P-ECAP挤压ZK60镁合金空心壁板工艺参数优化

Optimization of process parameters for ZK60 magnesium alloy hollow plate in P-ECAP extrusion

为了确定合理的工艺参数可行域,利用有限元法模拟了ZK60镁合金空心壁板挤压成形宏观场变量分布,并通过实验验证了模拟结果。研究分三个步骤,首先通过等温热压缩实验获得ZK60镁合金应力应变关系,其工艺参数覆盖典型的加工工艺状态;其次,建立不同工艺参数的有限元模型;最后,根据等效应变、温度场、速度场分析确定工艺参数可行域。结果表明:坯料温度度400~420℃时,等效应变和温度场分布不均匀;480℃时,等效应变分布均匀,但出口温度太高,超过520℃。在挤压速度为5~7.5 mm/s时,温升小,温度均匀性好;挤压速度大于10 mm/s,温升大,温度不均匀;挤压速度越大,流速场越不均匀。因此,合适的温度为440~460℃,挤压速度小于7.5 mm/s。

Finite element modeling(FEM) was applied for predicting the processing window in extruded ZK60 magnesium alloy and simulated results were experimentally validated. First, stress-strain relationship of ZK60 magnesium alloy during deformation was studied by means of isothermal compression test, where the processing parameters were chosen to reproduce the typical industrial conditions. Second, FEM of deformation of ZK60 magnesium alloy were established. Finally, the processing window was confirmed by temperature field, velocity filed and strain-effective analysis. The finite element analysis results show that distribution of strain-effective and temperature are nonuniform in die bearing at 400-420 ℃. The distribution of strain-effective is uniform but the temperature of workpiece in die bearing is too higher than 520 ℃ at billet temperature of 480 ℃. The temperature rise is insignificantly at ram speed of 5-7.5 mm/s and obviously at ram speed over 10 mm/s. The processing window of temperature is between440 ℃ and 460 ℃ and the ram speed is less than 7.5 mm/s.