The aluminum alloy thin-walled shell casting is produced according to the actual engineering demand. After the production is completed, the casting system of the shell casting is cut off by machining method, and the outer surface of the casting is cleaned and pricked, as shown in Figure 6. In order to effectively observe the microstructure of the material during the solidification process at different temperatures and strain rates,
The high temperature compression experiment can provide more accurate data for numerical simulation. Sample preparation: according to GB / T 2975 standard, the sample is processed into a 3 × 8 mm cylinder compression sample. A group of compression samples with strain rate of 0.01 s-1, 0.1 s-1, 1 s-1, 5 S-1 and 20s-1 at 100 ℃, 300 ℃ and 550 ℃ respectively are selected for magnification of 100 times. The appropriate solidification speed of the new material at different temperatures can be obtained by analysis.
In the process of casting and solidification, with the decrease of temperature, the solid phase in the structure increases gradually, and the existence of liquid phase ensures the overall fluidity of the condensed solid metal when it shrinks. When the compression test temperature is 550 ℃, the temperature is close to the eutectic temperature of the material, and the microstructure of the solid after deformation and contraction changes more evenly under 1 S-1 strain rate, showing low stress and good deformation ability; while at higher strain rates, 5 S-1 and 20 Under the action of S-1, the shrinkage and aggregation of solid particles are faster, resulting in larger microstructure of solid; under the action of low strain rates of 0.01s-1 and 0.1s-1, the slow shrinkage deformation causes the solid particles to fully condense into large particles, resulting in larger microstructure of solid.
When the compression test temperature is 300 ℃, due to the increase of solid particles in the material, under various strain rates, the aggregation and condensation of existing solid particles can not be prevented, resulting in the increase of solid microstructure. At the temperature of 100 ℃, due to the large proportion of solid phase, only at the strain rate of 1 s-1, can the change of solid microstructure after deformation and contraction be guaranteed to be better, while at other strain states, internal cracks begin to appear in varying degrees.