激光熔敷Cr2Ni3Si／Cr3Si金属硅化物复合材料涂层组织与高温耐磨性

以Cr-Si-Ni高纯预合金化粉末为原料、利用激光熔敷技术在奥氏体不锈钢1Cr18Ni9Ti表面上制得了以金属硅化物Cr3Si为增强相、以复杂多元金属硅化物Cr-Ni-Si为基体的快速凝固金属硅化物复合材料冶金涂层，分析了该涂层的显微组织，在高温滑动磨损条件下测试了其耐磨性能。研究结果表明，Cr3Si金属硅化物的体积分数对激光熔敷Cr2Ni3Si／Cr3Si复合材料涂层的硬度和高温耐磨性有显著影响。由于涂层中硬质耐磨相Cr3Si的抗磨骨干作用，在高温滑动磨损条件下该涂层具有优良的耐磨性能。     

Fe2TiAl结构和热力学性质的第一原理计算

采用基于密度泛函的第一原理平面波赝势方法,研究了Fe2TiAl的几何结构、电子结构和热力学性质,结果表明:Fe2TiAl相比TiAl,晶格常数有所增加,Fe加入会增加费米能级处的d电子数,增加面间可动性,从而改善合金塑性;Fe2TiAl在零温和零压下的晶格常数、体弹性模量及弹性常数与实验值符合较好。利用准谐德拜模型,得到了不同温度和不同压强下Fe2TiAl的热容、体弹性模量和德拜温度,发现德拜温度随压强增加而增加,热容随压强增加而减小,高压下温度对Fe2TiAl热膨胀系数的影响小于压强的影响,并成功获得了相对体积、体弹性模量、热膨胀系数与温度和压强之间的变化关系。     

金属Zr热力学性质的第一原理研究

应用基于密度泛函与密度泛函微扰理论的平面波赝势方法计算了一组不同晶格常数下hcp结构金属Zr的声子谱及相应的静态总能,由此得到不同晶格常数下的自由能,由准谐近似及自由能极小判据得到自由能与温度的关系,进而计算了金属Zr热膨胀系数、体弹性模量、定容及定压摩尔热容与温度的关系,计算结果在较宽的温度范围内与实验相符.对热膨胀系数,同时应用Debye-Grüneisen模型进行了计算,并与第一原理方法的结果进行了比较.对摩尔热容的计算考虑了电子的贡献,表明在高温区电子热容的贡献不能忽略.     

激光熔炼W/W2Ni3Si金属硅化物“原位”复合材料的耐磨性

采用水冷铜模激光合金熔炼炉制备了以初生w树枝晶为增强相、以w2Ni3Si三元金属硅化物为基体的金属硅化物“原位”耐磨复合材料．分别在室温干滑动磨损及600℃高温滑动磨损条件下测试了上述W／W2Ni3Si金属硅化物“原位”增强耐磨复合材料的耐磨性，并讨论了其磨损机理．结果表明，上述金属硅化物耐磨复合材料在室温干滑动磨损和高温滑动磨损条件下均具有优异的耐磨性能．     

Ti3Si（1-x）AlxC2在900℃～1300℃空气中的氧化行为

热压摩尔比为n(TiC)n(Ti)n(Si)n(Al)=2110.2混合粉末制备的Ti3Si(1-x)AlxC2(0＜x≤0.16)材料在900℃～1 300℃空气中的恒温氧化行为遵循抛物线规律,但在1 200℃和1 300℃是一个两步抛物线过程.随着温度升高,氧化抛物线速率常数kp从900℃的2.45×10-10 kg2·m-4·s-1增大到1 300℃的5.71×10-9 kg2·m-4·s-1,计算的氧化活化能为110 kJ·mol-1±10kJ·mol-1.弥散分布在基体中的Al改变了Ti3SiC2材料的氧化机制,使试样表面形成由大量α-Al2O3和少量TiO2与SiO2组成的致密氧化层,从而提高了材料的抗氧化性.     

立方氮化硼的热膨胀性

通过高温高压方法合成了目前制作c-BN工具的最常用的琥珀色c-BN磨料,利用超大功率高温X射线衍射仪精确测定c-BN的晶格常数,得出晶格常数随温度变化的关系,从而精确计算c-BN的本征热膨胀系数.从室温到1000℃温度范围内,c-BN的平均线膨胀系数α=4.92×10~(-6)/℃,平均体膨胀系数万β=1.47×10~(-5)/℃.     

