Effect of Nb on the corrosion behavior of continuous bulk metallic glass-coated steel wire composites

(Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5)_100?xNb_x (at%, x=0 and 8) bulk metallic glasses (BMGs) were coated on the surface of Q195 steel wires by a continuous coating process. The potentiodynamic polarization tests of these BMGs were conducted in 3.5wt% NaCl aqueous solution. It is found that the addition of 8at% Nb into Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5 alloy results in the improvement of corrosion resistance with the pitting potential of ?52 mV, the open circuit potential of ?446 mV, and the corrosion current density of 9.86×10?6 mA/cm2. This may be attributed to that Nb is beneficial to passivate and stabilize Zr and Ti.     

Novel titanium particles reinforced Zr-based bulk metallic glass composites prepared by infiltration casting

A novel Ti/Zr_41.2Ti_13.8Cu_12.5Ni_10.0Be_22.5 composite was successfully prepared by infiltrating the melt into sintered Ti preform. It shows that the introduction of Ti particles into the composite results in an increase in elastic strain to 3% and an enhancement of the strength up to 2.1 GPa. High specific strength has been obtained because of the decrease in density of the composite. It is suggested that an improvement in the mechanical properties of the composite may be attributed to the generation of multiple shear bands and some deformation in the Ti particles.     

Zr50.5Cu36.5Ni4Al9块体非晶合金低温动态压缩特性

通过铜模铸造法制备Zr_50.5Cu_36.5Ni₄Al₉块体非晶合金. 利用分离式霍普金森杆（SHPB）,S-4800型扫描电镜等测试分析手段,研究Zr_50.5Cu_36.5Ni₄Al₉块体非晶合金在室温（25℃）和低温下（-40℃）动态压缩特性和断口形貌特征. 结果表明:在动态压缩载荷作用下,Zr_50.5Cu_36.5Ni₄Al₉块体非晶合金抗压强度随载荷增加而降低. 在-40℃低温条件下,动态抗压强度具有低温敏感性. 在室温条件下,Zr_50.5Cu_36.5Ni₄Al₉块体非晶合金断口微观形貌特征主要是脉状花样,伴随裂纹和非晶合金熔化现象;在-40℃ 低温条件下,Zr_50.5Cu_36.5Ni₄Al₉块体非晶合金微观形貌特征主要是鱼骨状花样.      

Bulk metallic glass rings prepared by a modified water quenching method

Bulk metallic glass rings have the potential applications as annular gasket and active solder in special fields. The bulk metallic glass ring of Zr_1.2Ti_13.8Cu_12.5Ni_10.0Be_22.5 with the outer diameter, the inner diameter, and the thickness of 38, 36, and 5 mm, respectively, was prepared by using a special shaped quartz tube water quenching method. The mechanical properties along the whole cross section were investigated by a nanoindentation method, and no evident variation of the Young's modulus and hardness was found, further indicating the single amorphous structure. Amorphous ring and tube-shape parts with different dimensions can be produced by this method.     

Dendritic and spherical crystal reinforced metallic glass matrix composites

Zr-based bulk metallic glass matrix composites (BMGMCs) with a composition of Zr_60.0Ti_14.7Nb_5.3Cu_5.6Ni_4.4Be_10.0 (at%) were fabricated by an innovative process, i.e., semisolid processing plus Bridgman solidification. Different morphologies, distributions, and volume fractions of the crystalline phases can be achieved by tailoring the withdrawal velocity. The largest fracture strain of Zr_60.0Ti_14.7Nb_5.3Cu_5.6Ni_4.4Be_10.0(at%) composites with the withdrawal velocity of 1.0 mm/s was found to be 16.7%. The mechanism of plasticity improvement is mainly attributed to the interpenetrated structure of the crystalline phase, which greatly confines the rapid propagation of shear bands.     

