固溶处理对铸态Mg-4Al-2Si合金组织和性能的影响

研究了固溶处理对铸态Mg-4Al-2Si(AS42)合金组织和性能的影响.结果表明,铸态与热处理态合金均由α-Mg基体、β-Mg17Al12相和Mg2Si相3部分组成.固溶处理使合金中的β-Mg17Al12相发生部分溶解,汉字状Mg2Si相颗粒出现球状化,合金的力学性能有较大幅度的提高.铸态与热处理态合金的断裂形式均为准解理脆性断裂.     

氟锆酸钾盐混合物对Mg-3Y-3.5Sm-2Zn合金组织和性能的影响

制备了三种氟锆酸钾(K2ZrF6)盐混合物(M),分别在三个温度下将三种盐混合物加入到铸态Mg-3Y-3.5Sm-2Zn合金中。通过差热分析(DSC),X射线衍射(XRD),光学显微镜(OM),扫描电子显微镜(SEM),能量色散谱(EDS)和拉伸试验研究了合金的显微组织和力学性能,讨论了K2ZrF6盐混合物在合金中的晶粒细化机理。结果表明,铸态Mg-3Y-3.5Sm-2Zn合金由α-Mg,Mg12(Y,Sm)Zn 和 (Mg,Zn)3(Y,Sm)三种相组成。SEM和XRD检测发现,添加K2ZrF6盐混合物不会在合金中产生新的相。在780°C下加入M3盐(60wt% K2ZrF6-20wt% NaCl-20wt% KCl)时,合金的晶粒细化效果最佳。通过在780℃下加入三种盐,铸态Mg-3Y-3.5Sm-2Zn合金的力学性能得到提高,由M3盐细化后的合金具有最佳的力学性能。K2ZrF6盐混合物可细化铸态Mg-3Y-3.5Sm-2Zn合金,这是由于Mg和K2ZrF6之间还原反应得到的细Zr质点和富锆区在合金中起到的晶粒细化作用。     

热处理对Mg-6Nd-2Al合金显微组织和力学性能的影响

采用光学显微镜、扫描电镜、透射电镜和万能拉伸试验机等研究了铸态、固溶态和时效态Mg-6Nd-2Al合金的显微组织及力学性能。结果表明,铸态合金的组织由α-Mg基体、不规则条状Mg_(12)Nd相、针片状Al_(11)Nd_3相和颗粒状Al_2Nd相组成。经固溶处理后,合金中第二相的数量明显减少,晶界处的Mg_(12)Nd相溶解,针片状Al_(11)Nd_3相出现断裂和球化现象,转变为Al_2Nd相。经时效处理后,合金内部有大量纳米尺度的β″相析出,力学性能明显提高;与铸态合金相比,时效态合金的抗拉强度由141.5 MPa提升至189.5 MPa,屈服强度由104.4 MPa提升至121.9 MPa,该合金具有较好的热处理强化效果。     

2D70铝合金铸态及均匀化态的显微组织演变

采用金相显微镜(OM)、扫描电镜(SEM)、能谱分析(EDS)、X射线衍射物相分析(XRD)、差示量热法(DSC)等方法,研究了2D70铝合金铸态组织的相组成,对比观察了该合金铸态、常规均匀化态、高温均匀化态的显微组织.研究结果表明,该合金铸态组织由Al2CuMg、Al2Cu、Al9FeNi、Al7Cu2Fe、Al7Cu4Ni等相组成.DSC和XRD分析表明,单级均匀化处理后可使Al2CuMg基本熔入合金基体中,然而合金中仍存在部分高熔点共晶相,但其起始溶解温度已提高,这为双级均匀化创造了条件.合金铸锭经双级均匀化后高熔点的共晶相回溶的更充分.铸锭中的Al9FeNi、Al7Cu2Fe、Al7Cu4Ni等相在均匀化处理过程中基本不变.     

