Effect of Test Temperature on Fatigue Behaviour in AC4CH Cast Aluminium Alloy
Effect of Test Temperature on Fatigue Behaviour in AC4CH Cast Aluminium Alloy
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试验温度对AC4CH铸造铝合金疲劳行为的影响
DOI：
10.2472/jsms.55.199
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
Y. Uematsu
中科院分区：
文献类型：
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作者：
Y. Uematsu
采用铸造铝合金AC 4CH平板试样，在室温、室温和室温三种不同温度下进行了全反向轴向疲劳试验。利用复型技术详细研究了150°C（423 K）和250°C（523 K）下的裂纹萌生和小裂纹扩展过程。在150°C和250°C下，疲劳强度几乎与室温下相同或显著低于室温下，分别以疲劳比σ/σB表征的疲劳强度在高应力区的所有温度下均相同，但在低应力区的250°C下略低。裂纹总是从室温下的铸件孔隙开始，而在高温下由于滑移变形引起的裂纹萌生成为主导。在250°C时，由于滑移变形，大量裂纹萌生，主裂纹与其它裂纹的合并非常频繁，特别是在低应力区。在固定的最大应力强度因子，Kmax，小裂纹扩展速率更快，随着试验温度的升高。当用Kmax/E（E：弹性模量）表征时，裂纹扩展速率在室温下变得相似。和150°C，但在250°C时仍然更快。结果表明，在250°C下，这种增强的裂纹扩展归因于主裂纹和其他裂纹的最频繁的合并，导致在该温度下的最低疲劳强度。
Fully reversed axial fatigue tests were conducted using plate specimens of a cast aluminium alloy, AC4CH, at three different temperatures of room temperature (R.T.), 150°C (423K) and 250°C (523K), and crack initiation and small crack growth were studied in detail by means of replication technique. At 150°C and 250°C, fatigue strength was nearly the same as, or significantly lower than, at R.T., respectively. The fatigue strength characterized in terms of fatigue ratio, σ/σB, was the same at all temperatures in high stress region, but slightly lower at 250°C in low stress region. Cracks invariably initiated from a casting porosity at R.T., while crack initiation due to slip deformation became dominant at elevated temperatures. At 250°C, a number of cracks were initiated due to slip deformation and the coalescence of the main crack and other cracks occurred very frequently, particularly in low stress region. At a fixed maximum stress intensity factor, Kmax, small crack growth rates were faster with increasing test temperature. When characterized in terms of Kmax/E (E : Elastic modulus), crack growth rates became similar at R.T. and 150°C, but still faster at 250°C. It was indicated that such enhanced crack growth at 250°C was attributed to most frequent coalescence of the main crack and other cracks, resulting in the lowest fatigue strength at this temperature.