铝合金挤压铸造扭转复合成形模具-工件界面换热行为

Heat transfer behavior of die-workpiece interface in squeeze casting-torsion complex forming for aluminum alloy

挤压铸造扭转复合成形(SQ-T)集挤压铸造(SQ)与扭转成形(T)的优势于一体,可实现铝合金工件的高效成形。为准确描述铝合金SQ-T工艺下的模具-工件界面换热行为并对成形效果进行评估,通过搭建SQ-T实验平台和构建界面换热系数(IHTC)反求模型,求解成形过程中的IHTC,并对IHTC的变化规律、工件成形效果及工件组织性能进行研究。结果表明:反算模型精度较高,96%以上反算结果的相对误差小于10%;在SQ中加入扭转变形后,工件的气孔数量减少、尺寸变小,模具-工件界面换热条件更好;SQ-T实验的IHTC前半段高于SQ实验,最大提升了60%;IHTC的增加使SQ-T实验工件的冷却速度加快,显微组织更加细小均匀,硬度提高了19.3%,动态峰值应力提升了7.6%。

Squeeze casting-torsion complex forming(SQ-T),combing the advantages of squeeze casting(SQ)and torsional deformation(Torsion),can realize the efficient forming of aluminum alloy workpiece.In order to accurately describe the interface heat transfer behavior between die and workpiece of the aluminum alloy under SQ-T process and evaluate the forming effect,the SQ-T experiment platform and the inverse model for the interface heat transfer coefficient(IHTC),were built to solve the IHTC during the forming process,and to study the IHTC evolution,forming effect and organization performance of the workpiece.The results show that more than 96%of the inverse calculated results are less than 10%in relative error,indicating that the inverse calculation model has high accuracy.By adding the torsional deformation into SQ,the number and size of the pores in the workpiece reduces,and the interface heat transfer condition between mold and workpiece becomes better.The IHTC of SQ-T experiment is higher than that of SQ experiment,and the maximum increases up to 60%.The increase of IHTC accelerates the cooling speed of workpiece of SQ-T experiment,causing that the microstructure is more fine and uniform,and the hardness increases by 19.3%and the peak stress increases by 7.6%.