Effect of heat treatment on electromagnetic shielding effectiveness of ZK60 magnesium alloy

摘要

Electromagnetic interference (EMI) shielding capacity of ZK60 magnesium alloy in different heat treat ment conditions was investigated in the testing frequency range of 30-1500 MHz. EMI shielding effec tiveness (SE) was measured by coaxial cable method at ambient temperature. Experimental results indicate that solid solution treatment enhances the SE of as-extruded ZK60 alloy at low frequency, while has an inverse effect on the SE at high frequency. Artificial aging treatment following solid solution improves shielding capacity obviously, moreover the SE value of the alloy increase gradually with increasing amount of second phase precipitates. Solution treatment at 400 ℃ for 5 h plus artificial aging at 170 ℃ for 25 h is determined as the optimum heat treatment condition. In this condition, a high shield ing effectiveness of 62-75 dB has been attained in the alloy, which is greatly higher than the value in extruded state. The above-mentioned observations were analyzed in terms of microstructural variation, especially solid solution and precipitation of alloying elements in ZK60 alloy in details.