Fatigue performance of dual‐phase steels for automotive wheel application

Abstract

AbstractFatigue performance of ferrite–martensite (FM) and ferrite–bainite (FB) dual‐phase (DP) steels used in automotive wheels has been compared in terms of (i) high‐cycle fatigue performance and failure mechanisms and (b) low‐cycle fatigue performance (Δεt/2 = 0.002 to 0.01) and associated deformation mechanisms. FBDP steel exhibits moderately better high‐cycle fatigue performance, owing to delay in microcrack initiation. In FBDP steel, microcracks initiate predominantly along ferrite grain boundaries, while that at FB interface is significantly delayed in comparison with FMDP steel, where few microcracks appear at FM interface even below the endurance limit. During low‐cycle fatigue, however, FMDP steel performs considerably better than FBDP steel till Δεt/2 ≤ 0.005 attributed to initial cyclic hardening, followed by cyclically stable behaviour exhibited by FMDP steel. In sharp contrast, at all Δεt/2 > 0.002, FBDP steel undergoes continuous cyclic softening. The latter may cause undesirable deformation of wheels in service.