Abstract
The effects of La addition on the microstructure, thermal conductivity and mechanical properties of as-cast and as-extruded Mg-3Al-xLa-0.3Mn (x = 1, 3 and 5 wt.%) alloys were studied. The results showed that the thermal conductivity of the alloys increased with the addition of La element, which was due to the formation of the Al11La3 phases by consuming the solute Al and the added La element. The yield strength of the as-cast Mg-3Al-xLa-0.3Mn alloys increased with the increase in La concentration. The thermal conductivity of the as-extruded alloys was lower than that of as-cast counterparts owing to lots of defects generated in the process of hot extrusion deformation, particularly the grain boundaries. The anisotropy of thermal conductivity was discovered in the as-extruded alloys on account of the formation of texture. As the La content increases, the tensile strength and yield strength of the as-extruded alloys decreased gradually. In contrast, the elongation first increased and then decreased, resulting from the combined effect of the texture strengthening and second phase strengthening.
Highlights
Received: 31 December 2021Magnesium (Mg) alloys have wide application potential in the 3C products aerospace, automobile industries owing to their lightweight, superior specific strength, excellent casting performance and high thermal conductivity [1,2,3,4,5]
The eutectic phase in the Mg-3Al-1La-0.3Mn alloy is intermittently distributed along the grain boundaries, and a small amount of granular second phase is dispersed in the grains
The X-ray diffractometer (XRD) spectrums of the as-cast alloys are given in Figure 2, which suggests that all the Mg-Al-La-Mn alloys are composed of α-Mg matrix, Al11 La3 phases, and Mg12 La phases
Summary
Magnesium (Mg) alloys have wide application potential in the 3C products aerospace, automobile industries owing to their lightweight, superior specific strength, excellent casting performance and high thermal conductivity [1,2,3,4,5]. It was reported that the affixion of rare-earth (RE) elements to the Mg-Al alloys gives rise to the Al-RE intermetallic compounds that possess high melting points and good thermal stability, which can enhance the tensile properties and creep resistance at elevated temperatures of the Mg alloys [14,15,16]. Al solute in Mg-Al alloy to form the intermetallic compound Al11 La3 , which has fine lamellar morphology and excellent thermal stability. These Al11 La3 phases can increase the strength and high-temperature performance of the alloys [24,25]. The impact of the La concentration on the microstructure evolution, mechanical properties and thermal conductivity of Mg-3Al-xLa-0.3Mn alloys were discussed, which provided a reference for the research and development of high thermal conductivity and high strength Mg alloys
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