Xiaolu YU
,
Fuguo LI
,
Yuanchun REN
材料科学技术（英文）
phase-field method to simulate non-dendritic growth during preparation of Al-4Cu-Mg semi-solid alloy by electromagnetic stirring method (EMS method). Several factors such as the disturbance intensity, anisotropy, the thickness of the interface and the ratio of diffusivity in solid and liquid were considered. It is shown that decreasing the thickness of the interface results in more circular outline of particles, and increasing the diffusivity in solid can reduce degree of microsegregation. The disturbance intensity in the model can be connected with current intensity of stator or magnetic induction density impressed. Simulation results show that the larger the disturbance intensity or magnetic induction density, the more globular morphology the original phase in the matrix.
关键词:
Semi-solid metal
,
微观组织
,
模拟
,
相场法
Wen LIU
材料科学技术（英文）
The energy dissipation caused by the viscous force has great effects on the flow property of semi-solid metal during rheological processes such as slurry preparing, delivering and cavity filling. Experimental results in this paper indicate that the viscous friction between semi-solid metal and pipe wall, the collisions among the solid particles, and the liquid flow around particles are the three main types of energy dissipation. On the basis of the hydromechanics, the energy dissipation calculation model is built. It is demonstrated that the micro-structural parameters such as effective solid fraction, particle size and shape, and flow parameters such as the mean velocity, the fluctuant velocity of particles and the relative velocity between the fluid and solid phase, affect the energy dissipation of semi-solid metal.PartⅡ：This study investigates the rheological behavior of semi-solid metal. An analytical model of apparent viscosity was built up based on analysis of energy dissipation during rheological processes such as slurry preparing, delivering and model filling. The rheological behavior of SSM slurries was described by an analytical model in terms of micro structural parameters, which consist of effective solid fraction, particle size and shape, and flow parameters such as mean velocity, fluctuation velocity and relative velocity between liquid and solid phase. The model was verified in the experiment of A356 alloys with a coaxial double-bucket rheometer. And the maximum relative error between the theoretical value and measured value is less than 10%. The results of experiment and theoretical calculation also indicate that the micro structural parameters and flow parameters are two major factors that affect the apparent viscosity of semi-solid alloys, and fluctuation velocity and relative velocity between liquid and solid phase are the key factors to distinguish between steady and transient rheological behaviors.
关键词:
Semi-solid metal
,
能量耗散
,
流变
,
表观粘度
,
模型
Hongbo DONG
,
Yonglin KANG
材料科学技术（英文）
With a geometrical model of porous material, a 3D finite-element analysis on the rolling process of spring steel- 60Si2Mn in the semi-solid state is carried out using software MARC. In terms of flat and groove rolling conditions, stress field and strain field are studied. The simulation results show that the rigid-viscoplastic model can accurately describe the semi-solid metal rolling process. Semi-solid slurry has the characteristics of low flow stress and good fluidity. During groove rolling, distribution of stress and strain on the cross-section of deformation zone is more uniform than that during flat rolling. The results of simulation are in good agreement with the experiment data, and show that semi-solid material fits for groove rolling.
关键词:
Finite-element analysis
,
null
,
null
,
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