloy in as high pressure die casting and subsequently heat treatment. All the specimens in different heat histories exhibit cyclic strain hardening in different degrees. It is difficult to distinguish the fatigue behavior of the die casting specimens from that of the solution aging specimens. The solution treated specimens show longer fatigue life at high strain amplitude and shorter fatigue life at low strain amplitude than the die casting and solution aging specimens though they have the lowest yield strength with higher strain hardening. Fatigue fracture surfaces for strain amplitude larger than 0.005 show very similar to those found by monotonic tensile tests. The SEM examination reveals that the regions of fatigue crack growth and final fracture can be characterized by quasi-cleavage mechanisms, but some shallow dimples, slip bands and secondary cracks are found on the fracture surface in the fracture crack growth areas.

关键词： Cracks Die casting Fatigue of materials Heat treatment

Advances in the treatment of autism spectrum disorder:Wharton jelly mesenchymal stem cell transplantation

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World Journal of Methodology 2025年第1期15卷 72-79页

作者： Serdar Kabatas ErdinçCivelek Eyüp Can Savrunlu Umut Karaaslan Özlem yıldız Erdal Karaöz Department of Neurosurgery University of Health Sciences TurkeyGaziosmanpaşa Training and Research HospitalIstanbul 34255Türkiye Department of Pediatric Allergy-Immunology Institute of Health Sciences Marmara UniversityIstanbul 34865Türkiye Center for Stem Cell&Gene Therapy Research and Practice University of Health Sciences TurkeyIstanbul 34255Türkiye Department of Child and Adolescent Psychiatry University of Health SciencesGaziosmanpaşa Training and Research HospitalIstanbul 34255Türkiye Department of Child and Adolescent Psychiatry Kocaeli University Faculty of MedicineKocaeli 41001Türkiye Center for Regenerative Medicine and Stem Cell Research&manufacturing Liv HospitalIstanbul 34340Türkiye Department of Histology and Embryology Istinye UniversityFaculty of MedicineIstanbul 34010Türkiye Center for Stem Cell and Tissue Engineering Research and Practice Istinye UniversityIstanbul 34340Türkiye

BACKGROUND Autism spectrum disorder(ASD)is a complex neurodevelopmental disorder with multifaceted *** recent studies,neuroinflammation and immune dysregulation have come to the forefront in its *** are studies suggesting that stem cell therapy may be effective in the treatment of *** To evolve the landscape of ASD treatment,focusing on the potential benefits and safety of stem cell *** A detailed case report is presented,displaying the positive outcomes observed in a child who underwent intrathecal and intravenous Wharton’s jelly-derived mesenchymal stem cells(WJ-MSCs)transplantation combined with *** The study demonstrates a significant improvement in the child’s functional outcomes(Childhood Autism Rating Scale,Denver 2 Developmental Screening Test),especially in language and gross motor *** serious side effects were encountered during the 2-year *** The findings support the safety and effectiveness of WJ-MSC transplantation in managing ASD.

关键词： Autism spectrum disorder Neurorehabilitation Stem cell transplantation Wharton jelly mesenchymal stem cells Inflammation