Thermodynamics of Component Interactions in Liquid Alloys of the Ternary Systems Ge(Al,Si) ― Ga ― Gd

The concentration dependence of the integral enthalpy of mixing in liquid alloys of the ternary systems Ge(Al, Si) Ga Gd at 1760 K, determined by the method of isoperibolic calorimetry and calculated using the surrounded atom model, was analyzed. Good agreement between H values obtained by both methods is noted. It was established that the interaction of gadolinium with components of the adjoining binary systems, which are characterized by the presence of intermetallic compounds, have a defining effect on the thermodynamics of alloy formation in the ternary systems Ge(Al, Si) Ga Gd.     

The Cr ― Ta ― C Melting Diagram in the (Cr) ― (Ta) ― (TaC) Region

It has been found from an experimental study on alloys in the Cr Ta C system in the region of the (Cr) (Ta) (TaC) subsystem at melting (crystallization) temperatures that there are two nonvariant four-phase equilibria of congruent type: L_E (Ta) + (Ta₂C) + (TaCr₂) at 1935°C and L_E (TaC) + (Cr) + (TaCr₂) at 1675°C; there is also one four-phase nonvariant equilibrium of incongruent transition type: L_U + (Ta₂C) (TaC) + (TaCr₂) at 1943°C, and two nonvariant three-phase equilibria of congruent type: L_e (Ta₂C) + (TaCr₂) at 1960°C and L_e (TaC) + (Cr) at 1695°C. The phase diagram for the subsystem has been constructed in the form of projections of the solidus and liquidus surfaces, and a melting diagram has been constructed.     

Deoxidation Behavior of Alloys Bearing Barium in Molten Steel

Asdeoxidizers ,siliconandmanganesewereusedinearlysteelmaking ,andaluminiumwasalsoadoptedsevendecadesago .Recently ,variouscom plexdeoxidizershavebeendeveloped ,amongwhichthealloysbearingbariumattractmoreattention .In196 9,HiltyDCetal[1] usedalloysbearingbariumtotreatmoltensteelforthefirsttime .Inthe 1970s ,variousalloysbearingbariumwereusedtotreatmorethan 2 0steelgradesinAmerica ,JapanandformerSoviet ,andmeantimealargeamountofpa persandbookswerepublished[2 -6] .InChina ,alloybearingbariumwa…     

Removal of Vanadium from Molten Aluminum—Part III. Analysis of Industrial Boron Treatment Practice

Transition metal impurities (V, Ti, Zr, and Cr) reduce the electrical conductivity of smelter grade aluminum. These impurities are removed in the form of their borides by reacting with added Al-B master alloys i.e., boron treatment. Although, boron treatment is widely used for the production of high purity aluminum alloys in casthouse the fundamental understanding is lacking and published industrial data are limited. In the current study, industrial trials on the removal of impurities were conducted at one of the high purity aluminum alloys producers in Australasia. Kinetics analysis revealed that the rate of reaction is controlled by the mass transfer of impurities in the bulk melt. The measured mass transfer coefficient (k _m) of V and Ti were 1.1 × 10^?4 and 2.6 × 10^?4 m/s respectively, in the naturally stirred molten aluminum. The rate of V and Ti removal was faster compared to Zr and Cr during the boron treatment of smelter grade aluminum. Mass balance analysis revealed that 70 wt pct of V and Ti combined as borides in the first hour of the total 12 hours of boron treatment process. The calculated amount of un-reacted B was approximately 25.5 wt pct of initial amount added that remained in the final alloy. There was no evidence of boride rings formation, although partially dissolved AlB₁₂ particles were observed under scanning electron microscope. Finally, implications for industrial practice are discussed for the improvement of current boron treatment process that include changing the source of boron, multiple stage addition of boron and better stirring of the molten aluminum.     

Physico-Chemical Investigation of Component Interactions of the Si ― Al ― O ― N ― Ti System in the Region Si3N4 ― AlN ― Al2O3 ― SiO2 ― TiN ― TiO2. Part 1. Subsystems Si3N4 ― Al2O3, Si3N4 ― TiN,and Al2O3 ― TiN

Using the methods of differential thermal and x-ray diffraction analysis an investigation was made of component reactions in the Si Al O N Ti system, particularly between the compounds Si ₃N₄ Al₂O₃, Si₃N₄ TiN, and Al₂O TiN under conditions approximating those used in the hot pressing of composites. It was established that in the reaction of Si₃N₄ with Al₂O₃, -sialon, SiO₂, AlN, and the intermediate reaction products (mullite and X-phase) are formed. In the reaction of Si₃N₄ with TiN, as a result of the decomposition of Si₃N₄ at 1650-1900°C titanium disilicide is produced, which forms eutectics with free silicon and residual TiN at 1320 and 1280°C, respectively. The reaction of Al₂O₃ with TiN similarly leads to the formation of a eutectic between Al₂O₃ and spinel at 1850°C. The presence of eutectic liquids in the specimens after sintering promotes densification of the material, and improves certain of its mechanical properties.     

