稀土元素La、Ce对Al-7Si-0.4Cu-1.0Fe压铸铝合金组织和性能的影响

研究了稀土元素La、Ce对Al-7Si-0.4Cu-1.0Fe压铸铝合金微观组织、导热性能及力学性能的影响。结果表明：添加稀土元素La、Ce能够细化合金α-Al晶粒，其形态从枝晶转变为胞状晶，平均二次枝晶臂间距从16.3μm减小至11.2μm,降低了31.3%;共晶Si明显细化变质，平均面积从1.4μm²降低至0.4μm²,平均纵横比从1.91降低至1.13。稀土元素La、Ce在合金中分布均匀，未发现明显的含La、Ce的金属间化合物。相较于未添加稀土合金，添加0.1%(质量分数，下同)La和0.1%Ce的合金热导率从140.33 W/(m·K)提高至159.68 W/(m·K),抗拉强度从176.1 MPa提高至213.6 MPa,断后伸长率从2.78%提高至6.62%,分别提高了13.8%、21.3%和238.1%。     

Sr变质对Al-Si-Mg合金的流动性、力学性能和导热系数的影响

采用扫描电镜、拉伸试验机和激光导热仪,研究了Sr变质处理对Al-3.2Si-0.8Mg合金铸造流动性、导热系数与力学性能的影响。结果表明:随着共晶Si相形貌的细化,Al-3.2Si-0.8Mg合金的上述性能逐渐提高。当Al-10Sr合金添加量为0.4%时,该合金的铸造流动性试样长度为922 mm(提高了8.2%),抗拉强度和伸长率分别为243 MPa(提高了3.8%)和11.3%(提高了11.9%),导热系数为187.6 W/(m·K)(提高了3.1%)。     

AlN变质对Al-4Si-0.45Mg合金性能的影响

在亚共晶Al-4Si-0.45Mg合金中添加微量AlN,以改善合金的显微组织并提高其力学性能和导热性能。结果表明，未添加Sr和AlN的合金，其抗拉强度为167.3 MPa,伸长率为10%,热导率为149.5 W/(m·K);添加Sr后的抗拉强度为176.2 MPa,伸长率为20%,热导率为166.8 W/(m·K),抗拉强度和热导率分别提高了5.4%、11.6%;添加AlN后的合金抗拉强度为194.8 MPa,伸长率为16%,热导率为170.1 W/(m·K),抗拉强度和热导率分别提高了16.4%、13.8%。力学性能的提高主要与α-Al的晶粒细化、二次枝晶臂间距(SADS)的减小和Si的变质有关。加入Sr和AlN后，共晶Si由片状变成块状和球状，Sr变质后共晶Si的尺寸明显减少，且AlN变质后共晶Si的平均尺寸更小，说明热导率的提高主要与共晶Si相的形态变化有关。其机制为细小的Si使得电子通道增加，电子散射概率降低，平均自由程增加，从而提高了热导率。     

TiB2/Al-Si-Mg-Er复合材料的组织与性能

采用重熔稀释法制备了Al-7Si-0.5Mg-0.1Er和0.5TiB₂/Al-7Si-0.5Mg-0.1Er合金,研究了TiB₂颗粒增强Al-Si-Mg-Er复合材料的组织性能。结果表明,复合材料铸态组织主要由α-Al基体、共晶Si相和TiB₂颗粒组成。TiB₂粒子的加入使Al-7Si-0.5Mg-0.1Er合金二次枝晶间距减小了7.1 μm。抗拉强度达到217.53 MPa,较Al-7Si-0.5Mg-0.1Er合金提升了12.1 %。TiB₂/Al-Si-Mg-Er复合材料的最优T6热处理工艺为530 ℃×12 h固溶+160 ℃×7 h时效,经该工艺处理后,TiB₂/Al-Si-Mg-Er复合材料抗拉强度达到319.49 MPa,相比热处理前提高了46.9%,相比Al-7Si-0.5Mg-0.1Er合金提高了5.9%;屈服强度达到266.75 MPa,相比热处理前提高了106.4%,相比Al-7Si-0.5Mg-0.1Er合金提高了14.9%。复合材料抗拉强度的提升主要源于TiB₂颗粒加入后产生的晶粒细化、变质和热处理强化。     

