Nanocrystalline LPSO Mg-Zn-Y-Al Alloys with High Mechanical Strength and Corrosion Resistance

Abstract

Interests in magnesium alloys increase as eco-material for its lightweight, and many investigations have been carried out on the development of manufacturing processes and alloy development. In 2001, Mg97Zn1Y2 (at%) alloy with a tensile yield strength of 610 MPa and an elongation of more than 5 % has been developed by rapidly solidified powder metallurgy (RS P/M) processing. The developed alloy was characterized by a novel phase with long period stacking ordered (LPSO) structure. Recently, we have investigated new compositions for LPSO RS P/M Mg-Zn-Y-X alloys in order to improve the corrosion resistance of the RS P/M Mg97Zn1Y2 alloy with maintaining the superior mechanical properties. Consequently, we have developed a RS P/M Mg96.7Zn0.85Y2Al0.45 alloy with high strength and high corrosion resistance. The RS P/M Mg96.7Zn0.85Y2Al0.45 alloy contained the LPSO phase and exhibited a tensile strength of 525 MPa, an elongation of 9 % and a fatigue strength of 325 MPa, which were similar to those of the RS P/M Mg97Zn1Y2 alloy. However, the corrosion resistance of the RS P/M Mg96.7Zn0.85Y2Al0.45 alloy was 1.5 times that of the RS P/M Mg97Zn1Y2 alloy. The specific tensile yield strength, the specific fatigue strength and the corrosion resistance of the RS P/M Mg96.7Zn0.85Y2Al0.45 alloy were about 1.7 times, 1.8 times, and twice those of extra-super-duralumin (7075-T6 or 7075-T73), respectively.

Magnesium extrusion alloys: a review of developments and prospects

“…After Kawamura et al reported a YS of 610 MPa in the Mg–6.7Y–2.5Zn alloy in 2001 [116], any YS exceeding 600 MPa was not reached in subsequent studies [227–229,237,238]. Even when the Mg–6.7Y–2.5Zn alloy was produced by a similar rapid solidification, powder metallurgy and hot extrusion methods, the YS of Mg–6.7Y–2.5Zn alloy was reported to be about 480 MPa [238].…”

“…After Kawamura et al reported a YS of 610 MPa in the Mg–6.7Y–2.5Zn alloy in 2001 [116], any YS exceeding 600 MPa was not reached in subsequent studies [227–229,237,238]. Even when the Mg–6.7Y–2.5Zn alloy was produced by a similar rapid solidification, powder metallurgy and hot extrusion methods, the YS of Mg–6.7Y–2.5Zn alloy was reported to be about 480 MPa [238]. For the Mg–Y–Zn alloys produced by conventional casting and hot extrusion, the tensile YSs of as-extruded alloys are found to be even lower, in the range between 200 and 400 MPa [93,227–229].…”

“…117 , any yield strength exceeding 600 MPa was not reached in subsequent studies 228-230, 238, 239 . Even when the Mg-6.7Y-2.5Zn alloy was produced by a similar rapid solidification, powder metallurgy and hot extrusion methods, the yield strength of Mg-6.7Y-2.5Zn alloy was reported to be about 480 MPa 239 .…”

The Effects of Pre-Consolidation Heat Treatment on the Tensile and Fracture Toughness Behavior of the Rapidly Solidified Mg–Zn–Y–Al Alloys

“…1214) Therefore, the RS ribbon-consolidated Mg0.85Zn2.05Y0.35Al (at%) alloys could be excellent material choice for aerostructures such as stringers and brackets. 15) In structural design, planestrain fracture toughness is an important property requirement. In our previous study, we demonstrated that a preconsolidation heat treatment of the RS ribbons was effective in improving the ductility and fracture toughness of the Mg 0.85Zn2.05Y0.35Al alloy.…”

Revealing the Microstructural Aspects of the Corrosion Dynamics in Rapidly Solidified Mg-Zn-Y Alloys Using the Acoustic Emission Technique

“…This idea has been applied to Mg-LPSO alloys as well. Several processing techniques, such as powder metallurgy [5,26], extrusion of recycled chips [27,28], equal channel angular pressing [27], rotary swaging technique [29,30] or rapidly solidified (RS) ribbon-consolidation [31][32][33], have been developed to reach the goal of developing the sub-micron grain-sized Mg alloys.…”