EFFECT OF TEST TEMPERATURE ON THE DYNAMIC TORSIONAL DEFORMATION-BEHAVIOR OF 2 ALUMINUM-LITHIUM ALLOYS

The objective of the present study is to investigate the effect of tes t temperature on the dynamic torsional deformation behavior of two Al- Li alloys, i.e., 2090 and 8090 alloys. Dynamic torsional tests were co nducted using a torsional Kolsky bar at room temperature and a low tem perature (-196 degrees C), and the torsionally deformed regions and th e fracture surfaces of the tested specimens were examined. The dynamic properties of the two Al-Li alloys at the low temperature were improv ed, owing to the modification of the deformation behavior. The dynamic deformation behavior at room temperature was dominated by intergranul ar cracks due to planar slips and by crack propagation along the grain boundaries. At the low temperature, plastic deformation proceeded mor e homogeneously as planar slip was prevented. These results indicated that the overall deformation mode of both the Al-Li alloys changed fro m planar slip to homogeneous deformation with decreasing temperature, resulting in the improvement of cryogenic properties under dynamic tor sional loading.