Through morphology observation on silicon particles of Al-Si-Cu-Mg cast alloy, it is found that during solution treatment the evolution of eutectic silicon morphology and their effect on mechanical properties can be c...Through morphology observation on silicon particles of Al-Si-Cu-Mg cast alloy, it is found that during solution treatment the evolution of eutectic silicon morphology and their effect on mechanical properties can be classified into three stages. In the initial stage, necking, stubbing and fragmentation of silicon particles result in the improvement of plasticity of alloy. In the intermediate stage, the mechanical properties of 354 alloy attain peak values due to spheroidization of silicon particles. In the final stage, the drop of hardness and strength is related to the deterioration of silicon morphology. The facets and lap occur in silicon particles and the coarsening process of silicon follows LSW model. During aging, the clusters of excess silicon can work as barriers for dislocation movement and thus enhance the strength of alloy. On the other hand, excess Si affects the process of aging precipitation and leads to a fine and highly dense distribution of GP zones, finally effectively strengthens the alloy.展开更多
Based on the industrial production of non-oriented silicon steel,calcium treatment by CaSi wire feeding during the RH refining process was studied. The thermodynamics of CaS inclusion formation was analyzed, and the m...Based on the industrial production of non-oriented silicon steel,calcium treatment by CaSi wire feeding during the RH refining process was studied. The thermodynamics of CaS inclusion formation was analyzed, and the morphology and the size distribution were observed. Furthermore, the change in inclusion characteristics after calcium treatment and the effect of calcium treatment on magnetic properties were discussed. The results show that the formation of MnS and A1N inclusions were restrained, and the aggregating, floating and removing of microinclusions after calcium treatment were effectively promoted. The cleanliness of liquid steel was obviously increased. The main type of inclusions was single phase of CaO, with some complex inclusions composed of CaO, SiO2 and MgO. No CaS inclusion was observed after an appropriate calcium treatment. The size of all inclusions was distributed in the range of 2 - 20 μm, and the number was about 1.8 × 10^5/mm3. In addition, as an increasing amount of calcium was added,the core loss gradually decreased to a stable level, and the magnetic induction decreased quickly after a slow increase. The optimal calcium treatment mode depends on the chemical composition of steel.展开更多
In this work we are interested in studying the effect of the heat treatments on the dopant segregation at the grain boundaries in the polycrystalline silicon films. The obtained results have shown that the heat treatm...In this work we are interested in studying the effect of the heat treatments on the dopant segregation at the grain boundaries in the polycrystalline silicon films. The obtained results have shown that the heat treatments reduce the number of segregation sites at the grains boundaries, and consequently they limit the structural changes that can appear there and the quantity of the dope atoms that can accumulate in these boundaries. In addition they are more and more dopant that are found inside the grains when the temperature of the heat treatment increases. On the other hand, we established that the arsenic atoms have a strong tendency to the segregation than the boron atoms, and we have noticed a strong migration of arsenic atoms from the boundaries towards the grains under the effect of the heat treatments. It was also shown that the segregation of arsenic atoms at the grains boundaries is about 4 times higher than that of the boron atoms.展开更多
Based on the industrial production of non-oriented silicon steel, the rare earth （RE） treatment during the Ruhrstahl Heraeus （RH） refining process was studied. The morphology and the size distribution were observe...Based on the industrial production of non-oriented silicon steel, the rare earth （RE） treatment during the Ruhrstahl Heraeus （RH） refining process was studied. The morphology and the size distribution were observed for the steel specimens treated with different RE treatment conditions. Furthermore, the formation and change of the nonmetallic inclusion characteristics of finished steel sheets after the RE treatment were discussed. The results have shown that in the present work,the suitable RE metal additions are 0.6 -0.9 kg/t steel. After the suitable RE treatment,the formation of AIN and MnS inclusions were restrained, and the aggregation, flotation and removal of nonmetallic inclusions were efficiently promoted and the cleanliness of liquid steel was significantly increased. Meanwhile, the total oxygen concentration reached the minimum value and thle desulfurization efficiency was optimal ,and the type of main inclusions was approximately spherical or elliptical spherical RE radicle inclusions whose size was relatively large.展开更多
The microstructures of the siliconized specimens of Ti-48Al alloy were analyzed by SEM equipped with XEDS. The specimens were pack siliconized with the two different cementations, 15%Si+85% A12O3 and 15%Si+85%ZrO2. Th...The microstructures of the siliconized specimens of Ti-48Al alloy were analyzed by SEM equipped with XEDS. The specimens were pack siliconized with the two different cementations, 15%Si+85% A12O3 and 15%Si+85%ZrO2. The results show that a composite siliconized layer is formed on the surface of the TiAl alloy. The outer layer is the continuous A12O3 where a lot of Si particles adhered; the inner layer is most of Ti5Si3 with amount of ALjOs particles dispersed in. It was deduced that the A12O3 in the cementation layer is formed by the Al atoms in the TiAl substrate react with the residual O in the furnace and in the TiAl substrate.展开更多
The thermal expansion behaviors of commercially-available SiC whisker reinforced pure aluminum composites subjected to different heat treatments were studied. The results indicated that the thermal expansion behaviors...The thermal expansion behaviors of commercially-available SiC whisker reinforced pure aluminum composites subjected to different heat treatments were studied. The results indicated that the thermal expansion behaviors were greatly affected by heat treatment. To explain the results, the microstructures and thermal mismatch stresses in the matrix of the composite were examined by the transmission electron microscope and X-ray diffraction, respectively. The results show that the dislocation density and thermal mismatch stresses in the matrix of the composites water-quenched from 600°C are much higher than those of the composite slowly cooled from 600°C. The analysis suggests that the coefficients of thermal expansion (CTE) are closely related to the change of thermal mismatch stresses and the yield strength of the matrix of the composite. The comparison of the coefficients of thermal expansion between experiments and calculations suggests that the temperature behaviors of CTE of SiC/Al composite agree better with those of Kerner's model within lower temperature range.展开更多
文摘Through morphology observation on silicon particles of Al-Si-Cu-Mg cast alloy, it is found that during solution treatment the evolution of eutectic silicon morphology and their effect on mechanical properties can be classified into three stages. In the initial stage, necking, stubbing and fragmentation of silicon particles result in the improvement of plasticity of alloy. In the intermediate stage, the mechanical properties of 354 alloy attain peak values due to spheroidization of silicon particles. In the final stage, the drop of hardness and strength is related to the deterioration of silicon morphology. The facets and lap occur in silicon particles and the coarsening process of silicon follows LSW model. During aging, the clusters of excess silicon can work as barriers for dislocation movement and thus enhance the strength of alloy. On the other hand, excess Si affects the process of aging precipitation and leads to a fine and highly dense distribution of GP zones, finally effectively strengthens the alloy.
