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An Available Technique for Preparation of New Cast MnCuNiFeZnAl Alloy with Superior Damping Capacity and High Service Temperature
Chapters
Summary September 23rd, 2018
Here we present a protocol to obtain a novel Mn-Cu-based alloy with excellent comprehensive performances by a high-quality smelting technology and reasonable heat treatment methods.
Transcript
The purpose of this work is to design and develop a noble cast age manganese-copper-nickel-iron-zinc-aluminum alloy with superior damping capacity and high usage temperature, which can act as a promising candidate towards engineering applications. The brief preparation process is as follows. The first step is to prepare raw materials.
The second is to melt these pure metals in a vacuum induction melting furnace and desert atmosphere. The third is to get the alloy castings by custom molten alloy liquid into silica sand mold smoothly. The fourth is to remove the castings by breaking up the sand mold when the temperature of the mold drops to a low level.
The fifth is to make the specimens from alloy castings subject to different heat treatments. Finally, thin microstructure, damping capacity, and usage temperature are investigated systematically by a series of characterization and test methods. Manganese-copper based alloys have been found to have damping capacity to reduce noise and vibration, which can be mainly attributed to the lattice distortion induced twin boundaries produced by face centered cubic, two faced centered tetragonal face transformation below the face transformation point.
While the face transformation temperature is directly dependent on the manganese content in manganese copper based alloys. That is to say, the higher the manganese concentration, the greater the lattice distortion is. The higher the Martensitic transformation temperature is, the more the FCT phase microtests damping saws obtained at room temperature is.
Thus, the better the damping capacity is. Among these manganese-copper based alloys, forged manganese-copper-nickel-iron alloy have been widely studied and used in the past decades. The researchers found that this kind of alloy can reach good damping capacity by aging treatment in appropriate temperature range, which is mainly due to the decomposition of gamma parent phase into nanoscale manganese rich ridges and nanoscale copper rich ridges, resulting in the improvement of damping capacity.
Compared with forge and forming, casting has been widely used so far, due to the simple manufacturing process, low integrated cost, and high production efficiency, etc. The research group and other lead researchers have investigated the influence factors on damping capacity and microstructure of S cast of M2052 alloy. However, the M2052 alloy was defective in castability.
For example, a wide range of crystallization temperature, the up risk of casting porosity, concentrated shrinkage, and so on, eventually leading to the unsatisfactory mechanical practice. Therefore, in order to resolve these problems, zinc and aluminum elements are added in the manganese-copper-nickel-iron alloy metrics in this work to improve its casting performance, and the preferable heat treatment process is screened for both good damping capacity and high usage temperature. Finally, a new type of manganese-copper-nickel-iron-zinc-aluminum casting aged alloy, with excellent damping capacity and high usage temperature, were obtained by alloy design and heat treatment optimization.
Therefore, there's a suitable reason to think that it is a good choice for engineering applications. Prepare raw materials. Prepare the new alloy by 65%electrolytic manganese, 26%electrolytic copper, 2%industrial pure iron, 2%electrolytic deco, 3%electrolytic aluminum, and 2%electrolytic zinc.
The raw materials were commercially available. Melting and casting process. Use a medium frequency vacuum induction melting furnace in the experiment.
Firstly, prepare patterns. Use two wood patterns in this work. Make sure that the size of the pattern is slightly enlarged to account for shrinkage, and machining allows this.
Secondly, prepare molding sand. Mix 4%to 8%sodium silicate and quartz sand together. Then, make the mold by hand.
Put two patterns in the molding flask. Then, roll over the flask after ramming the molding sand around the patterns and withdraw the patterns from sand. Brush the surface of the sand mold with coating for sand casting to improve casting surface quality and reduce casting defects.
At last, to obtain a dry sand mold, put the sand mold in an oven to bake it at 180 degrees for more than eight hours. Thirdly, fit in raw materials. Open the furnace lid, put manganese, copper nickel, iron, zinc, and aluminum materials in the crucible.
