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Numerical simulation and experiments were introduced to develop AA4045/AA3003 cladding billets with different clad-ratios. The temperature fields, microstructures and mechanical properties near interface were investigated in detail. The results show that cladding billets with different clad-ratios were fabricated successfully. Si and Mn elements diffused across the bonding interface and formed diffusion layer. With the increase of clad-layer thickness, the interfacial region transforms from semisolid–solid state to liquid–solid state and the diffusion layer increased from 10 to 25 μm. The hardness at interface is higher than that of AA3003 side but lower than that of the other side. The bonding strength increased with the clad-layer thickness, attributing to solution strengthening due to elements diffusion. The cladding billets were extruded into clad pipe by indirect extrusion process after homogenization. The clad pipe remained the interfacial characteristics of as-cast cladding billet and the heredity of clad-ratio during deformation was testified. 相似文献
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ABSTRACTIn this paper, an electromagnetic torque device based on the theoretical model was established to determine the optimum frequency accurately and conveniently in billet and bloom continuous casting with in-mould electromagnetic stirring (M-EMS). Magnetic characteristics with M-EMS was investigated by numerical simulation and physical experiment with the application of electromagnetic torque device and gauss meter. In addition, the effects of stirring frequency with M-EMS on macro segregation and equiaxed crystal ratio were compared and analysed for 55SiCr with 150?mm?×?150?mm billet caster and BU with 310?×?360?mm bloom caster by a series of plant trials, respectively. The results showed that maximum magnetic flux density and maximum electromagnetic torque occurred with different frequency and same current in M-EMS, and central equiaxed crystal ratio and macro segregation has been significantly improved by optimum frequency with M-EMS. 相似文献
4.
为了解决中频炉烧结钍钨坯条密度偏低的问题,对中频炉进行了炉底、炉体、顶盖技术改造,改造后提高了工装的隔热效果,使中频炉耐热温度由2 300 ℃提高到2 800 ℃,然后进行钍钨坯条的烧结,研究了中频烧结钍钨坯条的工艺参数,结果表明:2 300 ℃烧结密度只有16.94 g?cm-3,提高烧结温度到2 800 ℃此时接近氧化钍的熔点(3 220 ℃),烧结后密度提升较大达到18.70 g?cm-3,达到后续加工要求,2 800 ℃烧结延长高温烧结时间和增加保温平台的方式对钍钨坯条的烧结密度影响不大。 相似文献
5.
《中国有色金属学会会刊》2020,30(12):3173-3182
7075 aluminum alloy was used to obtain elbow parts by complex thixoextrusion and the microstructure evolution and mechanical properties during this process were studied by SEM, TEM and other analytical methods. The results show that different parts in 7075 aluminum alloy show quite different microstructures. The microstructure of the thin walls formed by back-extrusion is stratified, and the bottom of the parts formed by angular extrusion is obviously deformed. Shear forces contribute to the crushing of grains and the coarse second phase. The main strengthening phases in the material are η phase and E phase, whose amounts greatly decrease during heating to semi-solid and thixoextrusion. After heat treatment, they can precipitate evenly to improve the mechanical properties of the material. The average tensile strength of whole part after thixoextrusion and heat treatment is 485.49 MPa, while the average elongation is 5.49%. 相似文献
6.
研究了传统液态挤压铸造与半固态挤压铸造成形ZL104铝合金连杆的充填状态、微观组织及力学性能。结果表明:传统液态挤压铸造成形连杆充填饱满,但其抗拉强度及伸长率低于半固态挤压铸造成形连杆。对于半固态挤压铸造成形,浇注温度高于565℃时,铸件充填性能良好;平均晶粒尺寸及形状因子随浇注温度的升高而逐渐增大;连杆抗拉强度及伸长率先增加后减小。挤压压力高于25MPa时,铸件均充填饱满;挤压压力升高,平均晶粒尺寸不断减小且形状因子不断增大,连杆机械性能不断提高。模具预热温度升高,平均晶粒尺寸和形状因子不断增大,连杆机械性能逐渐提高。但当模具预热温度超过300℃时,平均晶粒尺寸进一步增大而其形状因子减小,导致连杆的机械性能下降。 相似文献
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8.
《中国有色金属学会会刊》2020,30(2):318-332
The hot cracking tendency of 7075 semi-solid alloy under different conditions was studied by critical diameter method. The experiment and simulation results show that the dendrite arms of the rod grow from the edge to the center. The smaller the diameter of the rod is, the more obvious the directional growth of dendrite is, and the greater the tendency of hot cracking is. Compared with ordinary melt, for semi-solid slurry, increasing mould temperature or decreasing pouring temperature can significantly decrease hot cracking tendency of 7075 alloy, decreasing hot cracking grade from 256 to 100 mm2. Furthermore, based on the RDG criterion, the effects of solidification conditions on the hot cracking tendency were discussed combined with simulation. At the same time, the application and development of RDG criterion were also researched. 相似文献
9.
《中国有色金属学会会刊》2020,30(3):710-726
Cylindrical samples of Ni-based GH4037 alloy were compressed at solid temperatures (1200, 1250 and 1300 °C) and semi-solid temperatures (1340, 1350, 1360, 1370 and 1380 °C) with different strain rates of 0.01, 0.1 and 1 s−1. High temperature deformation behavior and microstructure evolution of GH4037 alloy were investigated. The results indicated that flow stress decreased rapidly at semi-solid temperatures compared to that at solid temperatures. Besides, the flow stress continued to increase after reaching the initial peak stress at semi-solid temperatures when the strain rate was 1 s−1. With increasing the deformation temperature, the size of initial solid grains and recrystallized grains increased. At semi-solid temperatures, the grains were equiaxed, and liquid phase existed at the grain boundaries and inside the grains. Discontinuous dynamic recrystallization (DDRX) characterized by grain boundary bulging was the main nucleation mechanism for GH4037 alloy. 相似文献
10.