文摘Based on the industrial production of non-oriented silicon steel,calcium treatment by CaSi wire feeding during the RH refining process was studied. The thermodynamics of CaS inclusion formation was analyzed, and the morphology and the size distribution were observed. Furthermore, the change in inclusion characteristics after calcium treatment and the effect of calcium treatment on magnetic properties were discussed. The results show that the formation of MnS and A1N inclusions were restrained, and the aggregating, floating and removing of microinclusions after calcium treatment were effectively promoted. The cleanliness of liquid steel was obviously increased. The main type of inclusions was single phase of CaO, with some complex inclusions composed of CaO, SiO2 and MgO. No CaS inclusion was observed after an appropriate calcium treatment. The size of all inclusions was distributed in the range of 2 - 20 μm, and the number was about 1.8 × 10^5/mm3. In addition, as an increasing amount of calcium was added,the core loss gradually decreased to a stable level, and the magnetic induction decreased quickly after a slow increase. The optimal calcium treatment mode depends on the chemical composition of steel.
文摘In this work we are interested in studying the effect of the heat treatments on the dopant segregation at the grain boundaries in the polycrystalline silicon films. The obtained results have shown that the heat treatments reduce the number of segregation sites at the grains boundaries, and consequently they limit the structural changes that can appear there and the quantity of the dope atoms that can accumulate in these boundaries. In addition they are more and more dopant that are found inside the grains when the temperature of the heat treatment increases. On the other hand, we established that the arsenic atoms have a strong tendency to the segregation than the boron atoms, and we have noticed a strong migration of arsenic atoms from the boundaries towards the grains under the effect of the heat treatments. It was also shown that the segregation of arsenic atoms at the grains boundaries is about 4 times higher than that of the boron atoms.
文摘Based on the industrial production of non-oriented silicon steel, the rare earth （RE） treatment during the Ruhrstahl Heraeus （RH） refining process was studied. The morphology and the size distribution were observed for the steel specimens treated with different RE treatment conditions. Furthermore, the formation and change of the nonmetallic inclusion characteristics of finished steel sheets after the RE treatment were discussed. The results have shown that in the present work,the suitable RE metal additions are 0.6 -0.9 kg/t steel. After the suitable RE treatment,the formation of AIN and MnS inclusions were restrained, and the aggregation, flotation and removal of nonmetallic inclusions were efficiently promoted and the cleanliness of liquid steel was significantly increased. Meanwhile, the total oxygen concentration reached the minimum value and thle desulfurization efficiency was optimal ,and the type of main inclusions was approximately spherical or elliptical spherical RE radicle inclusions whose size was relatively large.
基金supported by the National Natural Science Foundation of China(No.50171046)the Natural Science Foundation of Shanxi Province,China(No.20021051)
文摘The microstructures of the siliconized specimens of Ti-48Al alloy were analyzed by SEM equipped with XEDS. The specimens were pack siliconized with the two different cementations, 15%Si+85% A12O3 and 15%Si+85%ZrO2. The results show that a composite siliconized layer is formed on the surface of the TiAl alloy. The outer layer is the continuous A12O3 where a lot of Si particles adhered; the inner layer is most of Ti5Si3 with amount of ALjOs particles dispersed in. It was deduced that the A12O3 in the cementation layer is formed by the Al atoms in the TiAl substrate react with the residual O in the furnace and in the TiAl substrate.
文摘The thermal expansion behaviors of commercially-available SiC whisker reinforced pure aluminum composites subjected to different heat treatments were studied. The results indicated that the thermal expansion behaviors were greatly affected by heat treatment. To explain the results, the microstructures and thermal mismatch stresses in the matrix of the composite were examined by the transmission electron microscope and X-ray diffraction, respectively. The results show that the dislocation density and thermal mismatch stresses in the matrix of the composites water-quenched from 600°C are much higher than those of the composite slowly cooled from 600°C. The analysis suggests that the coefficients of thermal expansion (CTE) are closely related to the change of thermal mismatch stresses and the yield strength of the matrix of the composite. The comparison of the coefficients of thermal expansion between experiments and calculations suggests that the temperature behaviors of CTE of SiC/Al composite agree better with those of Kerner's model within lower temperature range.
