Isothermal fatigue and in-phase thermo-mechanical fatigue of a 6061Al/SiC_w

The isothermal low cycle fatigue (IF) at 300°C and in-phase thermo-mechanical fatigue (IP-TMF) with temperature cycling between 150-300°C of a 6061 Al alloy reinforced with 28 vol % SIC_w were studied. Experimental results indicate that IP-TMF shows continuous cyclic softening until failure, while IF loading initially shows several cycles of cyclic hardening followed by cyclic softening till final fracture. A comparison of IF and IP-TMF lives has been made and various damage mechanisms operative under different strain ranges and loading conditions have been explained. SEM micrographs show that the damage processes under both IF and IP-TMF conditions consist of initiation, growth and coalescence of voids in the matrix around whiskers.