Friction stir processing （FSP） was investigated as a method of repairing cracks in 12 mm thick 304L stainless steel plate. Healing feasibility was demonstrated by processing a tapered crack using a PCBN/W- Re tool w...Friction stir processing （FSP） was investigated as a method of repairing cracks in 12 mm thick 304L stainless steel plate. Healing feasibility was demonstrated by processing a tapered crack using a PCBN/W- Re tool with a 25 mm diameter shoulder and a pin length of 6.4 mm. The experiment showed that it was possible to heal a crack that begins narrow and then progressively grows up to a width of 2 mm. Bead on plate experiments were used to find the best parameters for creating a consolidated stir zone with the least amount of hardness difference compared to the base metal. Grain refinement in some specimens resulted in much higher stir zone hardness, compared to base metal, A plot of grain size versus microhardness showed a very strong inverse correlation between grain size and hardness, as expected from the Hall- Perch relationship. Corrosion testing was carried out in order to evaluate the effect of FSP on potential sensitization of the stir zone. After 1000 h of intermittent immersion in 3.5% saline solution at room temperature it was found that no corrosion products formed on the base material controls or on any of the friction stir processed specimens.展开更多
In this paper, we use femtosecond laser pulse to scribe 304 stainless steel foil, detect the Fourier transform infrared spectrum of the sample before and after processing, confirm the "cold processing" and &...In this paper, we use femtosecond laser pulse to scribe 304 stainless steel foil, detect the Fourier transform infrared spectrum of the sample before and after processing, confirm the "cold processing" and "thermal processing" and their mutual conversion, and determine the "cold processing" parameter window. The ablation threshold and incubation coefficient of 304 stainless steel foil are calculated, and the effects of scanning speed and effective pulse number on the ablation threshold are analyzed. The ANSYS software is used to simulate the radial and axial temperature distributions of the surface on 304 stainless steel foil sample and the heat-affected zone with a femtosecond laser fluence of 10 J/cm2 and an effective number of pulses of 1 200 are obtained. In the aspect of spectral detection, the Fourier transform infrared spectra of the sample before and after processing are measured and two processing mechanisms of "cold processing" and "hot processing" are confirmed, which proves that we can achieve the conversion between "cold processing" and "hot processing" by changing the laser fluence and determine the "cold processing" laser fluence range.展开更多
Texture inhomogeneity usually takes place in ferritic stainless steels due to the lack of phase transformation and recrystallization during hot strip rolling,which can deteriorate the formability of final sheets.In or...Texture inhomogeneity usually takes place in ferritic stainless steels due to the lack of phase transformation and recrystallization during hot strip rolling,which can deteriorate the formability of final sheets.In order to work out the way of weakening texture inhomogeneity,conventional hot rolling and warm rolling processes have been carried out with an ultra purified ferritic stainless steel.The results showed that the evolution of through-thickness texture is closely dependent on rolling process,especially for the texture in the center layer.For both conventional and warm rolling processes,shear texture components were formed in the surface layers after hot rolling and annealing;sharp α-fiber and weakγ-fiber with the major component at{111}〈110〉 were developed in both cold rolled sheet surfaces,leading to the formation of inhomogeneousγ-fiber dominated by{111}〈112〉after recrystallization annealing.In the center layer of conventional rolled and annealed bands,strongα-fiber and weakγ-fiber textures were formed;the cold rolled textures were comprised of sharpα-fiber and weakγ-fiber with the major component at{111}〈110〉,and inhomogeneousγ-fiber dominated by{111}〈112〉 was formed after recrystallization annealing.By contrast,in the centre layer of warm rolled bands,the texture was comprised of weakα-fiber and sharpγ-fiber,andγ-fiber became the only component after annealing.The cold rolled texture displayed a sharpγ-fiber with the major component at{111}〈112〉and the intensity ofγ-fiber close to that ofα-fiber,resulting in the formation of a nearly homogeneousγ-fiber recrystallization texture in the center layer of the final sheet.展开更多
316L stainless steel is widely used for fashion jewelry, but it can carry a large number of bacteria and bring the risk of infection since the steel has no antimicrobial performance. In this paper, the effects of Ce o...316L stainless steel is widely used for fashion jewelry, but it can carry a large number of bacteria and bring the risk of infection since the steel has no antimicrobial performance. In this paper, the effects of Ce on the antibacterial property, corrosion resistance and processability of 316L were studied by microscopic observation, thin- film adhering quantitative bacteriostasis, and electrochemical and mechanical tests. The results show that a trace of Ce can distribute uniformly in the matrix of 316L and slightly improve its corrosion resistance in artificial sweat. With an increase in Ce content, the Ce is prone to form clustering, which degrades the corrosion resistance and the processability. The Ce-containing 316L exhibits Hormesis effect against S. aureus. A small Ce addition stimulates the growth of S. aureus. As the Ce content increases, the modified 316L exhibits an improved antibacterial efficacy. The more Ce is added, the better antibacterial capability is achieved. Overall, if the 316L is modified with Ce alone, it is difficult to obtain the optimal combination of corrosion resistance, antibacterial performance and processability. In spite of that, 0.15 wt.%-0.20 wt.% Ce around is inferred to be the best trade-off.展开更多
基金financial support of the project by National Science Foundation award CMII-1405508
文摘Friction stir processing （FSP） was investigated as a method of repairing cracks in 12 mm thick 304L stainless steel plate. Healing feasibility was demonstrated by processing a tapered crack using a PCBN/W- Re tool with a 25 mm diameter shoulder and a pin length of 6.4 mm. The experiment showed that it was possible to heal a crack that begins narrow and then progressively grows up to a width of 2 mm. Bead on plate experiments were used to find the best parameters for creating a consolidated stir zone with the least amount of hardness difference compared to the base metal. Grain refinement in some specimens resulted in much higher stir zone hardness, compared to base metal, A plot of grain size versus microhardness showed a very strong inverse correlation between grain size and hardness, as expected from the Hall- Perch relationship. Corrosion testing was carried out in order to evaluate the effect of FSP on potential sensitization of the stir zone. After 1000 h of intermittent immersion in 3.5% saline solution at room temperature it was found that no corrosion products formed on the base material controls or on any of the friction stir processed specimens.
