Microstructure And Corrosion Behavior Of ZK60-1Nd Magnesium Alloy

Abstract:

Microstructure and the corrosion behavior of ZK60-1Nd magnesium alloy in 3.5 wt % NaCl aqueous solution was studied by scanning electron microscope (SEM) , electrochemical workstation and brine weight loss method. The results indicate that the as-cast microstructure of ZK60-1Nd alloy is mainly composed of matrixα-Mg, a coarse network eutectic phase containing rare earth Nd distribute along the grain boundaries and the distribution of fine MgZn₂ phase in the matrix. The corrosion rate of ZK60-1Nd magnesium alloy in 3.5 wt % NaCl aqueous solution was 0.2 mg ? cm_-2 ? h_-1 in NaCl solution. After homogenization at 300 ℃ for 8.0 h , the microstructure was improved;after annealing at 400 ℃ for 96 h, A portion of the eutectic phase is fused to a particle with a maximum size of 1.5 μm and the corrosion rate is reduced to 0.1 mg.cm_-2.h_-1; After annealing at 500 ℃ for 8.0 h , fishbone eutectic phase composition of patchy, the MgZn₂ phase is dissolvedSintoSmatrix , the contents of Nd, Zn and Zr were increased and the distribution was uniform in the matrix , corrosion rate reached a minimum of 0.03 mg.cm_-2.h_-1. The main reason for the improvement of corrosion resistance is that the increase of the content of solid solution Nd in matrix α-Mg lead to the improvement of corrosion potential and the decrease in the number of micro galvanic corrosion.

Key words:ZK60-1Nd; Magnesium; Homogenization; Microstructure; Corrosion Resistance