High Temperature Materials and Processes
Corrosion problems in waste incinerators or in other advanced combustion power generation systems are usually rather serious due to the deposition of ashes composed of heavy and alkali metal chlorides or sulfates of metals such as Zn, K, Pb etc. This paper presents the individual and combined effects of ZnCl2 and KCl on the corrosion behavior of some heat-resistant steels, the M38G Ni-based alloy, 2205 duplex steel and several other Fe-based alloys as well as pure metals were examined at 623K and 723K in pure oxygen. All the materials tested suffered from accelerated corrosion due to the formation of non-protective porous oxide scales and in many cases from local attack in the alloy matrix induced by chlorine. The Cr addition to the alloys can hardly provide sufficient corrosion resistance against such environments as a result of the bad adherence of Cr2O3 to the alloy matrix. This detrimental effect is discussed on the basis of thermodynamic considerations.
关键词:
chloride deposits;corrosion;alloys;waste incineration;stainless-steels;molten chlorides;hot corrosion;environments;behavior
李俊
,
刘新才
,
李明
,
潘晶
功能材料
在850～880℃真空热变形4min、变形量70%制备了Nd14Fe80B6各向异性磁体,实验结果表明随着热变形温度的提高,磁体的各向异性先上升后降低,870℃热变形时磁体的（006）晶面峰为X衍射图谱的主峰、（004）相对极密度最大值达到130.01、I（006）/I（105）为1.88,获得（006）磁织构,磁体的饱和磁化强度达到1.453T。如热变形过程消除平均宽度为25μm的带状组织,减少与热变形压力垂直的片状晶之间夹角为19°左右的局部片状晶,则磁体的各向异性可望进一步提高。Nd2Fe14B相在热变形过程中从等轴晶变形为片状晶,且磁体宏观变形量≥65%时,才能形成（006）磁织构,局部富稀土相只起到有利晶粒滑移、有利片状晶形成的作用。细化热变形磁体的片状晶厚度可使磁体具有高矫顽力、高剩磁与饱和磁化强度之比值。850℃热变形Nd14Fe80B6磁体的片状晶平均厚度为76nm,磁体的矫顽力为450.6kA/m,Mr/Ms为0.92。
关键词:
热变形
,
变形温度
,
剩磁
,
织构
,
显微组织
CHAI Feng
,
YANG Caifu
,
SU Hang
,
ZHANG Yongquan
,
XU Zhou
钢铁研究学报(英文版)
Effects of Mg on the chemical component and size distribution of Tibearing inclusions favored grain refinement of the welding induced coarsegrained heat affected zone (CGHAZ), with enhanced impact toughness in Tikilled steels, which were examined based on experimental observations and thermodynamic calculations. The results indicated that the chemical constituents of the inclusions gradually varied from the TiO+TiMgO compound oxide to the TiMgO+MgO compound oxide and the singlephase MgO, as the Mg content increased from 0002 3% to 0006%. A trace addition of Mg (approximately 0002%) led to the refinement of Tibearing inclusions by creating the TiMgO compound oxide and provided favorable size distribution of the inclusions for acicular ferrite transformation with a high nucleation rate in the CGHAZ, and a high volume fraction of acicular ferrite was obtained in the CGHAZ with enhanced impact toughness. Otherwise, a high content of Mg (approximately 0006%) produced a singlephase MgO, which was impotent to nucleate an acicular ferrite, and a microstructure comprised of a ferrite side plate and a grain boundary ferrite developed in the CGHAZ. The experimental results were confirmed by thermodynamic calculations.
关键词:
nonmetallic inclusion;magnesium;acicular ferrite;coarsegrained heat affected zone (CGHAZ)
HOU Qingyu
,
HUANG Zhenyi
,
WANG Jingtao
钢铁研究学报(英文版)
The effect of austempering temperature on the microstructure and properties of a high chromium white cast iron was investigated with the Rietveld refinement method. The result shows that the upper bainite exists in the sample austempered at 623 K and the martensite, lower bainite, M7C3, and retained austenite exist in the samples austempered at 563 K and 593 K. The relative content of the retained austenite increases with increasing the austempering temperature from 563 K to 623 K. The higher hardness, impact toughness and impact abrasive wear resistance can be obtained for the specimen austempered at 593 K.
关键词:
high chromium white cast iron;austempering;retained austenite;Rietveld refinement;microstructure;properties
Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing
Single-pass equal channel angular extrusion (ECAE) experiments of an extruded Mg-Zn-Y-Zr alloy with an intense initial basal texture were performed in two inter-perpendicular billet orientations and at 473 and 623 K. The study was aimed to determine the effects of ECAE temperature and billet orientation on the microstructure, texture evolution and mechanical properties of the ECAEed alloy. It was found that the grain refinement achieved through the single-pass ECAE in the Orient-I billet orientation (the normal direction (ND) of the extruded plate parallel with the ECAE exit direction) was more effective than that in the Orient-II billet orientation (the ND of the extruded plate perpendicular to the ECAE exit direction). The average grain sizes after ECAE at 473 K were much smaller than those after ECAE at 623 K. The pole figures of the alloy ECAEed at 473 K showed that most of the basal planes in the Orient-I and Orient-II samples were inclined about 40 and 35, respectively, with respect to the longitudinal direction of the ECAE extrudate. However, for the alloy ECAEed at 623 K, most of the basal planes were parallel with the longitudinal direction of the ECAE extrudate. It was remarkable that the yield strengths of the alloy ECAEed at 473 K were lower than those at 623 K. The peculiar relationship between ECAE temperature and the mechanical properties of the alloy was ascribed to the texture evolution during ECAE. (C) 2008 Elsevier B.V. All rights reserved.