Sc含量对含Zr的Al-0.36Mg-1.23Si合金板材组织和性能的影响

利用OM、TEM,拉伸试验机和杯突试验机研究了添加质量分数(下同)0.15%的Zr及同时添加不超过0.09%Sc的T4P态Al-0.36Mg-1.23Si合金板材显微组织、成形性和烤漆硬化性。结果表明：Al-0.36Mg-1.23Si、Al-0.36Mg-1.23Si-0.15Zr、Al-0.36Mg-1.23Si-0.15Zr-(0.03～0.09)Sc合金板材基体中弥散相粒子分别为(Al, Si)₃Ti相、(Al, Si)₃(Zr, Ti)相以及(Al, Si)₃(Zr, Sc, Ti)相。添加0.15%Zr将T4P态Al-0.36Mg-1.23Si合金板材的等轴状再结晶晶粒尺寸由53μm细化至23μm,再添加0.03%～0.09%Sc后，板材的再结晶晶粒略微细化至20μm左右。Sc含量增加，T4P态Al-0.36Mg-1.23Si-0.15Zr合金板材的屈服强度和抗拉强度均略有降低，断裂伸长率、n_10～20值、r₁₀值和杯突值I_E均无明显变化，板材再...     

V合金化对Al-9Si合金凝固组织与力学性能的影响

研究了V合金化对Al-9Si合金凝固过程、微观组织和力学性能的影响。结果表明,在Al-9Si合金中添加V,析出化合物Si₂V,而无Al V化合物析出,V对初生α-Al的析出温度无明显影响。随着V量增加,Al-9Si合金的初生α-Al的形核温度和形核过冷度同步增加,0.4%V(质量分数)使形核温度由未添加V的607.5℃上升至612.6℃,过冷度由24℃增加至27.1℃;继续增加V量,形核温度略有升高,但形核过冷度略有减小。V添加使Al-9Si合金初生α-Al晶粒形态由枝晶向等轴晶转变,Al-9Si-0.4V合金的α-Al晶粒尺寸由Al-9Si的593μm细化至302μm。V对共晶Si无变质作用,但V能使针状β-Al5FeSi转变为鱼骨状的Al₁₂(Fe,V)3Si相。0.6%Sb(质量分数)变质Al-9Si-0.4V合金的抗拉强度、屈服强度和伸长率为153.9 MPa、78.5 MPa和6.56%,较Al-9Si合金分别提高23.8%、14.1%和102.4%;硬度由47.3 HV提高至59.1 HV。Al-9Si合金的拉伸断口由撕裂棱和解理...     

La和Ce对铸造Al-7Si-0.6Cu-0.8Fe合金组织及性能的影响

采用光学显微镜、扫描电镜和激光导热等手段，研究了单独或复合添加La、Ce对铸造Al-7Si-0.6Cu-0.8Fe合金微观组织、力学性能和热导率的影响。结果表明，添加0.3%的(La+Ce)后，合金中α-Al相得到了较大程度的细化，二次枝晶臂间距(SADS)达到较小值(13.1μm),共晶Si形貌转化为细小的颗粒状且均匀地分布于晶界处，富Fe相长度降低了57.51%,其合金的热导率为159.68 W/(m·K)、抗拉强度为231.3 MPa、伸长率为6.89%,与未添加稀土合金相比，分别提高了13.79%、24.96%和118.73%。     

