Papers by Author: Z.G. Zhang

Abstract: The effect of the addition of 5 and 10 at.% Cr on the oxidation of a binary Fe-10 at.% Al alloy (Fe-10Al) was studied in 1 atm O2 at 1000°C. Fe-10Al underwent a very slow initial nearly-parabolic stage followed by a breakaway composed of two subsequent parabolic stages with a smaller rate constant for the final period. The two ternary alloys (Fe-5Cr-10Al and Fe-10Cr-10Al) presented two parabolic stages with final rate constants similar to each other and much lower than that for Fe-10Al. The alumina scale developed initially on Fe-10Al was replaced later by a layered scale containing mixtures of Fe and Al oxides plus many Fe-rich oxide nodules. Fe-5Cr-10Al was mostly covered by a thin alumina layer just above the alloy surface with some Fe-rich nodules formed in the beginning of oxidation, which later on were healed by alumina with a large decrease of the oxidation rate. A continuous alumina layer formed on the whole sample surface without any Fe-rich nodule for Fe-10Cr-10Al. Therefore, the addition of chromium is obviously beneficial for the oxidation resistance of Fe-10Al by inhibiting the formation of fast-growing Fe-containing oxides and promoting the development of an exclusive alumina layer. However, the effect of chromium is different from the classical third-element effect.

Abstract: The problem of an interface edge crack between two dissimilar piezoelectric materials is analyzed under the conditions of anti-plane shear and in-plane electrical loading. The crack is considered to be traction-free, but electric permeable one across which the normal component of the electric displacement are continuous. A series form of electromechanical solution and field intensity factors are obtained. The results show that all fields including strain, stress, electric field strength and electric displacement are singular in the front of crack tip. At last, the stress intensity factor is solved by the boundary collocation method (BCM), numerical results are given and discussed.