The corrosion behaviour of Mg−6Gd−3Y−1Zn−0.3Ag(wt.%)alloy components with different sizes after cooling was investigated.The alloys in the small components(SC)cooled fast,which were composed ofα-Mg matrix and coarse ...The corrosion behaviour of Mg−6Gd−3Y−1Zn−0.3Ag(wt.%)alloy components with different sizes after cooling was investigated.The alloys in the small components(SC)cooled fast,which were composed ofα-Mg matrix and coarse long-period stacking ordered(LPSO)phases.The alloys in the large components(LC)cooled slowly,and there were thin lamellar LPSO phases precipitating inside the grains,except forα-Mg matrix and coarse LPSO phases.The hydrogen evolution test revealed that the corrosion rate of LC sample was higher than that of SC sample.Electrochemical impedance spectroscopy(EIS)test showed that the surface film on LC alloys provided worse protection.The corrosion morphologies indicated that the precipitation of the thin lamellar LPSO phases in LC sample caused severe micro-galvanic corrosion,which accelerated the rupture of the surface film.展开更多
The effects of surface state and applied stress on the stress corrosion cracking （SCC） behaviors of thermally treated （TT） Alloy 690 in 10 wt% NaOH solution with 100 mg/L litharge at 330 ℃ were investigated using...The effects of surface state and applied stress on the stress corrosion cracking （SCC） behaviors of thermally treated （TT） Alloy 690 in 10 wt% NaOH solution with 100 mg/L litharge at 330 ℃ were investigated using C-ring samples with four kinds of surface states and two different stress levels. Sample outer surfaces of the first three kinds were ground to 400 grit （ground）, shot-peened （SP） and electro-polished （EP） and the last one was used as the as-received state. Two samples of every kind were stressed to 100% and 200% yield stress of Alloy 690TT, respectively. The results showed that the oxide film consisted of three layers whereas continuous layer rich in Cr was not found. The poor adhesive ability indicated that the oxide film could not protect the matrix from further corrosion. Lead was found in the oxide film and the oxides at the crack paths and accelerated the dissolution of thermodynamically unstable Cr in these locations and also in the matrix. The crack initiation and propagation on Alloy 690TT were effectively retarded by SP and EP treatments but were enhanced by grinding treatment, compared with the cracks on the as-received surface. The cracking severity was also enhanced by increasing the externally applied stress. The accelerated dissolution of Cr and the local tensile stress concentration in the near-surface layer caused by cold-working and higher applied stress reduced the SCC-resistance of Alloy 690TT in the studied solution.展开更多
In this study, the surface passive films, dissolution behavior and biocompatibility of Ti-Ag alloys （with 5%, 10% and 20% Ag） were evaluated by X-ray diffraction （XRD） tests, electrochemical corrosion tests, X-ray...In this study, the surface passive films, dissolution behavior and biocompatibility of Ti-Ag alloys （with 5%, 10% and 20% Ag） were evaluated by X-ray diffraction （XRD） tests, electrochemical corrosion tests, X-ray photoelectron spectroscopy （XPS） tests, dissolution tests and in-vitro cytotoxicity tests. The surface films on the Ti-20Ag alloy are rich in Ti and much deficient in Ag with respect to alloy composition, as identified by XPS. Compared to CP Ti, Ti-SAg and Ti-20Ag alloys show larger impedances and lower capacitances, which can be associated with an increase of the passive layer thickness. Moreover, all Ti-Ag alloys exhibit negligible or low metal release in the test solutions. The in-vitro cytotoxicity results show Ti-Ag alloys seem to be as cytocompatible as CP Ti. From the viewpoint of surface passive film and cytotoxicity, Ti-SAg and Ti-20Ag are considered to be more suitable for dental applications.展开更多
按照ASTM G28—2002(Reapproved 2015)《Standard Test Method for Detecting Susceptibility to Intergranular Corrosion in Wrought,Nickel-rich,Chromium-bearing Alloys》中方法A对供货态和表面处理后SB-444 N06625镍基合金材料进...按照ASTM G28—2002(Reapproved 2015)《Standard Test Method for Detecting Susceptibility to Intergranular Corrosion in Wrought,Nickel-rich,Chromium-bearing Alloys》中方法A对供货态和表面处理后SB-444 N06625镍基合金材料进行腐蚀试验,对腐蚀试验后的材料进行取样和金相检测及对比分析。研究结果表明,供货状态材料表面的保护油脂会在热处理时燃烧并分解为碳及碳化物,造成试样渗碳现象,C元素含量的增多直接导致Cr元素与C元素在镍基合金材料近表面生成Cr23C6并析出,最终造成合金材料耐腐蚀性的下降。而对合金表面先进行脱脂处理,然后进行同样的热处理,试样的腐蚀性能只有轻微下降,可以满足使用要求。展开更多
基金the financial supports from the National Natural Science foundation of China(Nos.51574291,51874367).