不同铸造方法对7075铝合金热导率及力学性能的影响

采用金属型铸造、液态挤压铸造和半固态挤压铸造方法制备了7075铝合金,研究了不同铸造工艺对7075铝合金热导率与力学性能的影响。结果表明,金属型铸造晶粒粗大,产生枝晶偏析降低塑韧性,抗拉强度及伸长率最小,分别为121 MPa和2.78%,但晶粒粗大使热量传导路径宽,对电子散射几率小,电子的平均自由程较长,热导率相对较高,达到了139.67W/(m·K);液态挤压铸造晶粒细化,抗拉强度和伸长率分别为239MPa和5.75%,但晶粒细小且枝晶臂较多,对电子散射程度大,热导率最低,为120.94W/(m·K);半固态挤压铸造的晶粒致密细小且圆整,抗拉强度及伸长率最高分别达到248MPa和7.46%,且热导率为126.07W/(m·K)。     

微合金化元素对7005铝合金铸态组织与性能的影响

采用金相显微镜、SEM、EDS等试验方法研究了Al-10Ti中间合金、细晶铝锭、Sc-Zr以及Ti-Sc-Zr等细化方式细化的7005铝合金铸态组织和铸态力学性能.结果表明,由Al-10Ti中间合金细化的合金晶粒最大,平均晶粒直径约为330μm;由细晶铝锭细化的合金晶粒明显变小,平均直径在170μm左右,抗拉强度由Al-10Ti细化时的280MPa提高到了304MPa,伸长率由3.2%提高到4.2%.由Sc-Zr细化的合金的晶粒直径约为50μm,抗拉强度达到了330MPa,但伸长率只有2%;由Ti-Sc-Zr细化的合金的晶粒直径约为35μm,力学性能最好,抗拉强度达到338MPa,伸长率达到4.5%.     

Mg、Sc对铸造铝合金导热和力学性能的影响

为了满足散热器件对压铸铝合金材料越来越高的导热及力学性能要求,在Al-Si-Fe系铸造铝合金中引入Mg、Sc元素,通过金相及SEM/EDS检测,考察了合金在不同元素添加量及不同冷却速率下的微观组织,并分析其导热及力学性能。结果表明,Mg、Sc元素的添加均会降低合金的导热系数,提高其强度,且Sc元素的影响幅度略低于Mg。当Sc添加量为0.2%时,Al-9Si-0.7Fe-0.2Sc合金的导热系数为153.9W/(m·K),屈服强度为92.9MPa,抗拉强度为197.3MPa,综合性能较好。     

20Wf/30ZrCp/W复合材料的组织结构与力学性能

采用真空热压烧结法制备了致密度为98.5%的20W     

Electronic structure and optical property of As2(Te1−xSx)3 and As2(Te1−xSex)3 crystals

Single crystals of S- and Se-incorporated As₂Te₃ have been grown by vertical Bridgman method. The electronic structure and optical property of As₂(Te_1−xS_x)₃ [ATS] and As₂(Te_1−xSe_x)₃ [ATSe] series compounds have been characterized experimentally by thermoreflectance (TR) measurements in a wide energy range of 0.7-6 eV. X-ray diffraction measurements showed that the diffraction peaks of sulfur- and selenium-incorporated As₂(Te_1−xS_x)₃ 0 ≤ x ≤ 0.3 and As₂(Te_1−xSe_x)₃ 0 ≤ x ≤ 0.6 crystals shift to higher diffraction angles with the increase of the sulfur or selenium incorporations. The analysis of X-ray measurement revealed similar crystalline phase for the As₂Te₃ and those of the S- or Se-incorporated As₂Te₃. The experimental TR spectra of As₂(Te_1−xS_x)₃ (0 ≤ x ≤ 1) and As₂(Te_1−xSe_x)₃ (0 ≤ x ≤ 1) exhibit a lot of derivative-like spectral features in the vicinity of band edge as well as in the higher-lying bands. Transition energies and broadening parameters of the TR features at 40 and 300 K were analyzed. Compositional dependences of band gap and interband transition energies of the ATS and ATSe series were evaluated. The origins for the interband transitions in the ATS and ATSe are assigned. Based on the experimental analyses, the electronic structure of the diarsenic trichalcogenides, As₂(Te_1−xSe_x)₃ and As₂(Te_1−xS_x)₃, is hence being realized.     

