Development of non-flammable high strength extruded Mg-Al-Ca-Mn alloys with high Ca/Al ratio

doi:10.1016/j.jmst.2018.03.019

Abstract

Abstract:

A series of non-flammable high strength Mg-Al-Ca-Mn alloys with high Ca/Al ratio were fabricated by water-cooled casting and hot extrusion. Microstructure and mechanical properties were investigated to study the effect of hot extrusion. The experimental results showed that hot extrusion significantly improved the mechanical properties by grain refinement and precipitates. Ignition temperature was measured by furnace test, and the highest temperature is up to approximately 1040 °C due to the composite oxide layer consisting of CaO and MgO. In addition, a laboratory-scale flame test was conducted to evaluate the flammability of smaller specimens. These alloys exhibited marvelous flame resistance attributed to the protective effect of dense and stable oxide film.

Key words: Magnesium alloys, Extrusion, Mechanical properties, Flammability

Guosong Han, Ding Chen, Gang Chen, Jianghua Huang. Development of non-flammable high strength extruded Mg-Al-Ca-Mn alloys with high Ca/Al ratio[J]. J. Mater. Sci. Technol., 2018, 34(11): 2063-2068.

Figures/Tables 9

Table 1 Chemical compositions of Mg-xAl-xCa-Mn alloys (wt%).

Alloys	Al	Ca	Mn	Mg	Ca/Al
Mg-2.5Al-2.5Ca-Mn	2.61	2.68	0.71	Bal.	1.03
Mg-3.5Al-3.5Ca-Mn	3.79	3.73	0.73	Bal.	0.98
Mg-4.5Al-4.5Ca-Mn	4.50	4.42	0.77	Bal.	0.98

Fig. 1. Optical and SEM images of microstructures of Mg-Al-Ca-Mn alloys: (a) as-cast and (d) as-extruded Mg-2.5Al-2.5Ca-Mn, (b) as-cast and (e) as-extruded Mg-3.5Al-3.5Ca-Mn, (c) as-cast and (f) as-extruded Mg-4.5Al-4.5Ca-Mn.

Fig. 2. XRD patterns of (a) as-cast and (b) as-extruded Mg-Al-Ca-Mn alloys.

Fig. 3. Comparison of mechanical properties for as-cast and as-extruded Mg-Al-Ca-Mn alloys.

Fig. 4. Ignition temperature of Mg alloys by averaging the testing values of repeated measurements.

Fig. 5. Elemental concentration-depth profile of Mg-4.5Al-4.5Ca-Mn alloy after oxidation at 750 °C for 2 h: (a) SEM cross-section image; (b) elemental concentration-depth profile by EDS linear scanning.

Fig. 6. Ignition of (a) sheet and (b) columnar specimen of WE43 following LPG flame exposure. (c) is the residue of columnar specimen after burning.

Fig. 7. Optical and SEM images of un-burnt specimens surface morphologies: (a, d, g) Mg-2.5Al-2.5Ca-Mn; (b, e, h) Mg-3.5Al-3.5Ca-Mn; (c, f, i) Mg-4.5Al-4.5Ca-Mn.

Fig. 8. Optical images of the columnar specimen of Mg-Al-Ca-Mn alloys after LPG flame exposure for 600 s.

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