高压下Zr41Ti14Cu12.5Ni10Be22.5大块金属玻璃的结构弛豫

利用X射线衍射及高分辨电子显微镜研究了Zr₄₁Ti₁₄Cu_12.5Ni₁₀Be_22.5大块金属玻璃在3 GPa, 573 K退火后的结构弛豫. 超声研究、密度测量、显微硬度等物性分析以及抗压、滑动磨损等力学性能测试结果表明: 与淬态大块非晶相比, 弛豫态非晶声学参数发生明显变化, 且力学性能得到改进. 对压力诱发非晶结构弛豫而导致显微结构变化进行了探讨.     

Zr41Ti14Cu12.5Ni10Be22.5大块金属玻璃压缩行为的同步辐射

利用室温高能同步辐射X光能量散射方法研究了Zr₄₁Ti₁₄Cu_12.5Ni₁₀Be_22.5大块金属玻璃0~24 GPa的压缩行为. 研究表明, 该非晶在这一压力范围内, 出现了压力诱发的结构弛豫. 低于8 GPa, 过剩的自由体积的存在, 导致快速结构弛豫, 随着压力逐渐升高, 结构弛豫引起非晶的结构硬化.     

`Pd40Ni10Cu20P20块状金属玻璃的高压相变

利用日本同步辐射装置研究了高温高压下Pd₄₀Ni₁₀Cu₂₀P₂₀ 块状金属玻璃的非晶-晶化转变. 在10 GPa的压力条件下加热该金属玻璃, 实时观察到了非晶-晶化-非晶的相变规律. 在7 GPa 和同样的温度条件下, Pd₄₀Ni₁₀Cu₂₀P₂₀金属玻璃仅存在非晶-晶化这样不可逆相变. 将该金属玻璃在7 GPa的压力条件下加热到熔化温度, 然后淬火到室温, 发现淬火后获得的晶化相与加热金属玻璃得到的 晶化相完全不同. 表明该金属玻璃在不同的压力条件下存在着不同的晶化机制.     

Cu60Zr29Ti11大块非晶合金的黏度特征和强液体行为

*采用铜模铸造法制备了Cu₆₀Zr₂₉Ti₁₁大块非晶合金, 用X射线衍射仪、三点压弯式黏度仪对该非晶合金的动力学性质进行了研究. 测定了大块非晶合金Cu₆₀Zr₂₉Ti₁₁在过冷液相区的黏度, 得到了它的动力学脆性系数m=31, 以及流变激活能E=63.4 kJ/mol. 表明大块非晶合金Cu₆₀Zr₂₉Ti₁₁是一种强液体, 有较强的非晶形成能力, 形成非晶比较稳定. 分析了合金在过冷态的流变激活能变化规律, 发现流变激活能的变化并不符合Kivelson的Super-Arrhenius公式.     

Cu/Ni3Ti原位复合材料的显微组织和力学性能

通过真空电弧熔炼法制备了Cu/Ni₃Ti原位复合材料。采用X射线衍射仪、扫描电子显微镜、显微硬度计和纳米压痕仪分别测试了Cu/Ni₃Ti原位复合材料的相组成、微观组织形貌、显微硬度和弹性模量。结果显示,Ni₃Ti相在铜基体中呈针状分布,且铸锭边缘与心部平均晶粒直径分别约为1.74和249 μm。Cu/Ni₃Ti原位复合材料在时效温度为550℃时的强化效果最佳,此时铜基体与Ni₃Ti相的显微硬度最大值分别达到了174和209。在热处理后,Ni₃Ti相的最大硬度和弹性模量分别达到10.5 GPa和249.7 GPa,远高于Cu基体,Ni₃Ti相是一种理想的增强相。     

Zr基大块非晶合金在过冷液相区内的本构关系的研究

在Zwick/Roell力学性能试验机上进行Zr₅₅Cu₃₀Al₁₀Ni₅大块非晶合金在过冷液相区的压缩试验, 根据应力-应变曲线的过冲现象, 提出了Maxwell-Pulse本构模型, 该模型由蠕变函数耦合脉冲函数得到. 通过对虚应力模型和脉冲指数模型的拟合, 得到了Maxwell-Pulse本构方程的各项参数. 对比试验及拟合所得的数据及曲线, 两者的真实应力-应变曲线吻合较好, 且能反映出应力过冲现象. 又通过数值模拟和杯形零件成形试验验证了该本构方程适于描述Zr55Cu30Al10Ni5大块非晶合金在过冷液相区的力学行为.     

