The cast structures influencing the electrochemical corrosion behavior of Co-Cr and Ni-Cr dental alloys were studied using potentiodynamic polarization and AC impedance in 0.9% (mass fraction) NaCl solution at (37...The cast structures influencing the electrochemical corrosion behavior of Co-Cr and Ni-Cr dental alloys were studied using potentiodynamic polarization and AC impedance in 0.9% (mass fraction) NaCl solution at (37±1) ℃. The phase and microstructure of the alloys that were fabricated using two different casting methods viz. centrifugal casting and high frequency induction casting, were examined using X-ray diffraction analysis, scanning electron microscopy and energy dispersive spectroscopy. The roles of alloying elements and the passive film homogeneity on the corrosion resistance of Co-Cr-Mo and Ni-Cr-Mo dental cast alloys were reviewed. The results of electrochemical study show that the dependence of corrosion resistance on the microstructure associated with the casting methods is marginal. The Co-Cr alloy exhibits more desirable corrosion resistance properties than the Ni-Cr alloy. There is severe preferential dissolution of Ni-rich, Cr and Mo depleted zones in the Ni-Cr alloy.展开更多
A novel, Nb- and Si-rich and Be-free Ni-based alloy was cast by two methods of investment casting and continuouscasting to study the microstructure evolution during solidification and its mechanical properties. The so...A novel, Nb- and Si-rich and Be-free Ni-based alloy was cast by two methods of investment casting and continuouscasting to study the microstructure evolution during solidification and its mechanical properties. The solidification of the alloy startedwith the primary crystallization of FCC-γ, followed by a binary eutectic reaction, with the formation of a heterogeneous constituent：FCC-γ＋G-phase, which replaced the low-melting eutectic （FCC-γ＋NiBe） in the Be-bearing alloys. AlNi6Si3 and γ′ formed during theterminal stages of solidification by investment casting, while the formation of AlNi6Si3 was suppressed by continuous casting. TheScheil solidification model agreed very well with the experimental results.展开更多
目的:观察4种金属铸造冠磁共振成像(MRI)检查时所产生金属伪影。方法:给实验犬依次佩戴钴铬合金、低钛合金、镍铬合金、纯钛4种试验铸造冠(右上第二前磨牙),分别进行常规3.0 T 6个序列及1.5 T 4个序列磁共振头部扫描,测量4种铸造冠所产...目的:观察4种金属铸造冠磁共振成像(MRI)检查时所产生金属伪影。方法:给实验犬依次佩戴钴铬合金、低钛合金、镍铬合金、纯钛4种试验铸造冠(右上第二前磨牙),分别进行常规3.0 T 6个序列及1.5 T 4个序列磁共振头部扫描,测量4种铸造冠所产生的伪影的最大面积和伪影涉及图像的层数。结果:2种场强下钴铬合金铸造冠所产生的伪影面积最大(P<0.01);1.5 T场强下其他3种合金冠之间差异均无显著性(P>0.05);3.0 T场强下镍铬合金冠伪影大于低钛合金冠和纯钛冠(P<0.05);低钛合金冠与纯钛冠差异无显著性(P>0.05)。在2种场强下和全部扫描序列中,伪影涉及的图像层数均以钴铬合金冠的最多,纯钛金属冠最少,其余2种合金冠相同。结论:钴铬合金伪影程度最大,镍铬合金和低钛合金次之,纯钛在4种金属中伪影程度最小。展开更多
文摘The cast structures influencing the electrochemical corrosion behavior of Co-Cr and Ni-Cr dental alloys were studied using potentiodynamic polarization and AC impedance in 0.9% (mass fraction) NaCl solution at (37±1) ℃. The phase and microstructure of the alloys that were fabricated using two different casting methods viz. centrifugal casting and high frequency induction casting, were examined using X-ray diffraction analysis, scanning electron microscopy and energy dispersive spectroscopy. The roles of alloying elements and the passive film homogeneity on the corrosion resistance of Co-Cr-Mo and Ni-Cr-Mo dental cast alloys were reviewed. The results of electrochemical study show that the dependence of corrosion resistance on the microstructure associated with the casting methods is marginal. The Co-Cr alloy exhibits more desirable corrosion resistance properties than the Ni-Cr alloy. There is severe preferential dissolution of Ni-rich, Cr and Mo depleted zones in the Ni-Cr alloy.
基金supported by the ARRS under the framework of the Slovenian-Brazilian Bilateral Project BI-BR/12-14-003funding from the European Union Seventh Framework Programme under Grant Agreement 312483-ESTEEM2(Integrated Infrastructure InitiativeI3)
文摘A novel, Nb- and Si-rich and Be-free Ni-based alloy was cast by two methods of investment casting and continuouscasting to study the microstructure evolution during solidification and its mechanical properties. The solidification of the alloy startedwith the primary crystallization of FCC-γ, followed by a binary eutectic reaction, with the formation of a heterogeneous constituent：FCC-γ＋G-phase, which replaced the low-melting eutectic （FCC-γ＋NiBe） in the Be-bearing alloys. AlNi6Si3 and γ′ formed during theterminal stages of solidification by investment casting, while the formation of AlNi6Si3 was suppressed by continuous casting. TheScheil solidification model agreed very well with the experimental results.
文摘目的:观察4种金属铸造冠磁共振成像(MRI)检查时所产生金属伪影。方法:给实验犬依次佩戴钴铬合金、低钛合金、镍铬合金、纯钛4种试验铸造冠(右上第二前磨牙),分别进行常规3.0 T 6个序列及1.5 T 4个序列磁共振头部扫描,测量4种铸造冠所产生的伪影的最大面积和伪影涉及图像的层数。结果:2种场强下钴铬合金铸造冠所产生的伪影面积最大(P<0.01);1.5 T场强下其他3种合金冠之间差异均无显著性(P>0.05);3.0 T场强下镍铬合金冠伪影大于低钛合金冠和纯钛冠(P<0.05);低钛合金冠与纯钛冠差异无显著性(P>0.05)。在2种场强下和全部扫描序列中,伪影涉及的图像层数均以钴铬合金冠的最多,纯钛金属冠最少,其余2种合金冠相同。结论:钴铬合金伪影程度最大,镍铬合金和低钛合金次之,纯钛在4种金属中伪影程度最小。
