Effect of cryogenic environment on tensile property and microstructure evolution of an Al-Mg-Sc alloy

The tensile behavior of an Al-6.0 Mg-0.4Mn-0.25Sc-0.10Zr alloy was studied in the temperature range of-196 degrees C (liquid nitrogen temperature, LNT) similar to 25 degrees C (room temperature, RT). The research has found that with the decrease of temperature, the tensile property of the alloy is significantly improved. The work hardening effect is also elevated. The improvement in strength and work hardening effect is attributed to the increase of dislocation density and the fraction of low angle boundary angles (LAGBs), which can enhance the resistance of dislocations movements and the grain boundary strengthening effects. The increase in elongation is due to the inhibition of dislocation cross-slip during cryogenic deformation, which alleviates the local stress concentration and leads to a more uniform deformation. In addition, when deformed at a lower temperature, dislocations tend to accumulate in the grains. The intragranular strength increases faster than the grain boundary strength as the temperature decreases. As a result, fracture mechanism gradually changes from transgranular fracture to intergranular fracture. At -150 degrees C, the alloy shows apparent characteristics of intergranular fracture.