固溶处理对(Mg_(96.5)Zn_(1.5)Er_2)_(99.82)Zr_(0.18)合金组织和硬度的影响

采用光学金相显微镜、SEM、EBSD、DTA分析以及硬度等试验手段,研究了固溶处理对(Mg_(96.5)Zn_(1.5)Er_2)_(99.82)Zr_(0.18)合金组织和力学性能的影响。结果表明,合金铸态及热处理态的微观组织均由α-Mg、X相和(Mg,Zn)_xEr相组成,对铸态的(Mg_(96.5)Zn_(1.5)Er_2)_(99.82)Zr_(0.18)合金进行固溶处理后,(Mg,Zn)_xEr相转变成弥散分布的X相。晶粒尺寸随着固溶时间和温度的增加而变大。与铸态相比,合金热处理后的硬度没有发生太大变化。     

Sb对Mg-5Sn-2Al-1.5Zn-0.8Si合金组织和性能的影响

在熔炼时以单质形式加入Sb元素,研究了不同含量的Sb对Mg-5Sn-2Al-1.5Zn-0.8Si合金显微组织和力学性能的影响。结果表明,Sb能与Mg基体结合生成Mg3Sb2相。加入0.9%(质量分数)的Sb对Mg2Si相的汉字状结构具有强烈变质作用,Mg2Si中的Si能与Sn发生取代作用,生成Mg2(Si,Sn)复合相,该相的物理性能介于Mg2Si与Mg2Sn之间。随着Sb含量的增加,铸态合金和挤压态合金的延伸率逐渐减小,而抗拉强度呈现先增加后降低的趋势。挤压态合金的强度和塑性明显优于铸态合金,并且Sb含量的增加有利于改善Mg-5Sn-2Al-1.5Zn-0.8Si合金的耐热性能。     

Ca含量对Mg-5Zn-2Al合金铸态组织和性能的影响

采用光学显微镜、XRD和SEM等手段,研究了Ca对Mg-5Zn-2Al合金铸态显微组织和力学性能的影响.结果表明:Ca的加入对Mg-5Zn-2Al合金铸态的晶粒能够显著地细化.合金的抗拉强度和伸长率均呈现先上升后下降的变化趋势.该合金中加入0.2wt％Ca细化效果最明显,其合金铸态时的抗拉强度和伸长率分别为为233MPa和13.33％.     

铸态Mg-4Al-4Si合金的显微组织与力学性能

摘 要:采用重力铸造法制备Mg-4A1-4Si(AS44)镁合金,研究铸态合金的显微组织和室温力学性能.结果表明,铸态AS44合金主要由α-Mg基体、β-Mg17Al12相及Mg2Si相组成;Mg2Si粗大的呈树枝状、块状和汉字状3种形态;铸态合金的硬度为66.5 HV3,室温抗拉强度为108.8 MPa,屈服强度为72.3 MPa,伸长率为2.6％;拉伸断裂形式为准解理脆性断裂.     

氟锆酸钾盐混合物对Mg-3Y-3.5Sm-2Zn合金组织和性能的影响（英文）

制备了3种氟锆酸钾(K_2ZrF_6)盐混合物(M),分别在3个温度下将3种盐混合物加入到铸态Mg-3Y-3.5Sm-2Zn合金中。通过差热分析(DSC),X射线衍射(XRD),光学显微镜(OM),扫描电子显微镜(SEM),能量色散谱(EDS)和拉伸试验研究了合金的显微组织和力学性能,讨论了K_2ZrF_6盐混合物在合金中的晶粒细化机理。结果表明,铸态Mg-3Y-3.5Sm-2Zn合金由α-Mg,Mg_(12)(Y, Sm)Zn和(Mg, Zn)_3(Y,Sm)_3种相组成。SEM和XRD检测发现,添加K_2ZrF_6盐混合物不会在合金中产生新的相。在780℃下加入M3盐(60%K_2ZrF_6-20%NaCl-20%KCl,质量分数)时,合金的晶粒细化效果最佳。通过在780℃下加入3种盐,铸态Mg-3Y-3.5Sm-2Zn合金的力学性能得到提高,由M3盐细化后的合金具有最佳的力学性能。K_2ZrF_6盐混合物可细化铸态Mg-3Y-3.5Sm-2Zn合金,这是由于Mg和K_2ZrF_6之间还原反应得到的细Zr质点和富锆区在合金中起到的晶粒细化作用。     