Al2O3对Mo-W-Co高温合金力学性能的影响

通过改变Mo-W-Co高温合金中Al₂O₃的含量,研究Al₂O₃对Mo-W-Co高温合金硬度和耐磨性能的影响.采用球磨、压制成形和真空烧结等工艺制备Mo-W-Co-Al₂O₃高温合金,利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和金相显微镜(OM)对制备好的合金的相结构、形貌和粒度进行分析,并测试合金的硬度和耐磨性能.结果表明:添加Al₂O₃能提高Mo-W-Co高温合金的硬度和耐磨性能,当w_Al2O3为5%时,Mo-W-Co高温合金的硬度和耐磨性能达到最佳效果;在真空烧结时,Al₂O₃在合金中形成了γ-Al₂O₃相,是影响合金组织和性能的关键相.     

ZrAl4 C4、Zr2 Al4 C5和Zr3 Al4 C6结构、弹性和电子性质对比

采用第一性原理方法,对比研究了Zr-Al-C体系纳米层状化合物ZrAl₄C₄、Zr₂Al₄C₅和Zr₃Al₄C₆的结构、弹性和电子性质,并探寻其规律性。结果表明：从晶体结构角度分析,三种材料均可看作由(ZrC)和(Al₄C₃)两个独立单元以不同比例组合而成,可统一表示为(ZrC)_nAl₄C₃(n=1,2,3),且三者的晶格常数a值近似相等,晶格常数c随着ZrC含量的增大而变大。三种化合物弹性性质中,体模量、剪切模量、杨氏模量的大小关系满足：ZrAl₄C₄< Zr₂Al₄C₅< Zr₃Al₄C₆。通过对三者电子态密度和Mulliken布局分析得到,ZrAl₄C₄、Zr₂Al₄C₅和Zr₃Al₄C₆均具有金属键、离子键和共价键的特征,且Zr-C键强于Al-C键,从微观电子角度解释了在(ZrC)_nAl₄C₃(n=1,2,3)体系中Zr-C键含量越高则对应材料的体模量、剪切模量、杨氏模量等弹性性质越大。本文计算结果与已有实验值和理论值吻合较好。     

纳米Al2O3颗粒对Cu-Al2O3性能的影响

采用溶胶-凝胶法制备纳米Al₂O₃颗粒,通过粉末冶金法制备氧化铝铜（Cu-Al₂O₃）。采用X射线光电子能谱仪、扫描电子显微镜、洛氏硬度仪和涡流计分别测试了Cu-Al₂O₃的结合能、微观组织、硬度和导电率。结果表明：随Al₂O₃颗粒含量的增加,Cu-Al₂O₃的硬度先升高后降低,当Al₂O₃颗粒的质量分数达到0.084%时,Cu-Al₂O₃的硬度达到最大值75.73（HRB）。Cu-Al₂O₃的导电率随着Al₂O₃颗粒含量的增加逐渐下降。Al₂O₃颗粒的质量分数为0.084%时为最佳值,Cu-Al₂O₃的硬度达到最大值,导电率达到69.1% IACS。     

Phase-selection and metastable phase formation in highly undercooled eutectic Ni78.6Si21.4 alloys

A large undercooling (250 K) was achieved in eutectic Ni_78.6Si_21.4 melt by the combination of molten-glass denucleation and cyclic superheating. The metastable phase formation process in the bulk undercooled eutectic Ni_78.6Si_21.4 melts was investigated. With the increase of undercooling, different metastable phases form in eutectic Ni_78.6Si_21.4 melts and part of these metastable phases can be kept at room temperature through slow post-solidification. Under large undercooling, the metastable phases β₂-Ni₃Si, Ni₃₁Si₁₂ and Ni₃Si₂ were identified. Especially, the Ni₃Si₂ phase was obtained in eutectic Ni_78.6Si_21.4 alloy for the first time. Based on the principle of free energy minimum and transient nucleation theory, the solidification behavior of melts was analyzed with regard to the metastable phase formation when the melts were in highly undercooled state.     

