Preparation of V-Ti-Fe master alloys by metallothermic reduction method

V-Ti-Fe master alloys were prepared by metaUothermic reduction method, and the influences of the mass ratio of V205 to TiO2, Al and Al-Mg alloy addition amounts on the metal recovery rates and alloy compositions were investigated. The results show that appropriate technological parameters are： the mass ratio of V205 to TiO2 is 0.5：1, Al addition represents 95% of the theoretical value, and the Al-Mg alloy addition amount is one third that of the Al addition. The results from energy spectrum analysis show that V and Fe distribute uniformly in the prepared alloy, while the segregation for Ti, i.e. Ti-rich phase is detected. A spray refming process was carried out to reduce the impurity contents of Al and O in the prepared alloys. The Al content drops from 4.27% to 1.86%, and the O content drops from 2.10% to 0.91% after the refining process.

Influence of Al-Mn master alloys on microstructures and electrochemical properties of Mg-Al-Pb-Mn alloys

Mg-Al-Pb alloy is one of the newly developed materials for the seawater activated batteries. As-cast Mg-6Al-5Pb and Mg-6Al-5Pb-0.5Mn alloys with different additions of Al-15%Mn （mass fraction）, Al-30%Mn and Al-50%Mn master alloys were prepared by melting and casting. Their microstructures were observed by optical microscopy and scanning electron microscopy. The electrochemical properties, hydrogen evolution and mass loss of Mg-6Al-5Pb-0.5Mn alloys were studied. The results show that Mg-6Al-5Pb-0.5Mn alloy added with Al-50%Mn master alloy provides more negative corrosion average potential （-1.66 V）, smaller corrosion current density （7 μm/cm2） and lower free corrosion rate （0.51 mg·cm-2·h-1） than other alloys. This is probably attributed to the presence of Al11Mn4 phase, which facilitates the self-peeling of corrosion products and enlarges the electrochemical reaction area as well as enhances the electrochemical activity.

Production of Al-B master alloys by mixing KBF_4 salt into molten aluminum

Two mixing techniques,the immersion method and the vortex method,were adopted in the production of Al-3%B master alloys since the generally used production route involving the direct addition of KBF4 salt to molten aluminum has several drawbacks.The experimental results demonstrate that the Al-B master alloys produced by the immersion method show a microstructure characterized by the appearances of AlB12 phase and many agglomerations of boride particles,while the Al-B master alloy produced by the vortex method exhibits a well dispersed microstructure of AlB2 particles in the matrix.The distinct microstructure features result from the differences in the stirring speed during the salt additions and the average size of the salt droplets achieved by the salt additions.

Influences of Preparation Conditions and Melt Treatment Procedures on Melt Treatment Performance of Al-5Ti-B and Al-10Sr Master Alloys

The influences of preparation conditions of Al-5Ti-B （as-cast and hot-rolled） and Al-10Sr （as-cast and hotextruded） and melt treatment procedures on the grain refinement and modification performance of A356 alloy are experimentally studied. For the two master alloys, the 50% reduction is sufficient to meet the demands of the efficient grain refinement and modification of A356 alloy. When Al-STi-B is introduced into the melt prior to degassing, the grain refinement efficiency of Al-5Ti-B will be greatly increased due to the better dispersity of TiB2 particles. Al-5Ti-B master alloy is less prone to affect the modification effect of Al-10Sr when they are used together.

Preparation of Scandium Bearing Master Alloys by Aluminum Magnesium Thermoreduction

The new preparation method of scandium bearing master alloys, in which scandium oxide was fluorinated by reaction with NH 4HF 2 and then reduced by aluminum magnesium in fused salt containing alkali and alkaline fluoride under atmosphere, was studied. The effect of sorts of metallic reductive and technique conditions such as reducing temperature and time on the recovery of Sc was discussed. When the liquid aluminum magnesium was used as the reductive agent, the all recovery exceeds 80% and the concentration of Sc in master alloy prepared exceeds 1.9%. The best reducing reaction temperature and time are 1100 K and 40 min respectively. The newly produced Sc from reduction combines with Al to produce the stable compound Al 3Sc, so the reduction progress is sustained and the recovery of Sc is increased.

