2.
In Part II of this study, the characterization by TGA, SEM and AFM of the oxidation behavior at 900°C of NiAl(001) samples with various sulfur concentrations is reported. The formation of interfacial cavities is observed for all samples. A constant ratio of the oxide thickness to cavity depth is found showing that the formation of cavities at the metal–oxide interface is not due to sulfur but only to vacancy injection during the cationic growth of transient -alumina. It is also observed that the presence of sulfur in the alloy decreases the oxidation rate of the nickel aluminide and, consequently, lowers the formation of interfacial cavities. This effect is interpreted as an indirect evidence of the control of the transient-alumina growth by the aluminium diffusion in the alloy, also advanced as an explanation for the interfacial nucleation of alpha alumina. These results are combined with those presented in Part I to propose a model that explains how sulfur, present in small quantities in the alloy, has a deleterious effect on the oxide adherence. The indirect role of the cavities formed during the growth of the transient alumina is to create transitory conditions for the rapid segregation of sulfur at the interface. The segregated sulfur remains as a vestige of the initial stages of growth after the transformation of the scale into mature alumina and weakens its adherence. 相似文献
3.
V. L. Arbuzov B. N. Goshchitskii V. V. Sagaradze S. E. Danilov Yu. N. Zuev A. E. Kar’kin V. D. Parkhomenko A. V. Kozlov V. M. Chernov 《The Physics of Metals and Metallography》2016,117(3):299-306
The processes of the accumulation and annealing of radiation-induced defects that occur under low-temperature (at 77 K) irradiation (with an energy E > 0.1 MeV) of V?4Ti?4Cr and V?10Ti?5Cr bcc alloys both nonmodified and modified with hydrogen isotopes in a concentration of 200 ppm, as well as the effect of these processes on the physicomechanical properties of these alloys, have been studied. It has been found that the saturation of these alloys with hydrogen leads to slight changes in their strength and ductility characteristics. The irradiation of the alloys at the temperature of 77 K results in a substantial increase in their yield stress and ultimate strength, as well as a decrease in their ductility. In the course of the postradiation annealing of the alloys at a temperature of 130 K, the stage related to the migration of interstitial atoms is observed. At temperatures of 290–320 K, the recovery stage occurs due to the formation of vacancy clusters. The stage that occurs at a temperature of 470 K can be attributed to the formation of impurity-vacancy clusters. Possible mechanisms of the radiation-induced strengthening of the alloys during irradiation and subsequent annealing have been discussed. 相似文献
4.
Weizhou Li Ke Han Rongmei Niu Tianquan Liang Canwei Lai Xiuhai Zhang 《Oxidation of Metals》2018,89(5-6):731-753
The effect of Si and Y2O3 additions on the oxidation behavior of Ni–xAl (x = 5 or 10 wt%) alloys at 1150 °C was studied. The addition of Y2O3 accelerates oxidation rate of alloys, especially growth rate of NiO, but improves adherence of the scale to the substrate. The addition of Si facilitates the selective oxidation of Al, suppresses the formation of NiO and therefore reduces the critical Al content to form continuous layer of alumina scale. Higher Al content decreases the oxidation rate of alloys in binary Ni–Al alloys and increases the oxidation rate of alloys in ternary Ni–Al–Si alloys. The effect of third-element Si is more significant and beneficial than that of Al content in ternary Ni–Al–Si alloys. 相似文献