Ti-Mo合金的结构及吸放氢性能研究

利用X衍射等技术对纯钛和5种成分（Ti-5,10,20,30和40Mo，质量分数，％）Ti-Mo二元合金吸氢前后的相组成、晶格常数变化和吸氢特性进行了研究，结果显示：5种成分Ti-Mo合金饱和吸氢后均形成了较单一的面心立方δ相氢化物（Ti(1-x)MoxH1.97）。δ相晶格常数随Mo含量增加先呈增加趋势，约10％Mo含量处达最大值，Mo含量继续增加则呈降低趋势，而体心立方β相TiMo合金的晶格常数随Mo含量的增加呈单一的减小趋势。随Mo含量的增加，氢化物的室温平衡压逐渐增加，但含Mo量不大于10％时，增加量并不明显，结合第一原理计算的相应结果，对上述现象进行讨论。     

钽低温离子渗氮工艺参数对渗氮层物相的影响

利用组合的二次回归正交实验设计方案 ,对钽低温离子渗氮条件下 ,表面物相及固溶体中氮的含量随渗氮温度、气氛总压力和氢氮摩尔比的变化进行了系统研究。发现表面渗氮层由化合物Ta6N2 .57、超晶格TaN0 .1和固溶体相组成。氮在钽中的固溶度随气压、温度和氢摩尔分数的增加而增加 ,化合物和超晶格相含量随温度增加而增加 ,同时化合物相随氢摩尔分数增加有一个极大值 ,该极大值随温度增加而下降。     

Re及温度对单晶镍基合金晶格常数及错配度的影响

通过对不同状态及不同Re含量单晶镍基合金进行高、低温X射线衍射谱线测定及组织形貌观察,研究Re含量及温度对单晶镍基合金中γ、γ′两相晶格常数及错配度的影响。结果表明:铸态合金中γ、γ′两相有较大的晶格常数及错配度;经完全热处理后,立方γ′相以共格方式嵌镶在γ基体中,合金中两相的晶格常数及错配度略有减小;长期时效使γ′相粗化后,两相之间出现界面位错,使合金中两相的晶格常数及错配度绝对值增加。随Re含量增加,合金中γ、γ′两相在室温的晶格常数增大,错配度的绝对值减小。与γ′相相比,γ基体相有较大的膨胀系数,因此,随温度提高,合金中两相晶格错配度的绝对值增大。     

V元素含量对钛合金中氢储备能力的影响

自制X值不同的Ti_(0.7)Zr_(0.3)(Cr_(1-x)V_x)_2合金,采用XRD和SEM对其成分及组织进行分析,同时利用Sieverts仪器测量结合贮氢量和贮氢密度数学计算模型,绘制合金的吸氢活化性能和压力-浓度-温度曲线。结果表明,Ti_(0.7)Zr_(0.3)(Cr_(1-x)V_x)_2合金为复杂的多相组织,由Laves相和不同晶格常数的bcc固溶相组成;合金具有较好的活化性能和抗氧化性能;随着V元素含量的增加,合金的贮氢含量增加,放氢含量减小。     

LaFe11.9-xCoxSi1.1B0.2(x=0.7,0.8,0.9)合金的磁热效应

使用电弧熔炼法制备了LaFe11.9-xCoxSi1.1B0.2(x=0.7,0.8,0.9)系列合金.XRD分析表明该系列合金除微量的α-Fe相外,均由NaZn13型立方结构单相组成.晶格常数随着Co含量的增加而增大,分别为1.1487,1.1496,1.1498nm;磁性测量表明该系列合金的Curie温度在室温附近,并且也随着Co含量的增加而分别增加到270,290,300 K.在外场变化△B=1.5 T时,该系列合金的最大磁熵变均为金属Gd的2倍左右,相对制冷能力与金属Gd基本相同.     