STUDY OF THE NUCLEATION MECHANISM OF α-Al GRAINS AFTER ADDITION OF Al-Ti-B MASTER ALLOYS

Nucleation sites of α-Al grains after addition of an Al-Ti-B master alloy into pure aluminium have been investigated using EPMA. The results show that either TiAl3 or boride particales can nucleate α-Al grains. But the number of TiAl3 nucleants is reduced with the holding time prolonged and the boride-nuclei are increasing gradually. Based on these results, a new refining method, adding molten Al-Ti-B into commercially pure aluminium, which has a quicker and better refining efficiency is presented.

Evolution of V-containing phases during preparation of Al-based Al−V master alloys

Al-based Al−V master alloys were prepared by both the stepwise heating melting experiment and stepwise melting cooling experiment with rapid solidification to investigate the transformation of V-containing phases which gave different effects on microstructures and properties of commercial Al alloys and Ti alloys,as both melting and solidification processes affect the evolution of V-containing phases largely.The results showed that the raw Al−50wt.%V alloy consisted of needle-like Al_(3)V phase and Al8V5 phase(matrix),while petal-like Al_(3)V,needle-like Al_(7)V and plate-like Al_(10)V phase were present in the Al−V master alloys.The metastable Al_(7)V phase was evolved from Al_(3)V phase and then evolved into Al_(10)V phase during melting process.The number of Al_(10)V phase increased with the decrease of temperature in the range of 800−1000℃.Petal-like Al_(3)V phases could be transformed from Al_(8)V_(5) phase,pre-precipitated from Al−V molten liquid during melting process and precipitated directly during rapid solidification,respectively.

Grain reinement limit of commercial pure Al inoculated by Al-Ti-C(B) master alloys

The grain reifnement limits of commercial pure Al inoculated by Al-5Ti-1B, Al-5Ti-0.25C and Al-5Ti-0.3C-0.2B master al oys were studied, and the inlfuence of melting temperature on the grain reifning performance of these three master al oys was investigated using a high scope video microscope （HSVM）, a ifeld-emission scanning electron microscope （FESEM）, an electron probe micro-analyzer （EPMA） and X-ray diffraction （XRD） method. Results show that there is a grain reifnement limit of commercial pure Al reifned by these three master al oys; with the same addition level of 1.5% under the present experimental conditions, the grain reifnement limits （smal est average grain size） of commercial pure Al reifned by Al-5Ti-1B, Al-5Ti-0.25C and Al-5Ti-0.3C-0.2B master al oys are 50 μm, 80 μm and 80 μm, respectively. In addition, with an increase in the melting temperature of the pure Al, the grain reifning performance of Al-5Ti-1B and Al-5Ti-0.25C master al oys decreases, but the grain reifning performance of Al-5Ti-0.3C-0.2B changes little.

Grain refining mechanism of Al-3B master alloy on hypoeutectic Al-Si alloys

Al-3B master alloy is a kind of efficient grain refiner for hypoeutectic Al-Si alloys. Experiments were carried out to evaluate the effect of undissolved AlB2 particles in Al-3B master alloy on the grain refinement of Al-7Si. It is found that the number and the settlement of AlB2 particles in the melt all have effect on the grain refining efficiency. On the basis of experiments and theoretical analysis, a new grain refinement mechanism was proposed to explain the grain refinement action of Al-3B on hypoeutectic Al-Si alloys. The formation of ＇Al-AlB2＇ shell structure is the direct reason for grain refinement and the undissolved AlB2 particles is the indirect nucleating base for subsequent α（Al） phase.