球磨时间对Mo_2FeB_2基金属陶瓷组织和力学性能的影响

以Mo、FeB、Cr、Ni、Fe粉末以及少量的C粉为原料,采用行星球磨法对其球磨后烧结制备Mo2FeB2基金属陶瓷,利用扫描电镜观察球磨粉及其烧结试样的组织形貌,并测定烧结试样的孔隙度、硬度和抗弯强度,研究原料粉末球磨时间对Mo2FeB2基金属陶瓷组织和力学性能的影响。结果表明,随着球磨时间的增加,粉末粒度逐渐变小,Mo2FeB2基金属陶瓷的孔隙度明显降低,其硬度和抗弯强度明显增大,晶粒也随之细化;球磨30h原料粉末所制Mo2FeB2基金属陶瓷的综合性能最优,其硬度(HRA)达到90.2,抗弯强度达到1850MPa。     

原位合成CNTs/Cu-Al2O3复合材料的性能研究

对Al的质量分数分别为0.20%,0.35%,0.60%的Cu-Al合金粉末进行内氧化,得到Cu-Al₂O₃粉末。采用化学气相沉积法在Cu-Al₂O₃粉末表面原位生长碳纳米管(carbon nano tubes, CNTs),采用放电等离子烧结工艺成功制备了CNTs/Cu-Al₂O₃复合材料。采用扫描电子显微镜和透射电子显微镜观察了CNTs/Cu-Al₂O₃复合粉末、复合材料断口的形貌。采用显微硬度计、微拉伸试验机、摩擦磨损试验机分别对纯Cu及复合材料的维氏硬度、抗拉强度、摩擦因数进行测试。采用电化学工作站测试复合材料在3.5%NaCl (质量分数)水溶液中的耐腐蚀性能。结果表明,随着Al的质量分数的增加,粉末表面合成的CNTs的数量也增多。Al的质量分数为0.35%时,CNTs/Cu-Al₂O₃复合材料的综合性能最佳,与纯Cu相比,复合材料的抗拉强度和腐蚀电势分别提高了86.4%和43.2%,分别为315 MPa和-0.268 V,摩擦因数降低了53.3%,仅为0.28。     

Zr50Cu50金属玻璃形成过程中自由体积与玻璃态转变温度关系的分子动力学模拟

利用分子动力学模拟了Zr50Cu50金属玻璃的形成过程,并获得了不同温度下合金的原子构型.借助金属玻璃中自由体积量等于金属玻璃与对应晶体的体积差理论提出一种自由体积湮没速度法,对Zr50Cu50金属玻璃形成过程中的临界玻璃态转变温度Tc以及热力学玻璃态转变温度Tg进行预测.用该方法确定出的Tc(969.5K)与利用模式耦合理论计算获得的Tc(978.4K)接近;Tg(731K)与利用平均原子体积随温度变化关系曲线确定的Tg(725K)相近.运用自由体积湮没速度法计算的Tc和Tg无需计算各温度下的原子扩散系数,节省了计算时间.     

Nanotribological behaviors of in situ nanoparticles doped molecular deposition films

The molecular deposition films of poly （diallyl dimethylammonium chloride） （PDDA） and poly （acrylicacid） （PAA） with Cu2＋ on quartz and glass substrates were prepared in laboratory first, then different bilayers films were dipped into fresh Na2S aqueous solution. As a result, CuS nanoparticles were fabricated in multilayer molecular deposition films in situ. The structure and nanotribological properties of the composite films were analyzed by ultraviolet-visible （UV-visible） spectroscopy, XPS and atomic force microscope （AFM）. It was found that the CuS nanoparticles were homogeneously distributed throughout the whole film. And these films had a much smaller friction force than their substrates and higher antiwear life than pristine PDDA/PAA molecular deposition films. The fluctuation and variation trend of the topography, hardness, and friction with the AFM indentation length were also investigated.     

Al2O3-SiC纳米复合陶瓷的制备及其表征

以分析纯Al(NO₃)₃·9H₂O, (CH₂)₆N₄和粒径为30 nm的SiC粉末为原料, 采用溶胶-凝胶(sol-gel)方法制备干凝胶, 经煅烧合成Al₂O₃-SiC纳米陶瓷粉, 利用真空热压装置对粉末进行烧结. 通过X射线衍射(XRD)、 扫描电镜(SEM)和维氏硬度实验分析了不同SiC含量和不同烧结温度的Al₂O₃-SiC陶瓷样品的结构、 形貌、 晶粒尺寸和硬度, 并研究了其机理.     

