射孔弹弹体Fe-Ni-Cu-C粉末材料组织及性能研究

为分析合金元素对Fe-Ni-Cu-C合金的强化机理,拓宽射孔弹弹体制造技术及材料应用范围,以Fe-Ni-Cu-C合金为对象,研究Cu、Ni、C等元素含量对油田射孔弹弹体用粉末冶金材料组织及性能的影响规律.结果表明:Cu会使基体孔隙率增加,进而降低延伸率;Ni含量的增加使合金中铁素体含量减少而珠光体含量明显增多,合金的抗拉强度和硬度呈增大趋势变化,延伸率在Ni质量分数为3%时达到极值后逐渐减小;在C含量不变的情况下合金延伸率随着Ni含量的增加,出现先增加后降低的趋势变化.     

有序度对Ni2Cr合金氢致脆断的影响

研究了环境气氛、动态渗氢及预渗氢对不同有序度Ni2Cr合金脆化的影响.结果表明,有序度对Ni2Cr合金在室温空气及氢气中的环境氢脆没有明显影响;动态渗氢拉伸时Ni2Cr合金存在严重的氢脆敏感性,无序和高度有序合金比部分有序合金脆化严重;预渗氢时,氢原子通过晶格扩散及晶界扩散进入合金,Ni2Cr合金氢脆敏感性随有序度的增大而减小.     

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。     

强磁场下Cu-50%Ag合金定向凝固过程中的组织及固液界面形貌演变

目的 研究强磁场下Cu-50%(质量分数)Ag合金定向凝固过程中的组织演变、固液界面形貌变化及溶质迁移行为,分析强磁场对金属凝固过程的作用机制,为强磁场下的金属材料制备提供理论借鉴和指导。方法 在不同的凝固速率与磁场条件下进行定向凝固和淬火实验,对合金的定向凝固组织、糊状区与固液界面形貌以及溶质分布行为进行考察。结果 强磁场破坏了凝固组织的定向生长,使凝固组织转变为枝晶与等轴晶共存的形貌;强磁场诱发了熔体对流,减少了糊状区中溶质的含量;强磁场改变了固液界面处的溶质分布和固液界面形貌,破坏了固液界面的稳定性。结论 强磁场通过洛伦兹力和热电磁力的共同作用,诱发了糊状区内液相的纵向环流,改变了固液界面及糊状区中的组织形貌与元素分布。     

Ni-Fe合金电沉积工艺参数对镀层铁含量的影响

以Ni-Fe合金电沉积层代替纯Ni层,可以节约贵金属Ni.在铝箔上电沉积了Ni-Fe合金镀层,研究了电镀液中不同Fe2+/Ni2+摩尔比、电流密度、pH值及温度等因素对Ni-Fe合金镀层中Fe含量及镀层结构的影响.结果表明:随Fe2+/Ni2+摩尔比增加,镀层中的Fe含量呈线性增加;开始时随着电流密度的增加,镀层中的Fe含量不断增加,超过4.5 A/dm2后,Fe含量反而不断减少;随镀液pH值的增大,镀层中Fe含量不断增加;随镀液温度提高,镀层中Fe含量不断下降;铝箔上的Ni-P合金镀层具有纳米晶体结构.     

溶质元素(Ni,Sn)总量对Cu-Ni-Sn合金导电性能的影响

为提升Cu-Ni-Sn合金的导电率,系统研究了溶质元素(Ni,Sn)含量对导电Cu合金导电率和硬度的影响。通过对现有典型牌号Cu合金进行成分解析,发现在Ni、Sn原子比为3/1时合金具有高的导电率和强度,故本工作固定Ni、Sn原子比为3,改变Ni和Sn总量,设计了一系列三元成分合金;采用真空电弧熔炼工艺制备合金锭,随后进行1093K/1h固溶+65%~75%变形冷轧+673K/2h时效处理。实验结果表明,经过固溶+变形+时效处理后的Cu合金的导电率随溶质元素(Ni+Sn)含量增加而降低,而硬度变化则呈相反趋势;系列Cu合金的弹性模量随(Ni+Sn)含量基本保持不变。由此,为使Cu合金的导电率不低于15.0%IACS、且保持一定的强度,溶质元素(Ni+Sn)含量应为10.0%≤y(Ni+Sn)≤16.0%(质量百分比含量为12.0%≤w(Ni+Sn)≤18.0%)。     

