MICROSTRUCTURE AND DECOMPOSITION OF RS Al-Fe-Cr-Zr ALLOY

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快速凝固Al—Zr—Ti合金的组织结构

利用透射电子显微镜研究了快速凝固Al-4Zr-2Ti(原子百分比）合金的组织结构。结果表明：快凝合金的显微硬度与其显微组织密切相关,快凝合金急冷态组织显示出单一相-过饱和Al基固溶体,此时显微硬度为220HV,快凝合金经420℃退火4h ,具有立方结构的亚稳相L12-Al3(Zr、Ti)析出,此时显微硬度达到峰值260HV,而经420℃退火20h,则L12相转为为DO23相,同时,显微硬度下降到150Hv。     

Phase relations of Al-4Mg-Sc-Zr quaternarysystem in Al-rich range at 430 ℃

1　INTRODUCTIONNon heat treatableAl Mgalloysarewidelyusedasastructuralmaterialduetotheirstrongweldability ,excel lentcorrosionresistanceandductility .AdditionofminoramountsofScandZrtoAl Mgalloyscangivethealloyahigherstrengthlevelwhiletheductilitystillremainsathigherlevel.Forexample 0 15 35 (Al 4 .2Mg 0 .3Sc 0 .1Zr)alloyscanbetreatedasapotentialuniversalstruc turalmaterialforitsexcellentworkability ,goodweldabil ityandcorrosionresistancetobothliquidoxygenandliq uidhydrogenmedia[13] .Th…     

Mg-Al-Ce-Y基压铸合金的微观结构稳定性和力学性能(英文)

为进一步提高Mg-Al-RE基合金的力学性能,采用高压压铸技术制备Mg-3.0Al-1.8Ce-0.3Y-0.2Mn合金,并研究其微观组织、金属间相的热稳定性和合金的力学性能。结果表明:合金由细小的初生α-Mg枝晶和枝晶间的共晶组成。共晶中存在两种金属间相,即Al11(Ce,Y)3和Al2(Ce,Y),其中Al11(Ce,Y)3是主要增强相。研究还表明,Al11(Ce,Y)3的热稳定性是有条件限制的,在200°C时效800h,它基本保持稳定,而在450°C时效800h,绝大部分的Al11(Ce,Y)3发生相分解,转变为Al2(Ce,Y)。添加Ce和Y后,合金强度在室温和200°C下得到明显的提高。合金性能的提高主要归因于Al11(Ce,Y)3的形成对枝晶间区域的增强作用、晶粒细化的影响以及由Y原子造成的固溶强化。     

Y对Al-Zr合金微观组织与性能的影响

采用电导率、显微硬度、扫描电子显微镜（SEM）和透射电子显微镜（TEM）研究Al-0．30Zr与Al-0．30Zr-0．08Y合金的微观组织与性能。铸态Al-Zr-Y合金中微米尺度初生Al3Y相通过共晶反应在晶内和晶界上同时生成。在Al-Zr-Y合金中,Y明显加速了Al3Zr（Ll2）的析出动力学。由于较大体积Al3（Zr,Y）析出相的生成,Al-Zr-Y合金的电导率明显高于Al-Zr合金的。在Al-Zr-Y合金中观察到了高密度的弥散球状Ll2结构Al3（Zr-Y）析出相。Al-0．30Zr-0．08Y合金具有比Al-0．30Zr合金更强的抗再结晶能力。     

Analysis of precipitation in a Cu-Cr-Zr alloy

Precipites in Cu-0.42%Cr-0.21%Zr alloy were analyzed by using scanning electron microscope （SEM）, energy dispersive X-ray spectroscopy （EDXS） and transmission electron microscope （TEM）. After the solid solution was performed at 980℃ for 2 h, water-quenched and aged at 450℃ for 20 h, the precipite had a bimodal distribution of precipitate size. The coarse precipitates are pure Cr and Cu5Zr, the dispersed fine precipitate is CrCu2（Zr, Mg） and pure Cr ranging from 1 to 50 nm. The coarse phases formed during solidification and were left undissolved during solid solution. The fine precipitates are the hardening precipitates that form due to decomposition of the supersaturated solid solution during aging.     

