High density nano-scale deformation twins were introduced in the surface layer of Cu sample by means of surface mechanical attrition treatment （SMAT） at room temperature. The Cu sample with deformation twins shows a...High density nano-scale deformation twins were introduced in the surface layer of Cu sample by means of surface mechanical attrition treatment （SMAT） at room temperature. The Cu sample with deformation twins shows a yield strength of about 470 MPa in tension tests. The significant strengthening may be attributed to the effective inhibition of slip dislocations by abundant twin boundaries.展开更多
Most of the challenges experienced by many engineering materials originate from the surface which later leads to total failure,hence affecting the resultant mechanical properties and service life.However,these challen...Most of the challenges experienced by many engineering materials originate from the surface which later leads to total failure,hence affecting the resultant mechanical properties and service life.However,these challenges have been addressed thanks to the invention of a novel surface mechanical attrition treatment(SMAT)method which protects the material surface by generating a gradient-structured layer with improved strength and hardness without jeopardizing the ductility.The present work provides a comprehensive literature review on the mechanical properties of materials after SMAT including the hardness,tensile strength and elongation,and residual stress.Firstly,a brief introduction on the different forms of surface nanocrystallization is given to get a better understanding of the SMAT process and its advantages over other forms of surface treatments,and then the grain refinement mechanisms of materials by SMAT from the matrix region(base material)to the nanocrystallized layer are explained.The effects of fatigue,fracture,and wear of materials by the enhanced mechanical properties after SMAT are also discussed in detail.In addition,the various applications of SMAT ranging from automotive,photoelectric conversion,biomedical,diffusion,and 3 D-printing of materials are extensively discussed.The prospects and recent research trends in terms of mechanical properties of materials affected by SMAT are then summarized.展开更多
The microstructure in the surface layer of iron and steel samples can be refined at the nanometer scale by means of a surface mechanical attrition treatment (SMAT) that generates repetitive severe plastic deformation ...The microstructure in the surface layer of iron and steel samples can be refined at the nanometer scale by means of a surface mechanical attrition treatment (SMAT) that generates repetitive severe plastic deformation to the surface layer. The subsequent nitriding kinetics of the as-treated samples with the nanostructured surface layer is greatly enhanced so that the nitriding temperatures can be reduce to 300 - 400 °C regions. This enhanced processing method demonstrates both the technological significance of nanomaterials in advancing the traditional processing techniques, and provides a new approach for selective surface reactions in solids. This article reviews the present state of the art in this field. The microstructure and properties of SMAT samples nitrided will be summarized. Further considerations of the development and applications of this new technique will also be presented.展开更多
A pipeline steel X80 with welded joint was subjected to surface mechanical attrition treatment （SMAT）. After SMAT, a nanostructure surface layer with an average grain size of about 10 nm was formed in the treated sa...A pipeline steel X80 with welded joint was subjected to surface mechanical attrition treatment （SMAT）. After SMAT, a nanostructure surface layer with an average grain size of about 10 nm was formed in the treated sample, and the fatigue limit of the welded joint was elevated by about 13% relative to the untreated joints. In the low and the high amplitude stress regimes, both fatigue strength and fatigue life were enhanced. Formation of the nanostructured surface layer played more important role in the enhanced fatigue behavior than that of residual stress induced by the SMAT.展开更多
Surface mechanical attrition treatment（SMAT） has been recently applied to bulk polycrystalline magnesium（Mg） alloys with gradient grain size distribution from the impact surface to inside matrix, hence effectively...Surface mechanical attrition treatment（SMAT） has been recently applied to bulk polycrystalline magnesium（Mg） alloys with gradient grain size distribution from the impact surface to inside matrix, hence effectively improving the alloys＇ mechanical performances. However, in-depth understanding of their mechanical property enhancement and grain size-dependent fracture mechanism remains unclear. Here,we demonstrated the use of in situ micro-tensile testing inside a high resolution scanning electron microscope（SEM） to characterize the microstructure evolution, in real time, of SMATed Mg alloy AZ31 samples with different grain sizes of ~10 μm（＇coarse-grain sample＇） and ~5 μm（＇fine-grain sample＇）, respectively, and compared the results with those of a raw Mg alloy AZ31. The quantitative tensile tests with in situ SEM imaging clearly showed that fracture of ‘fine-grain sample＇ was dominated by intergranular cracks,while both trans-granular and intergranular cracks led to the final failure of the ‘coarse-grain samples＇.It is expected that this in situ SEM characterization technique, coupled with quantitative tensile testing method, could be applicable for studying other grain-refined metals/alloys, allowing to optimize their mechanical performances by controlling the grain sizes and their gradient distribution.展开更多
基金This work was supported by the National Natural Science Foundation of China under grant No.50021101,50431010,50571096M0ST of China(Grant No.2005CB623604).