医用多孔NiTi合金表面微弧氧化改性研究

为解决多孔Ni Ti合金耐蚀性降低和Ni离子释放量增大而引起的使用安全性问题.本文采用微弧氧化技术对医用多孔Ni Ti合金进行表面改性处理,研究结果表明,微弧氧化处理并未改变多孔Ni Ti合金原有的孔隙结构和孔隙率,只在其外表面和孔隙内表面均形成了典型的微弧氧化多孔涂层.该涂层主要由氧化铝相组成,并含有少量的Ti和Ni元素,且外表面涂层的Ti和Ni含量要略低于孔隙内表面涂层.微弧氧化涂层提高了多孔Ni Ti合金的表面接触角,将原有的亲水表面转变成了疏水表面.经微弧处理后,多孔Ni Ti合金的耐蚀性较基体提高了1个数量级以上,Ni离子释放量也较基体降低了1个数量级以上.     

造孔剂法制备孔隙率可控的多孔镍钛合金

用常规粉末冶金烧结法结合造孔剂技术制备了多孔镍钛形状记忆合金.研究结果表明,孔隙特征主要取决于所用造孔剂的尺寸和形貌,而孔隙率可以通过加入造孔剂的含量来调控;所制备合金的主要成分是B2相和B19'相的NiTi,在经高温固溶处理后仍有极少量的Ti2Ni,Ni3Ti和Ni4Ti3等杂质相存在,而且合金杂质相的含量随造孔剂加入量的增加而相应提高.对合金的相变热分析表明,在从高温降至低温过程中多孔镍钛发生特殊的三阶段相变,这主要是由合金成分和相组成在晶界的不均匀造成的.最后,研究表明相变对多孔镍钛合金的阻尼性能(内耗)有独特的影响,而孔隙率对阻尼的影响则不明显.     

机械合金化的Cu-Sn纳米晶合金的热力学稳定性研究(英文)

在纳米结构的金属及合金中,随着晶粒尺寸的下降,晶界体积分数显著增加,使得晶粒长大的驱动力提高,因此纳米金属在加热时(甚至是室温下)是不稳定的。对Trelewicz/Schuh(TS)模型进行了修正,并利用修正的模型对Cu-Sn纳米晶合金的热力学稳定倾向做了计算研究。利用机械合金化的方法制备不同溶质含量的Cu-Sn纳米晶合金,在不同温度下进行退火实验。实验结果及理论计算表明,随着溶质原子的加入及在晶界的偏聚,Cu-Sn纳米晶合金的晶粒长大得到抑制,热力学稳定性提高。     

Mg与Ag含量对Al-Cu-Mg-Ag新型耐热铝合金晶间腐蚀性能的影响

采用晶间腐蚀性能测试研究Mg与Ag含量对Al-Cu-Mg-Ag合金抗腐蚀性能的影响,结合透射电子显微分析技术与电化学分析技术等探讨了不同成分合金的晶间腐蚀机理。结果表明:增加Mg与Ag含量能够提高合金的时效硬化速率。随Mg含量的增加,强化相Ω相尺寸逐渐减小,体积分数逐渐增大,晶界析出相增多,无沉淀析出带(PFZ)中溶质原子减少,PFZ与基体的电位差增大,合金的抗晶间腐蚀能力逐渐降低。随Ag含量的增加,合金中的强化相由大量的θ′相和少量的Ω相,逐渐转变为大量的Ω相和少量的θ′相。Ag含量的改变对PFZ的电位差影响不大,合金的耐蚀性主要取决于PFZ的宽度。增加Ag含量能够细化晶界析出相,减小PFZ宽度,腐蚀通道变窄,合金的抗晶间腐蚀性能得到提高。     

An acousto-ultrasonic study of the effect of porosity on a sintered glass system

An assessment of the applicability of an acousto-ultrasonic (AU) technique for the monitoring of porous ceramic systems has been carried out. Sintered glass was used as a model system and it was found that the AU parameters, such as normalized ringdown count, normalized pulse width, velocity and frequency interval (f) between adjacent peaks in the frequency spectra, decrease with increasing porosity. The porosity dependence of the normalized AU parameters has been attributed to attenuation which analysis showed depended on the pore size and content. The velocity and frequency interval changes also depended on pore content but, unlike the normalized parameters, were found to be sensitive to pore shape and size. The decreasing f with increasing porosity was explained in terms of the longer path lengths traversed by the waves in the higher pore-density samples.     

