B2FeAl合金晶格动力学的嵌入原子模型计算

应用改进分析型EAM模型,系统计算了B2FeAl合金的晶格动力学性能,包括晶格常数、形成热、弹性常数、声子谱、态密度、比热、德拜温度和热膨胀系数等,并将计算结果与已有实验数据及其他理论计算结果进行了比较。总的来说,仅从合金组成元素的性质出发,不涉及合金本身性质而构建的改进分析型EAM模型成功地描述了B2FeAl合金原子间的相互作用,所得计算结果与实验值符合很好。     

D03结构Fe3Al合金晶格动力学的嵌入原子模型计算

应用改进分析型嵌入原子模型，系统地计算了D03结构Fe3Al合金的晶格动力学性能，包括晶格常数、形成热、弹性常数、声子谱、态密度、摩尔定容热容、德拜温度和热膨胀系数等，并将计算结果与已有实验数据和其他理论计算结果进行了比较。计算所得声子谱相对于其他理论计算结果而言，与实验值的符合程度更好；计算的热膨胀量在低温区与实验结果基本一致，而在高温区明显偏低于实验结果。     

CeO2的晶格动力学性质和热输运性质的第一性原理计算

采用基于密度泛函理论的有限位移法和玻尔兹曼方程,计算了CeO2的晶格动力学性质、热力学性质和热输运性质,计算结果和实验结果基本符合.通过分析CeO2所有声子模式的振动频率、Grüneisen系数和散射率,揭示了光学声子对增强晶格振动的非简谐性和声子散射率所起的重要作用.此外,还计算了不同自由程的声子模式对热导率的贡献,...     

Pt-Rh二元合金系表面偏聚的分析型EAM模型计算

应用分析型EAM多体势和Monte Carlo模拟方法研究了Pt-Rh合金系的表面偏聚情况．模拟结果显示,不同Pt含量的合金以及不同的表面,最外层都富集Pt原子,次外层富集Rh原子,剖面成分呈振荡分布．(111)面和(100)面的成分偏聚量差别较大：(111)面的Pt原子偏聚量较(100)面小得多,且前者只有最表面3层原子发生偏聚,而后者的成分偏聚影响表面至少10层．模拟结果与已有理论和实验结果符合得很好．     

过渡金属元素在NbCr2 Laves相中晶格占位的第一性原理计算

采用全势线性缀加平面波方法和广义梯度近似对过渡金属元素V,Ti和W在C15结构的NbCr2 Laves相中的晶格占位进行了研究．计算结果表明,过渡族元素V,Ti和W在NbCr2中的晶格占位不尽相同．V优先占据NbCr2中Cr的晶格位置,W占据Cr的晶格位置的倾向很弱,而Ti优先占据Nb的晶格位置;生成热计算结果表明,当V占据NbCr2中Cr的晶格位置和Ti占据Nb的晶格位置时,可以使NbCr2Laves相更加稳定．结合电子结构计算结果对上述占位特性进行了讨论．     

冷金属过渡条件下镁-钢的润湿动力学特征及界面结构

研究了冷金属过渡条件下AZ61镁合金分别在Q235钢板和镀锌钢板表面润湿的动力学特征,同时利用扫描电镜观察和能谱分析考察了界面微观结构.结果表明,镁合金在钢表面的最终润湿性随送丝速度的增加而变好,其中镀锌层蒸发带走热量进而相对降低了界面上的热输入,导致界面反应变弱,润湿性变差;在镁-镀锌钢界面上形成了Al-Fe金属间化合物层和脆性的Mg-Zn共晶层,导致界面结合较弱;在不同送丝速度下,镁在裸钢表面的熔滴过渡更为有效,镁-镀锌钢中镀锌层对润湿的动力学特征影响较小,两者的动力学特征都与温度依赖的毛细力相关.     

泡沫金属吸声系数的计算模型

多孔金属材料应用于吸声方面有很多优点,且用于计算多孔材料吸声性能的理论模型也有很多。利用多孔材料吸声Johnson-Allard模型来计算泡沫金属铝的吸声系数,结果表明在声波频率低于3500Hz时模型与实验数据吻合良好,但当声波频率高于3500Hz时模型与实验数据偏差较大。为了拓宽模型对声波频率的适用范围,引入了e指数修正因子对模型进行改进,其中包含2个相关子因子。修正结果显示,改进后的模型计算值与实验数据在实验频率范围内均符合良好。     

短路过渡CO2气体保护焊结合型热源模型的研究

为准确地模拟短路过渡CO2气体保护焊焊接温度场分布特点,根据试验结果推导出了适用于短路过渡的熔滴热热源模型,建立了结合电弧热和熔滴热共同作用的结合型热源模型。并将结合型热源模拟结果、高斯热源模拟结果与实际温度场的测量试验结果进行了比较分析。结果表明,与高斯热源模型相比,使用结合型热源模型更能准确地模拟短路过渡CO2气体保护焊焊接温度场的分布特点。     

第四过渡族金属基准晶形成规律的抛物线模型

利用键参数函数和尺寸因数对第四长周期过渡族金属元素基准晶形成规律进行研究。发现可以用抛物线y=a-bx^2将准晶形成区与准晶不能形成区区分开,准晶形成区的准确率达到了93．12％。同时,发现抛物线的参数a,b可以由基体元素的相关参数确定,即a∝E,b∝EμR0^3.     

