Effects of Bi addition on as-cast microstructure

mechanical properties of Mg-4Zn-Y alloys and corrosion behavior in 3.5% NaCl solution were investigated by X-ray diffraction（XRD）

optical microscope（OM）

mechanical property testing

weight loss measurement

electrochemical polarization curves and electrochemical impendence spectrum.The results show that the microstructure of Mg-4Zn-Y-xBi（x is 0

0.5

1

2） alloy consists of the matrix α-Mg phase

the ternary I（Mg3Zn6Y） and Y5Bi3 phase

and the morphology of I phase on the grain boundary is changed from semi-continuous net structure into dispersed particle ones.With the increase of Bi addition

Y5Bi3 phase is increased with the coarseness of grain size.The tensile strength

yield strength and elongation of the alloy at room and at high temperature are increased with the increase of Bi addition

however

they are deteriorated with excessive Bi content（2%）.Corrosion resistance of the alloy is decreased with Bi addition increase and the corrosion rate is the 2

3

times faster than Mg-4Zn-Y alloy.With 2% Bi addition

the corrosion current reaches the maximum value

0.913 mA

exhibiting the worst corrosion resistance.