Zr_(55)Al_(10)Ni_5Cu_(30)大块非晶合金在过冷液相区内虚拟应力模型的改进

针对描述非晶合金在过冷液相区流动行为的虚拟应力模型虽然能定性分析应力-应变关系,但定量计算误差很大的问题,以Zr55Al10Ni5Cu30为例,采用MATLAB遗传算法优化弹性模量、最大应力和最大松弛时间,提高了模型对应力峰值及稳态应力值的计算精度;提出时间调整因子概念,可提高对应力变化历史描述的准确度;改进后的虚拟应力模型与Zr55Al10Ni5Cu30大块非晶合金单轴压缩实验的结果吻合较好。     

Electrochemical investigations on the bulk glass forming Zr55Cu30Al10Ni5 alloy

The electrochemical behaviour of the Zr₅₅Cu₃₀Al₁₀Ni₅ amorphous alloy prepared as cylindrical bulk samples with 7 mm diameter has been investigated. Cyclic potentiodynamic polarization measurements carried out on the cross section areas of the samples in air-saturated and nitrogen-purged sulphate and hydroxide solutions, respectively, show that the alloy rapidly forms protective passive layers with low electron conductivity which are stable in a wide pH-value and potential range. Anodic layer formation reactions are characterized. In chloride containing electrolytes a pitting corrosion susceptibility of the bulk material exists. The effect of crystalline defects as active sites for the initiation of localized corrosion processes is critically discussed.     

Laser welding of annealed Zr55Cu30Ni5Al10 bulk metallic glass

Laser welding is one of the promising ways for manufacturing metallic glass products with complicated shape and geometry. In this work we focus on the effect of annealing treatment and welding parameters on laser welding of annealed Zr₅₅Cu₃₀Ni₅Al₁₀ bulk metallic glass as intended and unintended heat treatment occurs in the process. We find that laser welding can produce well welded specimen plates with no obvious welding defects in the joints and high welding speed may lead to better joints. Although higher annealing temperature or longer annealing time leads crystallization, bulk metallic glass material still remains largely amorphous in the heat affected zone. Compared with the welded joint without annealing, the micro-hardness and bending strength are enhanced due to the presence of the nanocrystals occurred in annealed welding joint. Therefore, appropriate annealing treatment with the annealing temperature near the glass transition temperature and annealing time as long as that in hot embossing of BMG parts may play a beneficial role in laser welding of metallic glasses.     

Zr55Al10Ni5Cu30大块非晶合金的超塑性挤压成形性能

通过示差扫描量热分析确定了Zr55Al10Ni5Cu30大块非晶合金的过冷温度区域范围,采用应变速率突变压缩实验分析了合金在450℃时的力学性能,研究了合金在不同挤压速度、不同真空度等工艺条件下的挤压成形性能.结果表明:Zr55Al10Ni5Cu30大块非晶合金的玻璃化转变开始温度Tg为422.4℃,晶化开始温度Tx为482.4℃;在450℃、应变速率小于5×10-3s-1的条件下,合金的流动应力小于40 MPa在挤压速度为0.002～0.004mm/s范围内挤压时,合金的最大挤压载荷变化较小;在挤压温度为450℃时,合金的最大挤压力随着真空度(2～2×10-3Pa)的提高而增加;大块非晶合金在超塑性成形时呈现出比一般金属材料更大的摩擦阻力.     

Influence of powder size on the crystallization behavior during laser solid forming Zr55Cu30Al10Ni5 bulk amorphous alloy