基金supported by the National Natural Science Foundation of China (No.11574159)the Open Fund of the State Key Laboratory of High Field Laser Physics,China (Shanghai Institute of Optics and Fine Mechanics)the Special Research Foundation of the Central University of Nankai University (No.63191108)。
文摘In this paper, we use femtosecond laser pulse to scribe 304 stainless steel foil, detect the Fourier transform infrared spectrum of the sample before and after processing, confirm the "cold processing" and "thermal processing" and their mutual conversion, and determine the "cold processing" parameter window. The ablation threshold and incubation coefficient of 304 stainless steel foil are calculated, and the effects of scanning speed and effective pulse number on the ablation threshold are analyzed. The ANSYS software is used to simulate the radial and axial temperature distributions of the surface on 304 stainless steel foil sample and the heat-affected zone with a femtosecond laser fluence of 10 J/cm2 and an effective number of pulses of 1 200 are obtained. In the aspect of spectral detection, the Fourier transform infrared spectra of the sample before and after processing are measured and two processing mechanisms of "cold processing" and "hot processing" are confirmed, which proves that we can achieve the conversion between "cold processing" and "hot processing" by changing the laser fluence and determine the "cold processing" laser fluence range.
基金Sponsored by National Natural Science Foundation of China(51271050,51004035)National Science and Technology PillarProgram During 12th Five-Year Plan of China(2012BAE04B02)Fundamental Research Funds for Central Universities ofChina(N100507002)
文摘Texture inhomogeneity usually takes place in ferritic stainless steels due to the lack of phase transformation and recrystallization during hot strip rolling,which can deteriorate the formability of final sheets.In order to work out the way of weakening texture inhomogeneity,conventional hot rolling and warm rolling processes have been carried out with an ultra purified ferritic stainless steel.The results showed that the evolution of through-thickness texture is closely dependent on rolling process,especially for the texture in the center layer.For both conventional and warm rolling processes,shear texture components were formed in the surface layers after hot rolling and annealing;sharp α-fiber and weakγ-fiber with the major component at{111}〈110〉 were developed in both cold rolled sheet surfaces,leading to the formation of inhomogeneousγ-fiber dominated by{111}〈112〉after recrystallization annealing.In the center layer of conventional rolled and annealed bands,strongα-fiber and weakγ-fiber textures were formed;the cold rolled textures were comprised of sharpα-fiber and weakγ-fiber with the major component at{111}〈110〉,and inhomogeneousγ-fiber dominated by{111}〈112〉 was formed after recrystallization annealing.By contrast,in the centre layer of warm rolled bands,the texture was comprised of weakα-fiber and sharpγ-fiber,andγ-fiber became the only component after annealing.The cold rolled texture displayed a sharpγ-fiber with the major component at{111}〈112〉and the intensity ofγ-fiber close to that ofα-fiber,resulting in the formation of a nearly homogeneousγ-fiber recrystallization texture in the center layer of the final sheet.
基金financially supported by NSFC-Guangdong Natural Science Mutual Funds(Item No.U1034002)
文摘316L stainless steel is widely used for fashion jewelry, but it can carry a large number of bacteria and bring the risk of infection since the steel has no antimicrobial performance. In this paper, the effects of Ce on the antibacterial property, corrosion resistance and processability of 316L were studied by microscopic observation, thin- film adhering quantitative bacteriostasis, and electrochemical and mechanical tests. The results show that a trace of Ce can distribute uniformly in the matrix of 316L and slightly improve its corrosion resistance in artificial sweat. With an increase in Ce content, the Ce is prone to form clustering, which degrades the corrosion resistance and the processability. The Ce-containing 316L exhibits Hormesis effect against S. aureus. A small Ce addition stimulates the growth of S. aureus. As the Ce content increases, the modified 316L exhibits an improved antibacterial efficacy. The more Ce is added, the better antibacterial capability is achieved. Overall, if the 316L is modified with Ce alone, it is difficult to obtain the optimal combination of corrosion resistance, antibacterial performance and processability. In spite of that, 0.15 wt.%-0.20 wt.% Ce around is inferred to be the best trade-off.
