Al-Li-Mg合金の極低温における機械的性質の温度依存性

抄録

Temperature dependence of tensile properties and fracture morphorogy were investigated in the temperature range from 7 to 293K for the as-quenched and peak-aged specimens of Al-2 mass%Li-0, 1, 2 mass%Mg alloys. The increase in the proof stress with decreasing temperature in the as-quenched specimens was explained in terms of the short-range interactions between dislocations and the solute atoms, whereas the small temperature dependence of the proof stress in the peak-aged specimens was explained in terms of the long range interactions between dislocations and δ'-Al₃Li precipitates. Constant tensile strength at very low temperatures (<-40K) was due to the grain boundary fracture. The increase in both the elongation to fracture and toughness defined as the work done for fracture with decreasing temperature to about 20K was attributed to the increasing difficultes of cross slip of dislocations as temperature decreased for an Al-Li binary alloy. The decrease in both the properties with decreasing temperature was due to both the acceleration of intergranular fracture and the increase in strain hardening with decreasing temperature. Magnesium addition to Al-Li alloys enhanced both the intergranular fracture and strain hardening, which resulted in the decrease in elongation and toughness with decreasing temperature.