压痕硬度测试的有限元分析

根据压痕硬度测试理论,建立了有限元模型。通过有限元手段分析了金属材料在不同载荷作用下的压入过程,了解在压痕硬度试验过程中压痕周围所产生的应力分布,计算了硬度HB值,与在硬度试验中所测的HB值吻合,证实了模型和材料特性描述的可靠性,在此基础上,研究了不同硬度的试件,载荷对压痕参数和压痕周围应力分布的影响。结果表明:载荷大小直接影响压痕深度、隆起部分、回弹量和塑性区域大小,随着载荷的增加,压痕深度、隆起部分、回弹量和塑性区域大小均有不同程度的增加,增加的程度与材料的硬度有关,而且随着载荷的增加,压入深度加深,压痕周围塑性区域逐渐扩大,其硬度值和塑性区域逐渐趋于稳定范围。     

Atomic packing and short-to-medium range order evolution of Zr-Pd metallic glass

A larger-scale Zr₇₀Pd₃₀ alloy system has been simulated using molecular dynamics (MD) to investigate structure evolution in Zr₇₀Pd₃₀ metallic glass. The simulated pair distribution function of Zr₇₀Pd₃₀ metallic glass agrees well with the experimental results. Voronoi polyhedron analysis indicates that the icosahedra are not randomly distributed in space, but form characteristic intercrossed icosahedral clusters with medium-range order. Intercrossed icosahedral clusters are the dominant local configurations in Zr₇₀Pd₃₀ metallic glass and probably cause the quasicrystalline phase discovered in Zr₇₀Pd₃₀ metallic glass.     

Knoop硬度测试中的压痕尺寸效应

从能量平衡角度对工程材料Ｋｎｏｏｐ硬度的压痕尺寸效应作出新的理论解释。认为在压痕过程中只有一部分荷载转化为材料发生不可逆体积形变所消耗的能量；荷载功的额外消耗是表现硬度随坟痕尺寸增大而减小的主要原因。     

Effect of La2O3 on microstructure, mechanical and tribological properties of Ni-W coatings

In this paper, a Ni-W-La2O3 composite coating was prepared by the electrodeposition method. Microhardness tester and environmental scanning electron microscope equipped energy dispersive spectroscopy were employed to investigate the microhardness and the surface morphology of the composite coatings respectively, and the high temperature friction behavior and corrosion resistance of the coatings against molten glass were investigated by using a high temperature tribometer. The results show that La2O3 can refine the microstructure effectively, and make the element distribution uniform, which leads to the increase of average microhardness. La2O3 particulates can reduce the friction coefficient between the composite coating and glass during the sliding process at about 973 K largely, and the corrosion resistance of the La2O3 added Ni-W coatings is effectively improved compared with that of the non-added one, furthermore the mechanism of friction-reducing and anti-corrosion is also discussed.     

Solid FeS lubricant:a possible alternative to MoS2 for Cu-Fe-based friction materials

Molybdenum disulfide (MoS₂) is one of the most commonly used solid lubricants for Cu-Fe-based friction materials. Nevertheless, MoS₂ reacts with metal matrices to produce metal sulfides (e.g., FeS) and Mo during sintering, and the lubricity of the composite may be related to the generation of FeS. Herein, the use of FeS as an alternative to MoS₂ for producing Cu-Fe-based friction materials was investigated. According to the reaction principle of thermodynamics, two composites-one with MoS₂ (Fe-Cu-MoS₂ sample) and the other with FeS (FeS-Cu₂S-Cu-Fe-Mo sample), were prepared and their friction behaviors and mechanical properties were compared. The results showed that MoS₂ reacted with the Cu-Fe matrix to produce FeS, metallic ternary sulfides, and Mo when sintered at 1050℃. The MoS₂-Cu-Fe and FeS-Cu₂S-Cu-Fe-Mo samples thereby exhibited similar characteristics with respect to phase composition, density, hardness, and tribological behaviors. Micrographs of the worn surfaces revealed that the stable friction regime for both composites stemmed from the iron sulfides friction layers rather than from the molybdenum sulfides layers.