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
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
In order to lower the boriding temperature of hot work steel H13, method of surface mechanical attrition treatment （SMAT）, which can make the grain size of the surface reach nano-scale, was used before pack boriding...In order to lower the boriding temperature of hot work steel H13, method of surface mechanical attrition treatment （SMAT）, which can make the grain size of the surface reach nano-scale, was used before pack boriding. The growth of the boride layer was studied in a function of boriding temperature and time. By TEM （transmission electron microscopy）, SEM （scanning electron microscopy）, XRD （x-ray diffraction） and microhardness tests, the grain size, thermal stability of the nano-structured （NS） surface and the thickness,appearance, phases of the surface boride layer were studied. Kinetic of boriding was compared between untreated samples and treated samples. Results showed that after SMAT, the boride layer was thicker and the hardness gradient was smoother. Furthermore, after boriding at a low temperature of 700℃ for 8 h, a boride layer of about 5 μm formed on the NS surface. This layer was toothlike and wedged into the substrate, which made the surface layer combine well with the substrate. The phase of the boride layer was Fe2B. Research on boriding kinetics indicated that the activation energy was decreased for the treated samples.展开更多
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.
文摘In order to lower the boriding temperature of hot work steel H13, method of surface mechanical attrition treatment （SMAT）, which can make the grain size of the surface reach nano-scale, was used before pack boriding. The growth of the boride layer was studied in a function of boriding temperature and time. By TEM （transmission electron microscopy）, SEM （scanning electron microscopy）, XRD （x-ray diffraction） and microhardness tests, the grain size, thermal stability of the nano-structured （NS） surface and the thickness,appearance, phases of the surface boride layer were studied. Kinetic of boriding was compared between untreated samples and treated samples. Results showed that after SMAT, the boride layer was thicker and the hardness gradient was smoother. Furthermore, after boriding at a low temperature of 700℃ for 8 h, a boride layer of about 5 μm formed on the NS surface. This layer was toothlike and wedged into the substrate, which made the surface layer combine well with the substrate. The phase of the boride layer was Fe2B. Research on boriding kinetics indicated that the activation energy was decreased for the treated samples.