快淬纳米晶/非晶Mg2-xLaxNi (x=0~0.6)合金的电化学贮氢性能

用铸造及快淬工艺制备Mg2Ni型Mg2-xLaxNi(x=0,0.2,0.4,0.6)贮氢合金。用XRD、SEM、HRTEM分析铸态及快淬态合金的微观结构。结果发现,在快淬无La合金中没有出现非晶相,但快淬含La合金显示了以非晶相为主的结构。用DSC研究快淬合金的热稳定性,表明La的含量及快淬对非晶相的晶化温度影响很小。电化学测试结果表明,铸态合金的放电容量随La含量的增加而增加,快淬态合金的放电容量随La含量的变化有极大值。La替代Mg显著地提高了铸态及快淬态合金的循环稳定性。     

First-principles study of electronic structure and magnetic properties of orthorhombic CrGa2Sb2 and MnGa2Sb2

By the first-principles calculations, we present the results of electronic structure and magnetic properties on bulk CrGa₂Sb₂ and MnGa₂Sb₂ in an orthorhombic structure with the linear chains of transition-metal Cr and Mn atoms, using four different exchange correlation potentials: the local density approximation (LDA), the generalized gradient approximation (GGA), GGA + U, and the Tran-Blaha modified Becke-Johnson functional (mBJ). The electronic structure calculations from four exchange correlation potentials show that CrGa₂Sb₂ is a pseudogap (negative gap) material with very small density of states (DOS) at the Fermi level, while MnGa₂Sb₂ has notably higher DOS at the Fermi level compared to CrGa₂Sb₂, exhibiting stronger metallic conductivity, although the mBJ potential obtains lower DOS at the Fermi level than LDA and GGA for both CrGa₂Sb₂ and MnGa₂Sb₂. The GGA + U method with a small value (1 eV) of the on-site Coulomb interaction parameter U obtains lower DOS at the Fermi level compared to the large value of U. In agreement with the measurement data, the total energy calculations reveal that both CrGa₂Sb₂ and MnGa₂Sb₂ have a stable ferromagnetic ground state with lower energies relative to antiferromagnetic state. Based on the Heisenberg model, the magnetic exchange constants between the nearest-neighbor Cr–Cr and Mn–Mn along transition-metal linear chains are calculated to be 48.6 meV and 27.5 meV for CrGa₂Sb₂ and MnGa₂Sb₂, respectively. By the mean-field approximation method, we calculated the Curie temperature of two compounds to be above room-temperature.     

氢分子在贮氢材料Li2MgN2H2表面的吸附与解离

采用第一性原理计算方法研究了Li-Mg-N-H体系贮氢材料的放氢产物Li2MgN2H2的吸氢反应过程中的过渡态、表面电子态密度和表面能。结果表明:氢分子在Li2MgN2H2低指数表面中最低能量(100)表面的Mg-Mg-Li穴位吸附位置能够形成最稳定的吸附结构并发生解离,氢分子吸附能为-0.1898eV,解离能约为0.84eV(81kJ/mol),表明该反应所需的反应活化能仍较高,吸氢反应速度缓慢。     

Fe-15Ce合金在H2-CO2、H2-H2S及H2-H2S-CO2气氛下的腐蚀

研究了600℃时Fe-15Ce合金在H2-CO2、H2-H2S及H2-H2S-CO2 3种气氛中的腐蚀行为，Fe-15Ce合金腐蚀后发生了Ce的内氧化或形成了复杂的腐蚀产物膜，而未出现Ce的选择性氧化或硫化，这主要是合金中存在着两相及Ce在Fe中极低的溶解度的结果。Fe-15Ce合金在本实验条件下的氧化-硫化腐蚀速度低于相同温度、压力下的纯硫化。     

IrO2-MnO2中间层Ti/RuO2-TiO2-SnO2电极制备及性能

通过热分解法制备了含IrO2-MnO2中间层Ti/RuO2-TiO2-SnO2电极,采用SEM、EDX、XRD、CV等检测方法对中间层进行表征,同时采用强化加速寿命试验对电极电化学稳定性进行表征。结果表明:450℃时前躯体完全氧化并形成固溶体,制备的中间层晶粒细小,表面结构致密,电化学孔隙率小。添加中间层使Ti/RuO2-TiO2-SnO2电极强化寿命由未加中间层的7.5h提高到995.8h,远高于国家标准20h。     