高速电弧喷涂Fe3Al/WC复合涂层高温冲蚀行为研究

采用自行研制的新型热喷涂Fe3Al/WC复合合金粉芯丝材,成功地用高速电弧喷技术制备出了Fe3Al金属化合物基金属陶瓷复合涂层。对涂层成分、显微组织、涂层相结构和组成进行了分析,结果表明,涂层由以Fe-26Al为主的Fe3Al基体相与约20%的WC、W2C和 a-Al2O3相组成。对比研究了Fe3Al/WC涂层和电站锅炉钢20 g从室温至650 ℃氧化环境条件下不同攻角的高温冲蚀磨损性能,结果表明Fe3Al/WC涂层的高温冲蚀磨损抗力高于20 g钢,650 ℃和30°攻角下的稳态相对冲蚀磨损抗力为20 g钢的3.14倍。温度对Fe3Al/WC涂层的冲蚀行为有较大影响：温度 < 450℃,涂层的冲蚀率变化不大,表现出塑性材料的冲蚀行为;温度 >450 ℃,涂层冲蚀率变化较大,呈现典型的脆性材料冲蚀磨损行为。并对其高温冲蚀磨损机理进行了分析。     

Mg3N2粉末的合成和光致发光性质研究

Mg粉在800℃氨气流中氨化60min，可得到高质量的Mg3N2粉末。XRD分析表明，Mg3N2粉末是体心立方结构，晶格常数α=0．99657nm。SEM分析表明，Mg3N2粉末有多种形貌。PL测试表明，在激发波长为490nm的情况下，氮化镁粉末存在1个位于545nm的绿光发光峰。     

Sintering densification and properties of Al2O3／PSZ （3Y） ceramic composites

1　INTRODUCTIONAl2 O3ceramicsisoneofthewide spreadingma terialsbecauseitholdsgoodfeaturessuchasresistancetohightemperature ,oxidation ,corrosionandabra sion .However ,thebrittlenatureofAl2 O3ceramicshaspromptedustoexploreavarietyofapproachestoenhanceitsfracturetoughness .SinceGarvieetal[1]advancedatheoryin 1975 ,thatistoimprovethefracturetoughnessandflexuralstrengthofZrO2 ce ramicswithmartensitictransformation ,ZrO2 hasbeenreceivingconsiderableattention .AddingMgO ,CaO ,Y2 O3andCeO2…     

添加Nb对LI2型Al3Ti—8Mn基合金的相组成影响

在单相Ll2结构Al67Mn8Ti25金属间化合物中加入少量Nb（0．5at％～4．0at％）,并相应调整Al,Ti含量后,其组织变化显著。在邻近Al－Ti－Nb-8Mn四元系Al3Ti－8Mn区域设计了32种实验合金,随Nb加入量的变化,其结构除单相Ll2外,尚有Ll2＋A12Ti,L12＋DO22,LI2＋LI0,Ll2＋Al2Ti＋DO22和Ll2＋Al2Ti＋Ll0等5种复相或多相组织。Nb含量一定,随Al／Ti比的降低,会导致片状或网纹状Al2Ti组织析出,Nb含量较高时会进一步促使波纹或针片状Ll0TiAl相的形成。初步制定了Al－Ti－Nb-8Mn四元系邻近Al3Ti-8Mn区域的室温相组成图。     

TiAl/Ni基合金反应钎焊接头的微观组织及剪切强度(英文)

以Ti为中间层,对TiAl基金属间化合物与Ni基高温合金进行反应钎焊连接,研究反应钎焊接头的界面微观结构及剪切强度。通过实验发现,熔融中间层与两侧母材反应剧烈,生成连续的界面反应层。典型的界面微观结构为GH99/(Ni,Cr)ss(γ)/TiNi(β2)+TiNi2Al(τ4)+Ti2Ni(δ)/δ+Ti3Al(α2)+Al3NiTi2(τ3)/α2+τ3/TiAl。当钎焊温度为1000°C,保温时间10min时,所得接头的剪切强度最高为258MPa。进一步升高钎焊温度或延长保温时间,会引起钎缝组织中组成相粗化和脆性金属间化合物层的生成,从而导致接头剪切强度的降低。     

Mechanical alloying characteristic and thermal stability of Al_(78)Fe_(20)Zr_2 amorphous powders

The powders of pure Al, Fe, and Zr for preparing Al78Fe20Zr2 were subject to a high-energy planetary ball milling.The microstructure evolution of the mixtures at the different intervals of milling was characterized by X-ray diffraction(XRD), transmission electron microscopy(TEM) and differential scanning calorimetry(DSC).It was found that a nearly complete amorphization could be achieved in the mixtures after ball milling for 23 h.Further ball milling led to the crystallization of the amorphous powders.A long time ball milling, e.g., 160 h, led to a complete crystallization of the amorphous powders and the formation of Al3Zr and Al13Fe4.The crystallization products caused by ball milling are almost the same as that produced by isothermal annealing of the amorphous powders in vacuum at 800 K for 1 h.     