文摘The corrosion behaviour of Mg−6Gd−3Y−1Zn−0.3Ag(wt.%)alloy components with different sizes after cooling was investigated.The alloys in the small components(SC)cooled fast,which were composed ofα-Mg matrix and coarse long-period stacking ordered(LPSO)phases.The alloys in the large components(LC)cooled slowly,and there were thin lamellar LPSO phases precipitating inside the grains,except forα-Mg matrix and coarse LPSO phases.The hydrogen evolution test revealed that the corrosion rate of LC sample was higher than that of SC sample.Electrochemical impedance spectroscopy(EIS)test showed that the surface film on LC alloys provided worse protection.The corrosion morphologies indicated that the precipitation of the thin lamellar LPSO phases in LC sample caused severe micro-galvanic corrosion,which accelerated the rupture of the surface film.
基金supported by the National Science and Technology Major Project(No. 20112x06004–009)the National Natural Science Foundation of China (No. 51025104)
文摘The effects of surface state and applied stress on the stress corrosion cracking （SCC） behaviors of thermally treated （TT） Alloy 690 in 10 wt% NaOH solution with 100 mg/L litharge at 330 ℃ were investigated using C-ring samples with four kinds of surface states and two different stress levels. Sample outer surfaces of the first three kinds were ground to 400 grit （ground）, shot-peened （SP） and electro-polished （EP） and the last one was used as the as-received state. Two samples of every kind were stressed to 100% and 200% yield stress of Alloy 690TT, respectively. The results showed that the oxide film consisted of three layers whereas continuous layer rich in Cr was not found. The poor adhesive ability indicated that the oxide film could not protect the matrix from further corrosion. Lead was found in the oxide film and the oxides at the crack paths and accelerated the dissolution of thermodynamically unstable Cr in these locations and also in the matrix. The crack initiation and propagation on Alloy 690TT were effectively retarded by SP and EP treatments but were enhanced by grinding treatment, compared with the cracks on the as-received surface. The cracking severity was also enhanced by increasing the externally applied stress. The accelerated dissolution of Cr and the local tensile stress concentration in the near-surface layer caused by cold-working and higher applied stress reduced the SCC-resistance of Alloy 690TT in the studied solution.
基金supported by the National Basic Research Program of China ("973 Program", Nos.2012CB619102 and 2012CB619100)the National High Technology Research and Development Program of China ("863 Program", Nos. 2011AA030101 and2011AA030103)+3 种基金the National Natural Science Foundation of China (Nos. 31170909 and 51041004)the Research Fund for the Doctoral Program of Higher Education (No. 20100001110011)the Fundamental Research Funds for the Central Universities (Nos. HEUCFZ1017and HEUCFR1020)the Natural Science Foundation of Heilongjiang Province, China (No. ZD201012)
文摘In this study, the surface passive films, dissolution behavior and biocompatibility of Ti-Ag alloys （with 5%, 10% and 20% Ag） were evaluated by X-ray diffraction （XRD） tests, electrochemical corrosion tests, X-ray photoelectron spectroscopy （XPS） tests, dissolution tests and in-vitro cytotoxicity tests. The surface films on the Ti-20Ag alloy are rich in Ti and much deficient in Ag with respect to alloy composition, as identified by XPS. Compared to CP Ti, Ti-SAg and Ti-20Ag alloys show larger impedances and lower capacitances, which can be associated with an increase of the passive layer thickness. Moreover, all Ti-Ag alloys exhibit negligible or low metal release in the test solutions. The in-vitro cytotoxicity results show Ti-Ag alloys seem to be as cytocompatible as CP Ti. From the viewpoint of surface passive film and cytotoxicity, Ti-SAg and Ti-20Ag are considered to be more suitable for dental applications.
文摘按照ASTM G28—2002(Reapproved 2015)《Standard Test Method for Detecting Susceptibility to Intergranular Corrosion in Wrought,Nickel-rich,Chromium-bearing Alloys》中方法A对供货态和表面处理后SB-444 N06625镍基合金材料进行腐蚀试验,对腐蚀试验后的材料进行取样和金相检测及对比分析。研究结果表明,供货状态材料表面的保护油脂会在热处理时燃烧并分解为碳及碳化物,造成试样渗碳现象,C元素含量的增多直接导致Cr元素与C元素在镍基合金材料近表面生成Cr23C6并析出,最终造成合金材料耐腐蚀性的下降。而对合金表面先进行脱脂处理,然后进行同样的热处理,试样的腐蚀性能只有轻微下降,可以满足使用要求。
