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The effects of Mn and Fe contents on the mechanical properties of aluminum-based A206 alloys were investigated quantitatively. Results showed that the addition of Fe caused a loss in both ductility and yield strength. Further addition of Mn could recover the ductility, but it caused a further loss in yield strength. In low-Mn alloys (0.29 wt% Mn) the primary constituent was the needle shape of Cu2FeAl7. Upon further addition of Mn, the Chinese script configuration of Mn-bearing particles formed instead. The Cu2Mn3Al20 particles formed in high-Mn alloys during solution treatment and resulted in grain-growth inhibition. The needle, Mn-bearing, and Cu2Mn3Al20 particles caused the solid solution level of copper in the matrix to decrease; meanwhile, increasing the Mn solution level retarded the precipitation of the strengthening phase. Differential scanning calorimetry analyses showed the kinetics and amount of decrease in θ′ phase precipitation when the contents of Fe and/or Mn were increased. The smaller grain size induced by the Cu2Mn3Al20 particles and the θ′ phase were the factors that determined the hardness of A206 alloys under as-quenched and T7-treated conditions, respectively.

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nformation security has become a major issue in recent years, as new ways of information exchange arise due to the rapid development of computing, communication and internet technologies. We propose the image communication systems to secure the information by using a steganographic system and empirical mode decomposition method. The concealed message between the sender and receiver is important in the steganographic system. The encrypted message is further decomposed by using the empirical mode decomposition. The information is transmitted via the public channel and secure channel. At the receiver side the weak message can be retrieved back effectively. The retrieved message carries the same characteristics as the original message. Simulation results have confirmed that this combination model is highly robust against various signal processing operations and geometric attacks. The system increases the security of information data given a variety of constraints and conditions. Our methods have been proven effective for application in various fields which require secure communication, such as mobile telephone, internet and others. By means of this method, researchers can better understand the characteristics of the secure communication.