Preparation of Yttrium－Barium－Copper Trinary Master Alloys by Electrolysis from Molten Fluoride－oxide

The electrochemical behaviour of Y￣(3+) and Ba￣(2+) on platinum and copper electrode in molten YF_3(70 wt% )-NaF (20 wt%)-CaF_2(10 wt%) has been studied by means of cyclic voltammetry. discharge curve and so on. The Y-Ba-Cu alloy is obtained by fused salt electrolysis with molten YF_3-NaF-CaF_2 as electrolyte and Y_2O_3 and BaO as raw materials. Graphite cell acted as an anode and copper rod as consumable cathode. The molten bath temperature was 1193 K. Cathode current density was 20 A/cm￣2. The contents of yttrium, barium and copper in alloy were about 20wt%, 9 wt% and 71 wt% respectively. Yttrium recovery efficiency was 90 wt%. The current efficiency was 70%～80 %.

Al-Si-P master alloy and its modification and refinement performance on Al-Si alloys

An Al-Si-P master alloy has been developed by an in-situ reaction and the electron probe microanalyzer （EPMA） results show that there are many pre-formed AlP particles contained in the master alloy. Silicon introduced into the system plays an important role in remarkably improving the distribution and content of AlP particles due to their similar crystal structure and lattice parameters. ZL109 alloys have shown fast modification response to the addition of 0.5% Al-15Si-3.5P master alloy at 720℃, with a mass of primary Si precipitating in size of about 15 μm. Also, coarse primary Si grains in AI-30Si alloy can be refined dramatically from 150 μm to 37 μm after the addition of 2.0% Al-15Si-3.5P master alloy at 850℃. The P recovery of the Al-15Si-3.5P master alloy is much higher than that of a Cu-8.5P master alloy due to the pre-formed AlP particles.

Refinement of primary Si in Cu-50Si alloys with novel Al-Zr-P master alloy

In this article, a novel Al-6Zr-2P master alloy with ZrP particles was successfully synthesized, and the refining performance of this novel master alloy for the primary Si in Cu-50Si alloys was also investigated. By means of the fracture plane observation, it is found that the ZrP phase would precipitate first in the solidification pro- cess, and then, the ZrAl3 phase grows around them. Fur- thermore, it is observed that the refining effect can be remarkably improved by changing the addition sequence of the raw materials. After the melting of commercial Cu, the 2.0 wt% Al-6Zr-2P master alloy and crystalline Si were added in sequence, and the mean size of the primary Si in Cu-50Si alloy can be significantly refined from 255.7 to 75.3 gm. Meanwhile, the refining mechanism was dis- cussed in detail.

Effect of Al-TiB master alloy addition on microstructure, wear and compressive deformation behaviour of aluminum alloys

Aluminum-10% TiB master alloy was added in various proportions in 7178 Al alloy in order to examine the effect of TiB on grain refinement, wear and compressive deformation of the later one. Microstructural characterization reveals that TiB particles act as grain refiners for primary base alloy and result in globular dendrites. It was observed that the wear resistance and strength of the alloy decreased when the master alloy addition increased beyond 20%, even though the dendrites become much finer and almost spherical in nature.

Effect of Al5Ti1B master alloy on microstructures and properties of AZ61 alloys

AZ61 alloys with different levels of Al5Ti1B master alloy additions were prepared by conventional casting method.The effects of Al5Ti1B contents and holding time on microstructures and microhardness of AZ61 alloys were studied by XRD,OM and microhardness testing techniques.The results show that when the addition level of Al5Ti1B master alloy is less than 0.5%(mass fraction),the average grain size of the alloys decreases with the increase of Al5Ti1B content at the same holding time.But the grain size increases somewhat with further addition of Al5Ti1B.The average grain size of the alloys decreases with the increase of the holding time as it is less than 30 min at the same addition level of Al5Ti1B.It is considered that TiB2 particles can serve as the heterogeneous nucleation sites ofα-Mg during solidification,and heterogeneous nucleation is the main reason for the grain refinement of AZ61 alloys.The microhardness of the refined AZ61 alloys with 1.0%Al5Ti1B addition is increased by about 8%.

