Density of Liquid Ni-Cr Alloy

The density of liquid Ni-Cr alloy was measured by a modified sessile drop methold.The density of liquid Ni-Cr alloy was found to decrease with increasing temperature and Cr concentration in the alloy,The molar volume of liquid Ni-Cr alloy increases with increasing the Cr concentration in the alloy ,The molar volume of Ni-Cr alloy determined in the present work shows a positive deviation from the linear molar volume.     

不同Cr含量的Ni基合金电化学腐蚀行为

利用电化学测试技术研究不同Cr含量的Ni基合金耐Cl-离子水溶液腐蚀的能力。结果表明：Ni基合金耐Cr离子腐蚀性能随着合金中Cr含量的提高而增强,溶液中Cl-离子浓度对Ni-9Cr、Ni-15Cr和Ni-20Cr合金有较大影响,特别是Ni-9Cr合金在0．6mol／LNaCl溶液中腐蚀最为严重,而对于Ni-25Cr和N...     

Cu-Cr二元合金宏观偏析与温度场的数值模拟

Cu-Cr材料是两相复合材料,铬粒子通常以嵌入在铜基体中的形式存在,凝固过程中存在着严重的偏析现象,进而对凝固温度场的分布产生影响.为分析Cr相偏析对温度场分布的影响,基于Eulerian-Eulerian方法,建立了三维凝固偏析模型,利用Fluent模拟计算,偏析模型采用浓度梯度"SCr和分布面积梯度▽SCr来表示,得到了Cu-6.5%Cr的凝固偏析分布和温度场分布.结果表明:由于Cr的熔点比较高,当tt_a时,Cr先发生侧向凝固,形成糊状区;同时,Cr相的密度比Cu小,内部Cr相会发生上浮,向合金顶部移动;当tt_a时,顶部的Cr会大量聚集,形成顶部偏析,两侧Cr相"困"于糊状区,形成壁面偏析;随着凝固界面横向推移,壁面偏析对壁面温度场的分布产生影响,Cu的传热系数是Cr的3.85倍,随着Cr相偏析度的增加,降低了基体壁面的传热效率,导致温度梯度变大.研究工作将模拟结果与实验结果进行了对比,证明了模型的准确性.     

Influence of Solid Fraction on Gravity Segregation of Sn in Al-20Sn Alloy Casting

The influence of solid fraction of Al-20Sn alloy mushy on gravity segregation of Sn in casting was studied and, the relationship between solid fraction and the temperature of alloy mushy and that between solid fraction of alloy mushy and size of Sn particle in ingot were determined. The results show that the relationship between solid fraction and the temperature of alloy mushy was fs=1683-4.86t+0.0035t2. The extent of gravity segregation of Sn in casting reduced gradually with the increasing of solid fraction of alloy mushy. When solid fraction of alloy mushy was arger than 40%, the gravity segregation of Sn in casting could be removed basically, and the relationship between solid fraction of alloy mushy and size of Sn particle in ingot was s=-0.64fs+70.8.     

Influence of solid fraction on gravity segregation of Sn in A1-20Sn alloy casting

1. IntroductionIn Al-Sn alloys Sn has excellellt lubricating property and Al has perfect thermal conductivity, so AISn alloy is the ideal material of lubricating layer ofsteel-backed bearing[1]. If Sn particles distribute inAl substrate evenly, Sn can play a lubricating role atthe whole colltact surface and reduce the abrasion ofAl substrate, and the friction heat can be led out byAl substrate rapidly. Otherwise, if Sn particles distribute in Al substrate unevenlyt in Sn--lean region,Al …     

镍铬合金薄膜的研究进展

镍铬合金薄膜是重要的精密电阻和应变电阻薄膜材料.简述了镍铬合金薄膜的3种制备方法:真空蒸发沉积、磁控溅射沉积和离子束沉积;讨论了基底、工作气压、沉积时间等薄膜制备工艺参数以及退火工艺对薄膜性能的影响.重点叙述了镍铬合金薄膜、改良型镍铬合金膜、含氮镍铬合金膜、镍铬合金多层膜和纳米镍铬合金薄膜等膜系的特征.阐明了制备具有高电阻率、低电阻温度系数、高应变灵敏系数、良好的热稳定性等优异综合性能的镍铬合金薄膜的新工艺发展趋势.     

电沉积Ni-Cr合金工艺研究

含有一定量Cr的Ni-Cr镀层具有良好的耐磨、耐腐蚀性能.选取柠檬酸钠作为配位剂,用动电位扫描法研究了电沉积Ni-Cr合金时的阴极行为,同时对镀层的耐腐蚀性进行了试验.试验结果表明:镀液中加入配位剂柠檬酸钠可以提高阴极极化;pH值、阴极电流密度、配位剂对镀层中铬含量影响较大,在一定范围内增大pH值,增加配位剂的用量,提高电流密度,有利于提高镀层中铬的含量,最佳工艺条件为pH值为2.5,阴极电流密度为25A/dm2,镀液中柠檬酸钠的含量为35g/L,镀层中铬质量分数为20%左右时,Ni-Cr合金镀层的耐腐蚀性能最好.     