激光熔敷Ti5Si3／NiTi金属间化合物复合材料涂层组织与耐磨性

以Ti14Si6Ni80合金粉末为原料，利用激光熔敷技术在BT9钛合金表面制得以金属硅化物Ti5Si3为增强相、以金属间化合物NiTi为基体的快速凝固金属间化合物复合材料涂层，分析了该涂层的显微组织，在室温干滑动磨损条件下测试了其耐磨性。研究结果表明，涂层硬度高、组织致密、与基材之间为完全冶金结合，在干滑动磨损试验条件下具有较好的耐磨性。涂层具有优异耐磨性的主要原因是作为耐磨增强相的金属硅化物Ti5Si3具有高硬高耐磨的特性，在涂层中起到了抗磨骨干作用，同时作为涂层基体的金属间化合物NiTi由于具有极强的原子结合键及应力诱发马氏体相变特性，本身具有优异的耐磨性，在摩擦过程中对耐磨增强相Ti5Si3起到了强力支撑作用。     

Stability, Elastic Constants and Thermodynamic Properties of (α, β, γ)-Nb5Si3 Phases

采用第一性原理计算了金属间化合物α-Nb5Si3,β-Nb5Si3和γ-Nb5Si3的结构稳定性、弹性常数、热力学性质和电子结构,并利用Voigt-Reuss-Hill方法计算了弹性常数。结构参数优化结果与实验值基本一致;结合能和形成焓结果表明α-Nb5Si3的结构稳定性最好。最后分析和讨论了3种不同Nb5Si3相的延展性和弹性各向异性。     

p—型FeSi2／Bi2Te3梯度热电材料的优值推证与界面温度优化

通过对两元 p-型梯度热电材料 Fe Si2 / Bi2 Te3界面温度的建模计算与实验验证 ,在固定热冷端温区内积分得出的 Z- ΔT值与界面温度 Ti 的关系曲线为 :Z- ΔT =0 .6 72 +11.7× 10 - 4Ti - 1.31× 10 - 6 T2i - 3.4 9× 10 - 9T3i该关系可用来表征两元梯度结构的热电性能。从拟合曲线上得出该梯度结构的最佳界面温度为 2 2 0℃～ 2 30℃ ,这与实验测出两单段材料 (Fe Si2 ,Bi2 Te3)长度比为 10∶ 1左右时所形成的界面温度较为接近。通过测试不同长度比的材料输出功率 ,也发现 10∶ 1梯度材料的最大输出功率较大 ,是相同温差下单段 β- Fe Si2 材料的 2倍～ 2 .6倍。     

镍基合金TLP扩散焊接头中二元共晶沉淀相Ni-M(B、Si、Zr和Hf)的性能

采用基于密度泛函理论的第一性原理平面波赝势计算方法,计算了Ni-M(B、Si、Zr和Hf)二元共晶沉淀相(Ni2B、Ni3B、Ni3B2、Ni23B6、Ni3Si、Ni5Zr和Ni5Hf)的相稳定性、弹性常数、硬度及相应的电子结构.相稳定性计算结果表明,二元共晶沉淀相结构稳定性变化趋势由高到低的顺序为Ni3Si、Ni5...     

Ti12Zr10Si5Fe2Sn非晶合金的制备与力学性能

利用快速凝固法制备Ti12Zr10Si5Fe2Sn非晶合金条带,采用XRD、TEM、SEM及拉伸试验机等手段研究其组织结构和力学性能。结果显示：该非晶钛合金力学性能优良,其抗拉强度高达399 MPa,屈服应力为329 MPa,断裂延伸率为2.5%,弹性模量为39 GPa,较晶态金属更接近于人体骨的弹性模量,另外对其断口形貌进行观察分析。     

