Rongfeng Zhou

Effect of cooling slope and manganese on the microstructure of hypereutectic Al-Si alloy with 2 %Fe

The effect of cooling slope (CS) on the microstructure of hypereutectic Al-22Si-2Fe (% w/w) alloys with 0%, 0.99%, and 1.36% Mn were studied. The results showed that primary Si particles (PSPs), needle-like Fe phases, coarse fishbone-shaped α-Al 15 (Fe, Mn) 3 Si 2 phases, and eutectic Si could be refined. With such a CS process, the intermetallic compounds in the alloys with different Mn/Fe ratios were examined with an optical microscope, scanning electron microscope, and X-ray diffraction. Moreover, the acicular δ-Al 4 (Fe, Mn)Si 2 and blocky α-Al 15 (Fe, Mn) 3 Si 2 phases were analyzed by transmission electron microscopy.

Effects of Pore Nucleation, Growth and Solidification Mode on Pore Structure and Distribution of Lotus Type Porous Copper

Effects of pore nucleation, growth and solidification mode of matrix on pore structure and distribution of lotus-type porous Cu fabricated by Gasar process were investigated. The results showed that it was difficult to obtain an ordered pore structure when the matrix contained equiaxed grain. An ordered pore structure, with increased pore length and circularity, could be obtained when the matrix consisted of columnar grains. The pore distribution moved from the grain boundaries to the interior of grain with increasing gas pressure. It was further noticed that the average pore diameter decreased and the pore density increased due to decreased activation energy and increased rate of nucleus formation. Due to slight depressions at grain boundaries of the solid/liquid interface, the pore nucleation was favored at grain boundaries and thus the average pore diameter in grain boundaries was larger than that in grains.

Effect of Melt Treatment on Fe-Rich Phase in Al–25Si–2Fe–2Mn Alloy

The Al–25Si–2Fe–2Mn alloy melt was treated by using electromagnetic stirring, cooling slope and spray deposition technologies, respectively. By using various methods including SEM, EDS, XED and TEM, the solidification microstructure of Al–25Si–2Fe–2Mn alloys and the separation behavior and crystal structure of Fe-rich phase under different treatment modes of melts were analyzed. The result showed that under the three treatment modes, the hard phases in the microstructure of Al–25Si–2Fe–2Mn were all refined at different degrees. Among them, spray deposition yielded had the best refining effect, where the primary Si with the average diameter of about 5 μm were shown as tiny particles while granular Fe-rich phases with the average diameter of about 7 μm were dispersed into the microstructure. For the microstructure treated by cooling slope, the primary Si particles and the blocky Fe-rich phase exhibited the average diameters of about 30 and 40 μm, respectively and some Fe-rich phases were centered on the primary Si particles. In comparison, the electromagnetic stirring presented the worst refining effect. The primary Si particles, mainly appeared as blocks, showed an average diameter of about 50 μm and the blocky Fe-rich phase exhibited an average diameter of about 30 μm. In addition, some Fe-rich phases were bonded with the primary Si particles to distributed in the neighbor of latter. When the two materials were regarded as a whole, the average diameter were measured to be about 100 μm. Fe-rich phases treated by using the three treatment modes of melts were all stable α-Al15(Fe,Mn)3Si2 phases, but their in the alloys undergoing different treatments shows significantly different morphologies and distributions.

Influence of Process Parameters by Enclosed Cooling Slope Channel on Microstructures of Semi-solid ZCuSn10P1 Alloy

Semi-solid ZCuSn10P1 alloy slurry was fabricated by a novel enclosed cooling slope channel (ECSC for short). The influence of process parameters on the microstructure and Tin segregation phenomenon of ZCuSn10P1 alloy semi-solid slurry was studied with optical microscope (OM), scanning electron microscope (SEM) and energy dispersive x-ray spectrum (EDS). The results showed that the primary α-Cu phase gradually evolved from the dendrite into worm-like or fine spherical crystal under chilling of ECSC and shearing of the gravitation. The finest microstructure, the equivalent diameter was 46 ± 3 μm, and its shape factor was 0.73, could be obtained under the conditions of the pouring temperature 1080 °C, 300 mm of cooling plate inclined at 45 degrees and 5 mm flow gap. The average concentration of Tin increased from 5.85% in the conventional casting to 6.46% in semi-solid slurry in primary α-Cu phase, and the average concentration of Tin decreased from 27.94% in the conventional casting to 20.59% in semi-solid slurry in liquid. The distribution of Tin element in microstructure was refined obviously and the dendrite segregation reduced.