Ni-Cr/Ti/瓷界面反应机制

采用磁控溅射技术,在Ni-Cr合金表面溅射一层Ti薄膜作为中间层,研究了Ni-Cr/Ti/瓷界面组织结构,产物种类、分布及反应机制。结果表明:Ni-Cr/Ti/瓷界面反应复杂,界面处形成的新物相有Ti2Ni,AlTi3,TiO2,SnCr0.14OX,NiCr2O4和Cr2O3。高温烤瓷过程中,Ti与Ni以稳定的化合物Ti2Ni形式结合,同时Ti与陶瓷中Al2O3反应生成AlTi3化合物,与SnO2和SiO2发生置换反应生成TiO2,TiO2与陶瓷中氧化物结合,更好的实现了Ni-Cr合金与陶瓷的连接。     

Cr颗粒含量对Ni-Cr纳米复合镀层组织结构的影响

使用Ni与纳米Cr颗粒共沉积方法制备Ni-Cr纳米复合镀层,研究了镀液中Cr颗粒浓度、搅拌强度和阴极电流密度等工艺参数对镀层中沉积Cr量的影响.结果表明:镀层中纳米Cr颗粒的复合改变了电沉积Ni的生长方向,Ni晶粒由原来沿(200)晶面取向生长,转变为沿(200)、(111)和(220)晶面均匀生长.镀层中Cr复合量越多,Ni晶粒的形核位置越多,Ni晶粒越细化.也探讨了Ni-Cr纳米复合镀的沉积机理.     

Measurement and Analyses of Molten Ni-Co-A1 Alloy Density

The density of molten Ni-Co-Al alloy was measured using a modified pycnometric method. It has been found that the density of the molten Ni-Co-Al alloy decreases with increasing temperature, Co concentration and the ratio of Co concentration to Ni concentration in the alloy. The coefficient of volume expansion of the molten Ni-Co-Al alloy decreases with increasing Co concentration and the ratio of Co concentration to Ni concentration. The temperature coefficient of density increases with increasing the Co concentration or the ratio of Co concentration to Ni concentration in the alloy. The density of the molten Ni-Co-Al alloy as functions of both temperature and Co concentration was expressed.     

Density of Ni-Al Alloys in Liquid and Solid-Liquid Coexistence State Measured by a Modified Pycnometric Method

The density of Ni-AI alloys in both liquid state and solid-liquid coexistence state was measured with a modified pycnometric method. It was found that the density of Ni-AI alloys decreases with increasing temperature and Al concentration in the alloys. The molar volume of liquid Ni-AI binary alloys increases with the increase of temperature and Al concentration. The partial molar volume of Al in Ni-AI binary alloy was calculated approximately. The molar volume of liquid Ni-AI alloy determined in the present work shows a negative deviation from the ideal linear molar volume.     

Measurement and Analyses of Molten Ni-CO-Al Alloy Density

The density of molten Ni-Cd-Al alloy was measured using a modified pycnometric method.It has been found thatthe density of the molten Ni-Co-Al alloy decreases with increasing temperature Co Concentration and the ratioof Co concentration to Ni concentration in the alloy.The coefficient of volume expansion of the molten Ni-Co-Al alloy decreases with increasing Co concentration and the ratio of Co concentration to Ni concentration.Thetemperature coefficient of density increases with increasing the Co concentration or the ratio of Co concentration toNi concentration in the alloy.The density of the molten Ni-Co-Al alloy as functions of both temperature and Coconcentration was expressed.     

Preferential dissolution behaviour in Ni-Cr dental cast alloy

A Ni-Cr-Mo dental alloy was fabricated by three different casting methods, viz. centrifugal casting, high frequency induction casting and vacuum pressure casting. The dependence of cast microstructure on the electrochemical corrosion behaviour was investigated using potentiodynamic cyclic and potentiostatic polarization techniques, impedance spectroscopy and scanning electron microscopy. The experimental results were compared and discussed with those obtained for a Co-Cr-Mo counterpart. The results of the study showed that the variation in casting morphologies with casting methods has only marginal influence in the overall corrosion resistance of Ni-Cr and Co-Cr dental alloys. There was severe preferential dissolution of Ni rich, Cr and Mo depleted zones from the Ni-Cr-Mo alloy. The overall corrosion resistance property of the Co-Cr base alloy was better than that of the Ni-Cr base alloy.     

Investigation of the thermo-stimulated surface segregation in the ternary Co-Cr-Mo alloy by means of Ionization Spectroscopy

Ionization Spectroscopy has been used to study thermo-induced surface segregation in the near-surface region of the ternary Co-Cr-Mo alloy. For the non-annealed alloy the Mo atoms preferred segregation in the outermost layers and Cr atoms segregation in the underlying layers of surface was observed at room temperature. Heating of the alloy promotes increasing of Co concentration and decreasing of Mo concentration in the near-surface region. For the annealed alloy the insignificant Mo atoms segregation on the outermost layers and enrichment with Co and Cr atoms in underlayers are displayed. The present results are compared with several theories of segregation.     

