2024变形铝合金半固态浆料在连续冷却和保温过程中的组织演变

摘要

采用液淬法研究2024变形铝合金半固态浆料在连续冷却和不同温度保温过程中的组织演变。结果表明：在连续冷却过程中，浆料固相率、初生固相颗粒尺寸及形状因子均随温度降低而连续增大；不同温度保温时，浆料固相率在对应值作微小波动，初生固相颗粒尺寸连续增大，形状因子先减小后增大，最后减小到1.3~1.4之间。连续冷却前期浆料固相率的增加主要受固相颗粒的析出控制，而后期主要由固相颗粒的长大控制。保温过程中浆料组织演变可分为聚集组织分解、颗粒合并粗化和颗粒熟化3个阶段，初生固相颗粒的长大规律符合动力学方程Dt -D 3=Kt03。%The microstructure evolutions of 2024 wrought aluminum alloy slurry during continuous cooling and isothermal holding were investigated by a simple technique of water quenching. The results show that during the continuous cooling course, the solid fraction, average particle size and shape factor increase continuously with temperature decreasing. While during the isothermal holding stage, the solid fraction of the slurry fluctuates at the corresponding values, the particle size of the primary solid phase increases continuously, and the shape factor decreases firstly, then increases and finally decreases to a value between 1.3 and 1.4. The increase of solid fraction during continuous cooling is dominated mainly by the precipitation of solid-phase particles in the early stage, and by the growth of solid-phase particles at last. The evolution process of isothermal holding can be divided into three steps:disaggregation of the chain structure, mergence and coarsening, and the final ripening of primary particles. These primary solid particles grow by obeying the kinetic law in the whole isothermal holding process.