In order to study the effects of aging treatment on the intergranular corrosion（IGC） and stress corrosion cracking（SCC） of 7003 aluminum alloy（AA7003）, the intergranular corrosion test, electrochemical test and ...In order to study the effects of aging treatment on the intergranular corrosion（IGC） and stress corrosion cracking（SCC） of 7003 aluminum alloy（AA7003）, the intergranular corrosion test, electrochemical test and slow strain rate test（SSRT）, combined with optical microscopy（OM） and scanning electron microscopy（SEM） as well as transmission electron microscopy（TEM） observations have been carried out. The IGC and electrochemical test results showed that the IGC resistance of AA7003 for peak aged（PA） temper is the lowest, with double peak aged（DPA） the moderate, and retrogression and re-aging（RRA） the highest among three tempers, which is attributed to the continuous feature of precipitation on grain boundary of PA temper and the interrupted feature of precipitation on grain boundary of DPA and RRA tempers, as well as the wide precipitation free zones（PFZ） of RRA temper. In addition, the SSRT results indicated that all three tempers AA7003 are susceptible to SCC in IGC solution, and the change tendency of SCC susceptibility（ISCC） of AA7003 for three tempers follows the order： ISCC（RRA）展开更多
Comparative investigations were carried out of the effect of heat treatment regimes Jor steel GC-4(40CrMnSiMoVA)on its crack propagating rates,from corrosion fatigue, (da/dN)_(CF),or stress corrosion cracking,(da/dt)_...Comparative investigations were carried out of the effect of heat treatment regimes Jor steel GC-4(40CrMnSiMoVA)on its crack propagating rates,from corrosion fatigue, (da/dN)_(CF),or stress corrosion cracking,(da/dt)_(SCC),in media with various constituents and pH values.Both(da/dN)_(CF) and(da/dt)_(SCC) accelerate with the increase of yield stress of the steel,yet the former is far less than the later.In comparison with media,the (da/dt)_(SCC) in distilled water is slightly greater than that in 3.5% NaCl solution,and the (da/dN)_(CF) in distilled water is far less than that in 3.5% NaCl solution.With the pH value increasing in 3.5% NaCl solution,the(da/dN)_(CF) lowers down and the(da/dt)_(SCC) speeds up.An explanation was also proposed with concept of the cyclic hardening and softening at crack tip,as well as the crack closure and occluded cell effect.展开更多
The healing mechanism of hydrogen-attacked cracks in low carbon steel andCr-Mo steel and its influencing factors during the healing process were studied by recovering heattreatment of split specimens in vacuum. The re...The healing mechanism of hydrogen-attacked cracks in low carbon steel andCr-Mo steel and its influencing factors during the healing process were studied by recovering heattreatment of split specimens in vacuum. The result showed that crack pacing turns much smaller underthe condition of pure heating, especially for crack tips. The healing effect is well related to thelength of cracks with the shorter in priority. By the primary mechanism of thermal diffusion, ironand carbon atoms must diffuse at the high speed in steel to realize that plasticity deformationenergy exceeds and overcomes surface tensile force energy. In addition, phase transformation andstress-stain relationship also have positive effects on the process.展开更多
In order to improve the stress corrosion cracking(SCC) resistance of 7A05Al alloy, four different heat treatment processes were performed. After the heat treatments, the stress corrosion cracking resistance, mechanica...In order to improve the stress corrosion cracking(SCC) resistance of 7A05Al alloy, four different heat treatment processes were performed. After the heat treatments, the stress corrosion cracking resistance, mechanical properties and microstructures of 7A05A1 alloys were studied. The results show that the retrogression and reaging(RRA) treated specimens possess the highest SCC resistance with slightly reduced strength compared with the other specimens. Thus RRA is the best process in terms of the optimal combination of SCC resistance and strength. Further TEM observation reveals that the RRA treated specimens are characterized by the fine equiaxed grains, dispersed second phase and wide PFZ. The pre-aging treated specimens show lower SCC resistance but higher strength as compared with the RRA treated ones. Equiaxed grains are also observed in the pre-aging treated samples by TEM, indicating that the anisotropy is eliminated. However, the dual aging and deformation plus aging treated specimens are demonstrated by large anisotropy.展开更多
The purpose of this study is to investigate the impact of family training based on matrix model in reducing the amount of drug consumption by heroin and crack addicts. The subjects were referral to Karaj Clinic, Karaj...The purpose of this study is to investigate the impact of family training based on matrix model in reducing the amount of drug consumption by heroin and crack addicts. The subjects were referral to Karaj Clinic, Karaj City, Iran, for crack abuse in 2013. In order to select participants convenience sampling was been used and totally 45 patients were selected (15 heroin addict, 15 crack addict, and 15 with combination of heroin and crack addiction) and put into two groups of experimental and control groups randomly. For collecting the data, Addiction Severity Index questionnaire was used. Descriptive and inferential statistics were used through one-way analysis of covariance for data analyzing. The results indicated that there was statistical difference between the experimental and control group with consumption of heroin and crack in family status, mental and substance use and also it has been shown that the experimental group with heroine consumption achieved better performance compared with the control group in the amount of consumption.展开更多
