Thermal stability and glass-forming ability of Y-Ce-Co-Al bulk metallic glasses

The thermal stability and glass-forming ability of Y56-xCexCo20Al24 (x=15, 20, 25, 28, 38, 41, 44) bulk metallic glasses with a diameter of 5 mm were investigated by differential scanning calorimetry and X-ray diffraction. The results show that the thermal stability of the alloys decreases with the addition of Ce. It has the best glass-forming ability when x=25, whose calculated values can reach about 30 mm in diameter. The effect of Ce element could be explained on the view of Miedema’s theory and elec- tronegativity difference of amorphous alloys.     

镁基大块非晶合金的制备与性能研究

采用铜模浇铸的方法成功制备了最大直径为12mm的Mg65Cu20Ag5Gd10非晶合金,并对其结构、热稳定性能、非晶形成能力、压缩性能及断口形貌进行了分析.结果表明,Mg65Cu20Ag5Gd10具有较强的玻璃形成能力和良好的热稳定性能;合金的断裂强度达895MPa,弹性应变为2.35%.     

Synthesis, structure and mechanical properties of Zr-Cu-based bulk metallic glass composites

The unusual glass-forming ability(GFA) of the Zr_(48)Cu_(36)Ag_8Al_8 alloy and the high ductility of the Zr_(48)Cu_(36)Ag_8Al_8 metallic glass-matrix composites containing Ta powder were reported.The bulk metallic glass rod with a diameter of 25 mm was successfully synthesized using copper mold casting for the Zr_(48)Cu_(36)Ag_8Al_8 alloy.High GFA of this alloy was found to be related to a large supercooled liquid region and a quaternary eutectic point with low melting temperature.The bulk metallic glass...     

Preparation and thermal stability of Pd_(40.5)Ni_(40.5)SixP_(19-x) bulk metallic glasses

With the addition of Si to replace some P,Pd_(40.5)Ni_(40.5)Si_xP_(19-x)(x=0,2.5,5,9.5,14,and 19 in atomic number fraction) bulk glassy samples with the diameter of about 5 mm were successfully prepared by use of flux treatment and water quenching technology.With the increase of Si content,the glass forming ability of Pd_(40.5)Ni_(40.5)Si-xP_(19-x) increases first for low Si content and then decreases for high Si content (Si≥9.5at%).The Pd_(40.50Ni_(40.5)Si_5P_(14) glassy alloy possesses the largest supe...     

Mg-Zn-Ca块体非晶合金及其强度可靠性

针对Mg-Ln-TM块体非晶合金脆性大、强度可靠性差等特点,研究了新型Mg-Zn-Ca非晶合金的性能并考察了成分变化对其热稳定性的影响。采用铜模铸造法制备出直径为2mm的Mg_70-xZn_25+xCa₅(x=1、2、3、4)系列非晶合金,利用扫描电镜(SEM)、X射线衍射仪(XRD)、差分扫描量热仪（DSC）以及电子万能试验机分别研究了铸态样品的组织、相结构、热稳定性以及力学性能。实验结果表明：该系列非晶合金的晶化过程分3~4步完成,初始晶化温度随Mg含量的提高而降低,同时对应较高的强度和一定的塑性应变。经Weibull统计分析表明：这4种非晶合金断裂强度的再现性存在差别,其中具有脉络纹断口的合金具有较高的Weibull模量,对应着良好的断裂强度再现性。     

Room temperature plastic deformation behavior of ZrCuNiAl bulk metallic glasses

The Zr62.55Cu17.55Ni9.9Al10 bulk metallic glass (BMG) was prepared by using copper-mold suction-casting. X-ray diffraction and differential scanning calorimetry were utilized to determine its structure and thermal stability. Uniaxial compression and Rockwell indenta-tion tests were adopted to study the plastic deformation behavior at room temperature. The results show that the glass transition temperature and the onset temperature of exothermic reaction of the BMG are 651.5 and 748 K, respectively. During the compression test, the BMGs undergo an engineering strain of about 2.5%, i.e., true strain of 2.8%, and then fracture. The BMGs deform via the formation and propagation of shear bands. Under indentation loading, the BMGs deform through the formation of radiation-like and circular shear bands. The circular shear bands form earlier than the radiation-like ones. The formation mechanism of shear bands in the BMGs was analyzed and discussed.     

Formation and thermal stability of Cu-Zr-Al-Er bulk metallic glasses with high glass-forming ability

The formation and thermal stabilities of Cu46.25Zr46.25xAl7.5Erx (x=0 to 8) bulk metallic glasses (BMGs) were investigated. The addition of a small amount of Er (2at%) for replacing Zr effectively improves the glass-forming ability of Cu46.25Zr46.25Al7.5 alloy, and the glassy rod with a diameter of at least 12 mm can be formed. The glass transition temperature (Tg), temperature interval of su- percooled liquid region △Tx (=Tx-Tg), and reduced glass transition temperature Trg (=Tg/Tl) of Cu46.25Zr44.25Al7.5Er2 glassy alloy are 699 K, 62 K and 0.607, respectively.     