A multiplanar model for the pore radius distribution in isotropic near-planar stochastic fibre networks

A model is presented for the pore radius distribution in isotropic near-planar stochastic fibre networks. At a given areal density, the mean pore radius of two-dimensional random networks is shown to decrease with increasing fibre width and to increase with increasing fibre linear density.For structures with a structural component in the third dimension the standard deviation of pore radii is shown to be proportional to the mean for changes in areal density and porosity in agreement with data reported in the literature. At a given porosity, near-planar networks exhibit an increase in mean pore radius with increasing fibre width and linear density.     

Analysis of the solidified structure of rheocast and VADER processed nickel-base superalloy

Conventional ingot processing of highly alloyed compositions results in a cast product which suffers from extensive macrosegregation, hot tears, and heterogeneities. By controlling the solidification journey, one can produce a fine grained cast product. This is achieved by manipulating the melt in the mushy zone. Rheocasting and vacuum arc double electrode remelting (VADER) are two such technologies where the melt is processed in the mushy zone. IN-100, a nickel based superalloy, was rheocast as well as VADER processed. The resultant cast structures are analysed, compared and discussed both on micro- and macrostructural levels. The effect of the rheocast processing variables (stirring speed, time and temperature) on the cast microstructure are also discussed     

Influence of cement type on ITZ porosity and chloride resistance of self-compacting concrete

With the increasing use of self-compacting concrete (SCC) its durability has come into focus. Concerning the microstructure of concrete, the porosity in the interfacial transition zone (ITZ) is regarded as a key feature for permeability and durability. Generally, a combination of cement and mineral admixtures is used for the production of SCC. In the present study, ITZ porosity of four SCC mixtures produced with ordinary Portland cement, Portland limestone cement, slag cement and ordinary Portland cement combined with fly ash is analyzed. Additionally, the chloride migration coefficient is determined. ITZ porosity and width of the SCC mixtures are similar. The substantial differences in the chloride migration coefficients show that the binder type has a stronger influence on permeability than the pore volume in the ITZ.     

Porosity formation in Al-9 wt% Si-3 wt% Cu-X alloy systems: measurements of porosity

A set of 72 experiments was carried out to study the effects of solidification conditions, hydrogen content and additives on the formation of porosity in Al-9 wt% Si-3 wt% Cu-X alloy systems. It was found that not all alloying elements contribute to porosity formation in the Al-Si-Cu base system. Some of these elements, e.g. magnesium, titanium and phosphorus, tend to reduce both pore size and density. Hydrogen is the strongest element that induces porosity formation, its effect being reinforced either by the addition of strontium or by increasing the solidification time, or both. Grain refining is found to reduce pore density and pore size, and results in a fine dispersion of the pores throughout the alloy matrix. The necessary precautions to be taken in measuring the porosity in these alloys are reviewed in this paper. Accurate measurements of porosity using image analysis need careful adjustment of optical parameters, namely focus, illumination and grey level, as well as a careful selection of the number of field measurements required to represent correctly the sample surface.     

Modeling of gas porosity and microstructure formation during dendritic and eutectic solidification of ternary Al-Si-Mg alloys

A two-dimensional(2-D)multi-component and multi-phase cellular automaton(CA)model coupled with the Calphad method and finite difference method(FDM)is proposed to simulate the gas pore for-mation and microstructures in solidification process of hypoeutectic Al-Si-Mg alloys.In this model,the pore growth,and dendritic and eutectic solidification are simulated using a CA technique.To achieve the equilibrium among multiple phases during ternary Al-based alloy solidification,the phase transition thermodynamics and kinetics are evaluated by adopting the Calphad method.The diffusion equations of hydrogen and two solutes are solved by FDM.The developed CA-FDM coupled model can be used for sim-ulating the evolution of gas microporosity and microstructures,involving dendrites and irregular binary and ternary eutectics,of ternary hypoeutectic Al-Si-Mg alloys.It has the capability of reproducing the interactions between the hydrogen microporosity formation and the growth of dendrites and eutectics,the competitive growth among the growing gas pores of different sizes,together with the time-evolving concentration fields of hydrogen and solutes.The simulated morphology of gas pore and microstructure has a good agreement with the experimental observation.The influences of the initial hydrogen concen-tration and cooling rate on the microporosity formation are investigated.It is found that the main portion of porosity formation occurs in the eutectic solidification stage through analyzing the profiles of porosity percentage and solid fraction varying with solidification time.The varying features of simulated porosity percentage,the maximum and average pores radii indicate that increasing initial hydrogen concentration promotes the formation of higher final porosity percentage and larger pores,while the size of gas pores will significantly reduce with increasing cooling rate,leading to a lower final porosity percentage.     

