Fracture of aluminum and titanium alloys at low temperatures

Conclusions

• 1. Cooling to cryogenic temperatures leads to an increase in the irregularity of the distribution of deformation due to the stress gradient through the section and the bulk stresses in the notch zone.

• 2. Aluminum and titanium alloys undergo ductile fracture at low temperatures. However, at −196 and −269° there is an increase in the percentage of the block structure undergoing brittle fracture in the early stages of fracture (discontinuous flow), which is responsible for the deep cracks in the direction of the main crack or at sharp angles to it in aluminum alloys.

• 3. From the ratio of the work of crack proparation to the work of crack initiation it is possible to determine the variation of the mechanical properties with temperature for aluminum and titanium alloys cooled to −269°. With lowering of the temperature from 20 to −196°, A_p/A_i decreases due to the larger decrease of the work of crack propagation. With lowering of the temperature to −269° this ratio increases for aluminum alloys due to the greater reduction of the work of crack initiation. For titanium alloys A_p/A_i continues to decrease with lowering of the temperature to −269°.