Effect of WC_p Content on Fatigue Crack Growth Behavior of Powder Metallurgy Cu/WC_p Composites

Abstract

The high voltage electric contact Cu/WCp particles reinforced composite material was prepared by powder metallurgy hot pressing sintering method.The effect of WCp particle contents (15% and 3%,volume fraction,the same as below) on the fatigue crack growth behavior of Cu/WCp composite was studied and the fracture surface was analyzed by SEM.The observation of the fatigue crack initiation and the influence mechanism of particle on fatigue crack growth was carried out by in-situ scanning electron microscopy (SEM).Results show that the fatigue crack growth rate of Cu/WCp/15p composites is faster than that of Cu/WCp/3p composites at the same stress intensity factor range (ΔK);with the increase of WCp content,the threshold stress intensity factor range ΔKth is not enhanced because the interface of the particles and the matrix are weak.From the results of in-situ SEM observation fatigue crack growth can be seen that the crack source is formed due to the particle debonding during fatigue process,different debonding microcracks connect and grow to form main cracks is the fatigue damage mode of Cu/WCp particle reinforced composites.When the main crack tips encounter WCp particles,cracks propagate forward along the particle interface.The fractographies show that the fracture mode of the composites is from particle debonding-transgranular fracture in matrix at the low content 3% to particle debonding-tear in matrix at the high content 15%.

Keywords

• Cu/WC_p composite
• volume fraction
• fatigue crack growth
• <i>in-situ</i> SEM
• interfacial debonding
• fracture mechanism