文摘High density nano-scale deformation twins were introduced in the surface layer of Cu sample by means of surface mechanical attrition treatment （SMAT） at room temperature. The Cu sample with deformation twins shows a yield strength of about 470 MPa in tension tests. The significant strengthening may be attributed to the effective inhibition of slip dislocations by abundant twin boundaries.
基金supports of the National Key R&D Program of China(Project No.2017YFA0204403)Hong Kong Themebased Research Scheme Ref.(T13-402/17-N).
文摘Most of the challenges experienced by many engineering materials originate from the surface which later leads to total failure,hence affecting the resultant mechanical properties and service life.However,these challenges have been addressed thanks to the invention of a novel surface mechanical attrition treatment(SMAT)method which protects the material surface by generating a gradient-structured layer with improved strength and hardness without jeopardizing the ductility.The present work provides a comprehensive literature review on the mechanical properties of materials after SMAT including the hardness,tensile strength and elongation,and residual stress.Firstly,a brief introduction on the different forms of surface nanocrystallization is given to get a better understanding of the SMAT process and its advantages over other forms of surface treatments,and then the grain refinement mechanisms of materials by SMAT from the matrix region(base material)to the nanocrystallized layer are explained.The effects of fatigue,fracture,and wear of materials by the enhanced mechanical properties after SMAT are also discussed in detail.In addition,the various applications of SMAT ranging from automotive,photoelectric conversion,biomedical,diffusion,and 3 D-printing of materials are extensively discussed.The prospects and recent research trends in terms of mechanical properties of materials affected by SMAT are then summarized.
基金supported by NSF of China(Grants No.50021101)Ministry of Science&Technology of China(G1999064505).
文摘The microstructure in the surface layer of iron and steel samples can be refined at the nanometer scale by means of a surface mechanical attrition treatment (SMAT) that generates repetitive severe plastic deformation to the surface layer. The subsequent nitriding kinetics of the as-treated samples with the nanostructured surface layer is greatly enhanced so that the nitriding temperatures can be reduce to 300 - 400 °C regions. This enhanced processing method demonstrates both the technological significance of nanomaterials in advancing the traditional processing techniques, and provides a new approach for selective surface reactions in solids. This article reviews the present state of the art in this field. The microstructure and properties of SMAT samples nitrided will be summarized. Further considerations of the development and applications of this new technique will also be presented.
基金supported by the CNPC (China National Petroleum Corporation) Innovation Foundation under grant No.07E1015
文摘A pipeline steel X80 with welded joint was subjected to surface mechanical attrition treatment （SMAT）. After SMAT, a nanostructure surface layer with an average grain size of about 10 nm was formed in the treated sample, and the fatigue limit of the welded joint was elevated by about 13% relative to the untreated joints. In the low and the high amplitude stress regimes, both fatigue strength and fatigue life were enhanced. Formation of the nanostructured surface layer played more important role in the enhanced fatigue behavior than that of residual stress induced by the SMAT.
基金supported by the National Key Basic Research Program (Grant No. 2012CB932203)the National Natural Science Foundation of China (Grant No. 51301147)+1 种基金the funding support from City University of Hong Kong (Grant Nos. 9610288 and 9680108)the funding support from the National Natural Science Foundation of China (Grant No. 51464234)
文摘Surface mechanical attrition treatment（SMAT） has been recently applied to bulk polycrystalline magnesium（Mg） alloys with gradient grain size distribution from the impact surface to inside matrix, hence effectively improving the alloys＇ mechanical performances. However, in-depth understanding of their mechanical property enhancement and grain size-dependent fracture mechanism remains unclear. Here,we demonstrated the use of in situ micro-tensile testing inside a high resolution scanning electron microscope（SEM） to characterize the microstructure evolution, in real time, of SMATed Mg alloy AZ31 samples with different grain sizes of ~10 μm（＇coarse-grain sample＇） and ~5 μm（＇fine-grain sample＇）, respectively, and compared the results with those of a raw Mg alloy AZ31. The quantitative tensile tests with in situ SEM imaging clearly showed that fracture of ‘fine-grain sample＇ was dominated by intergranular cracks,while both trans-granular and intergranular cracks led to the final failure of the ‘coarse-grain samples＇.It is expected that this in situ SEM characterization technique, coupled with quantitative tensile testing method, could be applicable for studying other grain-refined metals/alloys, allowing to optimize their mechanical performances by controlling the grain sizes and their gradient distribution.