Ni、Cu含量对Mn-Ni-Cu-O系NTC热敏材料电性能的影响

研究了Ni、Cu含量对Mn系NTC热敏陶瓷材料电学性能的影响。研究结果表明,随着Ni含量的增加,Mn~(3+)/Mn~(4+)离子对浓度先增加后减少,室温电阻率ρ25呈U型变化;材料晶格常数随着Ni含量的增加而增大,导致电子跳跃距离增大、迁移激活能增加,材料常数B值增大。随着Cu含量的增加,材料室温电阻率ρ25和材料常数B值都减小,同时由于Cu具有促进烧结的作用,材料的烧结温度随着Cu含量的增加而下降,而过高的烧结温度会使得材料的室温电阻率ρ25增加。     

Y2Fe17—xMnx的结构和磁性

Ｘ射线衍射证实了Ｙ２Ｆｅ１７－ｘＭｎｘ的结构与Ｙ２Ｆｅ１７相同Ｙ２Ｆｅ１７－ｘＭｎｘ化合物晶格常数，居里温度，饱和磁化强度和研究结果表明：晶格常数并非随Ｍｎ含量的增加而连续增大，而是在ｘ＝２．０处出现一最小值。     

V-Fe二元合金的吸放氢特性

Fe的添加,提高了金属钒的活化性能和放氢平台压力,降低吸放氢容量.Fe含量<1%(原子分数,下同),对二氢化物并无明显影响,Fe含量>1%,二氢化物平台压明显升高,容量明显下降,氢化物的生成焓明显降低;Fe的添加对一氢化物并无明显的影响.随着Fe含量的增加,合金的晶格常数和晶胞体积呈线性趋势降低.     

Mg_(1-x)Zn_x合金的弹性和热力学性质的第一性原理研究

基于密度泛函理论及密度泛函微扰理论为基础的第一性原理计算,采用虚晶近似的方法,研究了具有hcp结构且Zn含量在2%(原子分数)范围内的8种Mg_(1-x)Zn_x合金的晶格常数、弹性性质和热力学性质。通过优化结构计算Mg和Zn含量不同的Mg_(1-x)Zn_x合金弹性常数,对Young's模量、Poisson比、弹性各向异性等进行了详细分析,给出了Mg及Mg_(1-x)Zn_x合金的晶格振动Helmholtz自由能、内能、熵和定容热容等随温度变化情况。结果表明,随着Zn含量增加晶格常数a和c均相应减小,弹性常数、自由能和内能增大,熵及定容热容减小;另一方面,随温度升高,Zn含量对自由能和熵的影响程度增大,而对定容热容的影响程度先增大后减小。Mg_(1-x)Zn_x合金中Zn含量的增加有利于提高材料硬度和韧性,但也增大了材料的各向异性。     

铸态和快淬态Mm(NiCoMnAl)5Bx(=0～0.2)贮氢合金的相结构与电化学性能

用铸造及快淬工艺制备了低钴AB5型Mm(NiCoMnAl)5BxBx=0～0.2)贮氢合金,测试了合金的微观结构及电化学性能,研究了B含量及快淬工艺的变化对合金晶格常数、热力学参数、微观结构及电化学性能的影响.结果表明:合金的晶格常数、晶胞体积及标准生成焓均随B含量的增加而增大;在一定的淬速范围内,快淬处理可以提高合金的放电容量,但淬速超过某一临界淬速时,快淬合金的容量低于铸态合金;合金的循环寿命随淬速的增加而单调增加.     

EFFECT OF HYDROGEN ON DEBYE TEMPERATURE AND LATTICE PARAMETER OF Ti-30Mo ALLOY

The variations of Debye temperature and lattice parameter of Ti-30Mo alloy with differenthydrogen contents were measured by means of X-ray diffraction.It was found that as thehydrogen content increases,the Debye temperature decreases,but the lattice parameter of theaUoy increases.The above results experimentally support the decohesion theory that the in-crease of hydrogen in metals will weaken the cohesive force between the atoms and make met-als brittle.     

INFLUENCE OF Ge ON THE ANTIFERROMAGNETIC TRANSITION AND γ → ε MARTENSITIC TRANSFORMATION OF Fe-24Mn ALLOYS

The aims of the work were to study the effect of Ge (0-6wt. %) on the paramagnetic-antiferromagnetic transition and martensitic transformation of Fe-Mn alloy using the susceptibility, micro structure examination, X-ray diffraction (XRD) and latticeparameter measurement. Ge lowers the Néel temperature, TN, and enhances the magnetic susceptibility x, changing the Pauli paramagnetism above TN to paramagnetismstate obeying the Curie Weiss law, which is essentially similar to that of γ-Fe-Mnalloys containing Al or Si; Ge depresses γ-ε martensitic transformation, whichattribute to Ge increasing the stacking fault energy; Moreover, Ge increases the lattice parameter of γ phase, and low content Ge increases the lattice parameter of γphase more than that of high Ge content. Comparing Ge(4s24p2) with Si(3s23p2) and Al(3s2 3p1), which have the same outer-shell of electron structures, we found that their effects on the martensitic transformation of Fe-Mn alloy are completely different. The result suggests the     