Fe–B–Si–Zr soft magnetic bulk glassy alloys

The present work is devoted to fabrication of Fe–B–Si–Zr multi-component bulk glassy alloys with good mechanical and soft magnetic properties. Glass formation in Fe–B system is first considered with an empirical cluster-plus-glue-atom model. A basic composition formula [B–B₂Fe₈]Fe is proposed as the framework for multi-component alloy design. Considering the structural stability of the model glass, Si and Zr are introduced to the [B–B₂Fe₈] cluster to replace the center B and shell Fe atoms, from which a series of Fe–B–Si–Zr alloys with composition formulas [Si–B₂Fe_8−xZr_x]Fe (x = 0–0.6) are derived. Copper mold casting experiment shows that bulk glassy alloys are formed within the Zr content range of x = 0.2–0.6, and the largest glass-forming ability appears at [Si–B₂Fe_7.6Zr_0.4]Fe with a critical size of 2.5 mm. The bulk glassy alloys exhibit high fracture strength as large as 3850 MPa. Magnetic property measurement indicates that these alloys exhibit good magnetic softness with high saturation magnetization (1.26–1.48 T) and low coercive force (1.6–6.7 A/m). The alloying effects of Si and Zr on bulk glass formation, thermal glass stability and magnetic softness are discussed with the empirical model.     

Mechanical and wear properties of Mo5Si3–Mo3Si–Al2O3 composites

Mo₅Si₃ and Mo₅Si₃–Mo₃Si–Al₂O₃ composite were synthesized use MoO₃, Mo, Si and Al as raw materials by mechanically induced self propagating reaction and then consolidated by hot-pressing. The microstructure of the materials was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) with X-ray energy dispersive spectroscopy (EDS). The effects of the Al₂O₃ on the mechanical and tribological properties of Mo₅Si₃–Mo₃Si–Al₂O₃ composite have been studied. It was found that benefits associated with the addition of the Al₂O₃ to Mo₅Si₃ and Mo₃Si include finer microstructure, higher strength, higher fracture toughness and higher hardness. The dry sliding wear properties of the composite were investigated using against GCr15 bearing steel in ball-on-disk system at room temperature. The results indicated that the friction coefficients and specific wear rates of Mo₅Si₃–Mo₃Si–Al₂O₃ composite were significantly reduced by the addition of Al₂O₃, and its specific wear rates decreased by an order of magnitude compare with the monophase Mo₅Si₃. The friction coefficients of test materials decrease with an increasing load. The dominant wear mechanism of the composites was interpreted by several different wear models involving plastic deformation, adhesion, brittle fracture and reaction to form a tribo-oxidation layer.     

Cu47Ti33Zr11Ni8Si块体非晶合金的制备与力学性能

采用差压铸造法制备了Cu47Ti33Zr11Ni8Si块体非晶合金试样，测定了试样的三点弯曲强度。结果表明，该块体非晶合金具有极佳的力学性能，其弯曲断裂强度高达3260MPa，断裂前弹性变形量为2．7％，弯曲模量为101GPa。     

A new semiconductor Al2Fe3Si3 with complex crystal structure

Al₂Fe₃Si₃, a new semiconductor with complex triclinic structure was synthesized by arc melting and spark plasma sintering, followed by heat treatment. The nominal compositions of samples have been changed to compensate Al evaporation during synthesis process, and single Al₂Fe₃Si₃ phase has been obtained with the nominal composition of Al: Fe: Si = 26: 37: 37 (6 at.% Al excess against stoichiometry). In this study, we measured the sound velocity, thermal expansion coefficient, Vickers hardness, fracture toughness, electrical conductivity, Seebeck coefficient, and thermal conductivity of the new semiconductor Al₂Fe₃Si₃. The Al₂Fe₃Si₃ sample displayed positive Seebeck coefficient from 300 to 850 K, with a maximum Seebeck coefficient of 110 μV/K at 430 K. The Debye temperature of Al₂Fe₃Si₃ was 640 K, which was similar to or higher than those of other Al, Fe, Si based thermoelectric materials, but the lattice thermal conductivity was lower, 4–5 W/mK, due to the complex crystal structure of Al₂Fe₃Si₃. The maximum ZT value was 0.06 at 580 K.     