Effects of AlMnCa and AlMnFe Alloys on Deoxidization of Low Carbon and Low SiliconAluminum Killed Steels

To confirm the effects of AlMnCa and AlMnFe alloys on the deoxidization and modification of Al2O3 inclusions, experiments of 4heat low carbon and low siliconaluminum killed steels deoxidized by AlMnCa and AlMnFe alloys were done in a MoSi2 furnace at 1 873 K. It is found that the 1# AlMnCa alloy has the best ability of deoxidization and modification of Al2O3 inclusions than 2# AlMnCa and AlMnFe alloys. Steel A deoxidized by 1# AlMnCa alloy has the lowest total oxygen content in the terminal steel, which is 37×10-6. Most of the inclusions in the steel deoxidized by 1# AlMnCa alloy are spherical CaOcontaining compound inclusions, and 891% of them are smaller than 10 μm. The diameter of the inclusion bigger than 50 μm is not found in the final steels deoxidized by AlMnCa alloys. Whereas, for the steels deoxidized by AlMnFe alloys, most inclusions in the terminal steel are Al2O3 or Al2O3MnO inclusions, and a few of them are spherical, and only 768% of them are smaller than 10 μm. Some inclusions bigger than 50 μm are found in the steel D deoxidized by AlMnFe alloy.     

The Role of Precipitates in the Behavior of Young’s Modulus in Aluminum Alloys

The behavior of Young’s modulus, E, was determined in aluminum alloys such as AA7075 and AA2024 at room temperature under various thermomechanical treatments. E was almost 2 pct (AA7075) and 3 pct (AA2024) lower for these materials after solution heat treatment and quenching than after annealing. When the aging time was increased, values of E tended to approach the annealing values. The variation observed was attributed to structural changes during the thermal treatments. However, when the alloys were cold deformed before or after aging, no appreciable changes in E were observed. This behavior is quite different to that observed in cold-worked pure aluminum (and also in pure iron), in which E decreased to a minimum (7 to 10 pct reduction in values) and then partially recovered with additional cold working. The variation in behavior with cold working observed in a pure material and other materials that contain a second phase with nanometric precipitates was correlated with the density of dislocations and the length of the dislocation segments generated during the cold working process.     

Direct Observation of Wetting and Spreading of Molten Aluminum on TiB2 in the Presence of a Molten Flux from the Aluminum Melting Point up to 1033?K (760?°C)

The wetting and spreading of molten aluminum on TiB₂ substrates between the aluminum melting point and 1033 K (760 °C) was investigated in the presence of different types of fluxes. The wetting and spreading behavior is observed to depend on the flux, its melting point, its chemistry, and its ability to dissolve alumina. When the flux melting point is higher than the melting point of aluminum, the molten aluminum takes on an initial spherical shape as a result of the thin alumina layer on its surface. After the flux is melted, it dissolves the alumina layer on the liquid aluminum surface causing the aluminum to wet and spread on the substrate. When the flux melts before the aluminum, the alumina layer on the solid aluminum surface is dissolved into the flux. In this case, the aluminum surface in contact with the molten flux is alumina layer free. Thus, the aluminum does not take a spherical shape after melting; it rapidly melts, wets, and spreads on the substrate. The use of a flux allows the wetting behavior of aluminum on TiB₂ to be observed at lower temperatures than previously reported.     

Interactions in the Al2O3 ― ZrO2 ― La2O3 System at 1250 and 1650°C

Triangulation has been determined for the Al₂O₃ ZrO₂ La₂O₃ system, and 1250 and 1650°C isothermal sections of the phase diagram have been constructed. The LaAlO₃ La₂Zr₂O₇ section is quasibinary, while the LaAlO₃ T-ZrO₂ and La₂O₃ ·11Al₂O₃ T-ZrO₂ ones are partially quasibinary. The triangulation of the ternary system is based on ZrO₂ and a phase containing it. No ternary compounds or regions of ternary solid solutions have been identified.     

Electroreduction of Y(Ⅲ)in Molten Chlorides and Alloying

The electroreduction of Y(Ⅲ)on tungsten electrode in NaCl-KCl-YCl_3 melt has been investi-gated by cyclic voltammetry.Deposition of Y(Ⅲ)to Y(0)is reversible in one step.The cyclic voltammetry,convolution voltammetry,potential-time curve after potentiostatic electrolysis and X-ray diffraction analy-sis were used to study the electrode process of Y(Ⅲ)reduced on iron electrode.Several Y-Fe intermetalliccompounds are formed before the deposition of metallic yttrium.The diffusion coefficient anddiffusion activation energy of Y in Y_6Fe_(23) were determined by current-time curve at potential step.The results indicate the diffusion of Y in its alloy phase is so slow that this step will control the electrode pro-cess.     

