关键词: stress corrosion cracking;martensite;deformation;AISI 321 stainless steel;boiling 42％ MgCl2 solution

Abstract: Specimens of AISI 321 stainless steel (0Cr18Ni9Ti) of various martensite contents were prepared by the low temperature(－70℃
) elongation method.X-ray diffraction (XRD) and transmission electron micrograph (TEM) techniques were used to study the
phase transition process and its structure.The relationship between deformation-induced martensite and stress corrosion
cracking (SCC) susceptibility of the steel in 42％ (boiling)MgCl2 solution was investigated using the constant load SCC test
with the normalized threshold values.The results reveal that when the α′-martensite content is less than 5％ and also in
the range of 15％—24％, the SCC susceptibility of this material decreases with the increase of α′-martensite
content.However, when the α′-martensite content is in the rang of 5％—15％ and more than 24％, the SCC susceptibility of
this material increases with the increase of the α′-martensite content.The SCC fracture surface of the specimens exhibits a
stepped fracture surface and transgranular stress corrosion fracture surface morphology.

Key words: stress corrosion cracking, martensite, deformation, AISI 321 stainless steel, boiling 42％ MgCl2 solution