Cover the materials with dry light at last. Fourthly, take out the casting mold from the oven and put it in the furnace. Adjust its position for successful pouring.
Close the lid, vacuum the furnace, and open the heat distribution system to start melting alloy. Pour the molten metal smoothly into the casting mold after the refining process. Finally, after molten metal is completely solidified, take out the casting mold.
Remove the castings from the casting mold when the temperature of the mold drops to a low level. Pretreatment of castings. Cut specimens from the casting using linear cutting machine.
The specimens for XRD measurements and metallographic observation are in size of ten times ten times one millimeter. The specimens for DNA measurement possess a dimension of 0.8 times ten times thirty-five millimeter. Heat treatment.
Divide the polishing specimens into seven groups, among which specimens one were free of treatment. Maintaining a cast state for commemoration and put others in a box type resistance oven for different heat treatments. The purpose of homogenization treatment is to reduce dendritic segregation.
The purpose of solution treatment is to immobilize impurities, as well as different aging times are used to find out the optimal parameters for excellent damping capacity and usage temperature. Test damping capacity. Use dynamic mechanical analysis for damping capacity measurement of specimens.
During the test, detect the face angle data between the stress applied to the specimen and the strain produced on the specimen. Then, characterize the damping capacity by q to the power of minus one. Which is determined by the formula q to the power of minus one equal to tangent delta.
The larger the delta value, the better the damping capacity. Simple characterization. For dendrites microstructure observation, etch all specimens for about one minute in a mixed solution of perchloric acid and alcohol after mechanical polishing.
Then, clean the specimens with acetone. Dry the sample with a blower and observe the dendritic structure with a metallographic microscope. Figure seven shows the strength amplitude dependency of q to the power of minus one for its cast manganese-copper-nickel-iron-zinc-aluminum alloy specimens, number one to number seven, and its cast M2052.
These curves show that subsequently carrying out homogenization aging, solution aging, and aging further improved the damping capacity of the S cast manganese-copper-nickel-iron-zinc-aluminum alloy respectively. In which, aging for two hours, result in the highest damping capacity among them. Figure eight shows the effect of heat treatment on microscopic manganese dendrite segregation.
Compared with the microstructure of specimen one, the manganese dendrite segregations of specimen five and six are weakened to some extent, while the counterpart of specimen seven has no distinctive difference. These results indicate that the homogenization aging and solution aging treatments weaken the microscopic manganese segregation, but the direct aging treatment has no obvious effect on it. According to the temperature dependent damping capacity curve, the damping capacity decreases rapidly and the temperature rises.
The surface temperature of specimen one, five through seven, are listed in Table 2. It can be seen clearly that aging at 435 degrees for two hours can call the optimal usage temperature. Figure nine shows the relationship among lattice distortion, q to the power of minus one, and usage temperature of S cast manganese-copper-nickel-iron-zinc-aluminum alloys subject to different heat treatments.
Evidently, the lattice distortion is positively related to the q to the power of minus one and usage temperature. Namely, the larger the lattice distortion, the better the damping capacity and usage temperature. All the results indicate that the optimal damping capacity of the highest usage temperature are achieved by aging at 435 degrees for two hours of S cast manganese-copper-nickel-iron-zinc-aluminum alloy, mainly due to the greatest nanoscale manganese segregation, resulting in the maximum lattice distortion in the alloy.
And noble S cast manganese-copper-nickel-iron-zinc-aluminum alloy, with superior damping capacity and high usage temperature, has been obtained by alloy design and heat treatment optimization in this work. The optimum heat treatment process is aging at 435 degrees for two hours, which can lead to the greatest nanoscale manganese segregation, thus significantly improving damping capacity and usage temperature compared with the original S cast alloy. This work will be of great significance in the design and preparation of new manganese-copper based damping alloys with excellent properties for practical industrial applications.
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