硼酸铝晶须增强6061铝合金复合材料的断口分形分析(英文)

硼酸铝晶须增强6061铝合金基复合材料中的界面反应影响其断口分形维数。该复合材料由压力铸造法制备,采用垂直剖面法分析拉伸断裂断口。当量尺度分别取3-15μm以及1-5μm时,可以在断口上发现分形现象。当量尺度在3-15μm的分形域,其分形维数与材料抗拉强度显著正相关。实验结果表明,随热处理时间的延长,界面反应产物的分布与状态可以改变材料的微观断裂模式,进而影响断口的粗糙度和分形维数,同时决定材料的抗拉强度。而当量尺度为3-15μm的分形域,其分形维数受热处理程度的影响不很显著。     

分形几何与Ti（C,N）基金属陶瓷的断裂

本文介绍了分形维数及其在材料断裂科学中的某些应用，用扫描电镜观察了大量金属陶瓷断口，用图象仪测量了断口的分形维数，研究了金属陶瓷在室温三点弯曲条件下，断裂表面的分形维数与横向断裂强度以及微观组织之间的关系。实验结果表明，横向断裂强度σｂｂ的对数值随分形维数ＤＦ增加呈单调上升的直线关系，显微组织的变化对分形维数有重要影响，分形维数与断裂机制之间存在一定的对应关系。     

不锈钢1Cr18Ni9Ti的冲击功及其分形行为研究

研究了含有不同体积分数ZrN和MnS夹杂物的1Cr18Ni9Ti钢中夹杂物含量、断口形貌与冲击功的关系。结果表明,随着分形维数DH的升高,材料的冲击功Ak逐渐增大。该钢在冲击功较高时呈韧性断裂,冲击功较小时呈脆性断裂。所以该钢的断口形貌、冲击功与分形维数具有对应关系。     

弥散质点和SiC颗粒复合强化Al基复合材料 Ⅱ．性能和断裂特征

对机械合金化制备的Ａｌ_４Ｃ_３、Ａｌ_２Ｏ_３弥散质点和ＳｉＣ颗粒复合强化Ａｌ基复合材料进行了拉伸试验和断口分析，并测定了弹性模量和热膨胀系数．研究表明，在ＳｉＣ_ｐ／Ａｌ复合材料中引入弥散的Ａｌ_４Ｃ_３和Ａｌ_２Ｏ_３质点可以明显提高复合材料的室温和高温强度，随加入Ｃ含量的增加或Ａｌ粉氧化时间的加长，复合材料的强度提高．在Ａｌ_４Ｃ_３／Ａｌ复合材料的基础上加入ＳｉＣ颗粒可以提高复合材料的弹性模量并进一步降低其热膨胀系数．复合材料断口为大韧窝加细小韧窝的混合断口，随复合材料基体强度的增加，拉伸断口上断裂的ＳｉＣ颗粒数量增多．     

基于激光共聚焦技术对16MnR钢高温损伤后疲劳断裂的分形研究

将16Mn R钢经过不同温度热处理后,制备成紧凑拉伸疲劳试验试样。通过疲劳试验获得了材料疲劳断裂的起裂值Ji。利用激光共聚焦显微镜对试样断口进行了分析,获得了断口表面的三维形貌。用分形理论计算了断口表面的分形维数,对断面的形貌进行了定量分析。结果表明,热处理温度对16Mn R钢的力学性能影响明显,随着热处理温度的变化,钢的起裂值Ji在900℃左右最低;断口表面分形维数也随之变化,起裂值Ji和分形维数之间存在对应关系。     

分形理论在陶瓷材料断裂行为中的应用

综述了近年来分形理论在陶瓷材料断裂行为和断裂机制方面应用的进展情况,主要包括分形理论的产生、陶瓷断口的分形特征和分形维数的测定方法、材料断裂的分形模型以及分形维数与材料性能之间的关系.通过对Al2O3-TiC(AT)和Al2O3-TiC-4%Co(ATC)(体积分数)两种复合材料表面压痕裂纹扩展特征分析和分形维数的计算,获得与其断裂行为相关的信息,结果表明ATC材料的断裂韧性和抗弯强度均有较大提高,其断裂模式从典型的沿晶断裂转变为沿晶/穿晶混合断裂模式,对两种材料表面压痕裂纹的分形计算表明ATC的压痕裂纹具有较高的分形维数,与其较高的断裂韧性存在正比例的对应关系.     

