Effect of Minor Alloying on Crystallization Behavior and Thermal Properties of Zr_(64.5)Ni_(15.5)Al_(11.5)Cu_(8.5) Bulk Amorphous Alloy

Minor alloying plays an important role in the synthesis and improvement of thermal stability of bulk metallic glasses(BMGs).The present study was conducted to investigate the effect of minor additions of Y,Ti and Nb on the crystallization behavior and the thermal properties of Zr64.5Ni15.5Al11.5Cu8.5 alloy.Thermal parameters and the activation energies for crystallization were calculated for four(Zr0.645Ni0.155Al0.115-Cu0.085)100-xMx(M=Y,Ti and Nb,while x=0,2 at.) alloys.The present alloys have wide supercooled liquid region of ≥87 K.Maximum activation energy was found to be greater than 300 kJ/mol for the base alloy.Four crystalline phases were identified in the samples annealed at 823 K for 20 min.Reduced glass transition temperature(Trg) and other thermal parameters such as γ,δ and β were improved by Y and Ti addition.Nb addition resists crystallization below annealing temperature 713 K,however,its effect on thermal properties is not very promising.     

Characterization of strengthened rapidly quenched Zr-based alloys

The nominal composition components of alloy Zr_66.4Nb_6.4Ni_8.7Cu_10.5Al₈ (Alloy A) were fabricated and characterized. The strengthening of in-situ alloys depends on the role of both the glassy matrix and the second phases. The glass transition and the crystallization kinetics were studied using DSC and X-ray diffraction as a function of element distribution. The amorphous and semi-crystalline structures were identified with the existence of nano crystals in the alloy nominal compositions. The Elastic compression modulus were found to increase with transition to crystallite phase. Where as, the microhardness decreases dramatically with the change from crystalline to amorphous phase. The compression fracture surface shows classic veins behavior. In mode of continuous heating and adiabatic annealing the glass transition, T _g , and the crystalline peak, T _p , temperatures display a strong dependency on heating rate. The activation energy for glass transition and crystallization were determined as E _g  = 226 KJ/mol based on Kissinger method, but during the isothermal process E _g  = 121 KJ/mol.     

非晶合金颗粒／树脂基复合材料的耐蚀性

采用内旋转溶液法制备非晶态Fe_(76)Cr_4P_(13)C_7合金粉末,在其中加入适量的合成树脂,压制成形,制备非晶合金颗粒/树脂基复合材料。研究了复合材料在1N H_2SO_4,1N HCl,1N H_2SO_4+0.5N NaCl,1N NaOH和3.5％NaCl溶液中的耐蚀性。实验结果表明:复合材料在试验介质中具有优异的耐蚀性。在非晶态合金粉末中加入合成树脂,压制成形,可以获得耐蚀的块体材料,具有工业应用价值。     

Er对ZrCuNiAl非晶合金结构、力学性能、热稳定性及非晶形成能力的影响

以(Zr_0.6336Cu_0.1452Ni_0.1012Al_0.12)_100-xEr_x(x=0,0.5,1,1.5,2,2.5,3,原子分数,下同)系块体非晶合金为研究对象,通过改变微量元素Er的含量来研究Er对非晶合金的结构、力学性能、热稳定性及非晶形成能力的影响。结果表明:添加Er元素所制备出的试样都是完全非晶结构的合金。随着Er含量的增加,各试样的弹性模量呈现出先增大后减小,压缩塑性应变呈台阶式上升,x=0,x=0.5,x=1试样的塑性应变在4%的范围内波动;x=1.5,x=2,x=2.5试样的塑性应变在11%的范围内波动;x=3试样的塑性应变最高,其值为23.19%,弹性模量为37.76GPa,屈服强度为1604MPa,抗压强度为2068MPa,断裂强度为2060MPa;随着Er含量的增加,锆基非晶合金的热稳定性和非晶形成能力均先减小后增大。     

