Initiation and Growth Behavior of Small Fatigue Cracks in Ultra Fine-Grained P/M Aluminum Alloys
Initiation and Growth Behavior of Small Fatigue Cracks in Ultra Fine-Grained P/M Aluminum Alloys
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超细晶粒粉末冶金铝合金中小疲劳裂纹的萌生和扩展行为
DOI：
10.2472/jsms.53.526
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
M. Jono
中科院分区：
文献类型：
--
作者：
A. Sugeta;Y. Uematsu;Soichi Nakamura;M. Yasuda;M. Jono
研究了两种超细晶粉末冶金铝合金的疲劳小裂纹萌生和扩展行为。根据化学成分和制造工艺，将这两种材料分别命名为M型和S。挤压不加硅的M型，锻造含硅的S型。粉末的形状随着制造工艺的不同而发生变化，其中M型细长粉末的长径比大于S型细长粉末的长径比。进行了反向平面弯曲疲劳试验，并用塑性复型技术观察到了细小的疲劳裂纹。研究了试件取向对两种材料疲劳性能的影响。结果表明，疲劳小裂纹萌生于C-C取向的夹杂物和C-C取向的粉末界面，C-C取向的粉末在C-L取向的粉末界面处萌生，而在S型的疲劳裂纹萌生于晶界处，而与样品的取向无关；S-N曲线与裂纹萌生方式有关，根据应力幅值和夹杂物或粉末团簇的大小计算的Kmax可以很好地估算裂纹萌生寿命。疲劳裂纹扩展行为与材料和试件取向几乎无关。
Small fatigue crack initiation and growth behavior were investigated for two kinds of ultra fine-grained P/M (Powder Metallurgy) aluminum alloys of which grain size was from 200 to 500nm. Those two materials were denoted as Types M and S according to the chemical composition and manufacturing process. Type M without Si addition was extruded, while Type S with Si was forged. The shape of powders changed through manufacturing processes, where the aspect ratio of elongated powders in Type M was larger than that in Type S. Reversed plane bending fatigue tests were conducted and small fatigue cracks were observed by means of plastic replicas technique. The effect of specimen orientation on fatigue properties in those two materials was also investigated. The specimen orientations evaluated were C-C and L-C for Type M, and C-C and C-L for Type S. It was found that small fatigue cracks initiated at the inclusions for C-C orientation and at the boundary between powders for C-L orientation in Type M, while they initiated at the boundary regardless of specimen orientation in Type S. S-N curves were dependent on the crack initiation mode, and the crack initiation life was well estimated by Kmax calculated with stress amplitude and the size of inclusions or cluster of powders. The fatigue crack growth behavior was almost irrelevant to the materials and specimen orientations.