اثر مورفولوژي مارتنزيت بر خواص خستگي فولادهاي دوفازي بعد از پيش كرنش در دماهاي پيركرنشي ديناميكي

The effect of martensite morphology on fatigue properties of Dual-phase steels after pre-strain at dynamic strain aging temperatures

A C-Mn low carbon steel was subjected to intercritical annealing to produce ferritic-martensitic dual-phase (DIʹ) steels with different morphologies of martensite, using different heat treatment cycles. To investigate the effect of dynamic strain aging (DSA) on mechanical properties, tensile specimens were deformed 3% at 573 K. Room temperature tensile tests of deformed specimens at DSA temperature range showed that both yield and ultimate tensile strengths increased, while total elongation decreased. The yield and tensile strengths increments were larger for fibrous morphology. The results of fatigue tests also showed that, fatigue strengths at 10(7) cycles were increased after pre-strain in the DSA temperature range. The effects of morphology of martensite on mechanical properties also discussed. Fracture surfaces studies were done, using SEM.