Analysis of the Effects of Al on the Ductile-to-Brittle Transition Behavior of Ferritic Heat-Resistant Stainless Steels

The effect of Al content on the microstructure and ductile-brittle transition temperature (DBTT) of 18Cr–Al–Si ferritic heat-resistant stainless steel have been studied by Charpy impact testing over temperatures ranging from 20 to 90 ℃. Charpy impact test results show that DBTT increased with increasing Al content. Meanwhile, fracture morphology changed with increasing Al content, where the amount of dimples decreased and cleavage facets increased, indicating increases in the tendency for brittle fracture. Furthermore, ferrite grain size, volume fraction and size of (Cr, Fe)23C6 carbides increased with increasing Al content, which led to decreasing toughness and increasing DBTT.