Lanthanum effect on improving CTE, damping, hardness and tensile response of Mg-3Al alloy

Abstract

In the present study, Mg-3Al-xLa (x ∼ 1, 2.5, 4) alloys were synthesized using disintegrated melt deposition technique followed by hot extrusion. These alloys were critically investigated for microstructure, tensile and compression properties, damping properties, microhardness and fracture morphology. The grain size of Mg-3Al was significantly reduced by the addition of Lanthanum (La) and it was minimum for 2.5 La-containing alloy (∼5.8 μm, 25% of pure Mg grain size). SEM and X-ray studies revealed the suppression of β-eutectic phase (Mg17Al12) due to the formation of Al11La3, Al2La, and Al2.12La0.88 intermetallic phases. Microhardness increased with the addition of La and it was recorded highest for Mg-3Al-4La (122 Hv). Mechanical characterization results show that the tensile yield strength (TYS), ultimate tensile strength (UTS) and ductility for Mg-3Al-2.5La alloy are the best reported values till date among all the available reports for this system of alloy (TYS ∼ 160 MPa, UTS ∼ 249 MPa and fracture strain ∼22%). Results of damping measurement revealed an increase in damping of Mg-3Al alloy due to the presence of La (2.5%). Compression results show that the addition of La to Mg-3Al caused gradual decrease in compression yield strength and elongation.