A study on the microstructure of D023 Al3Zr and L12 (Al+12.5 at.% Cu)3Zr intermetallic compounds synthesized by PBM and SPS

The spark plasma sintering (SPS) of L1₂ phase Al₃Zr and (Al+12.5 at.% Cu)₃Zr powders with a nanocrystalline microstructure has been studied to produce bulk intermetallic compounds which maintain metastable structures such as L1₂ structure and nanocrystalline microstructure. The powders were prepared by 10 h planetary ball milling (PBM). Full-density L1₂ (Al+12.5 at.% Cu)₃Zr intermetallic compounds were obtained by SPS for 0 min at 600 °C. The specimens prepared with a longer holding time than 0 min at 600 °C or a higher temperature than 600 °C had local melting areas where micro-cracks were found. They had a lower relative density than the specimen SPS sintered at 600 °C for 0 min. The smallest grain size was obtained in the specimen prepared at 600 °C for 0 min, which was 20–30 nm as confirmed by TEM observation. This was the smallest grain size ever reported in the trialuminide specimens processed by various consolidations of nanocrystalline powders. Accordingly, the highest micro-hardness, 989.5 H_V, was obtained in the specimen and this value was three times higher than those of the specimens with micro grain sizes. Full density Al₃Zr intermetallics were prepared by SPS at 700 °C for 0 min. However, their crystal structure was D0₂₃ and micro-hardness was 778.1 H_V. By using SPS, the sintering time can be reduced within 10 min. It was thought that the decrease in sintering temperature for the PBM Al₃Zr and (Al+12.5 at.% Cu)₃Zr powders by 200–300 °C compared with the conventional sintering temperature resulted in the refinement of microstructure to the nano-size level.     

造渣剂对激光熔覆制备铁铝金属间化合物的影响

通过激光熔覆添加和不添加造渣剂的铁铝混合粉末在Q235钢基体上制备出铁铝金属间化合物熔覆层,研究了造渣剂对熔覆层的组织和性能的影响.结果表明,向熔覆粉末中添加造渣剂不仅可以显著细化熔覆层晶粒,还可以影响熔覆层的物相结构.当熔覆粉末中Fe,Al原子比例接近3:1时,所制备的熔覆层均由B2结构的FeAl相和DO3结构的Fe₃Al组成,但添加造渣剂后所得熔覆层中含有较多DO3结构的Fe₃Al.结果表明,添加造渣剂的熔覆层有着更高的显微硬度、更好的抗氧化性能和耐蚀性能.     

Au-Pd-M(M=Mo,Y,Zr)合金相结构稳定性的模拟计算研究

采用基于密度泛函理论的第一性原理赝势平面波方法,计算了Au-Pd-M(M=Mo,Y,Zr)合金中可能存在的各种合金相的结合能与生成焓,讨论了合金相的稳定性。结果表明,Au-Pd-M固溶体中,添加质量比为1%的Mo元素形成的固溶体,其结合能与生成焓是Au-Pd-M(M=Mo,Y,Zr)系固溶体中最低的。Au-Pd-Y系合金中最为稳定的中间相是YPd3。Au-Pd-Zr系合金中,形成PdZr2的反应最容易发生,生成的合金相也是最为稳定的,其次是AuZr3。     

多弧离子镀Ti-Al-Zr-Cr-N系双层膜的结构与力学性能

采用多弧离子镀技术和Ti-Al-Zr合金靶及Cr单质靶,在WC-8%Co硬质合金基体上制备了(Ti,Al,Zr)N/(Ti,Al,Zr,Cr)N和Cr N/(Ti,Al,Zr,Cr)N 2种四元双层氮化物膜。利用扫描电镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)分析2种双层膜的微观组织、成分和结构;利用划痕仪和显微硬度计对比2种双层膜的力学性能。结果表明,获得的2种双层膜均具有B1-NaCl型的TiN面心立方结构;双层膜的组织均是典型的柱状晶结构;沉积偏压为–50~–200 V时,双层膜的力学性能均优于(Ti,Al,Zr,Cr)N单层膜,并与Ti-Al-Zr-Cr-N系梯度膜的力学性能相当,同时(Ti,Al,Zr)N/(Ti,Al,Zr,Cr)N双层膜可获得更高的硬度(HV_(0.01)最高值为41 GPa),而CrN/(Ti,Al,Zr,Cr)N双层膜可获得更强的膜层与基体间结合力(所有值均大于200 N)。     