Fe70Zr10B20非晶合金的制备及其热稳定性和磁性能研究

采用机械合金化技术制备了Fe70Zr10B2。磁性非晶合金粉末。分析Fe70Zr10B20非晶合金的形成机制、晶化机制：研究Fe70Cr10B20非晶合金不同热处理温度下的磁性及球磨过程中样品的磁性。结果表明：Fe70Cr10B20非晶相的形成是由原子的扩散和晶格崩渍共同作用的结果；Fe70Cr10B20非晶合金的热致晶化模式为一次晶化；球磨过程厦非晶熟处理后样品的磁性与其结构、晶粒尺寸、应力和缺陷等因素有关。     

MgNiSi非晶的制备及其热稳定性和腐蚀性能研究

通过机械球磨的方法成功制得Mg55Ni35Si10非晶粉末,并采用X射线衍射(XRD)对其非晶形成过程进行研究,发现Mg55Ni35Si10粉末样品在球料比为20:1、转速为600r/min的条件下,经过54h球磨后开始形成完全的非晶结构.还采用差示扫描量热仪(DSC)对Mg55Ni35Si10非晶粉末的热稳定性进行了研究,通过Kissinger方程得到样品开始晶化的表观激活能为(280.6±44.5)kJ/mol,与文献中报道的Mg65Cu25Gd10的激活能((285.2±27.6)kJ/mol)相近,说明样品具有较好的热稳定性.此外,还对Mg55Ni35Si10非晶在NaCl溶液中的腐蚀行为进行了研究,发现该样品的腐蚀电位远远正于AZ31和AZ61镁合金,表明Mg55Ni35Si10非晶具有较好的耐腐蚀性能.     

Thermal Expansion Behavior of Precursor—Derived Amorphous Si—C—N and Si—B—C—N Ceramics

Thermal expansion behaviors of some precursor-derived amorphous Si-C-N and Si-B-C-N ceramics, which were shaped by plastic forming after crosslink, were studied. To complete the shrinkage and densification, after thermolysis specimens were heat treated at a temperature of 1400℃ for 10 h in nitrogen atmosphere. The thermal expansion coefficient of VT50-derived amorphous Si-C-N ceramic increases from 1.98×10-6/K at 400℃ to 3.09×10-6/K at 1000℃, of NCP200-derived amorphous Si-C-N ceramic increases from 2.35×10-6/K at 400℃ to 3.45×10-6/K at 1000℃, and of T2-l-derived amorphous Si-B-C-N ceramic increases from 2.08×10-6/K at 400℃ to 3.18×10-6/K at 1000℃. No glass transition for these amorphous ceramic materials was detected, indicating that as-thermolyzed precursor-derived Si-(B-)C-N ceramic materials are amorphous solids, but not glasses.     

Synthesis and Characterization of Fe_(50)Cr_(14)Mo_(14)C_(14)B_6Gd_2 Bulk Amorphous Steel

Bulk amorphous steel having 7 mm thickness was synthesized to evaluate its thermal stability and mechanical properties.The steel was synthesized by Cu mold casting technique using 1-2N pure metals.Characterization of the material was done by X-ray diffraction,differential scanning calorimetry and scanning electron microscopy.The activation energies were calculated by Kissinger equation and it was found that the steel had better stability against crystallization.Mechanical properties like Vicker s hardness,n...     

Thermal Stability and Transformation-mediated Deformability of Cu-Zr-Al-Ni Bulk Metallic Glass Composite

The glass-forming ability and the thermal stabilityof Cu45Zr45Al5Ni5 metallic glass were systematically investigated by the differential scanning calorimetry.The activation energies for the glass transition and the onset crystallization and the crystallization peak were calculated to be 255.1,308.7 and 311.5 kJ/mol,respectively,while the corresponding liquid fragility was determined to be 23.4.By controlling the casting process,Cu45Zr45Al5Ni5 bulk metallic glass composite with the presence of ductile B2 CuZr phase was fabricated.The composite shows a pronounced plastic strain of 6.8 0.05% with obvious work hardening,which results from the formation of multiple shear bands and the deformation-induced martensitic transformation.     