Thermodynamics and phase diagrams in the binary systems Na2O-SiO2, Na2O-GeO2, Na2O-B2O3, Li2O-B2O3, CaO-B2O3, SrO-B2O3, and BaO-B2O3

We applied our model to the enthalpy of mixing data of the binary systems Na₂O-SiO₂, Na₂O-GeO₂, Na₂O-B₂O₃, Li₂O-B₂O₃, CaO-B₂O₃, SrO-B₂O₃, and BaO-B₂O₃. The most stable composition in the liquid, that is where the enthalpy of mixing is most negative, is with a metal-oxygen ratio of 4 to 3, for monovalent metals (Na and Li) and 3 to 4 for divalent metals (Ba and Ca) in liquid silicates or borates. The same applies to the CaO-SiO₂, CaO-Al₂O₃, PbO-B₂O₃, PbO-SiO₂, ZnO-B₂O₃, and ZnO-SiO₂ systems. The oxygen to metal ratio, its constant value in various types of systems, reflects and describes the structure of the liquid. Using the analyzed enthalpies of mixing data and the available phase diagrams, we calculated the enthalpies of formation of the various binary compounds. The results are in excellent agreement with data in the literature that were obtained from direct solid-solid calorimetry.     

Viscosities of Fe_nO-MgO-SiO_2 and Fe_nO-MgO-CaO-SiO_2 slags

1　INTRODUCTIONTheviscosityofliquidslagsisanimportantphysicalproperty .Innickelflashsmeltingprocesses ,slagscontainmainlyironoxidesandsilicainadditiontoMgO ,CaO ,Cr2 O3andAl2 O3aswellasvaluemet alsandotherimpurities .Manyinvestigationsontheviscosityofironsilicatemeltwerealreadyreport ed[14 ] .Butonlyfewstudiesarereportedontheslagsinthecompositionrangeoccurringinnickelmattesmelting.Thismaymainlybeattributedtoexperi mentaldifficultiesinviscositymeasurementsforthehighmeltingtemperatureofi…     

La_2O_3,CeO_2掺杂Sm_2Zr_2O_7陶瓷制备及热物理性能

以Sm_2O_3, La_2O_3, ZrO_2和CeO_2为原料,采用固相反应法制备了(Sm_0.5La_0.5)_2(Zr_0.6Ce_0.4)_2O_7陶瓷.用X射线衍射(XRD),扫描电镜(SEM)研究了样品的相成分和微观组织,用激光脉冲法和推杆法测量了样品的热导率和热膨胀系数.结果表明,所制备的样品具有萤石晶体结构,且组织致密晶界清晰,并具有较低的热导率和满足热障涂层要求的热膨胀系数.     

Magnetic and related properties of Ce5CoGe2, CeCoGe and CeCo2Ge2

Magnetic susceptibility, magnetization, specific heat, electrical resistivity and thermoelectric power of polycrystalline Ce₅CoGe₂, CeCoGe and CeCo₂Ge₂ were studied at temperatures down to 2 K and in magnetic fields up to 5 T. The novel phase Ce₅CoGe₂ was found to be a ferromagnet with the Curie temperature of about 11 K, which exhibits in the paramagnetic region some features of a dense Kondo system with strong crystal field effect. The re-investigated CeCoGe was found to order antiferromagnetically below 4.6 K, while CeCo₂Ge₂ is an intermediate-valence system, in agreement with previous reports. The thermoelectric power of the latter compound is large (up to 40 μV/K) and positive in the whole temperature range studied, while in the magnetically ordered systems Ce₅CoGe₂ and CeCoGe it is mostly negative and distinctly smaller (down to −1.5 and −11 μV/K, respectively).     

Yb2Ge,Eu2Ge and Eu2Si: new PbCl2-type compounds

The intermetallic compounds Yb₂Ge, Eu₂Ge and Eu₂Si were synthesized from the elements by HF melting in tantalum crucibles. The three phases crystallize in the PbCl₂ structure type, as shown by Rietveld refinement of powder pattern intensity data. The structure of Yb₂Ge was confirmed by a single crystal study.