Research On Preparation Of Semi-solid Slurry And Microstructure By Tilting-Vibration Method

Rheological casting has a good application prospect in the field of lightweight due to its short process,near-final shape and low cost.The preparation of semi-solid slurry is the core of rheological casting and has always been a research hotspot and frontier.This article aims to independently develop the tilt-vibration method,taking A356 aluminum alloy as the research object,using the method of combining experiments and AnyCasting numerical simulation,focusing on the changes in the flow field and temperature field under the tilt-vibration condition,process parameters and crystal The effect of grain refiner on the microstructure of semi-solid slurry,combined with three-dimensional reconstruction to discuss the formation mechanism of semi-solid slurry microstructure,the main conclusions are as follows:(1)AnyCasting simulation results show that when the tilting speed drops from 36 °/s to 18 °/s,the flow velocity at the front end of the melt decreases accordingly.Turbulent entrainment will be generated when the flow velocity at the front end of the melt exceeds 0.5 m/s.If the flow velocity of the melt is too slow,it will solidify prematurely during the transfer process.The best tilting time is 7s and the rotation speed is 51.4-7.3t(t?[0,7])°/s,to achieve first acceleration and then deceleration.Combined with the experiment,compared with the semi-solid slurry prepared by the mechanical stirring method,the semi-solid slurry obtained by the tilt-vibration method is more complete and dense,which can effectively reduce the pollution of the semi-solid slurry.(2)Under the condition of tilting vibration,when the temperature drops from 660 ? to 635 ?,the equivalent grain diameter first decreases and then increases,and the shape factor first increases and then decreases.When the temperature is 650?,the grain equivalent diameter is 74.51 ?m,and the shape factor is 0.517.When the temperature is lower than 650?,a solidified layer will be formed on the inner wall of the barrel,which will weaken the vibration effect and the grain refinement effect.(3)The optimal addition amount of Al-10Y is 0.05%,the equivalent grain diameter is 61.83?m,and the shape factor is 0.656;the optimal addition amount of Al-5Ti-1B is 0.2%,the equivalent grain diameter is 68.91?m,and the shape factor is 0.656.;The optimal addition amount of Al-2.8Nb-0.3B is 0.06%,the equivalent grain diameter is 65.47 ?m,and the shape factor is 0.622;when 0.15%Al-l0Y and 0.2Al-5Ti-1B are added for composite experiment,the refinement effect is the best Good,the grain equivalent diameter is 61.57 ?m,and the shape factor is 0.746.(4)Compared with two-dimensional metallography,three-dimensional reconstruction can obtain richer information,and both can effectively reflect the influence of preparation parameters on the microstructure of semi-solid slurry.(5)Under the condition of tilting vibration,the formation mechanism of the microstructure of semi-solid slurry is:during the tilting process,the melt is chilled to form a large amount of nucleation,and there are a lot of crystal nuclei in the melt according to the mechanism of crystal grain dissociation;Continue the formation of crystal nuclei to make the solute and temperature field uniform,and at the same time,the crystal grains become spherical due to the effect of vibration.