Effects of Composition and Thermal Cycle on Transformation Behaviors, Thermal Stability and Mechanical Properties of CuAlAg Alloy

The phase transformation behavior, mechanical properties, and the thermal stability of CuAlAg alloy were studied and minor rare earth (0.1 wt pct La Ce) was added to improve the mechanical property of the studied alloy. It was found that Ag addition in the CuAl binary alloy can improve the stability of martensitic transformation and high Al content leads to the disappearing of martensitic transformation. The tensile strength and strain of the Cu-10.6Al-5.8Ag (wt pct) alloy were measured to be 383.5 MPa and 0.86%, respectively. With rare earth addition, the tensile strain increased from 0.86% to 1.47%. The CuAlAg alloy did not exhibit martensitic transformation on the second heating process. Its poor thermal stability still needs to be improved.     

热氧化对Zr基块体金属玻璃腐蚀行为的影响

本文系统研究了空气中热氧化对Zr-Cu-(Nb)-Ag-Al-Be块体金属玻璃在含Cl~-溶液中腐蚀行为的影响。热氧化后:样品表面生成0.3~0.4μm厚的氧化层,层内Al和O富集;含Nb样品点蚀电位和自然腐蚀电位明显增大,不含Nb样品极化曲线却无明显变化;浸泡实验中样品表面的腐蚀坑密度显著降低,腐蚀坑内Cu富集、Zr贫化。X射线光电子能谱结果显示热氧化后含Nb样品表面含有Nb_2O_5和更低的Cu含量,而其它元素与不含Nb样品相似。因此,热氧化能更显著地改善含Nb样品耐蚀性能的原因可能是含Nb_2O_5的氧化膜更加致密,以及该氧化层能更有效阻碍Cl~-扩散。     

Effect of Er on properties of Zr-based bulk metallic glasses

(Zr_0.6336Cu_0.1452Ni_0.1012Al_0.12)_100-xEr_x(x?=?0～6) bulk metallic glasses were fabricated by copper mould suction casting method, and the effect of Er on properties was studied. The compressive plastic strain (ε_p) and compressive strength (σ_max) at room temperature increases first and then decreases with the increase of Er content. The compressive plastic strain (ε_p) of the specimen is 35.1% when x?=?2.6, which is about eight times than that of the specimen with x?=?0. The compressive strength (σ_max) is 2513?MPa, which is much higher than that of the specimen with x?=?0. It indicates that Zr-based bulk metallic glasses could be strengthened and toughened by adding Er. The thermal stability decreases gradually and the glass-forming ability increases first and then decreases with the increase of Er content.     

斜离子束辅助沉积对Co30Nb70薄膜结构及其热稳定性的影响

本文研究了离子束辅助沉积(IBAD)Co30Nb70薄膜过程中离子束入射角对薄膜微结构及热稳定性的影响.实验结果表明,在0°到75°范围内改变离子束入射角均可得到Co30Nb70非晶薄膜,但样品微结构出现变化,观察到多孔和沟槽结构.所有样品经300℃退火30 min,入射角为45°制备的样品出现强织构bcc亚稳相,其它入射角沉积的样品均保持非晶相.继续将样品在450℃退火30 min,入射角45°沉积的样品中bcc亚稳相消失,溶人非晶相;15°和75°入射沉积的样品开始晶化.分析认为离子束入射角变化引起的原子混合效应的改变,以及薄膜中的多孔结构对上述变化有重要影响.     

机械合金化Co-Zr非晶软磁合金粉末的形成及热稳定性分析

研究了Co-Zr二元相图上4个共晶点成分配方Co90Zr10、Co53Zr47、Co35Zr65和Co21Zr79在球磨条件下的非晶态合金形成能力。采用X射线衍射和差热分析(DTA)对粉末的结构及热稳定性进行了分析。XRD分析结果表明,4种配方在一定的球磨时间内都能形成非晶态合金,其中非晶形成能力最强的为Co35Zr65。DTA分析结果表明,该合金系具有较高的热稳定性,并具有较高的非晶形成能力。球磨时间对非晶的形成有重要影响,球磨时间过长,使形成的非晶态合金粉体反而向晶体转化。     

Structure and Thermal Parameters of Ni20Pd80 Alloy

The structure and thermal parameters of Ni20Pd80 alloy were studied by X-ray diffraction(XRD). The diffraction experiments performed in the temperature range of 308–1100 K revealed that the alloy formed a face centered cubic (fcc) A1-type structure. The temperature dependence of the lattice parameters was investigated by using the Bragg line displacement method showing that the lattice parameter increases with the increase of temperature. The mean linear thermal expansion (MLTE(%)), coeffcient of thermal ex...     

