Intrinsic factors that trigger the coaxing effect in binary Fe-C ferritic alloys with a focus on strain aging

Motomichi Koyama, Bohong Ren, Nobuyuki Yoshimura, Eisaku Sakurada, Kohsaku Ushioda, Hiroshi Noguchi

研究成果: ジャーナルへの寄稿学術誌査読

7 被引用数 (Scopus)

抄録

The coaxing effect has been recognized as a phenomenon that enhances the fatigue resistance associated with work hardening and strain-age hardening. To uncover the intrinsic factors that affect the degree of coaxing effect, rotating bending fatigue tests including a process of stepwise stress increases every 107 cycles were carried out at ambient temperature in interstitial free steel and binary Fe-C ferritic alloys. The effects of the work hardening capacity, aging time, stress amplitude increment, and carbon concentration were examined in this simple alloy system. The work hardening capacity was changed by controlling carbon state in a Fe-0.017C (wt%) steel. However, the degree of coaxing effect did not show a significant correlation with work hardening capacity. For the effect of aging time, a fatigue test at a high stress amplitude was interrupted, aged for 2 weeks, and subsequently restarted. Although this process is sufficient to induce strain-age hardening in terms of aging time and plastic strain, a fatigue life of the aged steel was not comparable to that with the coaxing effect. Moreover, an increase in stress increment for each step deteriorated a degree of coaxing effect. It was concluded that the effect of work hardening is minor, and the other factors affecting strain-age hardening must be optimized simultaneously to show a coaxing effect. In addition, the degree of coaxing effect of smooth steel specimens was predominantly controlled by the intergranular fatigue crack initiation behavior. Consequently, a considerable amount of solute carbon and an alternate process for the stress amplitude increment and aging time are required for strain-age hardening that suppresses intergranular fatigue crack initiation.

本文言語英語
ページ(範囲)358-364
ページ数7
ジャーナルisij international
57
2
DOI
出版ステータス出版済み - 2017

!!!All Science Journal Classification (ASJC) codes

  • 材料力学
  • 機械工学
  • 金属および合金
  • 材料化学

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