W.Liang
,
X.X.Ma
,
X.G.Zhao
,
J.Zhang
,
D.X.Zou
金属学报(英文版)
The Ti-48Al alloy was pack siliconized with 15i+85Al2O3. The microstructure of the siliconized coating on the TiAl-based alloy was analyzed and its effect on oxidation resistance was investigated. The specimens before and after cycle oxidation were examined by XRD and SEM equipped with XEDS. The results showed that the coating is composed of a thin Al2O3 outer layer and a composite inner layer of Ti5Si3 with an appropriate amount of Al2O3 dispersed in. Cycle oxidation tests showed that the high temperature oxidation resistance of TiAl-based alloy was greatly improved by forming such composite coating. No spallation and crack happened and the weight gain was very small after cycle oxidation at 900℃ for 314h.
关键词:
TiAl-based alloy
,
null
,
null
X.G.Luan
,
L.F.Cheng
,
S.R.Qiao
,
J.Zhang
金属学报(英文版)
The samples made from a SiC-C/SiC composite were pretreated in Ar under creep, fatigue, creep and fatigue interaction, as well as in dry oxygen and wet oxygen under fatigue at 1300℃ for 15 hours, The fracture behaviors of the pretreated samples were investigated at 1300℃. The loading-strain curves and the microstructures of the sample were compared with each other. The various of high temperature tensile behaviors was attributed to the different microstructures resulted from different high temperature pretreatments.
关键词:
C/SiC
,
null
,
null
X.Ju
,
J.Zhang
,
B.Y.Wang
金属学报(英文版)
A series of poly(phenylenevinylene) (PPV)/titanium oxide (TiO2) nanocompositeswith different contents of TiO2 nanoparticles were prepared from mixtures of PPVprecursor and titanium butoxide ethanol solution in a sol-gel process. TEM imagesshowed the formation of the connected network of TiO2 nanoparticles with a highercontent of TiO2, which resulted in the titanium butoxide hydrolyzed to form Ti organiccompound. Meanwhile, the conjugation of PPV polymer chains can be interrupted bythe TiO2 network structure. The PL spectra revealed that the emitted light of thePPV/TiO2 nanocomposites blue shifted without fine structure and the PL intensityenhanced when the TiO2 network formed. In the lifetime spectroscopy of positronannihilation, the structural properties of the PPV dominated the character of thenanocomposites, in which the formation of the o-Ps was presented in free volume pfpolymer, when the content of TiO2 was below 10%. Further increasing the contentof TiO2 nanoparticle introduced much more vacancies, vacancy clusters and grainboundaries at their interfaces, which led to the corresponding lifetime and intensityclose to that of the nano-TiO2 bulk materials. With the TiO2 content of 50%, theholes formed by aggregating vacancy clusters and increased the component of longlifetime. These phenomena suggested that the optical and structural properties of thePPV/TiO2 nanocomposites are dependent on the interfacial structure between PPVand TiO2 nanoparticles.
关键词:
PPV/TiO2 nanocomposite
,
null
,
null
G.Z.Kang
,
Q.Gao
,
J.Zhang
金属学报(英文版)
Based on the experimental results of the ratcheting for SS304 stainless steel, a new visco-plastic cyclic constitutive model was established to describe the uniaxial and multiaxial ratcheting of the material at room and elevated temperatures within the framework of unified visco-plasticity. In the model, the temperature dependence of the ratcheting was emphasized, and the dynamic strain aging occurred in the temperature range of 400-600℃ for the material was taken into account particularly. Finally, the prediction capability of the developed model was checked by comparing to the corresponding experimental results.
关键词:
constitutive model
,
null
,
null
