Mechanical properties of Al-Li-Cu-Mg-Zr alloy at very low temperatures.

Temperature dependence of tensile strength, ductility, toughness, work-hardenability, the parameter of serrated deformation and fracture morphology were investigated in the temperature range from 7 to 293K for under-aged and peakaged specimens of Al-2.32Li-1.20Cu-0.67Mg-0.12Zr alloy (by weight%). Uniform elongation, reduction of area, work done for fracture are improved significantly as temperature decreases, and the maximum value of each property is achieved at about 20K. The remarkable improvement in these properties is attributed to the remarkable increase in the work-hardenability which is due to increasing difficulties of the cross slip of dislocations as temperature decreases. Therefore, the addition of some elements which decrease the stacking fault energy may cause more improvement in ductility and toughness at very low temperatures. The serrated deformation occurs remarkably below about 20K. The load drop is due to thermally assisted discontinuous glide of dislocations. Disturbance of the uniform deformation which is due to the discontinuous glide of dislocations may be the main cause of the gradual degradation of the mechanical properties below about 20K.

Hali tarjima qilinmagan