THE PHENOMENON OF STRESS INSTABILITIES IN Al-Li BINARY ALLOYS AND MICROSCOPIC MECHANISMS CONNECTEDReport as inadecuate




THE PHENOMENON OF STRESS INSTABILITIES IN Al-Li BINARY ALLOYS AND MICROSCOPIC MECHANISMS CONNECTED - Download this document for free, or read online. Document in PDF available to download.



Abstract : For several years it has been well established that aluminium alloys with lithium additions are very attractive for aerospace applications, since they offer interesting combinations of high specific strength and high specific modulus -1- -2-. Numerous studies were carried out in order to obtain optimum mechanical properties by modifying suitably microstructures -3- -4- -5-. Mechanical properties are mainly dependent on interactions between dislocations and precipitates, especially δ- Al3Li precipitates. Fundamental studies were carried out on Al-Li binary alloys exhibiting only δ- precipitates -6-. We have entered upon a study concerning the identification of microscopic mechanisms which control the cyclic deformation of Al-Li binary alloys. During fatigue tests, we have discovered an interesting substructure in hysteresis loops corresponding to stress instabilities in fatigue behaviour which are rigorously coupled with a strain age hardening phenomenon. The aim of this paper is to describe this phenomenon which is typical of the fatigue behaviour of Al-Li binary alloys with small δ- precipitates. In the last part of this paper, this unstable behaviour is compared to the PORTEVIN-LE CHATELIER PLC phenomenon. In addition, microscopic mechanism that control stress instabilities and strain age hardening are analysed in terms of interactions between dislocations and δ- precipitates.





Author: J. Gentzbittel G. Vigier R. Fougeres

Source: https://hal.archives-ouvertes.fr/



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