Effect of different injection pressure on mechanical properties of rheo squeeze casting parts

The effect of injection specific pressure on the mechanical properties of 7075 alloy by rheo squeeze casting is shown in the figure. With the injection pressure from 50MPa to 110MPa, the tensile strength increases continuously, from 275mpa to 310.4mpa, because the pressure difference selected in the experiment is small, and the rising proportion is not very large, and the elongation (selected average value) fluctuates greatly, from 7.0% to 21.77%, and then to 13.82%. From the data results, when the pressure is 80 MPa, the elongation is the highest, and the elongation of the tensile test bar is the best, reaching 23.33%, which is the best elongation level of 7075 semi-solid squeeze casting in the current literature.

Due to the deviation of experimental data, the up and down deviation of elongation and tensile strength are also characterized as shown in the figure. From the elongation point of view, the stability and deviation of the sample are relatively large, which should be related to the involvement of impurities such as oxide scale, liquid phase segregation and intergranular segregation in rheo squeeze casting. The tensile strength data show relatively stable, with the pressure to a certain value, the increase proportion is not obvious.

Based on the experimental data and results, it is preliminarily inferred that when the specific pressure exceeds 80 MPa, the decrease of elongation is related to the increase of liquid phase segregation and intergranular segregation, but the influence of other impurities and micro pores can not be excluded, which needs further research and demonstration. Considering the comprehensive properties of elongation and strength, the injection pressure of 80 MPa is the best.