轧制塑性变形对Zr65Al7.5Cu12.5Ni10Ag5非晶合金力学性能的影响

采用维氏显微硬度仪、扫描电子显微镜对铸态、轧制态Zr₆₅Al_7.5Cu_12.5Ni₁₀Ag₅非晶合金的硬度及剪切带形貌进行了研究,并对轧制变形量与合金的力学性能之间的关系进行了分析。结果发现,在室温轧制条件下,该合金最大变形量达到了95%;铸态试样的半圆形剪切带规律、平滑,随着轧制变形量的增加剪切带形貌变得越来越混乱,合金的硬度总体呈下降趋势。     

Limitation of the Johnson-Mehl-Avrami equation for the kinetic analysis of crystallization in a Ti-based amorphous alloy

The primary crystallization of the Ti₄₀Zr₂₅Ni₈Cu₉Be₁₈ amorphous alloy was studied by isochronal differential scanning calorimetry (DSC). The activation energy was determined by the Kissinger-Akahira-Sunose method. Trying to analyze the crystallization kinetics of the Ti₄₀Zr₂₅Ni₈Cu₉Be₁₈ amorphous alloy by two different methods, it was found that the crystallization kinetics did not obey the Johnson-Mehl-Avrami equation. A modified method in consideration of the impingement effect was proposed to perform kinetic analysis of the isochronal crystallization of this alloy. The kinetic parameters were then obtained by the linear fitting method based on the modified kinetic equation. The results show that the isochronal crystallization kinetics of the amorphous Ti₄₀Zr₂₅Ni₈Cu₉Be₁₈ alloy is heating rate dependent, and the discrepancy between the Johnson-Mehl-Avrami method and the modified method increases with the increase of heating rate.     

Strain rate response of a Zr-based composite fabricated by Bridgman solidification

Zr_58.5Ti_14.3Nb_5.2Cu_6.1Ni_4.9Be_11.0 bulk metallic glass matrix composites, containing β-Zr dendrites, were fabricated by Bridgman solidification at the withdrawal velocity of 1.0 mm/s through a temperature gradient of ～45 K/mm. Subjected to the increasing compressive strain rates, the monotonic increasing and decreasing were obtained for the maximum strength and the fracture strain, respectively. The results show that high strain rate may induce the insufficient time for the interaction between shear bands and the crystalline phase, and early fracture occurs as a result. The fractographs are consistent with the mechanical properties, and the failure mode of the present Zr-based composites is in agreement with the frame of the ellipse criterion.     

Zr77.1Cu13Ni9.9非晶合金破片侵彻LY12铝合金及TC4钛合金靶板毁伤后效及机理对比研究

锆基非晶合金是极具发展潜力的含能结构材料,由其制备的破片侵彻不同材质装甲时,会表现出显著不同的毁伤效果.本研究中利用弹道枪发射装置,针对Zr_77.1Cu₁₃Ni_9.9非晶合金破片,以1 200 m/s速度分别侵彻8 mm厚LY12铝合金和TC4钛合金屏蔽靶,结合高速摄影技术比较了破片碎裂形成碎片云并造成毁伤后效的过程;同时基于FEM/SPH自适应耦合法,再现了破片对两类屏蔽靶开坑、稳定侵彻、穿透等系列阶段,以及碎片云形成的复杂物理过程,揭示了其对后效靶的毁伤机理.结果表明,由于TC4钛合金相比LY12铝合金具有更高的强度,穿透TC4屏蔽靶所需的时间更长,且靶板内最大等效应力是后者的3倍左右;破片在侵彻TC4屏蔽靶时与靶板间发生了更强的相互作用,使得破片前端出现更大面积的高应变区域,由此导致破片发生了更严重的破碎并产生分布范围更大的碎片云,从而在后效靶上产生更大面积的损伤.     

