In this paper, the serpentine channel pouring process for preparing a semi-solid A390 alloy slurry and refining the primary Si grains of the A390 alloy, was used. The effects of the pouring temperature, the cooling water flow and the number of the curves on the size of the primary Si grains in the semi-solid A390 alloy slurry were investigated. The results show that the pouring temperature, the cooling water flow and the number of the curves have a major effect on the size and the distribution of primary Si grains. Under the experimental condition of the four-curve copper channel whose cooling water flow was 500 L·h-1 and the pouring temperature was 690 oC, the primary Si grains of the semi-solid A390 alloy slurry were refined to the greatest extent and the lath-like grains were changed into granular ones. Additionally, the equivalent grain diameter and the average shape factor of the primary Si grains of the satisfactory semi-solid A390 alloy slurry are 18.6 μm and 0.8, respectively. Further, the refinement mechanism of the primary Si grains through the serpentine channel pouring process was analyzed and discussed. In summary, the primary Si nuclei could be easily precipitated due to the chilling effect of the channel inner wall, thus the primary Si grains were greatly refined. Meanwhile, the subsequent alloy melt fluid also promoted the separation of primary Si grains from the inner wall, further refining the primary Si grains.
Zhi-kai ZhengWei-min MaoBing-quan YanRui YueZhi-yong Liu
In this study, a serpentine channel pouring process was used to prepare the semi-solid A1-20%Si alloy slurry and refine primary Si grains in the alloy. The effects of the pouring temperature, number of curves in the serpentine channel, and material of the serpentine channel on the size of primary Si grains in the semi-solid A1-20%Si alloy slurry were investigated. The results showed that the pouting temperature, number of the curves, and material of the channel strongly affected the size and distribution of the primary Si grains. The pouring tempera- ture exerted the strongest effect, followed by the number of the curves and then the material of the channel. Under experimental conditions of a four-curve copper channel and a pouring temperature of 701℃, primary Si grains in the semi-solid A1-20%Si alloy slurry were refined to the greatest extent, and the lath-like grains were changed into granular grains. Moreover, the equivalent grain diameter and the average shape coefficient of primary Si grains in the satisfactory semi-solid A1-20%Si alloy slurry were 24.4 μm and 0.89, respectively. Finally, the re- finement mechanism and distribution rule of primary Si grains in the slurry prepared through the serpentine channel pouring process were analyzed and discussed.
In this paper, the effects of rheo-diecast process parameters and T6 heat treatment on the microstructure and mechanical properties of the rheo-diecasting（RDC） semi-solid A390 alloy prepared through pure copper serpentine channel were investigated. The results indicate that the mechanical properties of the RDC samples change with the pouring temperature and injection pressure. In this case, a lower pouring temperature results in better tensile strength and elongation of the RDC A390 alloy; however, the tensile strength and elongation decrease when the pouring temperature decreases to 660°C. Higher injection pressures result in the improved mechanical properties of the RDC A390 alloy. To some extent, T6 heat treatment improves the tensile strength and ductility of the RDC A390 alloy compared to those of the non-heat treated alloy. However, when the pouring temperature and injection pressure are greater than 670°C and 70 MPa, respectively, the mechanical properties are sharply diminished.
Kunhyok RiWei-min MaoZhi-kai ZhengMyongsik KimYongho Sin
The effects of various structure factors on the properties(superelasticity mainly) of Cu-based shape memory alloys(SMAs) were systematically evaluated in this review article through literatures combining with our work. It is concluded that besides the decisive role of grain orientation, the grain boundary(GB) characteristics also play important roles in the superelasticity, which include GB area, GB type, GB morphology and GB direction in descending order of the effect significance. According to the above results, the prior principles of structure design are proposed for high-performance Cu-based SMAs from most to least important:(1) obtaining grain orientation with high phase transformation strain;(2) increasing grain size or reducing GB area;(3) obtaining straight low-energy GBs, especially low-angle GBs;(4) trying to make GB direction parallel to external stress. Consistent with the main or all principles, the bamboo-like-grained and columnar-grained(CG) Cu-based SMAs show excellent comprehensive properties.
The effects of annealing temperature（with the annealing time being constant at 1 h） on the microstructure, ordering, residual stress, mechanical properties, and subsequent cold rolling workability of Fe-6.5wt%Si electrical steel with columnar grains were investigated, where the steel was warm rolled at 500℃ with a reduction of 95%. The results show that recrystallization began to occur in the sample annealed at 575℃ and that full recrystallization occurred in the sample annealed at 625℃. When the annealing temperature was 500℃ or greater, the extent of reordering in the sample was high, which reduced the room-temperature plasticity. However, annealing at temperatures below 300℃ did not significantly reduce the residual tensile stress on the edge of the warm rolled samples. Considering the comprehensive effects of annealing temperature on the recrystallization, reordering, residual stress, and mechanical properties of the warm rolled Fe-6.5wt%Si electrical steel with columnar grains, the appropriate annealing temperature range is 300℃-400℃. Unlike the serious edge cracks that appeared in the sample after direct cold rolling, the annealed samples could be cold rolled to a total reduction of more than 71.4% without the formation of obvious edge cracks, and bright-surface Fe-6.5wt%Si electrical steel strips with a thickness less than 0.1 mm could be fabricated by cold rolling.
Yuan-ke MoZhi-hao ZhangJian-xin XieHua-dong FuHong-jiang Pan
The rheo-diecasting mold filling capacity and the microstructure of the semi-solid A380 aluminum alloy slurry were investigated. The results show that the mold filling capacity was strengthened with increasing pouring temperature or increasing injection pressure. Under certain process parameters, the mold cavity was fully filled. However, the mold filling capacity decreased with increasing holding time. The mold filling capacity was improved with increasing shape factor of primary α(Al) grains; however, the solid fraction and the grain size significantly increased at the same time. In addition, the microstructures along the route of the spiral samples obviously differed. The grain size decreased gradually from the near-end to the far-end, whereas the shape factor increased gradually.
