Observations about tempered martensite embrittlement

Abstract

An investigation on the embrittlement of tempered martensite has been carried out with AISI 4340 steel using the static torsion and bending tests together with the instrumented Charpy tests. After the mechanical tests, the specimens were studied by scanning electron microscope. It was observed that in Charpy tests the use of energy was minor when the fracture spread out in the test specimen especially after annealing at tempered martensite embrittlement region. Based on the test results the idea was presented that at the embrittlement region the fracture is not critical, instead the point where dτ/dtgγ becomes negative.