Structural defects in L 10 FePt by modified analytic embedded-atom method

The structural defects of L10 FePt are investigated by the molecular dynamics （MD） with a modified analytic embedded-atom method （MAEAM）. The L10 ordered structure of FePt is relaxed from a trial fcc structure. The defect formation energies are calculated. The vacancy formation energies of Fe and Pt are 1.89 eV and 2.11 eV respectively. The antisite formation energy of Fe in Pt sublattice is 0.35 eV. The antisite formation energy of Pt in Fe sublattice is 0.09 eV. The tendency of the vacancy formation energy is in agreement with other calculation. The point defect structure types are Pt antisite in dch-Pt side and Fe antisite in rich-Fe side.     

Simulation study on transition mechanisms of microstructures during forming processes of amorphous metals

1　ＩＮＴＲＯＤＵＣＴＩＯＮＩｔｉｓｗｅｌｌｋｎｏｗｎｔｈａｔａｍｏｒｐｈｏｕｓｍｅｔａｌｓａｎｄａｌ ｌｏｙｓｐｒｅｐａｒｅｄｂｙｍｅｌｔｑｕｅｎｃｈｉｎｇ ｐｏｓｓｅｓｓｖａｒｉｏｕｓｅｘ ｃｅｌｌｅｎｔｐｒｏｐｅｒｔｉｅｓ ,ｗｈｉｃｈａｒｅｍａｉｎｌｙｄｅｔｅｒｍｉｎｅｄｂｙｔｈｅｉｒｓｐｅｃｉａｌｍｉｃｒｏｓｔｒｕｃｔｕｒｅｓ .Ｆｏｒｕｎｄｅｒｓｔａｎｄｉｎｇｔｈｅｒｅｌａｔｉｏｎｓｈｉｐｂｅｔｗｅｅｎｔｈｅｓｔｒｕｃｔｕｒｅｓａｎｄｐｒｏｐｅｒｔｉｅｓ ,ｉｔｉｓｖｅｒｙｉｍｐｏｒｔａｎｔｂ…     

Rules for maximum solid solubility of transition metals in Ti,Zr and Hf solvents

1　INTRODUCTIONThemaximumsolidsolubility (Cmax)ofasolutemetalinasolventmetalrestrictstheadjustablerangeofcomponentsinanalloy .Itisveryimportantforstudyingnewalloysornewheattreatmentmethods .Vanadium basedsolidsolutionalloysareveryattrac tivehydrogenstoragematerials .Thistriggeredscien tiststoinvestigatesolidsolutionalloysforhydrogenstorage .TisubgroupbasedalloysadjacenttoV basedonesinPeriodicTableareassociatedwithsolidsolu tionhydrogen storagematerialsandthiswillbein structivefordevelop…     

Density of liquid NiCoAlCr quartemary alloys measured by modified sessile drop method

The densities of liquid NiCoAlCr quaternary alloys with a fixed molar ratio of Ni to Co to Al （x（Ni）：x（Co）：x（Al）≈ 73：12：15） which is close to the average value of the commercial Ni-based superalloys TMS75, INCO713, CM247LC and CMSX-4, and the mass fraction of chromium changes from 0 to 9% were measured by a modified sessile drop method. It is found that with increasing temperature and chromium concentration in the alloys, the densities of the liquid NiCoAICr quaternary alloys decrease, whereas the molar volume of the liquid NiCoAICr quaternary alloys increases. And the liquid densities of NiCoAICr quaternary alloys calculated from the partial molar volumes of nickel, cobalt, aluminum and chromium in the corresponding Ni-bases binary alloys are in good agreement with the experimental ones, i.e. within the error tolerance range the densities of the liquid Ni-based multi-component alloys can be predicted from the partial volumes of elements in Ni-based binary alloys in liquid state. The molar volume of liquid NiCoAICr binary alloy shows a negative deviation from the ideal linear mixing and the deviation changes small with the increase of chromium concentration at the same temperature.     

Phase transition of Al-Fe-V-Si heat-resistant alloy by spray deposition

1　INTRODUCTIONAtpresent ,rapidlysolidifiedAl Fe V Siheat resistantalloyisgenerallypreparedby planarflowcasting ,andisonlyveryrarelypreparedbysprayingdeposition .Thecoolingrateofsprayingdepositionisslowerthanthatofplanarflowcasting ,itmusthasgivenimportanteffecttothealloys phaseconstitutesandphasetransition[112 ] .Thispaperaimsatreportingtheresearchonfor mationandtransitionofheat resistantphasesinAl Fe V Si (closetoAA80 0 9)alloy .2　PHASETRANSITIONINEQUILIBRIUMCON DITIO…     

Synthesis and properties of nanocrystalline nonferrous metals prepared by flow-levitation-molding method

Nanocrystalline nonferrous metals （Cu, A1, and Ag） were synthesized by flow-levitation-molding method. The microstructure of the as-prepared nanocrystalline metals was characterized by XRD and FESEM. The microhardness and electrical resistivity were tested by the HMV-2 type Microhardness Tester and 6157 type Electrometer, respectively. The synthesis process was also studied. The results show that the spheriform particles in nanocrystalline metals have average grain size of 20-30 nm. The relative density of nanocrystalline Cu, A1, and Ag are 95.1%, 98.1% and 98.3%, respectively. The microhardness of nanocrystalline Cu, Al and Ag are 2.01, 2.11 and 1.26 GPa respectively, which are larger than those of their coarse-grained counterparts by the factor of 4.5, 14, and 2.5, respectively. The electrical resistivity of nanocrystalline Cu at room temperature is 1.5× 10^-7Ω.m, which is higher than coarse-grained Cu by a factor of 7.5. The pressure is the predominant factor influencing the density of the as-prepared nanocrystalline nonferrous metals.