通过粉末冶金热压烧结法制备高压电触头Cu/WCp颗粒增强复合材料,研究WCp颗粒含量(15％和3％,体积分数,下同)对Cu/WCp复合材料的疲劳裂纹扩展行为的影响,并结合SEM进行断口分析;利用原位SEM疲劳裂纹观测系统原位观察微裂纹萌生,分析颗粒对裂纹扩展路径的影响机制.结果表明:在相同应力强度因子幅(ΔK)下WCp含量为15％的Cu/WCp的疲劳裂纹扩展速率大于WCp含量为3％的复合材料;颗粒含量的增加并没有提高复合材料的裂纹扩展门槛值ΔKth,这主要是因为颗粒和基体的界面属于弱界面;在疲劳过程中颗粒脱粘形成裂纹源,不同脱粘微裂纹连接长大形成主裂纹是Cu/WCp颗粒增强复合材料的疲劳损伤形式;当主裂纹尖端和颗粒WCp相互作用时裂纹基本沿着颗粒界面往前扩展;复合材料的断裂模式从WCp低含量3％时的颗粒脱粘-裂纹在基体里穿晶断裂,过渡为WCp高含量15％时颗粒脱粘-基体被撕裂为主.
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 (AK);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％.
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