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研究了一种SiCp及Al2O3w增强铸态混杂金属基复合材料(MMC)的疲劳裂纹扩展(FCG)机理,同时对比研究了Al2O3w增强铸态金属基复合材料和铸态铝合金的疲劳裂纹扩展机理。在研究近临界和裂纹稳定扩展区域的疲劳裂纹扩展(FCG)机理时,发现混杂MMC的临界应力强度因子?Kth值高于其他两种材料的?Kth值,说明应力强度因子?K值较低时混杂MMC可以更好地抵抗裂纹扩展。随着?K值的降低,两种MMC在近临界区域显示出相似的FCG机理,即主要由增强相–基体界面的剥离控制,随后由铝基体中空隙的形核与合并控制;在裂纹稳定或中等扩展区域,?K值较高时FCG除了受界面上周期性裂纹扩展引起的增强相–基体界面剥离的影响之外,还显著受到铝基体中疲劳条带的影响。此外,在高?K值下,因为局部失稳断裂机制,可见铝基体中空隙的形核与合并以及SiCp和Al2O3w中的穿晶断裂。对于铸态铝合金,在低?K值下,FCG主要受空隙的形核与合并所控制;在高?K值下,FCG主要受铝晶粒的疲劳条带控制,随后受Si团簇中空隙的形核与合并控制。
A mechanism of fatigue crack growth (FCG) of SiCp and Al2O3w reinforced cast MMCs was studied. The fatigue crack growth mechanism of Al2O3w reinforced MMCs and cast aluminum alloys was also studied. When studying the mechanism of fatigue crack growth (FCG) in the near-critical and crack-steady extended regions, it is found that the critical stress intensity factor (Kth) of hybrid MMC is higher than that of the other two materials, indicating that the value of stress intensity factor When mixed MMC can better resist crack growth. With the decrease of K value, the two MMCs showed a similar FCG mechanism in the near-critical region, ie controlled mainly by the exfoliation of the enhanced phase-matrix interface, followed by the nucleation and incorporation of voids in the aluminum matrix, Or moderately extended region. At higher values of K, FCG is significantly affected by the fatigue band in the aluminum matrix in addition to the enhanced phase-matrix interface delamination caused by the periodic crack growth at the interface. In addition, at high K values, nucleation and consolidation of voids in aluminum matrix and transgranular fracture in SiCp and Al2O3w are visible due to local destabilizing fracture mechanisms. For as-cast aluminum alloys, FCG is dominated by the nucleation and merging of voids at low K values; at high K values, FCG is dominated by the fatigue banding of aluminum grains, followed by Si clusters Gap nucleation and merge control.