Eutectic reaction and cored dendritic morphology in yttrium doped Zr-based amorphous alloys

The microalloying effect of yttrium on the crystallization behaviors of (Zr_0.525Al_0.10Ti_0.05Cu_0.179Ni_0.146)_100-x Y_x, and (Zr_0.55Al_0.15-Ni_0.10Cu_0.20)_100-x Y_x (x=0, 0.4, and 1, thus the two alloy systems were denoted as Zr52.5, Zr52.5Y0.4, Zr52.5Y1, and Zr55, Zr55Y0.4, Zr55Y1, respectively) was studied. Transmission electron microscopy (TEM) results suggested that the crystalline phases were different in the two Zr-based alloys and with different yttrium contents. ZrNi-phase and Al₃Zr₅ phase precipitations can be well explained by the mechanisms of nucleation and growth. Al₃Zr₅ phase is mainly formed by a peritectic-like reaction, while ZrNi-phase by a eutectic reaction. The contents of elements Y, Al, and Ti may dominate the reaction types. The orientation relationship between Y₂O₃ particles and Al₃Zr₅ phase is also discussed.     

Effects of small amount Ta on the characteristics of the Zr-Al-Ni-Cu-Ta bulk metallic glass

The effects of Ta on the characteristics of the Zr-base BMG (bulk metallic glass) were investigated. Zr₅₅Al₁₀Ni₅Cu_30-xTa_x (x=1, 2,4) bulk metallic glasses (BMGs) with 3.5 mm diameter and 70 mm length were successfully prepared by using combined jet and copper mold casting. A small amount of Ta addition does not change the glass transition temperature, crystallization temperature,and supercooled liquid region obviously, but Ta promotes composition separation and two-stage crystallization. The stable crystalline phases include Zr₂Ni, CuZr₂, Al₂Zr₃ intermetallic compounds and Ta-rich solid solution after annealing the Zr-Al-Ni-Cu-Ta alloys at 753 K. Zr₅₅Al₁₀Ni₅Cu_30-xTa_x (x=1,2,4) bulk glassy alloys exhibit a better compressive strength. The stress-strain curve shows a zigzag feature, and the fracture surface shows intersecting of shear bands. It may correlate with the inhomogeneous feature of amorphous structure.     

添加元素对Mg-基非晶合金非晶形成能力和热稳定性的影响

研究Mg₆₀Ni₂₅Gd_15-xNd_x（x=0,7.5,15）和(Mg₆₀Ni₂₅Gd₁₅)_100-xM_x(M=Fe或Co)（x=0,3,5）非晶态合金快淬甩带样品的非晶形成能力(GFA)及热稳定性随成分的变化关系. 结果表明, 用Nd替代Gd可提高Mg₆₀Ni₂₅Gd_15-xNd_x（x=0,7.5,15）合金的GFA和热稳定性, Fe或Co与主元素间的正混合热降低了(Mg₆₀Ni₂₅Gd₁₅)_100-xM_x(M=Fe或Co)合金的GFA和热稳定性.      

基于动态三点弯曲实验的Zr41.2Ti13.8Cu12.5Ni10Be22.5大块金属玻璃断裂行为

基于改进的分离式霍普金森压杆实验,研究了金属玻璃分别在预刻Ⅰ/Ⅲ缺口和Ⅰ型缺口条件下断裂行为的差异性。发现在冲击载荷下,Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni_(10)Be_(22.5)试样发生Ⅰ/Ⅲ型断裂的起裂时间相对于Ⅰ型断裂明显被延迟;并且Ⅰ/Ⅲ型断裂的卸载过程明显被延阻。Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni_(10)Be_(22.5)试样所承受的峰值载荷呈现出随着冲击速度增加而增大的趋势;当冲击速度相近时,试样发生Ⅰ/Ⅲ型断裂比发生Ⅰ型断裂承受了更大的峰值载荷。通过对试样电镜扫描图的分析,从形貌学和剪切带形成机理角度对实验结果进行了解释。     