基金Funded by the National Natural Science Foundation of China(No.51371039)
文摘In order to study the effects of aging treatment on the intergranular corrosion（IGC） and stress corrosion cracking（SCC） of 7003 aluminum alloy（AA7003）, the intergranular corrosion test, electrochemical test and slow strain rate test（SSRT）, combined with optical microscopy（OM） and scanning electron microscopy（SEM） as well as transmission electron microscopy（TEM） observations have been carried out. The IGC and electrochemical test results showed that the IGC resistance of AA7003 for peak aged（PA） temper is the lowest, with double peak aged（DPA） the moderate, and retrogression and re-aging（RRA） the highest among three tempers, which is attributed to the continuous feature of precipitation on grain boundary of PA temper and the interrupted feature of precipitation on grain boundary of DPA and RRA tempers, as well as the wide precipitation free zones（PFZ） of RRA temper. In addition, the SSRT results indicated that all three tempers AA7003 are susceptible to SCC in IGC solution, and the change tendency of SCC susceptibility（ISCC） of AA7003 for three tempers follows the order： ISCC（RRA）
文摘Comparative investigations were carried out of the effect of heat treatment regimes Jor steel GC-4(40CrMnSiMoVA)on its crack propagating rates,from corrosion fatigue, (da/dN)_(CF),or stress corrosion cracking,(da/dt)_(SCC),in media with various constituents and pH values.Both(da/dN)_(CF) and(da/dt)_(SCC) accelerate with the increase of yield stress of the steel,yet the former is far less than the later.In comparison with media,the (da/dt)_(SCC) in distilled water is slightly greater than that in 3.5% NaCl solution,and the (da/dN)_(CF) in distilled water is far less than that in 3.5% NaCl solution.With the pH value increasing in 3.5% NaCl solution,the(da/dN)_(CF) lowers down and the(da/dt)_(SCC) speeds up.An explanation was also proposed with concept of the cyclic hardening and softening at crack tip,as well as the crack closure and occluded cell effect.
基金This work was financially supported by the National Natural Science Foundation of China (No.59971011) and "973" Science Foundation of China (No. 19990650).
文摘The healing mechanism of hydrogen-attacked cracks in low carbon steel andCr-Mo steel and its influencing factors during the healing process were studied by recovering heattreatment of split specimens in vacuum. The result showed that crack pacing turns much smaller underthe condition of pure heating, especially for crack tips. The healing effect is well related to thelength of cracks with the shorter in priority. By the primary mechanism of thermal diffusion, ironand carbon atoms must diffuse at the high speed in steel to realize that plasticity deformationenergy exceeds and overcomes surface tensile force energy. In addition, phase transformation andstress-stain relationship also have positive effects on the process.
基金Project(Z172003A001) supported by the Ministerial Level Research Foundation
文摘In order to improve the stress corrosion cracking(SCC) resistance of 7A05Al alloy, four different heat treatment processes were performed. After the heat treatments, the stress corrosion cracking resistance, mechanical properties and microstructures of 7A05A1 alloys were studied. The results show that the retrogression and reaging(RRA) treated specimens possess the highest SCC resistance with slightly reduced strength compared with the other specimens. Thus RRA is the best process in terms of the optimal combination of SCC resistance and strength. Further TEM observation reveals that the RRA treated specimens are characterized by the fine equiaxed grains, dispersed second phase and wide PFZ. The pre-aging treated specimens show lower SCC resistance but higher strength as compared with the RRA treated ones. Equiaxed grains are also observed in the pre-aging treated samples by TEM, indicating that the anisotropy is eliminated. However, the dual aging and deformation plus aging treated specimens are demonstrated by large anisotropy.
文摘The purpose of this study is to investigate the impact of family training based on matrix model in reducing the amount of drug consumption by heroin and crack addicts. The subjects were referral to Karaj Clinic, Karaj City, Iran, for crack abuse in 2013. In order to select participants convenience sampling was been used and totally 45 patients were selected (15 heroin addict, 15 crack addict, and 15 with combination of heroin and crack addiction) and put into two groups of experimental and control groups randomly. For collecting the data, Addiction Severity Index questionnaire was used. Descriptive and inferential statistics were used through one-way analysis of covariance for data analyzing. The results indicated that there was statistical difference between the experimental and control group with consumption of heroin and crack in family status, mental and substance use and also it has been shown that the experimental group with heroine consumption achieved better performance compared with the control group in the amount of consumption.