Development and Application Prospects of Aluminum–Lithium Alloys in Aircraft and Space Technology

Metallurgist - New models of competitive aviation and space technology cannot be created without contemporary materials. The development of aluminum–lithium alloys was mainly determined by...     

Electroreduction of Dy~(3 ) on Ni Cathode in Molten Chlorides

ＥｌｅｃｔｒｏｒｅｄｕｃｔｉｏｎｏｆＤｙ~（３＋）ｏｎＮｉＣａｔｈｏｄｅｉｎＭｏｌｔｅｎＣｈｌｏｒｉｄｅｓＴｏｎｇＹｅｘｉａｎｇ（童叶翔）；ＬｉｕＧｕａｎｋｕｎ（刘冠昆）；ＹａｎｇＱｉｑｉｎ（杨绮琴）ＨｏｎｇＨｕｉｃｈａｎ（洪惠婵）；ＣｈｅｎＳｈｅｎ?..     

Electroreduction of Ho~(3 ) on Nickel Cathode in Molten KCl-HoCl_3

The holmium metal can be prepared bymolten salt electrolysis with high consumptionof electric energy and low recovery of holmiumat the high electrolytic temperature. As weknow, the electrolytic temperature would bedecreased, provided rare earth alloy was prepared by electrolysis. We are interested in investigating the preparation of Ho-Fe, Ho-Co,Ho-Ni and Ho-Cu alloys by molten salt electrolysis on consumahle transition metal cathodes and the mechanism of forming alloys so asto provide scie…     

20 Aluminum Producers Stop Production in 1~(st)Half

In the first half of 2004,the primary aluminumindustry in China had a profit plunge and 20primary aluminum enterprises in the wholecountry have completely stopped productiondue to the power price hikes,small margin ofalumina price reduction,price declining of pri-mary aluminum since May and other factors,making the Chinese producers more and moredifficult to survive.The statistics from theChina Non-Ferrous Metals Industry Associa-tion show that the first six months witnessed     

Heat Treatment of Alloys(Ⅳ)

2. Heat - treatment of steels(Conlinued) The diagram of Fig, 2 is Particularly simple because the isothermal decomposition product,pearlite (or a modified structure, bainite, at lower temperatures, as discussed below )has the same com-position as the austenite from which it is formed. In hypo - eutectoid and hyper - eutectoid steels an ex-tra line appears in the high - temperature part of the diagram, representing the preliminary formation     

Heat Treatment of Alloys(Ⅴ)

3. Formation of pearlite Experimental work mainly by Mehl [1] has shown that pearlite nucleates beterogeneously. In ahomogeneous eutectoid steel the pearlite nuclei form in the austenitic grain boundaries and then growinto the adjoining grains as nodules. Each nodule contains one or more colonies. A colony consists ofalternate sheets of ferrite and cementite, the boundary of the colony corresponding [2] to a change inthe crystallographic orientation of the ferrite and to a change in the direction of the cementite sheets. The pearlite-austenite interface is incoherent and advances radially outwards from its nucleus into     

Heat Treatment of Alloys (Ⅵ)

4. Pro—eutectoid reactions In a steel not of eutectoid,composition the transformation at temperatures above about 550℃begins with the separation of pro—eutectoid ferrite or cementite, usually at the austenitic grainboundaries. The composition of the separating structure is now different from that of the parentaustenite so that[1]long—range migration of carbon is necessary to change the composition in thetwo regions of the decomposing grain. If the grain size is large the central region of a grain is so     

Heat Treatment of Alloys (Ⅶ)

Because of the speed of the transformation to martensite there is no time for separation of atomsfrom solid solution and so the composition of the martensite is identical with that of the austenite fromwhich it is formed.There is thus an ideal temperature T_0 for the formation of martensite, i. e. the     

Heat Treatment of Alloys(Ⅱ)

1. Decomposition of supersaturated Solid Solution(Cont'd) X-ray diffraction and electron microscope observations, and the measurement of physical proper-ties such as electrical resistivity and heat content, have shown that in supersaturated solid solutionsthere often develops[1] a fine-scale clustering into a zone structure. Although not completely proved,it seems most likely that these G. P. zones, So-named after their discoverers, A. Guinier and G. D.preston,are produced by spinodal decomposition,They form homogeneously on a fine scale through-