基于高熵合金中间层的铜/钢TIG焊接头组织与性能

铜/钢复合结构不仅能够满足不同环境对材料性能的要求,还可减少铜材的消耗,将大大降低构件的成本;但铜与钢之间物化性能差异较大,其中极差的相溶性会导致焊后出现液相分离或缺陷。基于焊缝金属固溶-高熵化思路,设计Fe₅Co₃₀Cr₃₀Ni₃₀Cu₅高熵合金作为中间层,对T2紫铜和Q235钢进行TIG焊接,并对中间层及接头的组织与性能进行分析。结果表明：Fe₅Co₃₀Cr₃₀Ni₃₀Cu₅高熵合金为单相FCC固溶体结构,具有良好的强度和塑韧性;采用该中间层材料,利用TIG焊方法可实现T2紫铜和Q235钢的可靠连接,焊缝成形良好且无气孔、裂纹等缺陷;焊缝区组织为单相FCC固溶体结构,具有显著的高熵化特征;焊接接头平均抗拉强度为225 MPa,达到铜母材强度的91%,平均断后延伸率达到44%;接头断裂发生在紫铜侧热影响区,且断口表面呈现有大量的韧窝结构,具有显著的韧性断裂特征。     

Dy对Nd60Fe30Al10磁性能的影响

通过X射线衍射仪、 差热扫描量热仪和振动样品磁强计研究Dy对Nd-Fe-Al非晶合金的热稳定性及磁性能的影响. 结果表明, 加入Dy可提高非晶合金的热稳定性, (Nd_1-xDy_x)₆₀Fe₃₀Al₁₀（x=0,0.1,0.2）非晶合金的剩磁随Dy质量分数的增加呈单调下降趋势, 矫顽力随Dy质量分数的增加而增加. Nd\|Fe\|Al非晶合金的矫顽力来源于稀土元素较大的磁晶各向异性场.      

全d族Ni–(Co)–Mn–Cu–Ti合金马氏体相变、力学性能和磁性能的第一性原理计算

全 d 族 Ni–Mn–Ti 基 Heusler 合金作为一种新型的智能材料,因其丰富的物理性质被广泛关注。与传统 Ni–Mn 基合金不同,Ni–Mn–Ti 基 Heusler 合金的d–d轨道杂化取代p–d 轨道杂化,提高了合金的塑韧性,解决了传统Ni–Mn 基合金固有脆性大、力学性能差的问题。由于卓越的机械性能和相变过程中较高的熵变,Ni–Mn–Ti 基合金在超弹性和弹热制冷方面具有广阔的研究前景。Cu掺杂和Cu–Co共掺Ni–Mn–Ti 合金的研究很少,本文旨在为Ni–Mn–Ti 基合金的成分设计提供理论支持。本文通过第一性原理计算对Ni₂Mn_1.5?xCu_xTi_0.5 (x = 0.125, 0.25, 0.375, 0.5) 和 Ni_2?yCo_yMn_1.5?xCu_xTi_0.5 [(x = 0.125, y = 0.125, 0.25, 0.375, 0.5) 和 (x = 0.125, 0.25, 0.375, y = 0.625)]合金系的马氏体相变,力学性能和磁性能进行了系统研究。Ni–(Co)–Mn–Cu–Ti合金马氏体的形成能始终低于奥氏体的形成能,表明合金均能发生马氏体相变。Ni₂Mn_1.5?xCu_xTi_0.5 和 Ni_2?yCo_yMn_1.5?xCu_xTi_0.5 (y < 0.625)合金的奥氏体和非调制马氏体都是反铁磁态的,当y = 0.625时, Ni_2?yCo_yMn_1.5?xCu_xTi_0.5合金的奥氏体由反铁磁态转变为铁磁态,而马氏体保持反铁磁态,马氏体相变时合金会伴随磁性的突变,即发生磁—结构耦合现象,这是合金具有磁热效应的物理基础。掺Cu能降低Ni–(Co)–Mn–Ti合金的热滞后和各向异性。提高Mn的含量并且降低Ti的含量能提高Ni–Mn–Cu–Ti合金抗剪切和抗正应力的能力,但会降低韧性。就延展性而言,Ni–Mn–Cu–Ti 和 Ni–Co–Mn–Ti合金强于Cu–Co共掺合金。     

Room temperature plastic deformation behavior of ZrCuNiAl bulk metallic glasses

The Zr_62.55Cu_17.55Ni_9.9Al₁₀ 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 indentation 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.     

