Study on Ultrasonic Fatigue Fracture of Fe-Cu-Mn-C Sintered Material

Abstract

The present work studied the ultrasonic fatigue fracture of the partially pre-alloyed Fe-Cu-Mn-C powder metallurgy steel fabricated by die-wall lubricated warm compaction. The microstructure and ultrasonic fatigue fracture behaviour were analyzed. A mathematical model was established to solve the fatigue crack growth process. Results indicate that the Fe-2Cu-0.5Mn-1C sintered material has good mechanial properties. The fatigue crack initiates at large pore cluster near the surface of sample, and the ultrasonic fatigue striations have been observed near crack source area. The crack source area is divided into several small regions: the micro fatigue source area, crack growth area and fast fracture area. In addition, if the material breaks at 10⁷ times of cycles loading in fatigue tests, the crack stabe growth stage accounts for about 8.3×10⁵ cycles, which is only a small part of the whole ultrasonic fatigue fracture process. The cycle times of crack stabe growth stage is inverse proportion to the square of the stress.