Design of Bulk metallic glasses with high glass forming ability and enhancement of plasticity in metallic glass matrix composites: A review

To overcome some of the limits of existing metallic alloys, a new alloy design concept has been introduced recently in order to control the crystallinity, i.e. to utilize crystalline, quasicrystalline, and amorphous structures. In particular, bulk metallic glasses (BMGs) receive great attention because of their unique properties due to their different atomic configuration. Recently, significant progress in enhancing glass forming ability (GFA) has led to the fabrication of BMGs having potential for application as structural and functional materials. Moreover, successful design of BMG matrix composite microstructure suggests that the plasticity of BMGs can be controlled properly. In this review article, we introduce recent research results on the design of BMGs with high GFA and on the enhancement of plasticity in metallic glass matrix composites.     

Zr-Al-Ni-Fe块体非晶合金的成分设计与优化

以等电子浓度和等原子尺寸为判据,以Zr-Al-Ni-Fe合金系为研究体系,设计并制备了7种电子浓度和平均原子尺寸相等但成分不同的系列块体合金.XRD结果表明,只有靠近Zr-Al-Ni三元系的4个合金得到块体非晶;DSC和DTA结果表明,这4个合金中的最佳成分,即具有最高玻璃形成能力和最好热稳定性的合金是Zr60 7Al15.5Ni15.5Fe8.3,其特征热力学参数Tg=710 K,Tx=770 K,△Tx=60 K,Tg/Tm=0.607,Tg/Tl=0.552.     

新型块体非晶合金Cu43Zr43Al7Pd7的形成能力及力学性能和腐蚀性能研究

利用铜模吸铸法成功制备了直径达5mm的新型块体非晶合金Cu43Zr43A17Pd7.利用XRD,DSC,DTA研究了该台金的非晶形成能力(GFA)和热稳定性.结果表明,Cu43Zr43A17Pd7表现出较好的非晶形成能力,表征非晶形成能力的参数Trg和分别为0.61和0.417,过冷液相区△Tx达75K.单轴压缩实验和SEM断口观察表明,该合金具有良好的力学性能,材料压缩断裂应变量和断裂强度分别达到4.9%和1876MPa.利用动电位极化研究了该非晶合金在1mol/L H2SO4和3%NaCl溶液中的电化学腐蚀行为.结果表明,非晶合金在这两种腐蚀介质中均存在自钝化现象,并形成较宽的稳定钝化区,钝化嚣电流密度在10-6-10-5 A/cm2间,远低于Cr18-Ni8不锈钢,表现出良好的耐蚀性能.     

High-temperature oxidation of a rapidly solidified amorphous Ta-Ir alloy

The oxidation products formed at 500 and 700°C on an amorphous Ta-44.5 at% Ir alloy in an Ar-0.1% O₂ gas mixture were characterized using SEM, XRD, EPMA, TEM, STEM, AES, and XPS. Initially, a thin (3–4 nm) layer of Ta₂O₅ formed at the surface of the alloy. Continued growth of the Ta₂O₅, which occurred very rapidly, involved diffusion of oxygen anions from the Ta₂O₅/gas interface to the alloy/Ta₂O₅ interface, where tantalum was selectively oxidized. Because the oxide grew more quickly than iridium could diffuse back into the alloy, the iridium coalesced into platelets of crystalline iridium-rich alloy that were oriented approximately parallel to the oxide/alloy interface, and which became embedded in a matrix of Ta₂O₅. The unoxidized core remained in the glassy state. The oxidation process and/or the dissolution of oxygen into the unoxidized alloy caused the alloy to become embrittled.     

Pd基大块金属玻璃过冷液相区与键参数的关系

通过计算机对Pd基大块金属玻璃的过冷液相区宽度△Tx的表达式进行回归处理分析，得到Pd基大块金属玻璃过冷液相区△Tx与反映合金混合热变化的3个键参数(电负性差△X、原子尺寸差的百分数δ和电子浓度n)之间存在如下关系：△Tx=29．36909 3602．45898(△x)^2 9992．76758δ^2-3．95897n^2/3，相关系数为97．2％。△Tx随多元合金的电负性差和原子尺寸差的百分数的增加而增加，而随电子浓度的增加而略有降低。     

