GH4742合金疲勞裂紋擴(kuò)展行為

GH4742合金疲勞裂紋擴(kuò)展行為Fatigue crack growth behavior of GH4742 alloy

研究GH4742合金在室溫、700 ℃及750 ℃的疲勞裂紋擴(kuò)展行為。分析溫度和應(yīng)力強(qiáng)度因子對(duì)疲勞裂紋擴(kuò)展壽命與速率的影響，利用掃描電鏡觀察不同溫度下的疲勞裂紋擴(kuò)展斷口。采用背散射電子衍射(EBSD)技術(shù)分析合金裂紋擴(kuò)展的晶體學(xué)機(jī)制。結(jié)果表明，隨著溫度的升高，合金的裂紋擴(kuò)展壽命降低，裂紋擴(kuò)展速率增加，沿晶斷裂特征更明顯。應(yīng)力強(qiáng)度因子越大，裂紋擴(kuò)展速率越大。在原始大變形晶粒中裂紋以穿晶方式沿著小角度晶界擴(kuò)展，裂紋擴(kuò)展到再結(jié)晶晶界時(shí)以沿晶擴(kuò)展為主，其擴(kuò)展方式取決于相鄰晶粒的面間角和取向差。

The crack propagation behavior of GH4742 alloy was studied respectively at room temperature, 700 ℃ and 750 ℃. Fatigue fracture was observed by scanning electron microscopy (SEM). Effects of temperature and stress intensity factor (ΔK) on crack growth life and rate were studied. The electron back scattering diffraction (EBSD) technique was applied to investigate the crystallographic mechanism of crack propagation. The results show that with the increase of temperature, crack propagation life of the alloy decreases and crack propagation rate increases as well as the intergranular fracture characteristics is more obvious. Crack growth in the original large deformation grain is in a transgranular manner along a low angle boundary. While crack meets the recrystallized grain boundaries, the mode of fracture is mainly the intergranular expansion and the way of crack growth depends on the magnitude of the interfacial angle and the misorientation of adjacent grain plane.

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