On brazing of cubic boron nitride abrasive crystals to steel substrate with alloys containing Cr or Ti

An investigation has been carried out to gain information about the capabilities of some filler alloys for direct brazing of CBN (cubic boron nitride) grits to a steel substrate. It has been found that a Ni-Cr alloy, known for effective diamond brazing, failed to show satisfactory wetting and bonding characteristics towards CBN under the same brazing conditions as that of diamond. The situation could not be improved either by increasing the wt% of Cr or the brazing temperature. Also, prolongation of the brazing time did not show any significant change. It was further revealed that a Ag-Cu-Ti alloy, which is well established for the brazing of diamond and ceramics, exhibited good wetting and bonding towards CBN at moderate temperature. Based on the thermodynamic properties of various materials, characteristic properties of elements of group IV B to VI B and the physical observations made during the investigation, it is suggested that the transition elements of group IV B, such as Ti or Zr, are preferred to transition elements of group VI B, such as Cr, as an activator to promote the wetting characteristics of the braze alloy towards CBN, which is far more chemically stable than diamond.     

Oxidation of Ion Plated Ni—Cr Alloy Film at 300℃

Investigation by using LAS 3000 surfaceanalysis system showed that the oxide of Fe,Cr,Al formed during oxidation were Cr_2O_3,Fe_2O_3and Al_2O_3,but only small amount of nickel oxidewas found.The composition of oxide layers for differentoxidation durations varied in a similar way.In all cases,there exists an oxygen concentrationpeak in the composition profile of oxide layer.There is a transitional zone between oxide layerand alloy film.The thickness of oxide layerincreases logarithmically with the time of oxida-tion.The ion plated Ni-Cr alloy film has verydense oxide layer and good oxidation resistance.     

电镀镍-铬合金添加剂的研究

镍铬合金电镀层由于具有优良的耐蚀性能而受到人们的关注,而添加剂的选取和用量的多少对能否获得优良性能的镀层起着关键作用.确定了适合氯化物硫酸盐混合体系电镀镍铬合金的添加剂WHT、光亮剂791以及表面活性剂十二烷基硫酸钠,通过试验分别讨论了它们的用量对镀层表面质量的影响,并采用稳态极化曲线和循环伏安法分别研究了它们的用量对镍铬合金共沉积的阴极电化学行为的影响.试验结果表明:添加剂WHT对镀层晶粒细化起主要作用,它的加入增大了合金共沉积的阴极极化程度;当镀液中添加剂WHT用量为4g/L,光亮剂791用量为7.5～15.0mL/L,十二烷基硫酸钠用量为0.15～0.20g/L时,所得合金镀层平滑、光亮、致密,且与基体结合力好.     

温度梯度条件下糊状区的凝固行为研究

利用一个垂直的定向凝固装置,研究了Al-6wt%Cu合金在温度梯度约12K/mm条件下,糊状区在保温不同时间并激冷后得到的微观组织及成分分布特征.SEM/EDX分析表明,糊状区在保温时间内将发生自发的、以扩散机制为主的、类似TGZM效应的凝固过程.完全凝固后所形成的成分梯度与温度梯度的对应关系对于预测定向凝固过程中固液相界面温度以及相平衡测定具有重要意义.     

Factors Affecting Transformation Temperatures in Fe-Mn-Si-Cr-Ni Shape Memory Alloy

1. IntroductionFe-Mn-St-Cr-Ni shape memory alloys exhibit notonly a good shape memory effect (SME), but also agood corrosion resistanced'2] ) compared with Fe-MuSt alloys. Fulthermore, it can be used in manufacturing pipe couplings because of its high phase transformation temperatures and great thermal hysteresis.But the recovery strain in these alloys is still low (lessthan 2%), which licits their application in pipe couplings. Therefore, to increase the recovery strain iskey to their pra…     

糊状区渗氮对Cr10Mn9Ni0.7合金氮含量及凝固相变过程的影响

研究了糊状区保温对Cr10Mn9Ni0.7合金凝固过程和氮含量及相变过程的影响。结果表明,随着糊状区保温时间的延长,铸锭中的氮含量逐渐升高,同时铸锭中的气孔率逐渐降低。当氮气压力为0.1 MPa时,氮含量由0.17%升高到0.23%,而气孔率则从1.86%降至1.37%;当氮气压力为0.4 MPa时,氮含量由0.29%升高到0.37%,而气孔率从1.41%降至1.06%。糊状区保温的增氮机制可归结为:在糊状区保温会促进包晶反应进程,使更多的铁素体转变为奥氏体;同时糊状区保温能够提高残留液相中的氮含量,进而提高"通道状"奥氏体中的氮含量。糊状区保温能够消除铁素体阱,从而降低气孔率。