Influence Of Heat Treatment On Mechanicalproperties Of Al-Li Binary Alloys

After adding element Li in Al alloys, the elastic modulus increases and the densitydecreases. While the hardening effect after quenching and aging is ensured to be good.Therefore, the application prospect of the Al-Li alloys in aerospace field is broad because oftheir low density, high elastic modulus, high stiffness and high strength. However, thedetermination of heat treatment technology and the variation of the microstructure andproperties after different heat treatment technology of theAl-Li binary alloy are to be studied.In this work, the Al-1Li alloy is prepared by vacuum induction melting. Themicrostructure of the alloy after different heat treatment technology is observed by opticalmicroscope (OM) and scanning electron microscope (SEM). The hardness and tensileperformance after different heat treatment technology of the alloy were tested and the fracturesurface was investigated by SEM. The optimum heat treatment process was determinedcombined the changes in microstructure and mechanical properties. The conclusions are asfollowing:(1) Al-1Li alloys don’t have age hardening effect; maximum tensile strength is63Mpa, thefracture contains a large number of tough, ductile fracture.(2) Al-2Li and Al-3Li alloys have significant age hardening and strengthening effect, theinitial aging hardness and tensile strength significantly increased, late changes slowly; themaximum tensile strength is162MPa and298MPa.The fracture of Al-2Li alloys contains alarge number of shallow dimples, ductile and brittle fracture mixed; The fracture of Al-3ialloys are like typical sugar, there are secondary cracks and delamination, brittle fracture.(3) As increasing Li content of the alloy hardness and tensile strength significantlyincreased toughness decreased from ductile to brittle fracture transition.