Study On Compression Properties And Creep Properties Of Semi-Solid Al-Fe Alloy

In recent years, semi-solid processing technology has been rapid development, its application from the traditional sub-eutectic aluminum alloy developed to the hypereutectic alloy, making some of coarse second-phase alloy refine possible. The research group has developed a hypereutectic Al-Fe-based alloy of semi-solid forming technology and realized the improvement of mechanical properties of such alloys, so the commercial application of this alloy is becoming possible. However, the thixotropic behavior research has not been carried out similar to hypereutectic Al-Fe type alloy of semi-solid yet, while the thixotropic deformation behavior of alloy in a semi-solid range have an important impact on its semi-solid forming process and the final alloys performance, also developing the main basis of forming process. In order to realize the control and process optimization of semi-solid Al-Fe alloy process and improve the quality of semi-solid products, this work must be carried out. So this paper carried out the research on the semi-solid Al-5.5Fe alloy characteristics of compressive deformation, and tested creep properties of alloys, analyzed the creep mechanism, aimed at further improving the semi-solid forming technology of this type alloy.The results show that, when Al-Fe-based alloy compresses in semi-solid temperature, the true stress decreases as the deformation temperature decreasing, the true stress peak (T=640℃) is only about one-eighth of 610℃. the true stress increases with the deformation rate increasing, when the stress reaches the peak, the strain softening phenomenon occurs. While the deformation degree increasing, the true stress increases.The internal liquid-solid phase flow mode and deformation mechanisms are different when the alloy compresses at different deformation degree, deformation temperature and deformation rate. The center and the edge region of sample are also different after compression deformation, the solid particles of center region deformed larger than the edge region.When the deformation degree is very small(ε=0.22), the center deformation mechanism is liquid-phase flow, when the deformation degree increases(ε=0.69), a liquid-solid mixture flow mechanism is major, when a high deformation degree(ε= 1.79) ,the solid-phase grain slides mutually and plastic deformation occurs. The edge deformation mechanism is solid-liquid mixed flow. When the deformation temperature increases, the centre deformation mechanism changes into a mixed solid-liquid phase from solid-phase plastic deformation and solid particles sliding mechanism, while the edge is from the liquid-solid mixture mechanism into a liquid flow-based mechanism. Al-Fe-based alloy is sensitive to the creep temperature and creep stress largly. In the test temperature of 200℃, 250℃, 300℃, the creep stress of 30Mpa, 50Mpa, 70Mpa, 80Mpa, 100MPa, the alloy steady creep rate is in line with semi-empirical formulaε=Aσnexp(-Qa/RT), the average of the stress exponent is 6.012, and the apparent activation energy Qa is 229.72KJ/mol.