分形理论在陶瓷材料断裂行为中的应用

综述了近年来分形理论在陶瓷材料断裂行为和断裂机制方面应用的进展情况，主要包括分形理论的产生、陶瓷断口的分形特征和分形维数的测定方法、材料断裂的分形模型以及分形维数与材料性能之间的关系。通过对Al2O3-TiC（AT）和Al2O3-TiC-4％Co（ATC）（体积分数）两种复合材料表面压痕裂纹扩展特征分析和分形维数的计算，获得与其断裂行为相关的信息，结果表明ATC材料的断裂韧性和抗弯强度均有较大提高，其断裂模式从典型的沿晶断裂转变为沿晶／穿晶混合断裂模式，对两种材料表面压痕裂纹的分形计算表明ATC的压痕裂纹具有较高的分形维数，与其较高的断裂韧性存在正比例的对应关系。     

DISPERSOID AND SiC PARTICULATE STRENGTHENED Al COMPOSITES Ⅱ. PROPERTIES AND FRACTURE BEHAVIOUR

对机械合金化制备的Ａｌ_４Ｃ_３、Ａｌ_２Ｏ_３弥散质点和ＳｉＣ颗粒复合强化Ａｌ基复合材料进行了拉伸试验和断口分析，并测定了弹性模量和热膨胀系数．研究表明，在ＳｉＣ_ｐ／Ａｌ复合材料中引入弥散的Ａｌ_４Ｃ_３和Ａｌ_２Ｏ_３质点可以明显提高复合材料的室温和高温强度，随加入Ｃ含量的增加或Ａｌ粉氧化时间的加长，复合材料的强度提高．在Ａｌ_４Ｃ_３／Ａｌ复合材料的基础上加入ＳｉＣ颗粒可以提高复合材料的弹性模量并进一步降低其热膨胀系数．复合材料断口为大韧窝加细小韧窝的混合断口，随复合材料基体强度的增加，拉伸断口上断裂的ＳｉＣ颗粒数量增多．     

弥散质点和SiC颗粒复合强化Al基复合材料 Ⅱ．性能和断裂特征SCIEI

对机械合金化制备的Ａｌ_４Ｃ_３、Ａｌ_２Ｏ_３弥散质点和ＳｉＣ颗粒复合强化Ａｌ基复合材料进行了拉伸试验和断口分析，并测定了弹性模量和热膨胀系数．研究表明，在ＳｉＣ_ｐ／Ａｌ复合材料中引入弥散的Ａｌ_４Ｃ_３和Ａｌ_２Ｏ_３质点可以明显提高复合材料的室温和高温强度，随加入Ｃ含量的增加或Ａｌ粉氧化时间的加长，复合材料的强度提高．在Ａｌ_４Ｃ_３／Ａｌ复合材料的基础上加入ＳｉＣ颗粒可以提高复合材料的弹性模量并进一步降低其热膨胀系数．复合材料断口为大韧窝加细小韧窝的混合断口，随复合材料基体强度的增加，拉伸断口上断裂的ＳｉＣ颗粒数量增多．     

Fe3Al基金属间化合物的塑性与断裂机制

用分形学研究了 Fe__3Al 基金属间化合物断裂表面的分形维数与温度、塑性及断裂机制之间的关系。结果表明,其拉伸塑性及断裂模式与分形维数 D_F 存在对应关系;其分形维数随温度变化的特征反映了塑性变化特征;且其 D_F 值随测量码尺范围的变化而变化,并分别与占主导地位的断裂机制或微观结构相联系。     

加工道次对FSP制备高熵合金增强铝基复合材料组织和性能的影响

采用搅拌摩擦加工制备了以AlCoCrFeNi_2.1高熵合金为增强相的6061铝合金复合材料(AlCoCrFeNi_2.1/6061Al),重点研究了加工道次对复合材料组织均匀性、界面结合以及力学性能的影响. 结果表明,随搅拌摩擦加工道次的增加,AlCoCrFeNi_2.1/6061Al复合材料组织均匀性及力学性能均得到明显改善. 复合材料中基体与增强相界面结合良好,界面处扩散层厚度随加工道次增加而增大. 相较于不添加增强相的6道次搅拌摩擦加工铝合金,AlCoCrFeNi_2.1增强相颗粒的引入可进一步细化晶粒并提高抗拉强度,且随着加工道次增加,复合材料抗拉强度及断后伸长率均显著升高. 2,4道次下的断口存在明显的颗粒聚集区,而6道次下断口表面颗粒分布均匀且呈现大量韧窝,为典型的韧性断裂. 该现象主要归因于载荷传递效应、弥散强化和细晶强化3大强化机制.     

Effect of TiO2 on high-temperature thermoelectric properties of ZnO

The as-sintered Zn_1−xTi_xO (0.01 ≤ x ≤ 0.05) samples contained a solid solution of Zn_1−xTi_xO with a wurtzite structure and a small amount of the cubic spinel Zn₂TiO₄. The amount of Zn₂TiO₄ increased with an increase in TiO₂ content. The density and grain size increased with the small TiO₂ content (≤0.01), and then they decreased gradually by further increasing the TiO₂ content. The addition of TiO₂ to ZnO led to a significant increase in the electrical conductivity and a decrease in the absolute value of the Seebeck coefficient, resulting in an increase in the power factor. The highest value of power factor (7.6 × 10⁻⁴ W m⁻¹ K⁻²) was attained for Zn_0.98Ti_0.02O at 1073 K. It is demonstrated that the TiO₂ addition is fairly effective for enhancing thermoelectric properties.     

