DTA studies on the liquidus temperatures of Cr complex with the addition of an anhydrous Ni complex

Determination of T–X_Cr diagram for a binary system of tris(2,4-pentanedionato)Cr(III) and anhydrous bis(2,4-pentanedionato)Ni(II) over the range of 1.000–0.506 for the mole fraction (X_Cr) of the Cr complex by employing DTA revealed the system to behave as an ideal eutectic exhibiting lowering of the melting point of the former complex with the addition of the latter one. The thermodynamic correlation between T and X_Cr yielded an average value of 109.9±0.4 kJ mol⁻¹ for the standard enthalpy of fusion of the Cr complex.     

Effect of interstitial impurities on liquidus temperatures in Ti–Al alloys

Development of intermetallics in Ti–Al alloys for high-temperature structural applications has long been impeded by embrittlement, partly because there has been a complete understanding at an electronic level on the Ti–Al phase transformation behavior. In this study, based on the Empirical Electron Theory of Solids and Molecules (EET), effects of interstitial impurities on valence electron structures and liquidus temperatures in Ti–Al phase diagram are analyzed. Based on the theoretical analysis, some unclear experimental results in Ti–Al phase diagram are further discussed. It is demonstrated that because of the effects of interstitial impurities, the valence electron structures become seriously anisotropic, leading to the lowest liquidus temperatures in Ti–Al phase diagram.     

Effect of previous loading on the properties of 1Cr18Ni9Ti steel at elevated temperatures

The effect of previous long-term loading on the strength of 1Cr18Ni9Ti steel at 20, 500, 650, 800, and 950° C was investigated.     

The effect of micro-alloying addition of Cr on age hardening of an Mg–Zn alloy

This work reports a chemical method called “co-deposition route” for fabricating ND (nanodiamond)/Cu composite at a molecular-level mixing. The main procedure of “co-deposition route” includes four steps. ND particles have been functionalized by HF acid before co-deposition. SEM, HRTEM (high-resolution transmission electron spectroscopy), XRD (X-ray diffraction), EDS (energy-dispersive spectrum analysis) and optical microscope were carried out to characterize the as-prepared composite powders and bulk composites. Results indicated that copper matrix composite with a homogeneous dispersion of functionalized ND particles can be prepared. The modification of ND particles was performed by HF (30 vol%) acid at 70 °C, and CF bond was successfully detected by XPS (X-ray photoelectron spectrum) and IR (Infrared spectroscopy). The properties of relative density, microhardness and electric conductivity of ND/Cu composites have been measured. With the comparison of conventional methods, it showed that the as-prepared ND/Cu composites with good combined performances have a promising future for industry application.     

Ni添加对 Ti0.39V0.29Mn0.12Cr0.2合金电化学性能的影响

通过X射线衍射谱(XRD)、扫描电镜(SEM)、X射线能谱(EDS)、气态吸放氢行为(PCT曲线)、电化学充放电性能、电化学阻抗谱(EIS)以及线性极化曲线，研究了Ni添加对Ti0.39V0．29Mno．12Cr0．2储氢合金电化学性能的影响。结果表明：Ti0.39V0．29Mno．12Cr0．2的电化学活性很差，在碱液中几乎不能放电，添加Ni之后得到明显改善。随着Ni含量的增加，Ti0.39V0．29Mno．12Cr0．2(x=0～0．2)合金电极的放电容量先增大后减小，在x=0．1时达到最大值273mAh／g。     

Peculiarities of the relaxation properties of the FeCrNi alloy spin system at low temperatures

The types of spin system exhibited by certain FeCrNi alloys were studied using the gamma resonance spectra technique. It was evident that the spin systems were significant in determining the magnetic and physical properties of these alloys at low temperatures. It was found that antiferromagnetic and ferromagnetic ordering of the alloys took place in small regions and the character of each region depended upon its Ni content.     

