Thermal analysis of Al-Cu-Mg-Si alloy with Ag/Zr additions

Heat-treatable aluminium alloys are widely used for structural applications. Their strength is obtained through age hardening phenomena, that are sensitive to microalloying. In the present paper the results of thermal analyses on the ageing behaviour of an Al-Cu-Mg-Si alloy with silver and zirconium additions are presented. Specimens were water quenched after solution heat treatment, then aged at 453 K and a hardness-versus-time plot was drawn. Samples representative of different ageing conditions were subjected to DSC scans. Peaks were identified taking into account θ and Q phases precipitation sequences. Solution treated samples showed GP/θ″/θ′/Q sequence, while in peak aged condition GP and θ″ precipitation peaks disappeared and a reduction of θ′ peak area was observed, witnessing the concurrent presence of θ″ and θ′ phases at peak hardness condition. Experimental data were compared with results from analogous investigations performed on a conventional commercial Al-Cu-Mg-Si alloy.     

硼和铈对Cu-Fe-P合金显微组织和性能的影响

Cu-Fe-P系合金是广泛应用的制造集成电路引线框架的材料。本文通过对Cu-0．22Fe-0．06P，Cu-0．22Fe-0．06P-0．05Ce，Cu-0．22Fe-O．06P-0．02B和Cu-0．22Fe-0．06P-0．05Ce-0．02B（％，质量分数）这4种合金的杂质元素含量、显微组织、力学性能和导电率进行测试分析，研究了添加铈和硼对Cu-Fe-P合金纯净度、组织和性能的影响。结果表明，添加微量的铈和硼，一方面具有显著的脱S，Bi，Pb等杂质元素作用；另一方面显著地提高合金的再结晶温度，使合金经冷轧加工＋时效处理后可以获得加工硬化和时效强化的效果，而对导电性的影响微小，从而使合金获得高强度和高导电率的良好结合。     

Mecanismes de durcissement structural des alliages plomb-cadmium (etain,argent) pour grilles de batterie I- alliages plomb-cadmium

The reequilibration of supersatured Pb-Cd alloys was studied by different experimental methods: hardness measurements, optical and electron microscopy, electron microprobe. Two structural states were considered: as-cast alloys, rehomogenised alloys. The Cd contents were 1, 1.5, 2 and 3.2 weight%. The explored temperatures were 20 and 80 °C. This last temperature corresponds to the curing temperature of battery's grids and to the highest operating temperature. The evolution of the quenched structure towards the equilibrium state was studied for the time range one minute to one year. The corresponding aging is characterized by a continuous precipitation and a discontinuous transformation. The hardening process is followed by an overaging which consists of a discontinuous transformation with a reprecipitation of the Cd from the fine hardening precipitates of the same phase.     

含钪、铒的Al-0.8%Mg-0.6%Si合金的低周疲劳行为

对固溶+人工时效(T6)处理的挤压变形Al-0.8%Mg-0.6%Si,Al-0.8%Mg-0.6%Si-0.2%Sc和Al-0.8%Mg-0.6%Si-0.3%Er合金进行了低周疲劳试验,探讨了合金的低周疲劳变形和断裂行为.结果表明,低周疲劳变形期间,含Sc,Er合金可以呈现循环应变硬化、循环应变软化和循环稳定;添加稀土元素Sc可提高合金的循环变形抗力,且含0.2%Sc的合金在疲劳变形期间发生双系滑移;含Sc,Er合金的弹性应变幅和塑性应变幅与断裂时的载荷反向周次的关系可分别用Basquin和Coffin-Manson公式来描述,其中Al-0.8%Mg-0.6%Si-0.2%Sc合金的塑性应变幅与断裂时的载荷反向周次之间呈双线性关系;含Sc,Er合金的疲劳裂纹均是以穿晶方式萌生于试样表面,并以穿晶方式扩展.     

