Cyclic deformation and fatigue behavior of 7075-T651 Al alloy with a gradient structure

Fully reversed stress-controlled tension-compression fatigue experiments (R = -1) were conducted to study the cyclic deformation and fatigue behavior of 7075-T651 aluminum alloys with and without a surface mechanical rolling treatment (SMRT). The strain amplitude, ratcheting effect, and asymmetric behavior of base metal (BM) and SMRT specimens were analyzed. SMRT specimens showed more remarkable ratcheting effects and tension-compression asymmetry under high stresses. Fatigue tests showed that the fatigue strengths of 7075 Al alloys were increased significantly by the SMRT. Both BM and SMRT specimens presented a failure-mode transition from the intrusions and extrusions failure modes to the Al18Ti2Mg3 constituent phase. The hysteresis loop was utilized to obtain the plastic-strain amplitude. Furthermore, according to the cyclic-deformation behavior combined with the Manson-Coffin law, strain-life evaluation of BM and SMRT specimens under the stress-control is given.

Automated summary

The fully reversed stress-controlled tension-compression fatigue experiments were conducted to study the cyclic deformation and fatigue behavior of 7075-T651 aluminum alloys with and without a surface mechanical rolling treatment (SMRT). Results showed that SMRT significantly increased the fatigue strengths of the alloys, but also led to more remarkable ratcheting effects and tension-compression asymmetry in the fatigue specimens. Additionally, a failure-mode transition from intrusions and extrusions to the Al18Ti2Mg3 constituent phase was observed in both base metal and SMRT specimens.