摘要：Tempered martensite embrittlement (TME) was investigated in an electroslag remelted (ESR) aeronautical grade SAE 4340 steel. The Charpy - V impact, plane strarn fracture toughness (K1") and energy crack zero (ECo) tests were employed to evaluate the reduced toughness of 300"C as compared with 200"C-tempered specimens after fracture in the temperature range from - 70'C to + 150"C. The ECo and Charpy - V results were comparable. The K1. test, however, failed to detect TME, even though a fatigue precracked specimen was used as in the ECo test. This discrepancy between the two tests is attributed to the different rnfluence of a microtough zone a few pm thick at the crack tip. Caution is therefore advised in the conversion of ECo values to their K6 equivalents.