铈在Fe-28Al合金中的作用

以稀土元素Ｃｅ为微合金化元素，研究了Ｃｅ对Ｆｅ３Ａｌ二元合金（Ｆｅ２８Ａｌ）室温力学性能的影响，采用光学显微镜、扫描电镜、透射电镜、Ｘ射线光电子能谱仪、等离子耦合光谱、Ｘ射线衍射仪以及俄歇能谱仪等现代微观分析手段，探讨了Ｃｅ微合金化对Ｆｅ３Ａｌ合金组织结构和力学性能影响的作用机制。研究结果表明，Ｃｅ的加入改善了合金的室温塑性和强度，并在合金中起到了脱硫、脱氧、改变夹杂物形态、细化晶粒以及表面改性等作用。此外还对富Ｃｅ相颗粒在合金中的形态分布作了分析。     

DSC analysis of phase transformations during precipitation hardening in Al–Zn–Mg alloy (7020)

The hardening of the Al–Zn–Mg alloys during ageing process is based on very complex phase transformations. In order to contribute to the comprehension of these phenomena, we proceed to study the phase transformations of 7020 alloy using differential scanning calorimetry and X-ray diffraction analysis. The results confirm the formation of hardening phase GP zones, intermediate hardening metastable phase η′ and the equilibrium phase η. The calorimetric and X-ray diffraction results are in good agreement and confirm the successive precipitation/dissolution sequence. The dissolution of the precipitates is accompanied by the increase in the crystallographic lattice parameter due to the increase in solid solution concentration and by the softening of the material. On the contrary, the precipitation produces a lower concentration of the Zn/Mg solutes in the Al matrix, which generates a decrease in the lattice parameter value. These precipitates produce the hardening of the alloy. The sequence of phase formation and dissolution explains the evolution of the 7020 hardness as a function of the ageing temperature.

     

Adjusting non-isothermal crystallization kinetics through similar solute element Ga microalloying for Al in novel La-Al-C metallic glasses

Journal of Thermal Analysis and Calorimetry - In this text, the influence of similar solute element Ga microalloying for Al on the non-isothermal crystallization kinetics between novel light...     

Modification of Weld Metal with Tungsten Carbide and Titanium Nitride Nanoparticles in Twin Submerged Arc Welding

The influence of tungsten carbide and titanium nitride nanoparticles on the structure and properties of the weld metal of welded joints made by automatic twin submerged arc welding is considered. The nanoparticles have been introduced into the weld pool as a part of the “master alloy” based on nickel powder (PNE-1 according to GOST 9722). It has been shown that modifying the weld metal with tungsten carbide nanoparticles holds promise for enhancing the impact strength. In addition, it has been found that titanium nitride is prone to dissociation under the same conditions. However, microalloying with titanium, which is due to the release of titanium from the nitride, leads to an increase in the impact strength of the weld metal.     

M_2M_2′Te_4型层状异金属簇合物的SCC—DV—Xα研究(M=Co、Ni;M′=Ta、Nb)

标题簇合物的电子结构采用电荷自洽离散变分Xα方法(SCC—DV—Xα)计算得到。在前线区轨道密集,具有半导体的特征;层状结构内存在离域性d-p(π+α)键,这是该类簇合物导电的依据;Ni—Ni或Co—Co之间不存在成键。描述了它们的态密度图,并说明了与合金的DOS图相似点。     

Application of the glow discharge mass spectrometry (GDMS) for the multi-element trace and ultratrace analysis of sputtering targets

Glow discharge mass spectrometry using a VG9000 high resolution mass spectrometer has been applied to both the multi-element trace and ultra trace analyses of sputtering target materials, i.e. aluminium-based alloys, cobalt-based alloys, titanium and platinum. Element dependent relative sensitivity factors (RSF) have been determined using reference materials in order to provide the possibility for quantitative analyses. Aluminium-based and cobalt-based alloys have been extensively analysed to demonstrate precision of GDMS analyses. Detection limits in the ng/g and sub-ng/g ranges, i.e. 0.2 ng/g for U and Th have been determined in aluminium-based alloys. Comparative analyses for alloy components in cobalt-based alloys as well as trace concentrations in titanium have been performed. GDMS has been also applied to multi-element depth profile analyses in contaminated and noncontaminated platinum targets.     

