Thermodynamic properties of Mg−Ge alloys

The thermodynamic properties of liquid alloys and two-phase mixtures in the Mg?Ge system have been investigated in the approximate temperature range 660° to 1130°C by means of a galvanic cell based on MgCl₂ as electrolyte. Derived thermodynamic properties for the germanium-rich liquid alloys have been found to be in good agreement with previous work. The standard free energy of formation of solid Mg₂Ge from liquid magnesium and solid germanium has been derived from this work, and from previous studies as: \(\vartriangle F_{Mg_2 Ge}^o = - 29,900 + 7.98T cal.\) valid from 687° to 1115°C. The phase diagram for the system has been found to differ only slightly from that due to Klemm and Westlinning.     

镁及镁合金的特性与挤压工艺特点

简略地介绍了镁及镁合金的基本特性之后,详细地论述了镁及镁合金的挤压特点及其与铝合金挤压的主要区别,例举了大量的热挤压工艺的参数实例,有一定的参考价值。     

EDTA容量法测定铝合金中的镁

试样以氢氧化钠溶解，使铝、锌转入溶液并与铜、铁、锰、镁等氢氧化物沉淀分离。将沉淀以酸溶解并调节溶液酸度近中性，用DDTC分离铜、铁、锰，然后在PH10的氨性溶液中。以铬黑T为指示剂，用EDTA标准溶液直接滴定镁，测试铝合金中镁的含量。     

铝合金中镁的快速测定

介绍了铝合金中镁含量的快速测定。在不需分离的情况下,采用DDTC、盐酸羟胺、三乙醇胺联合掩蔽剂,掩蔽大量的铝及铜、铁、锰离子,在pH=10的缓冲液中以络黑T为指示剂,用EDTA滴至溶液由紫红色变为纯兰色为终点。该方法简单、快速、准确度高,适合于铝合金中各种镁含量的测定。     

铝合金中镁的快速测定

该文介绍的铝合金中镁的快速测定不需分离，采用DDTC、盐酸羟胺、三乙醇胺联合掩蔽剂掩蔽大量的铝及少量的铜、铁、锰离子，在pH10条件下，以铬黑T为指标剂，用EDTA滴至溶液由紫红色变为纯蓝色为终点。方法简单、快速、准确度高，适用于铝合金中镁含量的快速测定。     

Contribution of Twinning to Low Strain Deformation in a Mg Alloy

Deformation twinning plays an important role in the yielding of extruded magnesium alloys, especially when loaded in compression along the extrusion axis. The magnitude of this contribution is not accurately known. The present study employs electron backscatter diffraction to reveal the influence of grain orientation on twin-volume fraction for alloy AZ31 tested in compression to strains between 0.008 and 0.015. For these strains, it is seen that approximately 45 pct of the deformation can be attributed to “tensile” twinning. The variation of twin-volume fraction over different orientation classes correlates closely with the maximum Schmid factors for both tensile twinning and basal slip. These effects are readily explained quantitatively using a mean field crystal plasticity model without recourse to stochastic effects. Encouraged by this, we introduce an analytical approximation based on the uniformity of (axial) work.     

Thermodynamic Modeling as a Strategy for Casting High Alloy Steels

Strategies based on thermodynamic calculations can be used to overcome the problems associated with oxides encountered in steel plant operations, which can lead to certain difficulties in the process such as clogging of submerged entry nozzle during continuous casting. Approaches to producing high alloy steels by continuous casting have been taken. One of the strategies to avoid the oxidation of chromium is to add a small amount of other elements (subject to other constraints), which do not cause subsequent problems. The problem has been studied using the Thermo-CalcR software, with related databases; and the results obtained for different process conditions or generic com-positions have been presented.     

镁及镁合金材料的应用及市场开拓前景

介绍了镁及镁合金材料在交通运输、航空航天、电子工业、核能工业、化工冶金等部门的应用方向与实例，指出镁合金是一种很有发展前景的新型金属材料，其加工技术将获得进一步的快速发展。     

Thermodynamic study of the Mg−Sb system

Reversible galvanic cell technique has been used to determine the activities, relative partial molar free energies, entropies, and enthalpies of magnesium in liquid Mg?Sb alloys. The potentials were measured in the temperature range 980° to 1250°K, employing the fused salt mixture NaCl+KCl (eutectic)+MgCl₂ as the electrolyte. The heat and entropy changes accompanying the formation of Mg₃Sb₂(s) from liquid components, 3Mg(1)+2Sb(1)=Mg₃Sb₂(s) were derived from the experimental results; the values are ΔH ^o=?87,200 (±700) cal per gfw and ΔS ^o=?31.50 (±1.00) cal per gfw,^oK.     