关键词:
Magnesium;Mg-Zn-Y-Zr alloy;Equal channel angular extrusion (ECAE);Texture;Mechanical property;az31 magnesium alloy;channel angular extrusion;tensile properties;ductility;deformation;enhancement;behavior
张勇
,
王艳
,
刘新才
,
潘晶
,
王红玉
,
潘建峰
,
董友仁
,
龙能兵
,
李天华
中国稀土学报
doi:10.11785/S1000-4343.20160104
采用熔体快淬法制备了Nd10.5Pr2.5Fe80Nb1B6快淬薄带,利用X射线衍射、扫描电镜分析了快淬薄带的显微组织,并用振动样品磁强计测量了其磁性能,分析了磁织构的形成机制.实验结果表明:Nd10.5Pr2.sFe80Nb1B6快淬薄带在快淬速度为5～20 m·s-1时,薄带自由面形成[006]磁织构、峰强比I(006)/I(410)为26.95 ～69.08,快淬薄带破碎小颗粒树脂2T磁场固化样品的约化剩磁比为0.69 ～0.74,内禀矫顽力Hci =375.84～712.48kJ·m-3,最大磁能积(BH)max=105.58 ～ 157.30 kJ·m-3;薄带沿与[006]织构垂直的方向测量的约化剩磁比为0.35～0.47,后者的磁能积只有前者的30％～43％.对于合适成分的钕铁硼合金,当钕铁硼熔体温度接近其熔点,熔体受辊触发以极快速度形成等轴晶、薄带自由面难以择优取向;提高钕铁硼熔体温度,在低快淬速度时在贴辊面孕育出强各向异性纳米晶等轴晶甚至可能形成织构,在等轴晶区之上生长柱状晶区具有[006]磁织构;当快淬速度增加,贴辊面不足以形成磁织构、但具有择优取向,如柱状晶区具有占整个薄带厚度的足够空间,能发展出自由面的磁织构;随着快淬速度的进一步增加,柱状晶区厚度减小,自由面难以形成织构;当快淬速度再增加时,薄带易形成非晶.
关键词:
快淬薄带
,
织构
,
织构形成机制
,
磁性能
,
微观组织
,
稀土永磁材料
Z.Y. Yao
金属学报(英文版)
The hydrogen permeation experiment of MANET II with hot dipping aluminized 1oat-ing was performed in temperature range of 573 to 623K, in gas phase and in liquiaPb-17Li phase. The hydrogen permeation reduction factor (PRF) evaluated in gasphase is 620 at 573K and 260 at 623K, and in liquid Pb-17Li phase is 24 45 at 573Kand 12-30 at 623K. The self-healing of coating is obvious and effective above 673K.The pressure dependence of permeation flux indicates strong surface contribution. Theway of filling hydrogen by continuous flow and/or bubble can increase permeation flux.The result of SEM-EDS shows that the microcrack is on the surface of the wetted part,but not on the not wetted part. The crack is superficial and affects only thin outsidelayer not penetrate aluminized layer. The surface elemental analysis shows that Al/Oatomic ratio changes from 2/3 of not wetted part to about 1 of wetted part. Thedamage of coating surface seems to be related to the interaction of outside layer withliquid Pb-17Li and thermal stress during heating sample.
关键词:
hot dipping
aluminized coating
,
null
刘静
,
赵显久
,
张旭
,
李谦
,
林根文
,
周国治
稀有金属材料与工程
采用熔盐保护熔炼法(SMPMS)成功制备了La2Mg17储氢合金.SEM和EDS研究发现,熔炼时液相在凝固过程中形成微观成分不均匀的非平衡组织.通过PCT性能测试发现,合金在523～623 K时可逆吸放氢量大于4.3%(质量分数, 下同).动力学分析结果表明,合金在473～623 K时具备良好的氢化动力学性能,并且在523 K时出现氢化速率极大值(25 s内吸氢3.2%).丰富的表面裂纹改善了合金的储放氢性能.
关键词:
熔盐保护熔炼法
,
储氢合金
,
La2Mg17
,
性能
材料科学技术（英文）
The creep behavior of Al2O3. SiO2 fiber reinforced ZL109 composites has been investigated at four temperatures ranging from 553 to 623 K. The results show high stress exponent and high apparent creep activation energy. A good correlation between the normalized creep rate and normalized effective stress means that the true stress exponent of minimum creep strain rate of the composite is very close to 5, and the minimum creep strain rate is matrix lattice diffusion controlled. The threshold stress decreases with increasing temperature linearly and disappears at a temperature close to 623 K. It is assumed that the long range internal back stresses generated in creep reduce the load transfer to fibers and the interaction between dislocations and strengthening precipitates decreases at high temperature. At a high temperature where the long range internal back stresses is very close to the applied stress, the threshold stress disappears.
关键词:
metal-matrix composites;solid-solution;aluminum;stress
