成形速度对7075半固态模锻组织均匀性的影响

摘要

在半固态模锻过程中,经常会出现液相偏析现象,使零件出现"弱点"或"弱区",这些"弱点"或"弱区"通常又是潜在的裂纹源和服役条件下失效的起因.为了分析研究半固态模锻液相偏析的影响因素,应用DEFORM-3D软件对7075铝合金半固态模锻充型过程进行了模拟,研究了成形速度对7075铝合金杯形件充型过程的影响规律.在模拟的基础上,利用压力机及杯形实验模具,进行了半固态7075铝合金流变模锻成形,研究了成形速度对7075铝合金杯形件半固态模锻组织均匀性的影响.模拟和实验结果表明:成形速度越高,充型越不平稳;在压头温度400 ℃、成形比压50 MPa、合金温度628 ℃的条件下,随着成形速度的增加,杯形件的液相偏析度增加,组织越不均匀,当成形速度为5 mm/s时,杯形件的液相偏析度高达18.2%.%Liquid phase segregation frequently occurs in the process of semi solid die forging, which makes the parts appear "weak point" or "weak region", and usually, the "weak point" or "weak area" is the reason of crack and service condition failure.In order to analyze the influence factors of the liquid phase segregation of the semi solid die forging, DEFORM-3D is used for the numerical simulation of semi-solid die forging forming process of 7075 aluminum alloy, to study the influence rule of forming velocity on the forming process of cup part.Based on the simulation results, the rheological die forging forming of 7075 aluminum alloythe part is conducted to research the influence of forming velocity on the uniformity of microstructure by means of press machine and cup mould.The simulation and experimental results show that as the filling velocity is faster, the forming process is more unstable;under the condition of head temperature of 400 ℃, the forming pressure of 50 MPa, and the alloy temperature 628 ℃, as the forming velocity increases, the liquid phase segregation degree of cup part increases, and the microstructure is far from uniformity.The segregation degree is up to 18.2% as the forming velocity is 5 mm/s.