New low-cost, lightweight magnesium sheet alloy with good formability for automotive applications; 1.5x stronger than aluminum
A research team at Japan’s National Institute for Materials Science (NIMS) and Nagaoka University of Technology has developed a new high-strength magnesium sheet alloy (Mg–1.1Al–0.3Ca–0.2Mn–0.3Zn) that has excellent room-temperature formability comparable to that of the aluminum sheet metal currently used in body panels of some automobiles.
The magnesium alloy becomes stronger than aluminum alloy after a heat treatment, uses only common metals, and could be a low-cost, lightweight sheet metal for automotive applications. A paper on the work is published in the journal Scripta Materialia.
Lightweight magnesium (Mg) alloys have attracted considerable attention for potential applications in the automotive industries. However, the low strength or poor formability at room temperature (RT) hinders the wider applications of wrought Mg alloy sheets. In general, stretch formability and yield strength are inversely correlated; therefore, it is difficult to obtain both high strength and high formability.
… Recent studies have reported that dilute Mg–Al–Ca–Mn (AXM) system could be industrially viable wrought alloys due to their extraordinary high-speed extrudability and rapid age-hardening response. If this system can be used as sheet alloys as well, then a huge impact on the automotive industries is expected. Therefore, attempts were made by the present authors to develop sheet alloys from the AXM system. During the processing of Mg–1.1Al–0.3Ca–0.2Mn at.% [atomic percentage] alloy, it was found that the addition of a small amount of Zn (0.3 at.%) to the Mg–1.1Al–0.3Ca–0.2Mn alloy substantially improved the stretch formability. Additionally, subsequent short time aging led to a significant increase in the strength of the resultant Zn-containing alloy. The purpose of the present paper is thus to report results of (i) assessments of mechanical properties of the T4 and T6 treated Mg–1.1Al–0.3Ca–0.2Mn alloy sheets, with or without Zn additions, and (ii) characterization of the microstructures and textures of these sheets.—Bian et al.
|Comparison of newly developed and conventional magnesium alloy sheets after they were subjected to Erichsen tests. Credit: National Institute for Materials Science. Click to enlarge.|
Named AXMZ1000, the newly developed alloy has room temperature formability comparable to that of medium strength aluminum alloys that are used in some automobile bodies. In addition, the new alloy is 1.5 to 2.0 times stronger than the aluminum alloy.
The addition of very small amounts of zinc (Zn) and manganese (Mn) led to the formation of fine grain structures; the high strength was accomplished by adding aluminum (Al) and calcium (Ca), which induced the strengthening of the alloy by the formation of atomic clusters.
The newly developed alloy is composed of only common metals, so the material cost is not expensive. It can be rolled into sheets using simple processes and heat treatments commonly used for aluminum alloys.
This study was conducted as a part of the JST Advanced Low Carbon Technology Research and Development Program (ALCA).
M. Z. Bian, T. T. Sasaki, B. C. Suh, T. Nakata, S. Kamado, K. Hono (2017) “A heat-treatable Mg–Al–Ca–Mn–Zn sheet alloy with good room temperature formability” Scripta Materialia Vol. 138, page 151 doi: 10.1016/j.scriptamat.2017.05.034