High spatial resolution PEELS characterization of FeAl nanograins prepared by mechanical alloying

We investigate the nanograin “chemical” structure in a nanostructured material of possible industrial application (Fe–Al system) prepared by conventional mechanical alloying via ball milling in argon atmosphere. We restrict ourselves to the structural and nanochemical behaviour of ball-milled nanocrystalline Fe–Al powders with atomic composition Fe₃Al, corresponding to a well-known intermetallic compound of the Fe–Al system. Scanning transmission electron microscopy (STEM) equipped with a parallel detection electron energy loss spectrometer (PEELS) has provided an insight on the “chemical” structure of both nanograins and their surface at a spatial resolution of better than 1 nm. The energy loss near edge structure of the Al L loss reveals that the Al coordination is similar to a B2 compound and the oxidation of the powder during processing may play a significant role in the stabilization of the intermetallic phases. Conventional transmission electron microscopy (TEM) was used for the structural characterization of the material after the ball milling; powder X-ray diffraction (XRD) aided the investigation.     

RELATIONSHIP BETWEEN CREEP PROPERTIES AND STRUCTURE OF STEEL 20Cr11MoVNbNB

Studies were made of the creep properties and structure change of steet 20Cr11MoVNbNB at550-650℃.It is found that at 550℃ when creep stress>180 MPa there exists linear rela-tion with two different slopes β_1 and β-2 between transitional creep strain ε_β and creeptime t~(1/3),and β_1(in initiol period)>β_2(in later period).The Creep rate of stable stage at550℃ can be expressed by =Aσ exp(-Q_ /RT),where,n=4.7.A exp(-Q_ /RT)=5.37×10~(-16).Apparent creep activation energy Q_ =430 kJ/mol at 550-650℃,which ismuch higher than the self-diffusion activation energy of atoms for matrix Fe.In creepprocess,as the creep stress and time increase,the total weight of precipitated phases and rela-tive weight of Cr,Mo and V increase,but those of Fe and Nb decrease in precipitated phases,     

退火温度对0Cr25Al5热轧态盘条钢组织及性能的影响

采用显微组织分析和分子动力学模拟等方法研究了退火温度对0Cr25Al5热轧态盘条钢组织及性能的影响。结果发现,晶粒尺寸随温度的升高逐渐增加并趋于稳定,但是断后伸长率和断面收缩率在950 ℃突然大幅度下降。试样组织形貌在800 ℃和950 ℃退火温度下的OM及SEM分析结果未见明显差别。于是使用分子动力学模拟对0Cr25Al5钢三元体系的自由能进行了计算,发现随着B2结构的FeAl或者DO3结构的Fe₃Al有序相尺寸的增大,系统自由能先减小后增大,其最小值随着退火温度的升高向有序相颗粒尺寸减小的方向移动。在1273 K的高温下仍然会保留60 nm左右大小的有序相颗粒。因此,推测0Cr25Al5钢在大于950 ℃的温度范围内韧性下降是由于60 nm左右的B2结构的FeAl或者DO3结构的Fe₃Al有序相造成,与晶粒尺寸无关。因此,针对该钢种应进行低温退火促使基体组织回复以消除缺陷,从而抑制Fe、Al等基体原子的扩散。     

Solid-state synthesis and electrochemical properties of SmVO4 cathode materials for low temperature SOFCs

A new cathode material fabricated by solid state reaction method was reported. The SmVO4 powder was obtained by firing the mixture of Sm2O3 and V2O5 powders in the temperature range of 700-1200 ℃. Its structure was identified by X-ray diffraction method and the electrochemical properties of SmVO4 as cathodes for solid oxide fuel cells (SOFCs) were investigated in single unit cell at the temperature ranged from 450-550 ℃. The results of the single fuel cell unit show that the maximum current densities are 641, 797, 688 mA·cm-2 and the maximum power output are 165, 268, 303 mW·cm-2 and the open circuit voltage are 1.04,0.96,0.92Vat 450, 500 and 550 ℃, respectively.