DSC study of precipitation processes in Cu-Co-Si alloys

Using differential scanning calorimetry (DSC) the precipitation processes of supersaturated solid solutions of three Cu-Co-Si alloys containing the same atomic cobalt content were investigated. Thermoanalytical and previous studies, reveal that the decomposition begins with cobalt clustering which initiates the precipitation of the Co₂Si stoichiometric particles, which in turn dissolves after further heating. Volume fractions are unequivocally determined by the amount of cobalt present in these alloys. It is infered that surplus silicon atoms retained in the solution increase the reaction rate and dispersity of precipitate structure. Kinetic parameters were obtained by a convolution method based in the Mehl-Johnson-Avrami (MJA) formalism. The lower activation energy associated with cobalt clustering is attributed to the contribution of quenched-in vacancies. Superimposed to the MJA formalism and adaptative spherical diffusion model was used for Co₂Si precipitation with particle size as a disposable parameter. This model further confirmed that as silicon content increases particle dispersity becomes more pronounced. Such results are also infered from a three dimensional diffusion dissolution model previously developed which adjusts quite well to such process in the present cases. Age hardening experiments are in line with all previous results obtained. This revised version was published online in August 2006 with corrections to the Cover Date.     

Spot tests for the identification of titanium alloys and their differentiation from zirconium and its alloys

During manufacture every precaution is taken to safeguard against inadvertent mixing of titanium and zirconium alloys. There arc, howcvcr, occasions when confirmation of identity is desirable, Simple spot tests are described for the rapid differentiation of a range of titanium alloys and fur distinguishing these materials from zirconium and its alloys After a preliminary attack of the abraded metal surface with either fluoboric or hydrofluoric acid, characteristic coloured reaction products arc formed with well known reagents. and these tests serve to classify the material.     

MgNi-x% TiNi0.5Mn0.5 (x＝10, 30, 50)贮氢合金的制备与电化学性能

用机械合金化法成功制备出MgNi和TiNi0.5Mn0.5合金, 并将不同质量的TiNi0.5Mn0.5与MgNi合金球磨复合10 h制备MgNi-x% TiNi0.5Mn0.5 (x＝10, 30, 50)合金. XRD结果表明球磨后几种合金均为非晶体, TiNi0.5Mn0.5均匀分散到MgNi合金主相中; 充放电结果表明MgNi-TiNi0.5Mn0.5复合合金的初始容量比纯MgNi合金(443.12 mAh/g)低, MgNi- 10% TiNi0.5Mn0.5首次放电容量是394.46 mAh/g, 但循环寿命有较大的改善, 50次循环后容量保持在232.57 mAh/g, 保持率达59%; 动电位扫描结果表明复合后合金电极抗腐蚀能力提高; 循环伏安法和电化学阻抗谱法研究结果表明: 复合后电极表面的电化学催化性能增强, H原子在合金电极内部的扩散阻抗减小.     

Effect of Molybdenum (Mo) Addition on Phase Composition,Microstructure, and Mechanical Properties of Pre-Alloyed Ti6Al4V Using Spark Plasma Sintering Technique

The effect of molybdenum additions on the phases, microstructures, and mechanical properties of pre-alloyed Ti6Al4V was studied through the spark plasma sintering technique. Ti6Al4V-xMo (where x = 0, 2, 4, 6 wt.% of Mo) alloys were developed, and the sintered compacts were characterized in terms of their phase composition, microstructure, and mechanical properties. The results show that the equiaxed primary alpha and Widmänstatten (alpha + beta) microstructure in pre-alloyed Ti6Al4V is transformed into a duplex and globular model with the increasing content of Mo from 0 to 6%. The changing pattern of the microstructure of the sample strongly influences the properties of the material. The solid solution hardening element such as Mo enhances mechanical properties such as yield strength, ultimate tensile strength, ductility, and hardness compared with the pre-alloyed Ti6Al4V alloy.     

Microscopic model of true strain softening and hardening in a polymer glass

A simple microscopic model is proposed to describe the true strain softening and hardening behavior of a polymer glass. Equations of motion for the polymer chain embedded in a polymer matrix have been derived and investigated both analytically and numerically. The model correctly predicts both true strain softening and hardening phenomena. The model also allows a new interpretation of the microscopic origin of true strain softening in a polymer glass.     

