High-Strength and Flame-Resistant LPSO Magnesium Alloys Produced by Rapidly Solidified Powder Metallurgy Processing

Magnesium alloys are very attractive structural materials in aerospace applications. The Federal Aviation Authority (FAA) has lifted the ban on the use of magnesium alloys to civil aircraft. However, low ignition temperatures (470~550 deg C) and low mechanical strength of magnesium alloys have restricted their use.

We have developed high-strength and flame-resistant Mg-Zn-Y alloys, which are strengthened by a novel phase with a long period stacking ordered (LPSO) structure. A rapidly solidified powder metallurgy processing brings out the 1.6-fold tensile yield strength, 10-fold corrosion resistance, high-strain-rate superplasticity, and symmetric and isotropic mechanical properties in LPSO magnesium alloys, as compared with the ingot metallurgy processing. A Mg_96.75Zn_0.75Y₂Al_0.5 alloy with LPSO structure, which produced by rapidly solidified powder metallurgy (RS P/M) processing, has tensile yield strength of 533 MPa, tensile elongation of 10.6 %, and fatigue strength (10⁷ cycles) of 325 MPa. Its specific yield strength and specific fatigue strength and corrosion resistance are 1.6, 1.7 and 2.8 times as high as those of extra-super-duralumin (7075-T6). The ignition temperature of the LPSO Mg-Zn-Y alloys is ranging from 780 to 940 deg C, which is higher than that of ordinary magnesium alloys. The LPSO Mg-Zn-Y alloys passed the FAA flammability tests very easily, with essentially no burning at all. The LPSO RS P/M Mg-Zn-Y-Al alloys are promising structural lightweight materials for aircraft and spacecraft. We are now promoting the R&D on aircraft-application and manufacturing technology of the LPSO RS P/M Mg-Zn-Y-Al alloys. A new era of magnesium is coming in aerospace field.