TRANSFORMATION BEHAVIOR OF RAPIDLY QUENCHED 3008 ALUMINUM ALLOY.

The defect structure and transformation characteristics of rapidly quenched 3008 aluminum alloy (Al-Mn-Zr) are investigated by TEM and selected area electron diffraction. Solution treatment in the solid state followed by quenching of the alloy leads to the formation of a high density of prismatic dislocaton loops; the insoluble particles, present after this treatment, are identified to be orthorhombic Al//6Mn. The microstructure of the rapidly quenched alloy is characterized by elongated grains, some of which reveal a high concentration of dislocation loops and tangles. Insoluble particles are rarely observed. Heating the thin foils in the hot stage of the electron microscope results in the formation of fine precipitate particles at approximately 693 K. Heterogeneous nucleation of precipitates on grain boundaries and dislocations is commonly observed. The particles present inside the grains, and identified as Al//6Mn, are mainly in the form of plates and needles.