Crystal structures and structural relationships of KFe2(SeO2OH)(SeO3)3 and SrCo2(SeO2OH)2(SeO3)2

The new phases KFe₂(SeO₂OH)(SeO₃)₃ and SrCo₂(SeO₂OH)₂(SeO₃)₂ have been synthesized under low-hydrothermal conditions and their structures were determined by single-crystal X-ray methods. Both compounds are monoclinic; KFe₂(SeO₂OH)(SeO₃)₃: space group P2, A = 9.983(4), B = 5.270(1), C = 10.614(4) Å, β = 97.42(2)°, V = 553.7 ų, Z = 2; SrCo₂(SeO₂OH)₂(SeO₃)₂: space group P2ln, A = 14.984(2), B = 5.286(1), C = 13.790(2) Å, β = 94.72(1)°, V = 1088.5 ų , Z = 4. The refinements converged to R-values of 2.9 and 3.6% respectively.

The atomic arrangement in KFe₂(SeO₂OH)(SeO₃)₃ and SrCo₂(SeO₂OH)₂(SeO₃)₂ is based on isolated MO₆ octahedra (M = Fe³⁺, Co²⁺), which are corner-linked via trigonal pyramidal selenite groups to a framework structure. Interstitials are occupied by potassium or strontium atoms in ten- or eight-coordination respectively, and by the lone-pair electrons of the Se⁴⁺ atoms. Both compounds are not isotypic but are closely related and may be interpreted as different distortions of an idealized structure type in space group P2/m, which was modelled for a theoretical compound SrFe₂(SeO₃)₄ by distance least squares refinement (program ).     

Sn1- x Sm x O2 微纳米纤维的红外发射率与激光吸收性能：实验研究与第一性原理仿真

采用静电纺丝法结合热处理工艺制备了Sn_1-xSm_xO₂(x=0%,8%,16%,24%,质量分数,下同)微纳米纤维,表征了产物的物相、形貌、激光吸收性能和红外发射率,同时基于密度泛函理论的第一性原理对比分析了Sn_1-xSm_xO₂(x=0%,16%)的相关光电性质,进一步从电子结构角度解释了Sm³⁺掺杂对SnO₂红外发射率和激光吸收的作用机理。结果表明：经600℃煅烧后,Sn_1-xSm_xO₂均为单一金红石型结构,呈现出良好的纤维形貌,纤维相互交错,形成无规则三维网状结构,且各元素在纤维上分布均匀。随着Sm³⁺掺杂量的增大,产物在1064和1550 nm处的反射率逐渐降低,红外发射率先减小后增大。当x=16%时,在1064 nm处的反射率为53.9%,在1550nm处的反射率为38.5%,在8-14μm波段的红外发射率为0.749...     

Extrinsic and intrinsic magnetic properties of Co1−x Fex Sb3

We report magnetic properties of iron in Co_1−x Fe_x Sb₃ for x in the range 0<x<0.2, since x=0.2 is found to be the limit of solubility of iron in the skutterudite lattice. The magnetic ions diluted in the matrix carry a small magnetic moment reduced to that of the spin-only S=1/2 value of the Fe³⁺ in the low spin d⁵ configuration in presence of a strong crystal field that screens the orbital momentum. The magnetic properties give evidence that a small fraction of iron is spin-frozen in magnetite ferrimagnetic clusters, and antiferromagnetic FeO clusters. Because both types of clusters represent only very minor phases, their detection by the usual analytical means such as X-rays is not possible. The remaining part is diluted in the matrix to form a semimagnetic semiconductor characterized by a Fe–Fe nearest-neighbor exchange interaction J that is antiferromagnetic, with |J|/k_B19.6  K.     