Effect of AlP master alloy on grain refinement of primary silicon in eutectic Al-Si alloys

To obtain the finer primary silicon crystals, the proprietary Al-P masteralloy was adopted to modify the eutectic Al-Si alloys and the most suitable modification process wasmade in the experiments. The SEM (Scanning Electron Microscope) and DSC (Differential ScanningCalorimeter) analysis indicate that the Al-P modifier has more advantages over Cu-P and Fe-Pmodifier in easily addition, no elemental alteration and less undercooling of primary silicon'ssolidification, which suggests the Al-P master alloy is an effective modifier of eutectic Al-Sialloys.

Effect of A1P master alloy on grain refinement of primary silicon in eutectic Al-Si alloys

To obtain the finer primary silicon crystals, the proprietary Al-P master alloy was adopted to modify the eutectic Al-Si alloys and the most suitable modification process was made in the experiments. The SEM (Scanning Electron Microscope) and DSC (Differential Scanning Calorimeter) analysis indicate that the Al-P modifier has more advantages over Cu-P and Fe-P modifier in easily addition, no elemental alteration and less undercooling of primary silicon’s solidification, which suggests the Al-P master alloy is an effective modifier of eutectic Al-Si alloys.

Effects of Si Content and the Addition Amount of Al-3B Master Alloy on the Solidification Structures of Hypoeutectic Al-Si Alloys

Effects of Si content and the addition amount of Al-3B master alloy on the solidification structures of hypoeutectic Al-Si alloys were studied. The addition amounts of the master alloy were 0.2%, 0.4%, 0.7% and 1% (mass fraction, so as the follows), respectively. The Si content of Al-Si binary alloys investigated varied from 1% to 11%. The observation of macrostructures of non-refined samples showed that 3% Si constitutes a transition point at which the minimum grain size can be obtained. It was also found that Al-3B master alloy can shift the transition point towards a higher Si value when its addition amount increases, making this point appear at 4%, 5% and 6% Si as its addition amount increases up to 0.4%, 0.7% and 1%, respectively.

Grain refinement mechanism of Al-5C master alloy in AZ31 magnesium alloy

Al-5C master alloy was prepared by powder in situ synthesis process, and its effects on grain refinement of AZ31 alloy and refining mechanism were investigated. The results indicate that the AI 5C master alloy consists of a（Al） and A14C3 phases, and the size distribution of Al4C3 particles is controlled by sintering time. The AI 5C master alloy can remarkably reduce the grain size of AZ31 alloy, which decreases with the increasing addition amount of AI-SC master alloy when the addition amount is below 2%. The refining mechanism is attributed to the formation of new compounds of Al-C-Mnparticles by Al4C3 and Mn, which might act as nucleating substrates for a-Mg grain.

Microstructure evolution of Al-Sr master alloy during continuous extrusion

The microstructure evolution of Al–Sr master alloy during continuous extrusion was investigated using X-ray diffractometer, scanning electron microscope and transmission electron microscope. Results indicate that the continuous extrusion process could change the Al4Sr particles of the alloy significantly in size and morphology. The as-cast needle-like Al4Sr particles are broken into small blocks in upsetting zone and crushed heavily in adhesion zone. Plenty of dislocations get tangled up in right-angle bending zone. Al4Sr particles grow in the extending zone. Finally, Al4Sr particles in products are approximately 28 μm in length. Al2Sr particles precipitate during the process. Compared with products by horizontal extrusion, Al4Sr particles by continuous extrusion are finer and distribute more evenly.

Effect of cooling rate on morphology of primary particles in Al-Sc-Zr master alloy

Al-1.0%Sc-1.0%Zr （mass fraction） master alloy was prepared at different cooling rates. The morphology and thermodynamics data of the primary particles of the master alloy were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and differential scanning calorimetry （DSC）. It shows that the primary particles are dendrite-shaped particles comprised of several attached small cubic, cusped-cubic or crucifer shape particles at slow cooling rate. However, the primary particles are separated with crucifer shape at intermediate cooling rate, and they are cubic with cusped-cubic shape at high cooling rate. Meanwhile, the separated and attached particles present AlaSc/AlaZr1-xScx core-shell structure. The formation mechanism of the structure was systematically investigated by a mathematical model.