搅拌摩擦增材成型过程仿真与显微性能预测

Simulation of friction stir additive process and its micro-properties prediction

搅拌摩擦增材制造(FSAM)是一种新型固态增材技术。逐层重复搅拌摩擦成型,是FSAM的显著特点。在剧烈流动变形、热力耦合作用下,母材晶粒逐层破碎细化,形成新的再结晶组织,最终形成增材成型构件。以AZ31镁合金板件FSAM为研究对象,首先建立多层薄板增材成型的计算流体力学仿真模型,研究转速对材料流变、温度场、应变率的影响规律,并与实验测量值对比验证。其次计算增材区域镁合金材料热变形过程的Zener-Hollomon参数,利用经验公式法关联Z参数与增材区再结晶晶粒尺寸。最终,结合1000 r/min转速工况下的显微硬度实验测量结果,提出FSAM搅拌区再结晶组织显微硬度的快速预测算法。结果表明:随着增材板件层数增加,增材区平均晶粒尺寸减小,平均硬度值增大;随搅拌头转速的增大,增材区材料的应变率、再结晶晶粒尺寸都呈逐渐增大趋势,显微硬度呈下降趋势。

The friction stir additive manufacturing(FSAM)is a new solid-state manufacture technology.The re-stirring process is a remarkable feature of FSAM.Under the action of severe deformation and thermal coupling,the grains of base metal were crushed and refined layer by layer to form a new recrystallized structure,and finally an additive forming component was formed.AZ31 magnesium alloy sheet for FSAM process was taken as the research object.Firstly,computational fluid dynamics model of FSAM was established.The influence of rotation speed on material rheology,temperature field and strain rate was studied,and compared with the experimental results.Secondly,the Zener-Hollomon parameters of the hot deformation process of the magnesium alloy material in the additive zone were calculated.Then,the Z parameters and the recrystallized grain size of in additive zone were correlated by empirical formula method.Finally,combined with the micro-hardness test results at 1000 r/min,a fast prediction algorithm for the recrystallized microstructure of the FSAM was proposed.The results indicate that,with the increase of layers,the average grain size and the average hardness in the additive zone decrease.With the increase of the rotation speed,the strain rate and recrystallized grain size of the material in the additive zone gradually increase,but the micro-hardness shows a downward trend.