Compositional dependence of thermal and elastic properties of Cu-Ti-Zr-Ni bulk metallic glasses

Starting from the quaternary Cu47Ti34Zr11Ni8 alloy, the compositional dependence of thermal and elastic properties of Cu-Ti-Zr-Ni alloys was systematically investigated. Quaternary Cu-Ti-Zr-Ni alloys can be cast directly from the melt into copper molds to form fully amorphous strips or rods with the thickness of 3-6 mm. The evidence of the amorphous nature of the cast rods was provided by X-ray spectra. The measured glass transition temperature (Tg) and crystallization temperature (Tx) were obtained for the alloys using differential scanning calorimetry (DSC) at the heating rate of 20 K/s. In the results, the differences between the glass temperature and the crystallization tempera-ture (△Tx=Tx-Tg) are measured with values ranging up to 33-55 K. The reduced glass transition temperature (Trg), which is the ratio of the glass temperature to the liquidus temperature (T1), is often used as an indication of the glass-forming ability of metallic alloys. For the present Cu-Ti-Zr-Ni alloys, this ratio is typically in the range of 0.5838-0.5959, characteristic of metallic alloys with good glass-forming ability. The elastic constants for several selected alloys were measured using ultrasonic methods. The values of the elastic shear modulus, bulk modulus, and Poisson's ratio were also given.     

块体非晶合金的研究进展

块体非晶合金具有比各种传统材料更为优异的物理、化学、力学性能及精密成型性,因而一直是材料科学与物理研究的热点。本文分析讨论了该领域中存在的一些基本的问题,并从成分结构条件、热力学条件、动力学条件等方面阐述了块体非晶合金的形成机制,介绍了块体非晶合金优异的性能和应用前景,并扼要介绍了块体非晶合金未来的发展趋势及方向。     

SiC颗粒增强锆基非晶材料的组织与变形行为

为获得高强度、低密度且有一定塑性的新型复合材料,在铜模喷铸条件下制备了体积分数分别为6%和10%的SiC颗粒增强Zr_5.05Al₉Ni_4.05Cu_36.45块体非晶合金复合材料.应用x射线衍射仪、透射电镜、材料试验机和扫描电镜分析了复合材料的相组成、微观组织、压缩性能及断口形貌.实验结果表明：界面微观组织的变化对复合材料力学性能有显著的影响.有限的界面反应物ZrC能够增强界面的结合强度,有效地传递应力,从而阻碍剪切带的局域化扩展,促使多重剪切带的萌生,有助于提高合金的强度和塑性.而过量的界面反应则弱化界面的结合强度,致使合金压缩变形时,沿界面迅速开裂,表现为脆性断裂.     

Glass forming ability, microstructure and magnetic property of NdAlNiCuFe alloys

The glass forming ability (GFA), microstructure and magnetic property in (Nd60Al10Ni10)Cu20-xFex (0≤ x≤ 20) alloys were investigated by using X-ray diffraction (XRD), differential scanning calorimetry (DSC), high resolution transmission electron mi- croscopy (HRTEM) and magnetic property measurement. It is shown that the GFA of the alloys decreases with Fe content. The sam- ples for bulk cylinders with x≤10 show a distinct endothermic peak in the DSC traces due to a glass transition in the range of 421-438 K. With further increasing Fe, the glass transition is masked by the crystallization. The microstructure of the Nd-based alloy can change progressively from full glassy state into composite state with nanocrystalline particles in the glassy matrix indicating the glass forming ability degrades with increasing Fe. The average size of nanocrystals increases with Fe and the distribution changes from homogenous to heterogeneous. The magnetic property varies from paramagnetic to hard magnetic when the Fe content increases up to about 4at% indicating that the magnetic property is related to the metastable phases.     

非晶合金摩擦焊装置设计

为了增大非晶合金尺寸,设计了一种新型摩擦焊装置,用来连接毫米尺度的非晶合金棒料.该装置主要由主轴旋转单元,直线驱动单元以及参数控制单元三部分组成,分别实现工件的旋转、直线运动、摩擦焊接参数控制及采集.采用LABVIEW软件搭建了操作界面,实现焊接过程中主要参数的输入及监控采集.以Zr 55Cu 30Al 10Ni5非晶棒料为焊接对象,在不同焊接参数下进行了摩擦焊试验.结果表明,较高的转速能更快的让摩擦界面较短时间内完全进入过冷液相区,成功实现工件连接.新型摩擦焊装置能够实现非晶合金棒料的连接,达到设计要求.     

Effects of processing technologies on mechanical properties of sic particulate reinforced magnesium matrix composites

Mg matrix composites with SiC particles ranging from 5vol%-25vol% were prepared using stirring casting method. Die casting, squeezing casting, and extrusion were applied for inhibiting or eliminating the defects such as gas porosity and shrinkage void. Through die casting and squeezing casting, most of the defects in Mg matrix composites could be eliminated, but the mechanical properties were improved limitedly. On the other hand, after hot extrusion, not only most of the defects of as-cast composites ingots were eliminated, but also the mechanical properties were improved markedly. With the addition of SiC, the tensile strength, yield strength and elastic modulus of as extrusion SiCp/AZ61 composites increased remarkably, and the elongation decreased obviously.     

