Microstructure of Al-12Al 4 C 3 material 

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... dispersion strengthened alloys Al-Al 4 C 3 prepared by mechanical alloying using powder metallurgy technology are promising structural materials enabling significant cuts of weight for use first in aircraft and car industry, also at elevated temperatures [1 – 3]. We have described in work [4] the optimised production technology by mechanical alloying. In work [5] the mechanical properties and plasticity at elevated temperatures were analysed. In [6] the high temperature stability of this alloy is described for long time exposition. In [7] the changes in microstructure were observed and analyzed after deformation at elevated temperatures, and in [8] the mechanism of fracture in creep were studied. In [9, 10] was described the model of “in-situ” fracture mechanism of these materials. Kinetics and mechanism of superplastic deformation of Al alloys are analyzed in works [11 – 16]. In the present work we analyze the fracture at different strain rates and temperature. Temperatures from 20 to 400 °C and strain rates from 2.5·10 –5 to 10 –1 s –1 had been used. Considering the results reported in [17] and the strain induced coefficient m ranging from 0.03 to 0.06 we have covered the strain rates from creep to the activation of superplastic behavior. The Al-Al 4 C 3 composite dispersion strengthened by 12 vol.% of Al 4 C 3 , has been prepared by the method of mechanical alloying. The milling of the Al powder grain size under 100 μ m with 1 % of KS 2.5 graphite lasted 90 minutes. Granulate was compacted under the pressure of 600 MPa and annealed at 550°C with a 94 % reduction. The dispersed particles are oriented in layers in the direction of extrusion, Fig. 1. The effective size of the particles as measured on the foils was 25 × 85 nm. ...