Chungen ZHOU
,
Jingsheng YU
,
Shengkai GONG
,
Huibin XU
材料科学技术（英文）
The oxidation of specimens with thermal barrier coating (TBC) consisted of nickel-base superalloy, low-pressure plasma sprayed Ni-28Cr-6Al-0.4Y (wt pct) bond coating and electron beam physical vapor deposited 7.5 wt pct yttria stabilized zirconia (YSZ) top coating was studied at 1050℃ respectively in flows of O2, and mixture of O2 and 5%H2O under atmospheric pressure. The thermal barrier coating has relatively low oxidation rate at 1050℃ in pure O2. Oxidation rate of thermal barrier coating in the atmosphere of O2 and 5%H2O is increased The oxidation kinetics obeys almost linear law after long exposure time in the presence of 5% water vapor. Oxide formed along the interface between bond coat and top coat after oxidation at 1050℃ in pure O2 consisted of Al2O3, whereas interfacial scales formed after oxidation at 1050℃ in a mixture of O2 and 5%H2O were mainly composed of Ni(Al,Cr)2O4,NiO and Al2O3. It is suggested that the effect of water vapor on the oxidation of the NiCrAlY coating may be attributed to the increase in Ni and Cr ions transport in the oxides.
关键词:
Oxidation
,
null
,
null
Fei CAI
,
Chungen ZHOU
,
Huibin XU
,
Shengkai GONG
材料科学技术（英文）
An oxidation resistant Al-Cu-Fe quasicrystalline coating was fabricated on substrate of Ti alloy by low pressure plasma spraying (LPPS) method. As-sprayed Al-Cu-Fe coating has a rapidly solidified lamellar microstructure consisting of quasicrystalline phase and crystalline phase. The formation of quasicrystalline coating is related to the annealing. The results from the oxidation experiments showed that Al-Cu-Fe quasicrystalline coating improved the oxidation resistance of Ti-base alloys. During the oxidation period there is no evident spallation of the coating from the substrate. Oxide formed on the surface of Al-Cu-Fe quasicrystalline coating after oxidation consisted of Al¬2O¬3. Oxidation occurs leading to a change of concentration and phase transformation in the coating surface. Selective oxidation of Al transforms the quasicrystalline phase into the phase.
关键词:
Low pressure plasma spray
,
null
,
null
,
null
,
null
Hongbo GUO
,
Shengkai GONG
,
Huibin XU
材料科学技术（英文）
The performances of gradient thermal barrier coatings (GTBCs) produced by EB-PVD were evaluated by isothermal oxidation and cyclic hot corrosion (HTHC) tests. Compared with conventional two-layered TBCs, the GTBCs exhibite better resistance to not only oxidation but also hot-corrosion. A dense Al2O3 layer in the GTBCs effectively prohibites inward diffusion of O and S and outward diffusion of Al and Cr during the tests. On the other hand, an "inlaid" interface, resulting from oxidation of the Al along the columnar grains of the bond coat, enhances the adherence of Al2O3 layer. Failure of the GTBC finally occurred by cracking at the interface between the bond coat and Al2O3 layer, due to the combined effect of sulfidation of the bond coat and thermal cycling.
关键词:
Gradient thermal barrier coating (GTBC)
,
null
F.T.Cheng
材料科学技术（英文）
The present communication addresses an interesting problem related to the indeterminacy in hardness of superelastic NiTi reported by Xu et al. The origin of the indeterminacy is attributed to the inadequacy of the conventional Vickers hardness testing measurement which does not record elastic deformation, and thus the indeterminacy may be removed with suitable techniques. Concepts of hardness in relation to deformation are clarified. Recommendations for measuring the hardness of NiTi and other elastic-plastic materials are suggested, together with comments on the advantages and disadvantages of each of these methods.
关键词:
Hardness
,
null
,
null
,
null
,
null
,
null
Jingpei XIE
,
Yaomin ZHU
,
Xiaoping WANG
材料科学技术（英文）
The M-s temperature, Delta G(gamma-->alpha), Delta G(gamma-->M) and mechanical energy under a non-severe impact loading in a medium manganese steel (Fe-7Mn-1.2C) have been calculated by means of Xu's Fe-X-C model. The relation between the yield strength of austenite and the driving force for martensite transformation has been established. It is proved that the martensite transformation can take place in a medium manganese steel (Fe-7Mn-1.2C alloy) under a non-severe impact loading.
关键词:
李莉
,
李庆芬
,
郑磊
,
徐庭栋
,
杜善义
钢铁研究学报
以工业用12Cr1MoV钢为研究对象,通过俄歇电子能谱分析方法(AES),对磷在恒温过程中的非平衡晶界偏聚浓度进行了测定.获得的磷在钢中的非平衡晶界偏聚动力学曲线直接验证了非平衡晶界偏聚动力学理论中的Xu-Song模型.
关键词:
晶界偏聚
,
临界时间
,
扩散
,
钢
陆樟献
,
龚雁
,
王渊明
,
王正才
,
陈善飞
功能材料与器件学报
doi:10.3969/j.issn.1007-4252.2012.01.005
基于Xu等人的经典振荡磁偶极子模型和Matsumoto等人给出的双折射驰豫理论,研究了磁致双折射和二向色性对磁性液体薄片的光透射率弛豫特性的影响.理论推导了磁性液体的双折射和二向色性函数的偏振光透射率具体表达式,并进行了数值模拟计算.该问题的研究对磁性液体光学各向异性的深入认识以及相关磁性液体光学器件的应用具有一定的指导意义.
关键词:
物理光学
,
双折射驰豫
,
二向色性驰豫
,
磁性液体
,
磁偶极子
Journal of Materials Research
Based on the best bulk metallic glass (BMG) forming alloy in the Mg-Cu-Y ternary system, we introduced Ag (or Ni) to partially substitute for Cu to improve the glass-forming ability (GFA). The objective of this paper is twofold. First, we illustrate in detail a recently developed search strategy, which was proposed but only briefly outlined in our previous publication [H. Ma, L.L. Shi, J. Xu, Y. Li, and E. Ma: Discovering inch-diameter metallic glasses in three-dimensional composition space. Appl. Phys. Lett. 87, 181915 (2005)]. The protocol to navigate in three-dimensional composition space to land large BMGs is spelled out step-by-step using the pseudo-ternary Mg-(Cu,Ag)-Y as the model system. Second, our ability to locate the best BMG former in the composition tetrahedron allows us to systematically examine, and conclude on, the effects of a given alloying element. The large improvement in glass-forming ability in the Mg-(Cu,Ag)-Y system relative to the based ternary will be contrasted with the reduced glass-forming ability in the Mg-(Cu,Ni)-Y pseudo ternary system. It is demonstrated that the improvement of glass-forming ability requires judicious choice of substitutional alloying elements and concentrations, rather than simple additions of multiple elements assuming the "confusion principle."
关键词:
bulk metallic-glass;shaped copper mold;amorphous-alloys;thermal-stability;ternary-system;casting method;p system;diameter;zr;mm
