Al-Li alloys have the combined advantages of high strength and high modulus in addition to a lower density than typical structural aluminum alloys. This combination of properties could be used to reduce the weight of aircraft by about 10% without loss of structural integrity. The mechanical properties of these alloys strongly depend on the morphology of the precipitates within the matrix. Therefore, quantitative NDE techniques for on-line monitoring of microstructural changes during the production of these alloys is desirable from both a quality and economic standpoint. Correlations between mechanical properties, of interest to the designer, and data, resulting from NDE measurements, are reported. Of particular interest is the detection of the T1 phase which is detrimental to the fatigue properties of such alloys. The results reveal that the appearance of T1 can be detected by the combined use of eddy current (or DC conductivity) and hardness measurements. The presence of T1 was verified by transmission electron microscopy (TEM).
Available at: http://works.bepress.com/david_jiles/16/