CAJ | 학술논문

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。
연구료일충SiCp급Al2O3w증강주태혼잡금속기복합재료(MMC)적피로렬문확전(FCG)궤리，동시대비연구료Al2O3w증강주태금속기복합재료화주태려합금적피로렬문확전궤리。재연구근림계화렬문은정확전구역적피로렬문확전(FCG)궤리시，발현혼잡 MMC 적림계응력강도인자?Kth치고우기타량충재료적?Kth치，설명응력강도인자?K치교저시혼잡MMC가이경호지저항렬문확전。수착?K치적강저，량충MMC재근림계구역현시출상사적FCG 궤리，즉주요유증강상-기체계면적박리공제，수후유려기체중공극적형핵여합병공제；재렬문은정혹중등확전구역，?K치교고시FCG제료수계면상주기성렬문확전인기적증강상-기체계면박리적영향지외，환현저수도려기체중피로조대적영향。차외，재고?K 치하，인위국부실은단렬궤제，가견려기체중공극적형핵여합병이급SiCp화Al2O3w중적천정단렬。대우주태려합금，재저?K치하，FCG주요수공극적형핵여합병소공제；재고?K치하，FCG주요수려정립적피로조대공제，수후수Si단족중공극적형핵여합병공제。
The fatigue crack growth (FCG) mechanism of a cast hybrid metal matrix composite (MMC) reinforced with SiC particles and Al2O3 whiskers was investigated. For comparison, the FCG mechanisms of a cast MMC with Al2O3 whiskers and a cast Al alloy were also investigated. The results show that the FCG mechanism is observed in the near-threshold and stable-crack-growth regions. The hybrid MMC shows a higher threshold stress intensity factor range, ?Kth, than the MMC with Al2O3 and Al alloy, indicating better resistance to crack growth in a lower stress intensity factor range,?K. In the near-threshold region with decreasing?K, the two composite materials exhibit similar FCG mechanism that is dominated by debonding of the reinforcement-matrix interface, and followed by void nucleation and coalescence in the Al matrix. At higher?K in the stable-or mid-crack-growth region, in addition to the debonding of the particle-matrix and whisker-matrix interface caused by cycle-by-cycle crack growth at the interface, the FCG is affected predominantly by striation formation in the Al matrix. Moreover, void nucleation and coalescence in the Al matrix and transgranular fracture of SiC particles and Al2O3 whiskers at high?K are also observed as the local unstable fracture mechanisms. However, the FCG of the monolithic Al alloy is dominated by void nucleation and coalescence at lower?K, whereas the FCG at higher?K is controlled mainly by striation formation in the Al grains, and followed by void nucleation and coalescence in the Si clusters.