The Zr₅₅Cu₃₀Al₁₀Ni₅ bulk metallic glasses (BMGs) were prepared using laser solid forming (LSF) process from the plasma rotating electrode process (PREP) powder. The effect of the powder size on the crystallization behavior of the remelted zone (RZ) and heat affected zone (HAZ) was investigated. It was found that the as-prepared powders were composed of the amorphous phase and Al₅Ni₃Zr₂-type phase. The RZ mainly kept the amorphous state after LSF. The residual Al₅Ni₃Zr₂-type phase could be observed in RZ only if the powder size was larger than 106 μm. Meanwhile, the NiZr₂-type nanocrystals at the boundary of RZ primarily formed from the solidification of remelted liquid. With the increase of the powder size, the lower overheating temperature and shorter existing time of the molten pool enhanced the heredity of Al₅Ni₃Zr₂ clusters and other intermetallic clusters in remelted alloy melt, which decreased the thermal stability of the already-deposited layer. The volume fraction of crystallization in the deposit increased with the increase in powder size. There was no crystallization occurred in the HAZ between the adjacent tracks and layers for the deposit prepared by the powder with the size range of 53–75 μm. However, the wide crystalline band with Al₅Ni₃Zr₂-type faceted phase, CuZr-type dendrite, CuZr₂-type spherulite and NiZr₂-type nanocrystal were observed in the entire HAZ for the deposit prepared by the powder with the size range of 106–150 μm. The finer powder was benefit to prepare the BMGs by LSF.     

Thermal stability of Zr_(55)Al_(10)Ni_5Cu_(30)bulk amorphous alloy during continuous heating and isothermal annealing

1　INTRODUCTIONBulkamorphousalloyspossessalongrangedis orderbutshortrangeorderstructure ,whichresem blesthestructureofliquid .Andthereisasupercooledliquidregionbeforecrystallizationofabulkamor phousalloy .Thisuniquestructureresultsinexcellentpropertiessuchashightensilestrength ,highhard ness,highimpactfractureenergy ,highelasticener gy ,highcorrosionresistance ,highviscousflowabilityandgoodsoftmagnetism[13] .Thesynthesisofmetallicglassesinabulkform (withthickness >1mm )wassuccessfullyachi…     

Characterization of free volume in cold-rolled Zr55Cu30Ni5Al10 bulk metallic glasses

Cold-rolled Zr₅₅Cu₃₀Ni₅Al₁₀ bulk metallic glasses (BMGs) exhibited volume dilatation across the entire range of thickness reduction fractions from 5.7% to 63%. The dilatation was dominantly attributed to the free volume generated during cold-rolling, together with any open volumes, like the voids or microcracks, or both, which survived even after sufficiently annealing the rolled sample at the temperature in the supercooled liquid region. The relaxation of free volume formed during cold-rolling resulted in more heat evolution per unit volume than that of as-cast glass. The structural change during cold-rolling could be ascribed to the increased fluctuation of atomic-level hydrostatic stress, 〈p²〉, in the glass.     

Arrhenius activation of Zr65Cu18Ni7Al10 bulk metallic glass in the supercooled liquid region

In the current research, the dynamic mechanical spectrum and compressive deformation of Zr₆₅Cu₁₈Ni₇Al₁₀ bulk metallic glass in the supercooled liquid region (SLR) are investigated. The experimental results prove the existence of transition from Newtonian flow to non-Newtonian flow in the metallic glasses. In addition, we found that the characteristic stress σ_tc, which is obtained by a stretched exponential function based on the normalized viscosity, can be regarded as a transition point from Newtonian to non-Newtonian flow. The correlation between strain rate sensitivity exponent and corresponding strain rate was obtained at a certain temperature. It is noted that the variation of transition strain rate from Newtonian to non-Newtonian flow with different absolute temperatures follows the Arrhenius equation. The activation energy is in good accordance with that using the mechanical spectroscopy method.     

Zr55Al10Ni5Cu30 amorphous alloy film prepared by magnetron sputtering method

In this work,amorphous Zr55Al10Ni5Cu30 alloy thin film was prepared on D36 steel substrate by magnetron sputtering method.The film was characterized by scanning...     

Viscosity measurements of Zr55Cu30Al10Ni5 supercooled liquid alloys by using penetration viscometer under high-speed heating conditions

The viscosity of Zr₅₅Cu₃₀Al₁₀Ni₅ supercooled liquid alloys having bulk metallic glass forming ability was measured using a penetration viscometer with a cylindrical probe under at heating rates as high as 400 °C/min. Viscosity decreased with an increase in the heating rate and tended to saturate at 200 °C/min and above. This may partly indicate a decrease in the oxygen contamination from the measuring atmosphere and partly due to differences in structural relaxation during heating at various rates. The viscosity of these alloys can be well represented by an Arrhenius relation. The activation energies for viscous flow with various heating rates were all at values of about 340–350 kJ/mol. Viscosity follows a Vogel–Fulcher–Tammann (VFT) relationship over the entire temperature range.     

