机械振动对AZ91充型凝固中铸件-铸型传热的影响

Effect of Mechanical Vibration on Heat Transfer of Casting-Mold Interface in Filling and Solidification Process of AZ91 Magnesium Alloy

研究了AZ91镁合金在充型凝固过程中不同振动频率对镁合金充型过程、凝固方式和铸件-铸型间隙的影响机制,并自主设计铸件-铸型界面传热效率装置,探讨了机械振动对铸件-铸型界面传热的影响。结果表明,机械振动使充型过程中合金液流体雷诺数变大,层流边界层厚度减小;破坏凝固初期型腔壁已凝固薄层,改变镁合金的凝固方式,使合金晶粒细化、改变晶体内部相形态及分布;凝固后,使铸件-铸型间隙处于动态变化过程。进而影响了铸件-铸型界面间的传热。当振动频率分别为0,20,50 Hz时,模具所达到的最高温度值分别为365.3,372.1,377.1℃,模具温度上升至最大温度值所需的时间依次为111,100,91 s,振动频率从0Hz增大到50 Hz,模具所达到的最大温度值逐渐增加,模具温度上升至最大温度值所需的时间逐渐减少。

The influencing mechanism of different vibration frequencies on the filling and solidification mode and casting-mold gap was investigated in the filling and solidification process of AZ91 magnesium alloy. And the effect of mechanical vibration on heat transfer efficiency of the casting-mold interface was studied through independently designed heat transfer device. The results show that the mechanical vibration enhances the Reynolds number and reduces the thickness of laminar boundary layer during the filling process. It also destroys the initially solidified thin layer on the cavi alloy, refines the grains and changes the phase morphology and distribution ty F wall, changes the solidification mode of magnesium inally, the vibration makes the casting-mold gap in a dynamic changing process after solidification and thus influences the heart-transfer of the casting-mold interface. Under vibration frequency of 0, 20 and 50 Hz, the mould＇s highest temperature is 365.3,372.1 and 377.1 ℃, respectively, while the required time of mould reaching the maximum temperature is 111 s, 100 s and 91 s, respectively. With the vibration frequency changing from 0 Hz to 50 Hz, the mould＇s maximum temperature increases gradually while the required time reduces