Woo-Sung Jung

Mg Content Dependence of EML-PVD Zn-Mg Coating Adhesion on Steel Strip

The effect of coating thickness and Mg concentration on the adhesion strength of electromagnetic levitation physical vapor deposited Zn-Mg alloy coatings on steel strip was investigated. The phase fraction of Zn, Mg2Zn11, and MgZn2 was determined for a coating Mg concentration in the 0 to 15xa0wt pct range. Coatings with a Mg content less than 5xa0pct consisted of an Zn and Mg2Zn11 phase mixture. The coatings showed good adhesion strength and ductile fracture behavior. Coatings with a higher Mg concentration, which consisted of a Mg2Zn11 and MgZn2 phase mixture, had a poor adhesion strength and a brittle fracture behavior. The adhesion strength of PVD Zn-Mg alloy coatings was found to be related to the pure Zn phase fraction. The effect of coating thickness on adhesion strength was found to be negligible. The microstructure of the interface between steel and Zn-Mg alloy coatings was investigated in detail by electron microscopy, electron diffraction, and atom probe tomography.

Evaluation of the Mechanical Properties of Zn-Mg Alloys with Composition of Mg

In this study, Zn-Mg alloys with various Mg contents were manufactured by the casting method using an induction melting furnace. Then microstructure analysis and mechanical property tests were carried out. In the Zn-Mg alloy with a content of less than 7 wt%Mg, the hardness of the Zn-Mg alloys gradually increased as the Mg content increased but in the alloy with more than Zn-7 wt%Mg, the hardness was almost the same. Enhanced hardness is induced by the intermetallic compounds phase of Mg2Zn11 and MgZn2. In the compression test, Zn-3 wt%Mg had the best compression strength at 610 MPa, but Zn-7 wt%Mg and Zn-10 wt%Mg had a low compression strength at 343 Mpa and 111 MPa, respectively, although these alloys have excellent hardness. This study verified that Zn-Mg alloys containing a Zn phase have more toughness than those composed of only intermetallic compounds such as Mg2Zn11 and MgZn2. (Received November 19, 2012)