High temperature low cycle fatigue and thermo-mechanical fatigue of a 6061Al reinforced with SiCW

The high temperature isothermal low cycle fatigue (IF) and thermo-mechanica l fatigue (TMF) of a 6061Al alloy reinforced with 28 vol.% silicon carbide whiskers were studied. IF experiments were conducted at a temperature of 30 0 degrees C, and two types of TMF tests, i.e. in-phase (IP) and out-of-phas e (OP), were performed with temperature cycling between 150 and 300 degrees C. All experiments were carried out under mechanical strain range control. Experimental results of mechanical behavior and mean stresses for TMF and IF loadings are provided. It can be seen that both IP and OP-TMF show conti nuous cyclic softening until failure, while IF loading initially shows seve ral cycles of cyclic hardening followed by cyclic softening until final fra cture. A comparison of TMF and IF lives has been made and various damage me chanisms operative under different strain ranges and loading conditions hav e been explained. SEM micrographs show that damage processes under both IF and TMF conditions consist of initiation, growth and coalescence of voids i n the matrix around whiskers. Due to the complexity of the relationship bet ween IF and TMF damage: IF data cannot be used to evaluate TMF life. (C) 20 00 Elsevier Science S.A. All rights reserved.