2060铝锂合金冷模热成形界面换热系数确定的实验与算法

Determination of interfacial heat transfer coefficient in cold die hot forming of 2060 Al-Li alloy:Experiment and algorithm

2060铝锂合金具有密度低、比强度高等优势,在航空航天零件制造领域已得到广泛应用。通过冷模热成形工艺可以提高2060铝锂合金成形性,减少开裂、拉毛、回弹等缺陷的发生,后续时效处理可以提高零件整体刚度。然而在实际成形过程中缺乏对温度场的准确预测,即缺乏2060铝锂合金在变压强下界面换热行为的准确描述,无法对成形效果进行评估。本文利用冷模热成形界面换热测试平台,对不同压强下2060铝锂合金与H13热作模具钢的换热行为进行测试研究,基于考虑模具钢变热物性参数的显式有限差分法反算模具表面温度,计算得到不同压强下的界面换热系数,并与Beck反传热算法进行对比,两者计算结果相近。实验结果显示2060铝锂合金IHTC随压强增大而增大,在20MPa下IHTC=1.9066kW/(m^(2)·K)。改进的有限差分法具有计算效率高、速度快、反映实际模具内部温度场、误差较低等优点,可拓展应用于其他薄板材料在冷模热成形条件下的界面换热系数求解。

With advantages of low density and high specific strength,2060 Al-Li alloy has been widely used in aerospace parts manufacturing.Cold die hot forming process can improve the formability of 2060 Al-Li alloy,reducing occurrences of defects such as cracking,drawing and springback,and subsequent aging treatment can improve the overall rigidity of the parts.However,lack of accurate prediction of the temperature field in the actual forming process,that is,an accurate description of the interfacial heat transfer behavior of 2060 Al-Li alloy under variable pressures hampers the evaluation of the forming effect.This study obtained heat transfer behavior between 2060 Al-Li alloy and H13 hot-work die steel under different pressures using the interfacial heat transfer test platform.The die surface temperature was calculated by Finite-Difference Method(FDM)in consideration of temperature effects of thermal properties.The Interface Heat Transfer Coefficient(IHTC)at different pressures was calculated and compared with Beck’s inverse heat transfer algorithm.The calculated results were similar.The experimental results showed that IHTC of 2060 Al-Li alloy increased with the increase of pressure,with IHTC=1.9066 W/(m^(2)·K)at 20 MPa.The improved FDM has the advantages of high computational efficiency,high speed,satisfactory reflection of the actual temperature field inside the mold,and low error.Therefore,it can be extended to the IHTC solution of other sheet materials in cold die hot forming.