Composition, surface structure, and thermal behavior of ZrO2 + TiO2/Ti and ZrO2 + CeOx + TiO2 composites formed by plasma-electrolytic oxidation

Specific surface structures of ZrO₂ + TiO₂ (I) and ZrO₂ +CeO_x + TiO₂ (II) coatings on titanium before and after annealing at 850°C for 24 h in air are studied. Whiskers are found on the surface of type-I coatings before annealing, and perfectly edged crystals composed of TiO₂ and ZrO₂ oxides are found upon annealing. Pores in both coatings have a multilevel structure. In the case of type-I coatings, orifices of pores are covered with titanium. In type-II coatings, pore orifices contain titanium, zirconium, and oxygen. Oxygen deficiency implies that titanium and zirconium are present in pore orifices in metallic state. In type-II coatings, the surface distribution of cerium is heterogeneous. Mechanical treatment of the annealed coatings causes their exfoliation from the substrate metal. In the case of both coatings, the exfoliating surfaces are composed of TiO₂ blocks containing excess oxygen.     

Synthesis and characterization of 0.3 Vf TiC–Ti3SiC2 and 0.3 Vf SiC–Ti3SiC2 composites

In this work, two composite compositions—one with 30% (v/v) SiC, the other with 30% (v/v) TiC, balance Ti₃SiC₂—were synthesized and characterized. Fully dense samples were fabricated by hot isostatically pressing Ti, SiC and C powders for 8 h at 1500 or 1600 °C and a pressure of 200 MPa. Both TiC and SiC lower grain boundary mobility in Ti₃SiC₂. Coarsening of the SiC particles was also observed. At comparable grain sizes, all composites tested were weaker in flexure than the unreinforced Ti₃SiC₂ matrix, with the reduction in strength being the worst for the SiC composites. This reduction in strength is most probably due to thermal expansion mismatches between the matrix and reinforcement phases. The composite samples were exceptionally damage tolerant; in one case a 100 N Vickers indentation (in a 1.5-mm thick bar) did not reduce the flexural strength as compared to an unindented or as-fabricated samples. The same is true for thermal shock resistance; quenching samples from 1400 °C in room temperature water, resulted in strength reductions that were 12% at best and 50% at worst. In the 25–1000 °C temperature range, the thermal expansion coefficients of the two composites were indistinguishable at 8.2×10⁻⁶ K⁻¹. The Vickers hardness values depended on load; at 100 N, the hardnesses were ≈15 GPa; at 300 N, they asymptote to 7–8 GPa. For the most part, very few cracks emanate from the corners of the Vickers indents even at loads as high as 500 N. In the few cases where cracks did initiate, fracture toughness values were crudely estimated to lie in the 5–7.5 MPa √m range.     

MnBi/Sm2Co17复合磁粉制备、磁性能及微结构研究

采用化学辅助高能球磨工艺制备了MnBi/Sm_2Co_(17)纳米晶复合磁粉,研究了MnBi合金添加量对复合磁体磁性能和微结构的影响。随着MnBi合金添加量的增加,复合磁粉的内禀矫顽力先稍上升,后基本保持不变,但均低于纯MnBi磁粉的864kA/m;磁粉的饱和磁化强度和剩余磁化强度均逐渐下降。复合磁粉中没有发现明显的元素互扩散现象。采用Henkel曲线分析了复合磁体的交换耦合作用,复合磁粉的δM在添加量为15%(质量分数)时达到极大值,说明该复合磁体具有较强的交换耦合作用,结合磁粉形貌分析了随着MnBi合金添加量的增加复合磁粉剩磁比的演变规律。     

Mechanical and thermal properties of Tb2(MoO4)3 crystals

The mechanical and thermal properties of single crystal Tb₂(MoO₄)₃ have been systematically studied. The result of microhardness measurement indicates that the crystal belongs to the soft materials category. The thermodynamic parameters obtained from DTA analysis were used for determining the type of liquid-solid interface during crystal growth. Negative thermal expansion along the c-axis was observed, and this behavior was attributed to the bent Tb-O-Mo bonds. The specific heat of the crystal was measured to be 0.122 cal g⁻¹ K⁻¹ at 293.15 K. The thermal conductivity of Tb₂(MoO₄)₃ at room temperature was found to be smaller than that of representative ferroelectric LiNbO₃.