TY - JOUR T1 - An Investigation on Mechanical Properties of 42CrMo4 Steel with Tempered Martensite and Ferrite-Bainite-Martensite Microstructure TT - مقایسه خواص مکانیکی ریز‌ساختار مارتنزیت بازگشت داده شده و ریزساختار فریت- بینیت- مارتنزیت در فولاد 42CrMo4 JF - mdrsjrns JO - mdrsjrns VL - 10 IS - 1 UR - http://mme.modares.ac.ir/article-15-8044-en.html Y1 - 2010 SP - 63 EP - 76 KW - 42CrMo Steel KW - Triple Microstructure KW - Yield Strain Effect KW - Cleavage Fracture N2 - This study is concerned with a correlation between the microstructure and mechanical properties of 42CrMo4 steel which was subjected quenched-tempered and step-quenching heat treatment. Quench tempering and step quenching heat treatment produced a tempered martensite and an equiaxed Ferrite-Bainite-Martensite (F-B-M) microstructure, respectively. Tensile test results indicated a yield drop effect in F-B-M microstructure with ferritic matrix. This effect was not observed on the specimens with tempered martensite and F-B-M microstructure with hard phase B-M matrix. This effect can be attributed to dislocation generation in ferrite phase during bainitic and martensitic transformations. Fractographic investigations indicated intergranular cleavage in F-B-M microstructure and micro-void coalescence in tempered martensite microstructure can be attributed to carbide formation in martensitic structure during tempering micro-void coalescence in tempered martensite microstructure M3 ER -