The Effect Of The Zn Addition On Microstructure And Mechanical/Corrision Properties Of Mg-4.0Y-2.5Nd Alloy

The relationship between microstructure and the properties of the metal, which included the mechanical properties and the corrosion properties, has been investigated by Optical microscopy (OM), hardness testing, tensile testing, X-ray diffraction (XRD), scanning electron microcopy (SEM), transmission electron microscopy (TEM), and electrochemical workstation in this paper. The microstructures in tested alloy in as-cast, solution treated and ageing treated were observed and the conclusions can be summarized as follows:1、The addition of Zn could form Long Period Stacking Ordered Structure (LPSO) in Mg-4.2Y-2.5Nd-xZn alloys. The compounds in as-cast Mg-4.2Y-2.5Nd alloy are Mg41Nd5and β phases, while in Zn-addition alloy is Mg12(NdYZn). The grain size decreases with the Zn content.2、After solution treated at515℃×4h, the eutectic compounds in Mg-4.2Y-2.5Nd alloy Mg41Nd5and β phase dissolved into the matrix. And in the subsequent ageing process, β" and β’were precipitated in the matrix. While in Mg-4.2Y-2.5Nd-Zn alloy, Mg12YZn and Y-rich cubic phases were found in solution treated state. In these Zn-addition alloy, the strength of these alloy were influenced by the interaction of fine strengthening β’phases which precipitated in ageing condition and LPSO phases.3、The strength of as-cast Mg-4.2Y-2.5Nd-xZn alloy increase with the addition of Zn. When Zn content reaches1.5%, the ultimate tensile strength, yield tensile strength and elongation were202MPa,134MPa and3.6%, respectively. Compared with Zn-free alloy, the properties of Mg-4.2Y-2.5Nd-xZn alloy in T6state, the elongation improved largely. A satisfied combination of strength and ductility was obtained when Zn addition is1.0%, the ultimate tensile strength, yield tensile strength and elongation were281MPa,162MPa and7%.4、The addition of Zn improved the self-corrosion potential, reduced the corrosion current and made the polarization curve shifted to more positive. The weight loss rate indicated that the corrosion resistant of Mg-4.2Y-2.5Nd-xZn alloy increase with the Zn addition as first, then decrease after Zn content reaches the peak. The Mg-4.2Y-2.5Nd-1.0Zn alloy exhibits the highest corrosion resistance property.