A nanocrystalline layer was produced on the surface of Ni3Al intermetallic by means of surface mechanical attrition treatment. The surface nanocrystallites were annealed at 250-750 ℃ for 30 min. Microstructure evolut...A nanocrystalline layer was produced on the surface of Ni3Al intermetallic by means of surface mechanical attrition treatment. The surface nanocrystallites were annealed at 250-750 ℃ for 30 min. Microstructure evolution of nanocrystallites during annealing was studied by X-ray diffraction(XRD) and transmission electronic microscope(TEM). The experimental results show that long-rang order recovers rapidly when annealing temperature is below 250 ℃ and changes slowly at 350-550 ℃,and then it increases rapidly at 750 ℃. The grain size of nanocrystallites of Ni3Al keeps stable and crystal defects recover when they are annealed below 550 ℃. The grains grow normally in low temperature annealing and abnormal growth occurs at 750 ℃ .展开更多
In order to improve the low ductility of nanostructured materials, a layered and nanostructured （LN） 304 SS （stainless steel） is prepared from warm co-rolled 304 SS pre-treated by surface mechanical attrition trea...In order to improve the low ductility of nanostructured materials, a layered and nanostructured （LN） 304 SS （stainless steel） is prepared from warm co-rolled 304 SS pre-treated by surface mechanical attrition treatment. The microstructure and mechanical properties, as well as strain hardening, are analyzed in details. The LN steels ex- hibit both high strength and large ductility resulting from good strain hardening behaviors. The strain hardening can be subdivided into two stages, which involves a multiple cracking along interlaminar at the first stage and a strain-in- duced martensite （SIM） transformation at the second stage. The SIM transformation of nanocrystallines and ultrafine grains induces a larger work hardening exponent by the formation of nanoscaled martensite phase. The effect of grain size on the transformation dynamics is discussed.展开更多
基金Project(0452nm053) supported by the Nano-Materials Program of Shanghai City of China
文摘A nanocrystalline layer was produced on the surface of Ni3Al intermetallic by means of surface mechanical attrition treatment. The surface nanocrystallites were annealed at 250-750 ℃ for 30 min. Microstructure evolution of nanocrystallites during annealing was studied by X-ray diffraction(XRD) and transmission electronic microscope(TEM). The experimental results show that long-rang order recovers rapidly when annealing temperature is below 250 ℃ and changes slowly at 350-550 ℃,and then it increases rapidly at 750 ℃. The grain size of nanocrystallites of Ni3Al keeps stable and crystal defects recover when they are annealed below 550 ℃. The grains grow normally in low temperature annealing and abnormal growth occurs at 750 ℃ .
基金Item Sponsored by National Natural Science Foundation of China(11202134,51271123)Funds from Shanghai Municipal Education Commission of China(5313310202)
文摘In order to improve the low ductility of nanostructured materials, a layered and nanostructured （LN） 304 SS （stainless steel） is prepared from warm co-rolled 304 SS pre-treated by surface mechanical attrition treatment. The microstructure and mechanical properties, as well as strain hardening, are analyzed in details. The LN steels ex- hibit both high strength and large ductility resulting from good strain hardening behaviors. The strain hardening can be subdivided into two stages, which involves a multiple cracking along interlaminar at the first stage and a strain-in- duced martensite （SIM） transformation at the second stage. The SIM transformation of nanocrystallines and ultrafine grains induces a larger work hardening exponent by the formation of nanoscaled martensite phase. The effect of grain size on the transformation dynamics is discussed.