The influence of Nb,Ti, and Si additions on the liquidus and solidus temperatures and primary microstructure refinement in 0.3C-30Ni-18Cr cast steel

This study explores the effect of niobium, titanium and silicon on the liquidus and solidus temperatures and primary structural refinement in creep-resistant 0.3C-30Ni-18Cr cast steel. Fifteen test alloys were investigated. The concentrations of niobium, titanium and silicon in these alloys ranged from 0.03 to 3.0 wt.%, 0.03 to 1.42 wt.%, and 1.39 to 4.26 wt.%, respectively. It was found that an increase of these elements in 0.3C-30Ni-18Cr cast steel lowered the beginning and ending temperatures of the solidification process, extended the range of solidification temperatures, reduced the density, and refined the microstructure, i.e., reduced the secondary dendrite arm spacing. Alloys with the highest content of the examined elements were reported to contain carbide precipitates, as well as the G phase in an as-cast state.     

Effect of molybdenum addition on the microstructure and mechanical properties of Cr3C2-20 wt. % Ni cermet

Effect of Mo addition on the microstructure and mechanical properties of Cr₃C₂-20 wt. % Ni cermet was investigated. Three different phases can be seen in the microstructure after adding appropriate molybdenum. The completely undissolved (Cr, Mo)₃C₂ phase maintains the original grain size and effectively prevents the (Cr, Mo)₇C₃ grains from merging and growing. The relative densities of the sintered specimens decrease slightly, while the hardness and bending strength increase firstly and then decrease slightly with the increase of Mo content. The maximum values of the hardness (88·6 HRA) and bending strength (1200 MPa) are achieved with 1 wt. % Mo addition.     

Comments on “Accurate measurement of power, energy, and trueRMS voltage using synchronous counting”

The authors comment on the principle of operation, on error calculation and on results presented by J.K. Kolanko in ibid., vol.42, p.752-4, (June 1993). They conclude that the paper has many errors and many details have been omitted which make it extremely difficult to understand. However, the paper documents a design which has probably been implemented successfully and is probably a useful device for its intended purposes     

Effect of rare earth element yttrium addition on microstructures and properties of a 21Cr–11Ni austenitic heat-resistant stainless steel

In this comparative study, the microstructure and the mechanical properties of a 21Cr–11Ni austenitic heat-resistant stainless steel with and without addition of rare earth (RE) element yttrium have been investigated. The results show that a number of fine spherical yttrium-rich oxide particles are not uniformly distributed in the matrix of steel with yttrium; instead, they are aligned along the rolling direction. The grains surrounding the alignment are nearly one order of magnitude smaller than those farther away from the alignment. The approximate calculation results indirectly show that the grain refinement may be mainly attributed to the stimulation for nucleation of recrystallization rather than to pinning by particles. Furthermore, the alignment has resulted in significant loss in transverse impact toughness and tensile elongation at room temperature. There is a trough in the hot ductility–temperature curve, which is located between 973 and 1173 K. The ductility trough of steel with yttrium becomes shallow within a certain temperature range, especially around 1073 K, indicating that improvement on hot ductility is achieved by yttrium addition. The results may be attributed to the increase of grain boundary cohesion indicated by the effective improvement on intergranular failure tendency, and the inhibitory effect of yttrium on sulfur segregation to grain boundaries is believed to be an important cause.     

Effect of Zr addition on the microstructure and properties of Cu–10Cr in situ composites

The Cu–10Cr–0.4Zr alloy and the in situ composites based on the alloy were prepared. Microstructure evolution and mechanical properties of Cu–10Cr–0.4Zr in situ composites were investigated. The results showed that the addition of 0.4 wt.% Zr in the Cu–10 wt.% Cr in situ composites gave birth to smaller as-cast Cr dendrites, which led to finer filaments at higher strain ratios. The ultimate strength of Cu–10Cr–0.4Zr composites reached 1089 MPa at draw ratio of η = 6.2, however that of Cu–10Cr prepared by the same procedure was only 887 MPa. The increasing strength of Cu–10Cr–0.4Zr in situ composites could be attributed to the combination of Hall–Petch strengthening of closely spaced Cr filaments, the strengthening effect of Zr and the strengthened Cu matrix.     