Influence of oxides on porosity formation in Sr-treated Al-Si casting alloys

The strength and quality of an Al-Si alloy casting are determined by its microstructure and the amount of porosity present in the casting. Modification is one of the processes used to improve the microstructural quality, where the addition of a modifying agent alters the shape of the eutectic Si from an acicular to a fibrous form that is extremely beneficial to the mechanical properties. Among various modifiers, strontium has been used extensively, as it is easier to handle and more resistant to fading. However, its addition is also associated with porosity formation in these alloys. The porosity formed in Sr-modified castings has been variously related to an increase in the hydrogen level of the melt, feedability problems in the mushy zone during solidification, and changes in the mode of eutectic nucleation—from near the -Al dendrites in the Sr-free alloy, to within the eutectic liquid itself in the Sr-containing alloy. The present study was carried out to determine the influence of oxides on the porosity characteristics observed in Al-Si alloys containing strontium. A series of experimental and industrial alloys viz., Al-7%Si, Al-12%Si, 319 and 356 were selected, to cover a variety of alloy freezing ranges. The techniques of thermal analysis, optical microscopy, and SEM/EDX and EPMA analyses were employed to obtain the results presented here. It is seen how the presence of oxides (Sr and Al) is responsible for the porosity formation observed in Al-Si alloys, and that the difference in porosity characteristics with the addition of Sr depends on the amount of Sr oxides present in the solidified structure. The presence of aluminum oxide films leads to the formation of large pores that are often linked together. Both aluminum and strontium oxides are favorable sites for the nucleation of other microconstituents.     

Statistical analysis of porosity in Al-9 wt% Si-3 wt% Cu-X alloy systems

A set of 72 solidification experiments was carried out on Al-9 wt% Si-3 wt% Cu-X alloys, varying the additives (namely, strontium, grain refiner and other alloying elements), hydrogen level and thermal parameters in order to obtain a statistical analysis of the resulting porosity in such alloy systems. For all the cases studied, it was found that in each case, the smaller sized pores (in terms of pore length or pore area) could be described by an exponential function, while the larger sized pores were distributed in an irregular fashion, small and large being distinguished by that limiting value of pore length or area at which the average value equalled the standard deviation. Two different approaches i.e. factorial and regression methods were utilized to quantify the importance of the parameters controlling the pore size and porosity volume fraction. Two main observations were made: (i) hydrogen is the strongest parameter enhancing porosity formation, with the hydrogen-grain refiner, strontium, strontium-titanium and solidus velocity-solidification time interactions being the other parameters that contribute significantly to porosity formation and increase in pore size; (ii) the grain refiner, hydrogen-phosphorus, strontium-magnesium and iron-phosphorus interaction parameters reduce the porosity, though in different magnitudes. The reliability of predicting the observed effects by the two methods has been discussed.     

Synthesis and degradation properties of b\boldsymbol{\beta} -TCP/BG porous composite materials

b\boldsymbol{\beta}-TCP/BG porous composite materials were successfully fabricated by foaming technology. X-ray diffraction was used to determine the crystal structure of powders. The pore size and distribution of the resulting materials were characterized using scanning electron microscopy. The porosity and degradation performance of materials were also investigated. The results showed that the porous composite materials possessed the pore size ranging from 100 to 500 m\boldsymbol{\mu} m in diameter, whereas the interconnection among macrospores was poor. The porosity in materials increased from 58·7% to 63·47% with BG content ranging from 0 to 3 wt%, further increasing of BG content results in a decrease in porosity. The degradation rate of composite materials can be adjusted by varying the BG content.