Effect of nano-precipitation on thermal conductivity and mechanical properties of Mg-2Mn-xLa alloys during hot extrusion

Abstract Effect of precipitation on thermal conductivity and mechanical properties of Mg –2Mn-xLa (x = 0, 0.5, 1.5 and 2.5 in wt.%) alloys during hot extrusion is studied. Precipitation during extrusion was analyzed by high-angle annular dark-field imaging (HAADF) technique. Bi-modal distributed nano-scaled α-Mn precipitates were observed. The larger precipitates of 30 nm in size initiated in shape of a rod during pre-heating before extrusion and transformed to round shape during extrusion. The smaller round particles of 10 nm in size precipitated during extrusion. The precipitation of nano-particles significantly increases both mechanical properties and thermal conductivity of the extruded Mg-2Mn-xLa alloys. The increased thermal conductivity is because precipitation of nano-scaled Mn particles consumes solute atoms in the Mg matrix. The mechanical properties and thermal conductivity of the extruded Mg–2Mn-2.5La alloy were: YS of 359 MPa, UTS of 367 MPa, elongation to failure of 3.0% and thermal conductivity of 135W/m·K.