净化对非晶形成能力和非晶热稳定性的影响SCIEI

采用玻璃熔体净化法和电磁悬浮循环过热法消除Ni_(75),B_(17)Si_R合金液内的异质核心,研究了净化对该合金液非晶形成能力和所形成的非晶合金热稳定性的影响。采用净化和忽冷相结合的工艺制备出了20×10×0.5mm的Ni_(75)B_(17)Si_8非晶试样,试样的厚度较净化前提高了4倍。     

Zr基块体非晶合金在过冷液相区的超塑性流变行为

研究了Zr41.25Ti13.75Ni10Cul2．5Be22.5(原子分数,%)块体非晶合金在玻璃转变终了温度Tg^end附近的4个特征温度点(616，636，656和676K)的等温拉伸行为．结果表明,块体非晶合金的超塑性能与环境温度及拉伸速度紧密相关．在656K，以5mm／min的速度拉伸时，获得了1625％的最大延伸率利用速度突变法测出了636，656及676K时的应力敏感指数分别为0．25，0．65和0．93．利用自由体积模型对块体非晶合金的超塑性流变行为的微观机制进行了分析．     

Superplastic deformation and crystallization behavior of Cu54Ni6Zr22Ti18 metallic-glass sheet

Superplastic deformation and crystallization behavior of a Cu₅₄Ni₆Zr₂₂Ti₁₈ metallic glass were investigated. A maximum elongation of 650% was obtained at 733 K at 1 × 10⁻² s⁻¹ from the sheet fabricated by squeeze copper-mold casting method. At low strain rates, the strain-rate-sensitivity exponent value was close to 1, suggesting that Newtonian-like behavior governed the plastic flow. At a high strain rate around 10⁻² s⁻¹, a transition from Newtonian to non-Newtonian behavior took place with decrease in m value. Large strain hardening by crystallization occurred during the course of deformation. The strain hardening was found to be caused by crystallization according to the analyses of the relation of true stress vs. testing time, T-T-T diagram and DSC characteristics. The time periods up to the strain before strain hardening at 733 K for the Cu₅₄Ni₆Zr₂₂Ti₁₈ metallic glass were similar to that of the Zr₆₅Al₁₀Ni₁₀Cu₁₅ metallic glass at 696 K as 180–300 s (3–5 min). This coincidence could be explained by comparison of their T-T-T diagrams showing that the incubation times for crystallization of the Cu BMG at 733 K and for Zr BMG at 696 K are similar.     

Zr-Al-Co块状非晶的成分优化

运用等电子浓度和变电子浓度线判据实现了Zr—Al—Co块状非晶合金的成分优化．在(Al50Co50)-Zr等电子浓度线(e／α=1．5)和(Zr9Co4)—Al及(Zr78．5Co21．5)—Al变电子浓度线上设计成分，并通过吸铸法制备块状合金．实验结果表明，在(Al50Co50)—Zr等电子浓度线和(Zr9Co4)—Al变电子浓度线上可形成块状非晶合金，且非晶合金的热稳定性与非晶形成能力随电子浓度的增大而单调递增．其中，(Al50Co50)-Zr等电子浓度线和(Zr9Co4)—Al变电子浓度线交点处形成的Zr53Al23．5Co23．5非晶合金，具有最大的热稳定性和非晶形成能力，特征热力学参数Tg=783K，Tx=849K，Tg／Tm=0．637，Tg／Ti=0．590。     

稀土钐钴永磁功能合金膜的电沉积制备及磁学性能

在尿素-NaBr-KBr-甲酰胺体系中电沉积制备稀土-铁系金属（Sm-Co）合金,研究沉积液中主盐浓度配比、电流密度等工艺参数对沉积膜的形貌及合金含量的影响。用扫描电镜（SEM）观察金属Sm-Co合金沉积膜表面形貌,结果表明,金属Sm-Co合金沉积膜较平整均匀,呈现银灰色;X射线衍射（XRD）分析表明稀土金属Sm-Co合金为SmCo5六方晶体;特征X射线谱（EDS）证明沉积膜由金属Sm、金属Co和极少量的O、C组成,单质Sm的含量（质量分数）为29.07%,单质Co含量为63.51%;Sm与Co的摩尔比约为1：5;经Ar离子对样品表面层溅射后,X射线光电子能谱（XPS）测定结果进一步证明,沉积层为单质Sm和单质Co。并研究了Sm-Co合金的磁学性能,如矫顽力、磁矩及最大磁能积。用聚乙烯醇保护膜涂附可以防止稀土合金氧化。