Cyclic symmetrical tension-compression fatigue tests in an axial plastic strain range of 2.0×10-4 to 1.5×10-3 were performed on three copper tetracrystal specimens containing two grain boundary triple lines ...Cyclic symmetrical tension-compression fatigue tests in an axial plastic strain range of 2.0×10-4 to 1.5×10-3 were performed on three copper tetracrystal specimens containing two grain boundary triple lines as well as one copper tricrystal specimen employing a multiple step method. Experimental results show that the strengthening effect of triple junction (TJ) on axial saturation stress increased with increasing plastic strain amplitude. The strengthening effects owe much to the strain incompatibilities at TJ. The cyclic stress-strain (CSS) curves of tetracrystals are higher than that of tricrystal. At low strain amplitude, deformation at TJ is smaller than that near grain boundary (GB), which results in that the width of TJ effect zone is smaller than that near GB. Whether GB split or not is associated with the angle between GB and loading axis, activation of slip systems beside GB and the accommodation and annihilation of residual dislocations on GB planes.展开更多
The weldability of a low-carbon copper-bearing age hardening steel was evaluated using cracking suscepti- bility calculation, HAZ maximum hardness measurement, and Y-groove cracking evaluation test. The results show t...The weldability of a low-carbon copper-bearing age hardening steel was evaluated using cracking suscepti- bility calculation, HAZ maximum hardness measurement, and Y-groove cracking evaluation test. The results show that the hardenability characteristics and cold cracking susceptibility of the steel are very low. The results also indicate that a crack-free weldment can be obtained during the welding of this type of steel even at an ambient temperature as low as -5 ℃ as well as in an absolute humidity lower than 4 000 Pa without any preheat treatment. A slight preheat treatment can prevent the joint from cracking when welding is carried out at lower ambient temperature or higher absolute humidity.展开更多
The fatigue cracking and fracture behavior of cold-drawn copper subjected to cyclic torsional loading were investigated in this study.It was found that with increasing stress amplitude,the fracture mode of cold-drawn ...The fatigue cracking and fracture behavior of cold-drawn copper subjected to cyclic torsional loading were investigated in this study.It was found that with increasing stress amplitude,the fracture mode of cold-drawn copper gradually changes from a shear fracture on transverse maximum shear stress plane to a mixed shear mode on both transverse and longitudinal shear planes and finally turns to the shear fracture on multiple longitudinal shear planes.Combining the cracking morphology and the relationship between torsional fatigue cracking and the grain boundaries,the fracture mechanism of cold-drawn copper under cyclic torsional loading was analyzed and proposed by considering the effects of the microstructure and axial stress caused by torsion.Because of the promotion of the grain boundary distribution on longitudinal crack propagation and the inhibition of axial stress on transverse crack grown,the tendency of crack propagation along the longitudinal direction increases with increasing stress levels.展开更多
In the present study,a film consisting of TiO_2 doped with copper was prepared for efficiently decomposing 4-nitrophenol(4-NP) by photocatalysis.The preparing process of TiO_2 doped with copper includes two procedures...In the present study,a film consisting of TiO_2 doped with copper was prepared for efficiently decomposing 4-nitrophenol(4-NP) by photocatalysis.The preparing process of TiO_2 doped with copper includes two procedures:preparing Ti(OH)_4 doped with copper and synthesizing anatase and rutile TiO_2 doped with copper.Ti(OH)_4 doped with copper could be achieved by hydrolyzing TiCl_4in the mixed solution containing deionized water and copper oxalate.The Ti(OH)_4 doped with copper can be gained successfully by the following procedures:rinsing,drying and vacuum drying.The Ti(OH)_4 doped with copper could be converted into anatase TiO_2 doped with copper and rutile TiO_2 doped with copper by incineration for 4.5 h at 723 and 1 073 K,respectively.Characterizations of anatase TiO_2 doped with copper and rutile TiO_2 doped with copper were determined by X-ray diffraction(XRD) and energy dispersion of X-ray(EDX).Anatase and rutile TiO_2 doped with copper were dissolved in a mixed solution containing isopropanol and diethylamine.Stainless electrode was submerged into with the solutions,the film of TiO_2 was formed by drying the thin layer at a ramp rate of 3℃/min until 373 K,and this temperature was held for 1 h.The temperature of the oven was subsequently increased to a final temperature of 823 K at a ramp rate of 3℃/min,and was held at this value for 1 h.The stainless steel covered with modified TiO_2 film was utilized as the anode.The stainless steel mesh was used as the cathode.The cathode and anode were connected with the source and immersed into the solution with 100 mg/L 4-NP.The whole reaction on photocatalysis was perfectly carried out after ultraviolet radiation and aerator were run.The experimental results showed that:cracking ratio of 4-NP ring,the removal ratio of chemical oxygen demand(COD) and total organic carbon(TOC) were respectively more than 90%,80% and 80% within 2 h.Degradation of 4-NP implied its potential application in associated wastewater.展开更多
文摘Cyclic symmetrical tension-compression fatigue tests in an axial plastic strain range of 2.0×10-4 to 1.5×10-3 were performed on three copper tetracrystal specimens containing two grain boundary triple lines as well as one copper tricrystal specimen employing a multiple step method. Experimental results show that the strengthening effect of triple junction (TJ) on axial saturation stress increased with increasing plastic strain amplitude. The strengthening effects owe much to the strain incompatibilities at TJ. The cyclic stress-strain (CSS) curves of tetracrystals are higher than that of tricrystal. At low strain amplitude, deformation at TJ is smaller than that near grain boundary (GB), which results in that the width of TJ effect zone is smaller than that near GB. Whether GB split or not is associated with the angle between GB and loading axis, activation of slip systems beside GB and the accommodation and annihilation of residual dislocations on GB planes.
