A novel testing machine for a continuous semisolid extending extrusion process (CSEP) has been designed and used to produce AA2017 alloy flat bar. Fine and homogeneous grains of AA2017 slurries with rosette structures were obtained at suitable casting temperatures. During preparation of semisolid AA2017 alloy by the proposed process, rosette grain formation was observed during the application of the large force provided by the rough roll. By controlling casting temperature, AA2017 products were produced with fine surfaces and rectangular transections of 14×25 mm. A casting temperature range of 710–750℃ was suggested. The microstructure of the product is fine and even with striped appearance and is composed mainly of h and a phases. The fracture strength of AA2017 product produced by the semisolid extending extrusion process is improved by 100 MPa, and elongation by 29%.

A novel sloping plate with wavelike surface was used to prepare semisolid alloy. Semisolid billets and slurries have been prepared by cooling or preheating the sloping plate. During preparation of the semisolid alloy by the proposed process, seed crystals derive from burst nucleation and breaking of dendrite and the coaction causes fine spherical microstructure formation. Casting temperature, sloping plate length, degree of cooling sloping angle are the main factors influencing the microstructure. Under current experimental conditions, in order to prepare good quality semisolid billets, proper casting temperature ranges of 660–690℃ for Al–3 wt-%Mg alloy and 660–680℃ for Al–6Si–2Mg (wt-%) alloy are suggested. The reasonable technological conditions for preparing Al–6Si–2Mg (wt-%) slurry are also proposed: the sloping plate preheating temperature is 300℃, and the casting temperature is 680℃. The optimum conditions for preparing semisolid billet of 1Cr–18Ni–9Ti stainless steel were obtained: the sloping plate length is 640 mm, and the casting temperature is 1600℃.

Abstract: A self-designed setup of modified sloping cooling/shearing process was made to prepare the semisolid Al-3wt%Mg alloy. A three-dimensional simulation model was established for the analysis of preparing the semisolid Al-3wt%Mg alloy. Through simulation and experiment, it is shown that the sloping angle of the plate greatly affects temperature and velocity distributions, and the temperature and velocity of the alloy at the exit of the sloping plate increase with the increase of the sloping angle. The alloy temperature decreases linearly from the pouring mouth to the exit. The alloy temperature at the exit increases obviously with the increase of pouring temperature. To prepare the semisolid Al-3wt%Mg alloy with good quality, the sloping angle θ=45° is reasonable, and the pouring temperature is suggested to be designed above 650-660℃ but under 700℃.

A vibrating wavelike sloping plate process (VWSP) was proposed. Heat and solute transformations, nucleation mechanism and grain growth as well as microstructure evolution were investigated. It is shown that the sloping plate can provide strong undercooling, and a large quantity of heterogonous nuclei appear on the sloping plate surface,wavelike flowand vibration can enable heterogonous nucleus to escape off the plate, which lead to nucleus multiplication. Moreover, wavelike flow and vibration improve solute diffusion coefficient and cause uniform solute and temperature field, which lead to eruptive nucleation. Grain growth has two typical ways, direct globular growth and dendritic growth. Under relative uniform temperature and solute fields, some grains can keep stable growth surface, go on growing with the round surface and finally maintain their globular structure. However, there are always some grains that grow along a certain preferred direction, but under wavelike flow and vibration their dendritic arms break and transform into near spherical structure. During the casting process, microstructural evolution from globular/dendritic structure to globular/equiaxed structure and to globular structure was observed.

研究了波浪型倾斜板振动参数对Al-6Si-2Mg合金凝固组织的影响，结果表明：倾斜板的倾角和长度影响合金在斜板表面的流动剪切强度和剪切时间，从而影响合金的组织，当浇注温度为660-690℃时，随着浇注温度的降低，合金晶粒细化和球化，平均晶粒直径为40μm，晶粒平均圆度值为2.5；浇注温度低于660℃时，晶粒有粗化和枝晶化的趋势，倾斜板的振动作用使表面形成的晶核离开表面进入熔体中，有效地减少了晶粒之间的粘连，解决了结壳问题，提高了形核率，细化了组织；随着倾斜板振动频率的提高，晶粒的平均圆度先降低后提高，振动频率为50-60 Hz出现最小值，倾斜板的波浪形表面对流动的金属具有搅拌作用，增大了熔体内部的剪切作用，使晶粒更加细小圆整。