The Research Of Flow Stress Behaviors At Elevated Temperature And Processing Maps For Aluminum Matrix Composites

Industrialized production of aluminum matrix composites (AMCs) has begun in the United States, Europe and other developed countries, and the material was classified as an important direction of new application materials for 21th century. However, due to the existence of hard particles in AMCs, hot-working ability of the material was much worse than the ability of aluminum alloy, which, to a certain extent, blocks the wide application of the material. Moreover, the existence of the particles will also make it more difficulty to control the microstructure changes of AMCs during hot deformation. Therefore, how to choose the appropriate hot deformation technology to improve the hot working ability of AMCs, and finally improve the microstructure of the production becomes a critical issue. In this paper, researches about the hot working ability of AMCs have been outspreaded by the ways of establishing of flow stress equations and developing processing maps, the main conclusion are as follows:Steady-state flow characteristics were observed during hot deformation of SiCp/7A04 composites, and the flow stresses increase with the increasing of strain rate and the decreasing of temperature. The hot deformations of the composites are controlled by thermal activation, and the flow stresses under the experimental range can be expressed as a function of parameter Z.Power dissipation efficiencies of SiCp/7A04 composites exhibit the trend that with the increasing of strain rate and the decreasing of temperature the values of efficiencies increased, because higher temperature and lower strain rate can accelerate the dynamic recrystallization nucleation and growth. Under almost conditions, power dissipation efficiencies of SiCp/7A04 composites were higher than that of 7A04 alloy, and microstructure observation confirmed that the adding of SiC particles promoted the dynamic recrystallization nucleation.The optimum working region and two instable regions were identified using processing map developed at a strain of 0.5 for 14%SiC/7A04 composite. The dynamic recrystllization zone with favorable interface bonding corresponding to the optimum hot working region is that temperature is 400~450℃and strain rate is 0.001~0.01s-1. The two instable regions might respectively be aroused by voids formation around particles at lower-temperature high-strain rate area and by wedge cracking at high-temperature mediate strain rate zone.