As shown in Figure 1, the pressure nephogram of aluminum alloy and magnesium alloy castings at different times (the pressure is static pressure) is given when the applied pressure is 70MPa. The results show that the solidified shell bears more pressure than the liquid region and the paste region, and the pressure gradually decreases with the increase of the thickness of the solidified shell in the region of incomplete solidification.
As shown in Figure 1, the pressure distribution in aluminum alloy casting is more uniform than that in magnesium alloy casting. For aluminum alloy, the early solidified shell shares the pressure more evenly. For magnesium alloy, the four corners of the casting bear more pressure. The reasons are as follows: the solidification of magnesium alloy casting is faster than that of aluminum alloy casting. For magnesium alloy, the cooling and solidification of the four top corners of the casting are faster. In addition, according to the material constitutive relationship given in Fig. 2, under the same temperature and strain rate, the magnesium alloy needs more force to deform. Therefore, the deformation of magnesium alloy is relatively difficult, the four corners of casting solidification will become harder, and the hard part will share more pressure. For aluminum alloy, deformation is relatively easy, so more parts are needed to share the pressure, so that the pressure distribution is more uniform.
For magnesium alloy, the pressure in the middle part of the casting has been reduced to 0mpa at 18S. However, for aluminum alloy, it is not until 26S that the pressure decreases to 0mpa. This means that the pressure in the middle part of magnesium alloy casting decreases faster than that in aluminum alloy casting. There are two reasons. Firstly, magnesium alloy solidifies faster than aluminum alloy, and the larger solid phase means that it can support the punch better. Secondly, under the same temperature and strain rate, magnesium alloy needs more force to deform, which means that the early solidified magnesium alloy can share more pressure from the punch, which is a good explanation for position 2 The reason why the peak value of the pressure at the casting die interface of magnesium alloy casting is lower than that of aluminum alloy, and the pressure reduction rate of magnesium alloy casting is higher than that of aluminum alloy.
Through the comparison of pressure distribution in aluminum alloy and magnesium alloy castings, the law of pressure transfer in castings can be clearly understood. And the pressure transfer in the casting greatly affects the pressure of the casting die interface, which also affects the contact state of the casting die interface.