Fatigue Crack Propagation Behavior of Thermally Degraded SiCp/Al Composites

Abstract

Silicon carbide particle reinforced aluminum 6061 composites (SiCp/Al) with 5 and 10% SiC particle volume fractions as well as aluminum 6061 alloy (AA6061) were used to examine their fatigue crack propagation behavior after degraded by thermal cycling and isothermal exposure. Fracture surfaces were observed under a scanning electron microscope. Thermally cycled specimens (TC-SiCp/Al and TC-AA6061) were prepared through 100 thermal cyclings between 200 C and 300 C and isothermally exposed specimens (IE-SiCp/Al and IE-AA6061) was prepared by isothermal exposure at 300 C for 80 h. Difference of fatigue crack propagation behavior in the IE- and TC-AA6061 was small with increase of stress intensity factor range, iK even if da/dN of the both types of AA6061 were different at the initial stress intensity factor range. Fatigue crack propagation behavior of the IE-SiCp/Al was similar regardless of SiC particle volume fractions. While for the TC-SiCp/Al, fatigue crack propagation behavior was different in the SiC particle volume fractions and to the TC-AA6061. Besides, it notes that there was good relation between exponent m and coefficient C of the Paris equation regardless of thermal cycling and isothermal exposure and SiC particle volume fractions. The relation between m and C could be described as C 1/4 AΘm where constants A and B were 1.668 E-5 and 0.165, respectively.