Glass formation of ternary Sm-based Sm-Al-Co bulk metallic glasses

Ternary Sm-based Sm-Al-Co alloys at specific compositions designed using an e/a- and cluster-related criteria exhibit high glass forming abilities and form bulk glassy rods of 3 mm in diameter by a copper mold suction-casting method. Four composi- tions of bulk metallic glasses (BMGs) are Sm50Al25Co25, Sm52Al24Co24, Sm54Al23Co23 and Sm56Al22Co22, which all satisfy a constant conduction electron concentration of 1.5. Among them, the BMG exhibiting the largest reduced glass transition temperature (Trg) is Sm50Al25Co25, which reaches 0.648. The glass transition temperature Tg and the onset crystallization temperature Tx of this alloy are respectively 579 and 640 K at a heating rate of 20 K/min.     

Formation and corrosion properties of Fe-based bulk metallic glasses

Bulk metallic glass (BMG) formation was explored in the Fe-B-Si-Nb alloy system though combined use of the atomic cluster line approach and the minor alloying strategy. The basic ternary compositions in the Fe-B-Si system were determined by the intersection points of two cluster lines, namely, Fe-B cluster to Si and Fe-Si cluster to B. 3at%-4at% Nb was added to the quaternary Fe-B-Si-Nb alloy. The casting experiments revealed that good glass-forming ability (GFA) occurred at the (Fe73.4Si8.2B18.4)96Nb4 composition, and 3-mm diameter BMG samples were made. The glass transition temperature (Tg), crystallization temperature (Tx, and supercooled liquid region (△Tx=Tx-Tg) of this BMG were measured to be 866, 889, and 23 K, respectively. The BMG shows a high Vickers hardness of about Hv 1164, a Young's modulus of 180 GPa, and a good corrosion resistance in the solutions of 1 mol/L HCl and 3 wt% NaCl.     

Characterization of plastic flow in two Zr-based bulk metallic glasses

1 Introduction Bulk metallic glasses (BMGs) have attracted a great attention due to their excellent properties, such as high strength, good wear resistance, excellent elasticity and easily forming in viscous state. However, structural applications are currently limited by the lack of macroscopic plasticity at room temperature, characterized by strain-softening which results in the formation of intense localized shear bands. Fracture typically occurs after very small plastic strain in compress…     

玻璃纤维的含量对复合材料的力学性能影响及表征研究

为研究不同质量分数的玻璃纤维对增强聚丙烯复合材料力学性能的影响,选择直径为10μm的玻璃纤维制备复合材料小样.测试在不同质量分数时材料的拉伸强度、弯曲弹性模量等力学性能,并应用扫描电镜(SEM)对其微结构进行表征.结果表明:玻璃纤维质量分数对复合材料的取向分布有很大影响,随着玻璃纤维质量分数增加,拉伸强度增大,但弯曲弹性模量、弯曲强度变化不明显.此外,随着质量分数的增加,复合材料的脆性变大;SEM分析表明复合材料中玻璃纤维有一定的取向且分布相对均匀,玻璃纤维和复合材料基体结合良好.     

Effects of yttrium on the formation and magnetic properties of bulk metallic glassy （Fe, Co）-B-Si-Nb alloys

The bulk metallic glassy (BMG) rods of [(Fe0.5Co0.5)0.72B0.192Si0.048Nb0.04]100-xYx (x=0-6) and [(FexCo1-x)0.72B0.192Si0.04]Nb0.04]96Y4 (x=0.5-0.8) were prepared by copper mold casting. The structure, thermal stability,and magnetic properties of the samples were studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and vibrating sample magnetometer (VSM). Adding lat% to 6at% of yt-trium, the bulk glassy alloy rods of [(Fe0.5Co0.5)0.72B0.192Si0.048Nb0.04]100-xYx (x=0-6) with the diameter of 3 mm were not formed, and the sample with 4at% of yttrium showed less crystalline phase than others. When the Fe/Co atomic ratio was between 5:5 and 7:3, the bulk glassy alloy rods of [(Fe1-xCox)B0.192Si0.048Nb0.04]96Y4 (x=0.5-0.8) with the diameter of 2 mm were fabricated. In the (Fe, Co)-B-Si-Nb-Y BMGs, when the Fe content increased, the thermal stability, the supercooled liquid region, and the glass-forming ability (GFA) decreased, but the saturation magnetization (Ms) increased.     

界面强度对纤维复合材料破坏及力学性能的影响

界面作为复合材料中的重要组成部分对其宏观力学性能及破坏模式有着不可忽视的影响. 本文采用自组装薄膜技术对玻璃纤维表面改性, 得到不同表面性质的玻璃纤维, 与环氧树脂基体复合得到不同界面强度的复合材料. 利用带偏光显微镜的拉伸仪, 研究在不同界面强度下玻璃纤维/环氧树脂基复合材料的破坏过程及力学性能. 结果表明, 复合材料在强界面情况下发生脆性破坏, 在弱界面情况下发生韧性破坏, 且增强纤维对复合材料性能的增强效果与界面强度有关.