Zr原子分数对Ti基非晶复合材料腐蚀性能的影响

采用磁悬浮熔炼水冷铜坩埚-负压铜模吸铸法制备了(Ti_0.5Ni_0.5－xZr_x)₈₀Cu₂₀(x=0、0.02、0.04、0.06)非晶复合材料,分析了各种合金试样的相组成,测试了合金试样在人工海水和模拟人体的PBS溶液中的极化曲线,观察了电化学反应后的腐蚀形貌,分析电化学腐蚀产物并进行表征.结果表明:几种合金的组织都是非晶基体与晶体相组成的复合材料,晶体相为B2-Ti(Ni, Cu)奥氏体相和B19’-Ti(Ni,Cu)马氏体相.与晶态TC4合金相比,合金在两种溶液中均具有较好的耐蚀性,且随着Zr元素原子分数的增加,合金的腐蚀抗性也不断增强;当x=0.06时,合金的耐腐蚀性能最为优异,其自腐蚀电位高,为－0.218 V,热力学倾向小不易腐蚀,自腐蚀电流密度较低,为0.912 μA·cm^－2,极化电阻大,为3.4 MΩ·cm²,腐蚀的动力学速率低,且在PBS溶液中合金具有更优异的耐蚀性,在腐蚀形貌中未发现明显的点蚀坑.     

退火处理对Dy4(Co21Cu79)96颗粒膜结构和巨磁电阻效应的影响

采用磁控溅射法制备Dy₄(Co₂₁Cu₇₉)₉₆颗粒膜,研究薄膜的巨磁电阻（GMR）效应及磁性能.应用X射线衍射仪（XRD）对薄膜微观结构随退火温度的变化进行分析,采用四探针及振动样品磁强计（VSM）测量薄膜的磁电阻和磁性能.X射线衍射实验结果表明:制备态的薄膜形成了单相亚稳态面心合金结构,退火处理将促进Cu和Co的相分离.磁电阻测试发现:所有不同成分的Dy_x(Co₂₁Cu₇₉)_100-x（x=0,4,8,9,12,14）薄膜样品均随着退火温度的升高,颗粒膜巨磁电阻（GMR）效应不断增大,当达到最佳退火温度之后,GMR值又随退火温度的升高而降低.当退火温度为425℃时,Dy₄(Co₂₁Cu₇₉)₉₆薄膜的巨磁电阻效应达到最大,GMR值为-4.68%.退火前后样品磁滞回线的变化表明薄膜中发生了从超顺磁性到铁磁性的转变,矫顽力H_c随退火温度的升高逐渐增大.     

NiMnGaTi铁磁形状记忆合金的马氏体相变和磁性能

对Ni₅₃Mn_23.5Ga_23.5-○xTi_○x(x=0,2,5和8)系列合金的微观组织、马氏体相变及磁性能进行了研究,探究不同制备方法和不同Ti含量对合金性能的影响规律.研究结果表明:随着Ti含量的增加,合金的晶粒变细且析出物数量显著增加,适量的韧性第二相析出有助于改善合金的高脆性,合金的马氏体相变温度和饱和磁化强度均降低.EDS能谱分析表明,Ti掺杂合金的析出物是富Ni和Ti的第二相.对于Ti₀和Ti₂合金,900r/min甩带样品的饱和磁化强度与铸态样品基本相同,但Ti₅和 Ti₈甩带样品的磁化强度明显高于铸态,这是甩带工艺抑制非磁性的第二相析出所致.