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。     

Au－Cu合金的微观结构和性质

依据建立在统计热力学和金属电子理论基础上的合金综合理论──合金相的特征晶体理论，对Ａｕ－Ｃｕ合金的微观结构和性质进行了研究．确定了特征性质（势能和体积）的相互作用方程，各特征原子的电子结构及演变特点；计算了合金的形成热、混合Ｇｉｂｂｓ自由能和晶格常数随成分的变化．这些性质的理论值和实验值符合很好。     

氮、氧杂质对V40Ti26Cr26Fe8 合金化学成分、微观组织和贮氢性能的影响

采用X射线衍射、扫描电子显微镜、光学显微镜和压力-成分-温度（PCT）等手段研究了氮、氧杂质对V-Ti-Cr-Fe合金微区化学成分、微观结构和贮氢能力的协同影响。V₄₀Ti₂₆Cr₂₆Fe₈合金的贮氢能力随着氮、氧杂质含量的增加而明显降低,主要作用机理如下：氧在V基合金中的溶解抑制了二氢化物相的形成,导致氢容量的降低（主要效应）,而氮与钛结合形成了新的富氮钛相,导致了主相成分的变化和晶格参数的减小（二次效应）。     

FCC，BCC和HCP结构两相合金中置换型元素理想分配比和分配系数及晶胞比的确定

从原子分数及晶胞原子数的角度导出FCC，BCC及HCP结构两相合金中元素分配比和分配系数．通过对上述3种典型合金相结构的9种组合计算发现，任意两相之间存在一致的元素分配比和元素分配系数；两相各自的晶胞数及其比值与合金及其组成相成分之间存在特征关系：采用合金元素分配系数法算得的合金相成分与其观测值或采用统计回归法算得的相应值吻合程度较好．     

Debye temperature, self-diffusion and elastic constants of intermetallic compounds

The Debye temperature of a material is a suitable parameter to describe phenomena of solid-state physics which are associated with lattice vibrations. It basically depends on the elastic constants. In recent work a simple method was put forward that allows one to derive precise Debye temperatures of crystals with cubic, hexagonal and tetragonal symmetry from the elastic constants. The type of chemical binding does not play any role. It is one aim of the present work to apply this method to various intermetallic compounds, i.e. to critically analyse published Debye temperatures and to calculate hitherto unknown values. It is a further aim to show that the activation energy of self-diffusion is also connected with the elastic constants by a simple law at least for the cubic B2 and L1₂ intermetallics, as it was recently found for face-centred cubic metals. Some consequences for high-temperature plasticity are discussed.     

Theoretical Investigation of Lattice Thermal Vibration Effects on Phase Equilibria Within Cluster Variation Method

First-principles phase equilibria calculations often overestimate an order-disorder transition temperature due to the neglect of local lattice distortion effects originated from the mixture of elements of different atomic sizes. The lattice vibration effects introduced through the Debye-Grüneisen theory within the quasi-harmonic approximation has proven to be quite effective in circumventing the inconveniences. With the preferential enhancement of the stability of a disordered phase by introducing the lattice vibration effects, the transition temperature was reduced considerably. In order to gain further insight into the lattice vibration effects, a systematic investigation of the vibrational free energy of the Debye-Grüneisen theory is attempted on the two-dimensional square lattice which constitutes a prototype study prior to the first-principles calculations on realistic alloy systems. A particular focus of the present study is placed on the effects of Debye temperatures of constituent phases on the transition temperature. It is shown that lattice softening by lattice vibration stabilizes the disordered phase by reducing the energy expended to accommodate atoms of different sizes, which is manifested by the reduction of the curvature of the atomic potentials. It is, however, predicted that an opposite case can also take place. When the Debye temperature of an ordered phase is lower than that of the pure metals, the ordered phase is more stabilized and the inclusion of the lattice vibration effects in the free energy raises the resultant transition temperature.     

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。