The Recrystallization Behavior of Unalloyed Mg and a Mg-Al Alloy

The static recrystallization behavior of pure Mg and Mg-4Al was characterized over a range of annealing temperatures. The electron backscatter diffraction grain orientation spread technique was used to quantify the level of recrystallization at various annealing times. Recrystallization kinetics were characterized using the Johnson–Mehl–Avrami–Kolmogorov (JMAK) relationship and it was found that two sequential annealing stages exist. Stage 1 involves heterogeneous nucleation of recrystallization in regions with a high stored energy, including twins and grain boundaries, and can be represented by an Avrami exponent of n₁ ranging from 0.35 to 0.6. During Stage 2, recrystallization occurred predominately in the interior of deformed grains with incomplete recrystallization generally observed even at annealing times in excess of two weeks. The second recrystallization stage exhibited a much lower Avrami exponent, n₂, ranging from 0.02 to 0.2. Increasing the starting grain size in the pure Mg condition led to a significant delay in recrystallization. The addition of Al had a minimal effect on the recrystallization kinetics of Mg.     

冶金热力学数据库应用系统的系统构成

本文从冶金热力学数据库应用系统如何在M-150计算机上实现的角度,介绍它的机器环境和系统构成。它由四部分构成:
1.数据库:存贮有399种二元系合金和2211种化合物(或元素)的热力学数据。
2.数据管理系统:主要完成对数据库中所有数据检索、修改、插入、删除等任务。
3.应用程序库:由七个复杂的计算程序组成,完成化学平衡体系的热力学性质的计算。
4.监控系统:协调整个系统,使之正常工作。     

含钡二元合金熔体热力学性质的计算

根据Miedema二元合金生成热模型，结合相关热力学数据，对Si-Ca二元合金熔体在1623K时的组元活度进行了计算，计算结果与实测结果吻合较好。并进一步对Ba-Si、Ba-Al和Ba-Ca3种二元含钡合金熔体的生成热△H及1873K时的过剩熵S^E、过剩自由能G^E以及不同温度下各组元的活度等热力学性质进行了计算。结果表明：3种合金的△H、S^E和G^E均为负值，且S^E绝对值的最大值为4．424J／mol，可以近似认为3种合金熔体的S^E为零；Ba-Si和Ba-Al合金熔体的活度相对于理想溶液存在较大负偏差，而Ba-Ca合金熔体的活度与理想溶液偏差较小。     

稀土镁合金的发展、应用及开发

叙述了国内外稀土镁合金的发展状况，对稀土镁合金的性能及应用作了较为详细的阐述。在对稀土镁中间合金的制备工艺进行比较的基础上，针对性地介绍了目前采用的新工艺。同时，就我国稀土镁合金的发展提出了具体看法。     

Mechanical Properties of Gradient Structure Mg Alloy

In this work, a surface mechanical attrition treatment (SMAT) process was applied to AZ31B magnesium alloy at room temperature. This method produced a gradient structure on the treated AZ31B, in which the grains of the topmost layer are refined to nanoscale sizes. A combination of nanocrystallites at the surface and coarse-grains in the center are the main features of this structure. This structure results in an excellent combination of both strength and ductility. The highest yield strength for the 30 minutes SMAT AZ31B samples increased to 249 ± 5 MPa and the uniform elongation decreased to 9.3 ± 0.8 pct, whereas the original yield strength was only 147 ± 4 MPa and the uniform elongation was 15.4 ± 1.1 pct. Microstructural observations, stress relaxation tests, and hardness tests were used to verify the results. Additionally, there is a specific volume fraction of gradient structure to achieve the best mechanical performance, which is shown to be in the range of 9.3 to 14 pct for the AZ31B alloy.     

稀土化合物热力学网络数据库的研究开发

叙述了建设稀土化合物网络数据库的必要性,介绍了利用Apache服务器、MySQL数据库服务器和PHP脚本语言进行稀土网络数据库开发的最新进展。该数据库的建设已经基本完成了稀土文献CA数据库、稀土相图数据库以及稀土热力学数据库的基本框架设计、搜索引擎的编写以及数据的部分填充,其中稀土文献CA数据库收录了1986年～2002年的22万余条稀土文献信息。三个子数据库均实现了局域网内部的浏览检索。     

Thermodynamic Model and Database for Sulfides Dissolved in Molten Oxide Slags

A thermodynamic model has been developed in the framework of the modified quasichemical model in the quadruplet approximation to permit the calculation of solubilities of various gaseous species (sulfide, sulfate, nitride, carbide, water, etc.) in molten slags. The model calculates the solubilities solely from knowledge of the thermodynamic activities of the component oxides and the Gibbs energies of the pure liquid components (oxides, sulfides, sulfates, etc.). In the current article, it is shown that solubilities of sulfur as sulfide in Al₂O₃-CaO-FeO-Fe₂O₃-MgO-MnO-SiO₂-TiO₂-Ti₂O₃ multicomponent slags, which are predicted from the current model with no adjustable model parameters, are in good agreement with all available experimental data. The article also provides a thorough review of experimental sulfide capacity data for this system. The model applies at all compositions from pure oxides to pure sulfides and from basic to acidic slags. By coupling this database with other evaluated databases, such as those for molten metal and gaseous phases, and with general software for Gibbs energy minimization, practically important slag/metal/gas/solid equilibria can be computed such as S-distribution ratios.     

Mg-Sc合金的热力学性质计算

根据Miedema模型,计算了Mg-Sc合金液态和固态时的生成焓.结合相关的热力学关系式,计算了该合金中Sc的活度曲线,并拟合了该合金的相互作用系数,发现本文所采用的Miedema模型和正规溶体模型对于Mg-Sc合金是适用的.