Effect of thermo-mechanical treatment on ductile-brittle transition behavior of chromium

High purity chromium powders were sintered into a block by means of hot isostatic pressing. Pieces taken from the sintered block were thermo-mechanically treated, i.e., repeatedly rolled at 973 K up to 50 and 85% in total reduction with and without intermediate annealing at 1273 K. The ductile-brittle transition temperature, DBTT, was determined by a tension test with the specimens cut from the as-sintered block and the rolled sheets. DBTT for the specimen rolled without intermediate annealing was about 600 K, while DBTT of the specimen rolled with the annealing was 400 K much lower than the above temperature 600 K and the temperature 500 K which was found in the as-sintered material. The reduction in DBTT through the thermo-mechanical treatment probably comes from the decrease of susceptibility to the occurrence of brittle fracture at grain boundaries.