DIFFUSION COUPLE INVESTIGATION OF THE Mg-Zn SYSTEM

摘要

Growing use and development of lightweightMg alloys has been the catalyst for morefundamental research in Mg based materialsystems to be completed. Zinc is one of the mostcommon alloying elements in Mg alloys. Phaselayer growth and interdiffusion in the binaryMg-Zn system was investigated utilizing solidto-solid diffusion couples. Anneals were carriedout at 295°, 315° and 325°C for 384, 168 and120 hours, respectively. The diffusionmicrostructures that developed were examinedby optical and scanning electron microscopy(SEM). Concentration profiles were determinedusing X-ray energy dispersive spectroscopy(XEDS) and electron microprobe analysis(EPMA). The phases observed were the Mgsolid solution, Mg_2Zn_(11), MgZn_2 and Mg_2Zn_3 inall three couples as well as the high temperature,Mg_(51)Zn_(20) phase in the 325°C couple. TheMgZn2 phase was observed to grow the thickestlayer, followed by the Mg_2Zn_3 and the Mg_2Zn_(11)phases. Parabolic growth constants weredetermined for each phase. Activation energiesfor the growth of the intermetallic phases werecalculated as 105 kJ/mol for the Mg2Zn3 phaseand 207 kJ/mol for the MgZn_2 phase.