Wetting behavior of Zr55Cu30Al10Ni5 melt on alumina

The wetting behavior of molten Zr55 Cu30 Al10 Ni5 on Al2O3 was studied by the sessile drop method in high vacuum. The results show that wetting kinetic at 1 163 K is composed of three stages., incubation, quasi-steady decrease and trend constant. Precursor film forms surrounding the wetting tip when wetting temperature is above 1 163K. Formation of precursor film is related to the change of triple line configuration and results in good wettability.Chemical reaction dos not occur at the wetting interface. Al2O3 is an excellent reinforcement for Zr55 Cu30 Al10 Ni5 matrix composite in terms of wettability and reactivity. The kinetic relationship of spreading ratio with spreading timewas also investigated.     

Wettability of molten Zr55Cu30Al10Ni5 on alumina and zirconia

The wetting behavior of molten Zr55Cu30Al10Ni5 on Al2O3 and ZrO2 was studied using the sessile drop method. The results show that the nonwetting-to-wetting transition for the Zr55Cu30Al10Ni5/ZrO2 wetting system takes place at 1193 K. The wetting of molten Zr55Cu30Al10Ni5 on Al2O3 is a non-reactive wetting. Owing to the formation of diffusion band at the front of the wetting tip in the Zr55Cu30Al10Ni5/Al2O3 system, the wettability of Al2O3 is better than that of ZrO2.     

Zr55Al10Ni5Cu30块体金属玻璃的摩擦焊焊接

采用摩擦焊对Zr55Al10Ni5Cu30块体金属玻璃进行了焊接,当焊机主轴转速为4.0×103-5.0×103 r/min,摩擦压力为80-100 MPa,摩擦时间为0.2-0.4 s,顶锻压力和保压时间分别为200 MPa和2 s时,能够成功实施Zr55Al10Ni5Cu30金属玻璃的焊接.用SEM,XRD和TEM观察分析未检测到晶化相,焊缝处金属仍保持非晶状态.金属玻璃的塑性在玻璃转变点Tg附近随温度变化很大,在Tg以上具有良好的塑性变形能力,这是实施摩擦焊焊接的重要基础.     

Zr55Al10Ni5Cu30合金熔体与金属W的润湿行为

用座滴法研究了Zr55Al10Ni5Cu30合金液滴与W基片在连续升温和不同温度下保温20min的润湿动力学。结果表明：箍着温度的升高，Zr55Al10Ni5Cu30与W基片的接触角不断减小，润湿半径不断增大，润湿过程大约在6min内完成．在连续升温过程中，润湿动力学分为孕育、准稳态和稳态三个阶段，在1173-1223K温度范围内等温润湿动力学分为准稳态和稳态两个阶段，Zr55Al10Ni5Cu30合金液滴与W之间的润湿为反应性润湿，在界面处发生了W的溶解和扩散现象，在制备Zr55Al10Ni5Cu30/W非晶复合材料时，必须合理选择制备工艺，严格控制界面反应。     

Zr55Al10Cu30Ni5非晶合金在NaOH溶液中的腐蚀行为

利用极化曲线方法、电化学阻抗技术和扫描电子显微镜研究了非晶合金Zr55Al10Cu30Ni5在NaOH溶液中的腐蚀行为。极化曲线测试表明，非晶合金Zr55Al10Cu30Ni5在NaOH溶液中具有很好的耐蚀性能，阴极过程由电化学反应所控制，而阳极过程表现出钝化特征，在所研究的浓度范围内，钝化电流密度非常低，为1μA／cm^2～2μA／cm^2。电化学阻抗测试表明，电荷转移电阻随浓度的增大而增大，而后又有所降低。在阴极极化、开路电位和钝化电位下，非晶合金的Nyquist图由单容抗弧构成，具有很高的电荷转移电阻，表现出优良的耐蚀性。SEM和EDAX表明非晶合金在NaOH溶液中腐蚀轻微，各合金元素的溶解程度不同，腐蚀后表面出现了少量的氧元素。