体育器材用TiAl3/AlSi11Cu3铝合金组织和力学性能优化

利用超声振动法制备体育器材用AlSi11Cu3铝合金,通过添加K₂TiF₆粉末原位反应生成TiAl₃增强相的方法对铝合金进行颗粒增强,研究了超声功率和颗粒增强对AlSi11Cu3铝合金微观组织和力学性能的影响。试验结果表明,最佳的超声功率为1 kW,超声振动和TiAl₃增强相的引入能明显细化铝合金组织,大幅提升铝合金的拉伸性能和硬度,抗拉强度、伸长率和硬度分别提升了33.9%、23.6%和38.8%,断裂特征由准解理断裂逐渐向韧性断裂转变。     

Microstructure and Mechanical Behavior of CrFeNi2V0.sWx (x=0, 0.25)High-Entropy Alloys

CrFeNi₂V_0.5W_x (x = 0, 0.25) alloys based on these parameters of mixing enthalpy (ΔH_mix), mixing entropy (ΔS_mix), atomic radius difference (δ), valance electron concentration, and electronegativity difference(Δχ) were designed and prepared. The microstructure and room-temperature mechanical behavior of both alloys were investigated. Compressive test results showed that the CrFeNi₂V_0.5W_0.25 alloy had higher yield strength than that of the W-free CrFeNi₂V_0.5 alloy, although they all exhibited quite larger compressive plasticity (ε > 70%). Compression fracture surface of CrFeNi₂V_0.5W_0.25 alloy revealed a ductile fracture in the face-centered cubic (FCC) phase and a brittle-like fracture in the σ phase. Moreover, tensile test results indicated that the CrFeNi₂V_0.5W_0.25 alloy exhibited excellent mechanical property with an ultimate tensile strength of 640 MPa and a high tensile elongation of 15.7%. The tensile deformation mode of the FCC phase in the CrFeNi₂V_0.5W_0.25 alloy is dominated by planar glide, relating to dislocation configurations, high-density dislocations, and dislocation wall. Therefore, dislocation slip plays a significant role in tensile deformation of CrFeNi₂V_0.5W_0.25 high-entropy alloy. The higher strength of CrFeNi₂V_0.5W_0.25 alloy is predominantly due to the solid solution strengthening of W element and σ phase precipitation strengthening. Combination of the higher tensile strength and plasticity suggests that the CrFeNi₂V_0.5W_0.25 alloy can be a promising aerospace material.     

A study of mechanical properties and fractography of ZA-27/titanium-dioxide metal matrix composites

This paper reports an investigation of the mechanical properties and the fracture mechanism of ZA-27 alloy composites containing titanium-dioxide (TiO₂) particles 30–50 μm in size and in contents ranging from 0–6 wt.% in steps of 2 wt.%. The composites were fabricated by the compocasting technique. The results of the study revealed improvements in mechanical properties such as Young’s modulus, ultimate tensile strength, yield strength and hardness of the composites, but at the cost of ductility. The fracture behavior of the composites was influenced significantly by the presence of titanium dioxide particles. Crack propagation through the matrix and the reinforcing particles resulted in the final fracture. Scanning electron micrscopy (SEM) analyses were carried out to furnish suitable explanations for the observed phenomena.     

Microstructure and mechanical properties of mechanically alloyed and spark plasma sintered amorphous–nanocrystalline Al65Cu20Ti15 intermetallic matrix composite reinforced with TiO2 nanoparticles

Multiphase Al₆₅Cu₂₀Ti₁₅ intermetallic alloy matrix composite, dispersed with 10 wt.% of TiO₂ nanoparticles, has been processed by mechanical alloying, followed by spark plasma sintering under pressure in the temperature range of 623–873 K. Differential scanning calorimetry and X-ray diffraction suggest that equilibrium crystalline phases evolve from the amorphous or intermediate crystalline phases. Transmission electron microscopy shows that the composite sintered at 873 K has partially amorphous microstructure, with dispersion of equilibrium, crystalline, intermetallic precipitates of Al₅CuTi₂, Al₃Ti, and Al₂Cu of 25–50 nm size, besides the TiO₂. The composite sintered at 873 K exhibits little porosity, hardness of 5.6 GPa, indentation fracture toughness in the range of 3.1–4.2 MPa√m, and compressive strength of 1.1 GPa. Indentation crack deflection by TiO₂ particle aggregates causes increase in fracture resistance with crack length, and suggests R-curve type behaviour. The study provides guidelines for processing high strength amorphous–nanocrystalline intermetallic composites based on the Al–Cu–Ti ternary system.     