Ce添加对Mg–Ca挤压合金力学性能与热稳定性影响研究

目的 研究在Mg–0.2Ca挤压合金基础上分别添加质量分数为0.3%的Ce和0.6%的Ca后对合金的组织、力学性能和热稳定性的影响,探究Ce和Ca 2种合金元素对镁合金的强化和中高温条件下的稳定化效果。方法 首先,熔炼制备Mg–0.2Ca、Mg–0.2Ca–0.3Ce和Mg–0.8Ca 3种成分的合金;随后,对3种合金进行挤压变形,并对挤压合金组织和力学性能进行表征和测试;最后,在300℃下对3种合金进行等温退火,研究其组织演变过程和力学性能的衰减情况。结果 在Mg–0.2Ca合金基础上添加质量分数为0.3%的Ce可将挤压态合金再结晶分数由约92%降至约53%,再结晶晶粒尺寸由约1.64μm细化至约0.86μm,Mg–0.2Ca–0.3Ce三元合金的屈服强度可大幅提升至约364 MPa,该屈服强度与Mg–0.8Ca合金相当（约361 MPa）,表明单位质量Ce的添加对强度提升的效果优于Ca。退火3 h后,Mg–0.2Ca–0.3Ce三元合金屈服强度的下降幅度约为124 MPa,显著低于Mg–Ca二元合金（约170 MPa）。以Mg–0.2Ca–0.3Ce合金为例进行静态再结晶组织演化分...     

Cyclic Fatigue Fracture of Zr55Al10Ni5Cu30 Bulk Amorphous Alloy with Quenched-in Crystallites

The effects of quenched-in crystallites on the fracture of bulk amorphous alloys under cyclic loading condition were investigated in this paper,For the fully amorphous alloy and specimen with fine crystallites the fatigue crack initiation occurred on the surface,For the specimen with larger cystallites the crack originated from a big broken crystallite near the surface,The average striation spacing on amorphous area is much larger than that on the crystallite Crack initiation occurred at the cystallites is due to that the brittle cyrstallites broke easily under cyclic deformation condition.The fine cystallites seemed to be protruded from the amorphous matrix and some bulges appeared on the surface of specimen with fine crystallites under cyclic loading.     

快速凝固Al-Si-Fe-Cu-Mg合金的热稳定性

研究了快凝Ａｌ－Ｓｉ－Ｃｕ－Ｍｇ合金在不同热暴露温度下的热稳定性。维氏硬度测试结果表明：合金长时间在１５０℃下热暴露时，硬度降低程度很小，而温度为３００℃时硬度呈显著降低趋势；微观组织分析发现：热暴露温度为１５０℃时，合金基体基本未发生再结晶，而３００℃时出现了大量再结晶组织；合金中的第二相形态在热暴露过程中基本不变。     

Investigation of Micro Formability of Bulk Amorphous Alloy in the Supercooled Liquid State Based on Fluid Flow and Finite Element Analysis

Research results on the viscous flow deformation behavior of bulk amorphous alloy in different systems are reviewed. The material exhibits an ideal Newtonian fluid at a high temperature. Analytical solution of lamellar fluid flow behavior is used to discuss the viscous flow behavior of the bulk amorphous alloy in the supercooled liquid state. A material model, which describes such deformation behavior of Mg60Cu30Y10 amorphous alloy,is introduced into the finite element method of microforming process. Surface feature size was investigated and found not sensitive to the micro formability. Bulk amorphous alloy may possibly be applied to microelectro-mechanical-systems (MEMS) fabrication.