Effect of rapid solidification on heat capacities of Al-Sr alloys

Heat capacities of both the ingot-like and melt-spun Al-Sr alloys have been measured through the temperature range 373 to 1060 K using differential scanning calorimetry. The experimental results show that rapid solidification has a slight effect on the temperature dependence of the heat capacities of the Al-Sr alloys. The heat capacities of the melt-spun Al-Sr alloys increase more slowly than those of the ingot-like alloys with increasing temperature from 373 to 900 K. Furthermore, the effect of rapid solidification on the heat capacities becomes more obvious with increasing Sr concentration in the Al-Sr alloys. The data of the heat capacities between 373 and 900 K have been fitted with the least square method and a linear dependence on temperature was assumed for that temperature range. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermodynamics of hydrogen solution and hydride formation in Pd-Mn alloys. 2. Ordered alloys

There are marked differences in H(2) solubilities between ordered and disordered Pd-Mn alloys with the largest difference found between the L1(2) and the disordered form of the Pd(3)Mn alloy. The thermodynamics of H(2) solution have been determined for the L1(2) form, the long-period superstructure (lps), and the disordered forms of the Pd(0.80)Mn(0.20) and Pd(0.75)Mn(0.25)(Pd(3)Mn) alloys. Relative partial molar enthalpies and entropies were determined mainly by reaction calorimetry over the range of H contents accessible from p(H)()2 approximately 10 Pa to approximately 0.3 MPa (303 K). The enthalpies for absorption of H(2) are more exothermic over most of the range of H contents for the L1(2) forms of the Pd(3)Mn and Pd(0.80)Mn(0.20) alloys than for their other forms. The reaction enthalpies are constant across a relatively wide range of H contents for the L1(2) form of the Pd(0.80)Mn(0.20) and Pd(3)Mn alloys indicating that there are two-phase coexistence regions (303 K). The H-H attractive interaction, which leads to hydride formation, is much greater for the L1(2) than for the other forms of the Pd(3)Mn alloy and for Pd itself. It has been found that the H-H interaction always decreases in magnitude and, accompanying this, the THS (terminal hydrogen solubility) always increases by alloying Pd.(1) The L1(2) ordered Pd(3)Mn alloy is an exception to this, and therefore, the generalization about THS must be restricted to disordered face centered cubic (fcc) Pd alloys.     

Determination of boron in titanium alloys by means of ion exchange

There is need for a rapid method for the determination of moderate amounts of boron in titanium alloys. In this paper a method is proposed which uses ion exchange. The method is applicable to titanium alloys containing 0.025 to 1 per cent. boron. One or two grams of the sample are dissolved in hydrochloric acid, and the titanium and boron are oxidized with nitric acid. The bulk of the titanium is removed by a cation exchanger. A calcium carbonate separation is made to remove the residual titanium and adjust the acidity. The boron is then titrated with sodium hydroxide, after the addition of mannitol. None of the elements found in commercial titanium alloys interferes with the method.     

Structural,magnetic and constitutional studies of a new family of ternary phases based on the compound Fe3GaAs

The compound Fe₃GaAs has been identified as a B8₂-type (hexagonal) phase which exists over a range of compositions represented by the general formula Fe₃Ga_{2 − x}As_x (0.875 ⩽ x ⩽ 1.125). For x ⩽ 0.85 there is a change in structure to another, closely related hexagonal modification which persists to x ≈ 0.21 and in which there is a doubling of the a spacing compared with that of the earlier structure. All the alloys are ferromagnetic¹ in nature with a marked rise in the Curie temperature with increasing gallium content. Curie temperatures as high as 644 K have been achieved in these alloys. There is a corresponding general increase in the M_s values but there is a dip at the composition where there is a change in the structure. Mössbauer measurements on the alloys are in agreement with the magnetic and structural data.     

Thermal Treatment of Iron-Copper Metastable Alloys

Mechanical alloying is a versatile technique for the solid state synthesis of many materials, including alloys such as iron-copper where the elements are immiscible under equilibrium conditions. The structural and magnetic state of these alloys, and their thermal stability, have been investigated by means of thermomagnetometry, DSC, X-ray diffraction and Mössbauer spectroscopy. Comparison of the thermomagnetometry curves for the various alloys together with analysis of intermediate reaction products enabled the individual thermal processes to be identified. The Curie temperature of the alloys was measured, and it was found that on heating the metastable alloys underwent phase segregation between 300-400°C.