文摘The weldability of a low-carbon copper-bearing age hardening steel was evaluated using cracking suscepti- bility calculation, HAZ maximum hardness measurement, and Y-groove cracking evaluation test. The results show that the hardenability characteristics and cold cracking susceptibility of the steel are very low. The results also indicate that a crack-free weldment can be obtained during the welding of this type of steel even at an ambient temperature as low as -5 ℃ as well as in an absolute humidity lower than 4 000 Pa without any preheat treatment. A slight preheat treatment can prevent the joint from cracking when welding is carried out at lower ambient temperature or higher absolute humidity.
基金supported by the National Natural Science Foundation of China (No.51771208)the Natural Science Foundation of Liaoning (No.2019-ZD-0059)
文摘The fatigue cracking and fracture behavior of cold-drawn copper subjected to cyclic torsional loading were investigated in this study.It was found that with increasing stress amplitude,the fracture mode of cold-drawn copper gradually changes from a shear fracture on transverse maximum shear stress plane to a mixed shear mode on both transverse and longitudinal shear planes and finally turns to the shear fracture on multiple longitudinal shear planes.Combining the cracking morphology and the relationship between torsional fatigue cracking and the grain boundaries,the fracture mechanism of cold-drawn copper under cyclic torsional loading was analyzed and proposed by considering the effects of the microstructure and axial stress caused by torsion.Because of the promotion of the grain boundary distribution on longitudinal crack propagation and the inhibition of axial stress on transverse crack grown,the tendency of crack propagation along the longitudinal direction increases with increasing stress levels.
基金Environmental Protection Department of Jiangsu Province,China(No.2013023)Jiangsu Key Laboratory of Industrial Water-Conservation & Emission Reduction,China(No.IWCER201202)
文摘In the present study,a film consisting of TiO_2 doped with copper was prepared for efficiently decomposing 4-nitrophenol(4-NP) by photocatalysis.The preparing process of TiO_2 doped with copper includes two procedures:preparing Ti(OH)_4 doped with copper and synthesizing anatase and rutile TiO_2 doped with copper.Ti(OH)_4 doped with copper could be achieved by hydrolyzing TiCl_4in the mixed solution containing deionized water and copper oxalate.The Ti(OH)_4 doped with copper can be gained successfully by the following procedures:rinsing,drying and vacuum drying.The Ti(OH)_4 doped with copper could be converted into anatase TiO_2 doped with copper and rutile TiO_2 doped with copper by incineration for 4.5 h at 723 and 1 073 K,respectively.Characterizations of anatase TiO_2 doped with copper and rutile TiO_2 doped with copper were determined by X-ray diffraction(XRD) and energy dispersion of X-ray(EDX).Anatase and rutile TiO_2 doped with copper were dissolved in a mixed solution containing isopropanol and diethylamine.Stainless electrode was submerged into with the solutions,the film of TiO_2 was formed by drying the thin layer at a ramp rate of 3℃/min until 373 K,and this temperature was held for 1 h.The temperature of the oven was subsequently increased to a final temperature of 823 K at a ramp rate of 3℃/min,and was held at this value for 1 h.The stainless steel covered with modified TiO_2 film was utilized as the anode.The stainless steel mesh was used as the cathode.The cathode and anode were connected with the source and immersed into the solution with 100 mg/L 4-NP.The whole reaction on photocatalysis was perfectly carried out after ultraviolet radiation and aerator were run.The experimental results showed that:cracking ratio of 4-NP ring,the removal ratio of chemical oxygen demand(COD) and total organic carbon(TOC) were respectively more than 90%,80% and 80% within 2 h.Degradation of 4-NP implied its potential application in associated wastewater.