B2－NiAl力学性质Cr合金化效应的第一原理计算

采用第一原理赝势平面渡方法和基于虚拟晶体势函数近似（VCA）,计算了Cr合金化（浓度x〈1．0at％）时完整与缺陷B2-NiAl晶体的弹性性质,并采用弹性常数G44、Cauchy压力参数（C12-C44）、杨氏模量E、剪切模量G及其与体模量B0的比值G／B0等,表征和评判了Cr合金化浓度X对NiAl金属间化合物延性与硬度的影响。结果表明：Cr合金化浓度在0～1at％范围内均对NiAl晶体的硬度有明显影响。无论点缺陷存在与否,Cr合金化均可使B2-NiAl晶体的硬度大幅提高。Cr合金化浓度在0at％～0．5at％区间,有利于无缺陷NiAl晶体材料延性的提高,且以0．05at％的合金化浓度为最好。Ni空位或Ni反位降低B2-NiAl晶体的本征延性。Cr合金化浓度在x〈1at％时,Ni空位的NiAl晶体增塑效应并不明显,而对于Ni反位的缺陷NiAl晶体,Cr合金化浓度在0．9at％附近存在比较明显的增塑效应。     

An investigation into the stability of the mechanical properties of 1 Cr18Ni9Ti steel,previously loaded at elevated temperatures

This article described the results of a study of the influence of protracted loading in argon and liquid lithium at elevated temperatures on the stability of the mechanical properties of 1Cr18Ni9Ti steel. A method of comparing the nature of the changes in the properties of the steel with respect to the stress level during previous loading was developed. Curves representing the dependence of the stability coefficients of these properties on the coefficients of the previous loading were constructed.Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 5, No. 5, pp. 517–523. September–October 1969.     

Character of the variation in certain properties of 1Cr18Ni9Ti steel under long-term loading conditions at elevated temperatures

The effect of preliminary loading of 1Cr18Ni9Ti steel specimens at 650° C on the stability of their properties was studied. It was shown that curves representing the stability of hardness, elongation, and endurance are analogous in character. Increasing the duration of preliminary loading shifts the stability curves toward the zone of lower stress, but there is no complete correlation between the stability of properties studied.     

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.     

Effect of Cr and Ni on diffusion bonding of Fe3Al with steel

Microstructure at the diffusion bonding interface between Fe₃Al and steel including Q235 low carbon steel and Cr18-Ni8 stainless steel was analysed and compared by means of scanning electron microscopy and transmission electron microscopy. The effect of Cr and Ni on microstructure at the Fe₃Al/steel diffusion bonding interface was discussed. The experimental results indicate that it is favourable for the diffusion of Cr and Ni at the interface to accelerate combination of Fe₃Al and steel during bonding. Therefore, the width of Fe₃Al/Cr18-Ni8 interface transition zone is more than that of Fe₃Al/Q235. And Fe₃Al dislocation couples with different distances, even dislocation net occurs at the Fe₃Al/Cr18-Ni8 interface because of the dispersive distribution of Cr and Ni in Fe₃Al phase.     

Comments on ‘Solidification modes and microstructure of Fe–Cr alloys solidified at different undercoolings’

The critical growth velocity for a planar solidification front in undercooled alloy melts is discussed on the basis of the absolute stability theory to reexamine the interpretation of a current analysis of the solidification modes in undercooled bulk Fe–Cr alloys contributed by Xuezhi Zhang. Theoretically, it is possible to produce a planar front in the solidification of undercooled bulk melts. But practically, it is imopssible for the undercooled bulk Fe–Cr melts to produce a planar front in the solidification. The dendritic growth theories as well as the calculations due to Zhang have been analyzed.     

A study of the effects of phosphorus on the kinetics and mechanism of the order-disorder transformation in an Ni2Cr alloy

Three Ni₂Cr alloys, with phosphorus (P) contents of 0.002, 0.017 and 0.078 wt % were prepared as cast slabs, which were then thermomechanically treated to a final thickness of 0.38mm, after which they were solution annealed at 900° C for 1 h and water quenched. The isothermal order-disorder transformations of the Ni₂Cr alloys were investigated in specimens aged at temperatures between 425 and 550° C, for times ranging from 2 h to 70 days, by surface hardness measurements and microstructural studies. From the surface hardness data, time-temperature-transformation (TTT) curves were constructed for each of the three alloys of different phosphorus content. It was found that increasing the amount of phosphorus greatly reduced the time required to start and complete the order transformation. However, it was found that the effect of phosphorus content on the rate of transformation was significantly reduced at ageing temperatures above 500° C. The results are discussed in terms of models for nucleation and growth of ordered phases.