添加Yb和Zr对Al7Si0.3Mg合金组织及力学性能的影响

研究了添加Yb和Zr元素对Al7Si0.3Mg合金组织及力学性能的影响,以及细化变质机理。结果表明,Yb、Zr元素的添加明显细化了α-Al基体,使其从粗大的树枝状晶转变为细小的花瓣状晶,晶粒尺寸明显减小,并且使共晶硅由粗大的针状变质为短棒状,这是由于Yb、Zr吸附在孪晶凹槽处（TPRE）改变共晶硅生长方式,最终改变共晶硅形貌;经热处理（T6）后,大量析出的Al₃(Yb, Zr)粒子起到了沉淀强化进而细化晶粒的作用。当Yb质量分数为0.3%、Zr质量分数为0.25%时,合金（T6）的抗拉强度和延伸率为296.3 MPa和9.2%,较未细化变质的合金分别提高了17%和1.1倍。     

First-principles investigations of structural,mechanical, electronic and optical properties of U3Si2-type AlSc2Si2 under high pressure

The structural, elastic, electronic and optical properties for U₃Si₂-type AlSc₂Si₂ compound under pressure were systematically investigated by using the first-principles calculations. The values of elastic constants and elastic moduli indicate that AlSc₂Si₂ keeps mechanical stability under high pressure. The mechanical properties of AlSc₂Si₂ are compared with those of Al₃Sc. The results indicate that AlSc₂Si₂ is harder than Al₃Sc. Anisotropic constant A^U and 3D curved surface of elastic moduli predict that AlSc₂Si₂ is obviously anisotropic under pressure. The electronic structure of AlSc₂Si₂ exhibits metallic character and the metallicity decreases with the elevated pressure. In addition, optical properties as a function of pressure were calculated and analyzed. The present work provides theoretical support for further experimental work and industrial applications.     

放电等离子烧结制备Fe75Zr3Si13B9磁性材料

采用机械合金化技术制备Fe75Zr3Si13B9非晶合金粉体,利用SPS放电等离子烧结技术在不同烧结温度下将非晶合金粉体制备成d20 mm×7 mm的块体非晶纳米晶合金。采用XRD和DSC分析了Fe75Zr3Si13B9非晶合金粉体的相组成、玻璃转变温度Tg、开始晶化温度Tx和晶化峰温度Tp。然后利用XRD、SEM、Gleeble3500、VSM分析不同烧结温度下块体的相转变、微观形貌、力学性能和磁性能。研究表明,在500 MPa的烧结压力下,随着烧结温度的升高,非晶相开始晶化形成非晶纳米晶双相结构,同时,样品的致密度、抗压强度、微观硬度、饱和磁化强度均显著提高。最后在500 MPa的烧结压力和863.15 K的烧结温度下,获得密度6.9325 g/cm3、抗压强度1140.28 MPa、饱和磁化强度1.28 T的非晶纳米晶磁性材料。     

Formation and properties of Ti-based Ti–Zr–Cu–Fe–Sn–Si bulk metallic glasses with different (Ti + Zr)/Cu ratios for biomedical application

Ti-based Ti–Zr–Cu–Fe–Sn–Si bulk metallic glasses (BMGs) free from highly toxic elements Ni and Be were developed as promising biomaterials. The influence of (Ti + Zr)/Cu ratio on glass-formation, thermal stability, mechanical properties, bio-corrosion resistance, surface wettability and biocompatibility were investigated. In the present Ti-based BMG system, the Ti₄₇Zr_7.5Cu₄₀Fe_2.5Sn₂Si₁ glassy alloy exhibited the highest glass forming ability (GFA) corresponding to the largest supercooled liquid region, and a glassy rod with a critical diameter of 3 mm was prepared by copper-mold casting. The Ti-based BMGs possess high compressive strength of 2014–2185 MPa and microhardness of 606–613 Hv. Young's modulus of the Ti₄₇Zr_7.5Cu₄₀Fe_2.5Sn₂Si₁ glassy alloy was about 100 GPa, which is slightly lower than that of Ti–6Al–4V alloy. The Ti₄₇Zr_7.5Cu₄₀Fe_2.5Sn₂Si₁ glassy alloy with high GFA exhibited high bio-corrosion resistance, and good surface hydrophilia and cytocompatibility. The mechanisms for glass formation as well as the effect of (Ti + Zr)/Cu ratio on bio-corrosion behavior and biocompatibility are discussed.