Improvement of the film thickness by modification of the hydroxymethylbenzene SAM with tetraethoxysilane and octanediol for protection of iron from corrosion in 0.5 M NaCl

For enhancing the protective efficiency, P of a film prepared by modification of a p-hydroxymethylbenzene HOC₆H₄ (HOMB) self-assembled monolayer (SAM) adsorbed on iron by the formation of a covalent bond, an increase in the film thickness, d was attempted. The HOMB SAM was modified with tetraethoxysilane (C₂H₅O)₄Si (TES), 1,8-octanediol HO(CH₂)₈OH (C₈DO), 1,2-bis(triethoxysilyl)ethane (C₂H₅O)₃Si(CH₂)₂Si(OC₂H₅)₃ (BTESE) and alkyltriethoxysilane C_nH_2n+1Si(OC₂H₅)₃ (C_nTES, n = 8 or 18). The P value of the film was determined by polarization measurement of a covered iron electrode in an aerated 0.5 M NaCl solution after immersion in the solution for 1.5–72 h of the immersion time, t. High values of P, more than 82% were obtained for the films of HOMB SAM modified with TES, C₈DO and C_nTES and with TES, C₈DO, BTESE and C_nTES in the range of t up to 72 h. The highest value was 93.2%, for the film of HOMB SAM modified with TES, C₈DO, BTESE and C₁₈TES, of which d was 4.7 nm. The film of HOMB SAM modified with TES, C₈DO and C₈TES was characterized by contact angle measurement, X-ray photoelectron spectroscopy and FTIR reflection spectroscopy.     

保护渣对铝钛系夹杂物溶解的吸收规律

以CaO-SiO₂-Al₂O₃-Na₂O-CaF₂-MgO为基础渣系,采用旋转动力学方法研究了不同碱度、BaO质量分数(0~15%)、B₂O₃质量分数(0~15%)对连铸保护渣吸收Al₂O₃或TiO₂速率的影响以及吸收前后矿相变化。结果表明,保护渣吸收TiO₂的速率要远大于吸收Al₂O₃的速率;添加BaO或B₂O₃后均能提高保护渣吸收Al₂O₃和TiO₂的能力;保护渣主要物相为钙镁黄长石(2CaO·MgO·2SiO₂)、钙铝黄长石(2CaO·Al₂O₃·2SiO₂)、枪晶石(3CaO·2SiO₂·CaF₂)及玻璃相(Na₂O·Al₂O₃·SiO₂);添加BaO后,钙镁黄长石转变为重硅酸钡钙镁(2CaO·MgO·2SiO₂·BaO),并抑制黄长石和枪晶石晶体长大;当添加B₂O₃的质量分数不低于10%,保护渣形成的物相为玻璃相。试验条件下,不同碱度的保护渣和添加B₂O₃的保护渣中TiO₂仍以TiO₂形式存在,而在添加BaO的保护渣中,TiO₂形成钙钛矿。     

AZ31镁合金电镀前处理工艺研究

采用扫描电子显微分析、失重实验等手段和方法探讨AZ31镁合金电镀前处理工艺。结果表明,采用CrO₃+Fe(NO₃)₃+KF酸洗后试样表面光亮,基本无失重;采用H₃PO₄+NH4HF活化,可有效去除试样表层氧化物,增强基体和浸锌层的结合力;采用硫酸盐浸锌工艺可获得致密的浸锌层。通过分析温度、电流密度、pH值对浸锌层的影响规律,获得了最佳的浸锌工艺：30g/L ZnSO_4?7H₂O, 150 g/L K₄P₂O₇10H₂O,7 g/L KF, 5g/L Na₂CO₃, 温度70℃～75℃, pH=10.2～10.4 ,浸锌时间10 min。在此前处理基础上电镀锌,镀层和基体结合力较好。     

Synthesis of iron（Ⅲ）-doped nanostructure TiO2/SiO2 and their photocatalytic activity

Iron(Ⅲ)-doped nanostructure TiO2-coated SiO2 (TiO2/SiO2) particles were prepared using the layer-by-layer assembly technique and their photocatalytic property was studied. TiO2 colloids were synthesized employing the sol-gel method with TiCl4 as a precursor. The samples were characterized by Fourier transform infrared spectroscopy (FTIR), SEM, EDS, XPS, and XRD. The experimental results show that TiO2 nanopowders on the surface of SiO2 particles are well distributed, the amount of TiO2 is increased with the adding of coating layers, the pure anatase-TiO2 coating layers are synthesized at 500℃, and the photocatalytic activity of Fe3 -doped TiO/SiO2 is higher than tnat of undoped TiO2/SiO2.