Effect of SiC particles on fatigue crack growth behavior of spray-formed SiC particulate-reinforced Al-Si alloy composites Li Wei*, Chen Jian, Qiu Wei, Ren Yanjie School of Energy and Power Engineering, Changsha University of Science and Technology, 410004, China * Corresponding author: lwzzgjajie@126.com Abstract Fatigue crack growth (FCG) and closure mechanisms in spray-formed Al-7Si alloy matrix composites reinforced with two different sizes of SiC particles has been studied. The experimental dates demonstrate that the composite containing 4.5μm SiC particles exhibits lower FCG rate and higher threshold stress intensity factor range ΔKth (3.878 a m ΜΡ • ) than the 20μm SiC particles composite(3.630 a m ΜΡ • ) and the unreinforced alloy (3.605 a m ΜΡ • ). The SEM crack path observations show that the extent of micoracking inside in the 4.5μm SiC particles induces higher level of fatigue crack closure, which effectively reduces the crack growth driving force to slow down fatigue crack growth. Crack deflection caused by the SiC particles attributes the lower FCG rate in the 20μm SiC composite to the high levels of roughness-induced crack closure at the low ΔK, then the propensity for the fracture of large SiC particles increased with increasing ΔK resulted in a higher FCG rate in the fast fracture state. Keywords Fatigue crack growth, spray-formed, SiC particulate-reinforced Al-Si alloy composites, closure mechanism, size 1. Introduction The outstanding mechanical, physical, and casting properties of Al-Si–Mg alloys, on the other hand, make them attractive for use in cheaper and lighter engineering components[1]. These composites are produced by several processing methods, such as stir casting, squeeze casting [2], powder metallurgy [3] and spray forming, etc. Amongst these methods, spray forming technique has drawn considerable research interest due to its scope of forming near-net shape product with a reduced number of process steps compared to the powder metallurgy. Apart from this, the process offers advantage of rapid solidification, such as refined equiaxed structure with negligible segregation, extension of the solid solubility limit [4], and wider compositional flexibility. With the engineering application of metal matrix composites (MMCs), the fatigue crack growth behavior will become critical in design, life-prediction and reliability analysis of the components made of these materials. The fatigue crack growth behavior in particle MMCs is very much dependent on a variety of factors, including reinforcement particle volume fraction, particle size, matrix and interfacial microstructure, the presence of inclusions and testing
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