高強度Al-Zn-Mg-Cu系P/M合金押出材のミクロ組織微細化と高速超塑性特性 Microstructure refinement and high strain rate superplasticity of Al-Zn-Mg-Cu P/M alloy extrusions
The effects of thermo-mechanical treatment (TMT) on grain refining and high temperature deformation properties have been investigated for the alloy with chemical composition of Al–9.6Zn–3.0Mg–1.4Cu–0.04Ag–0.4Zr in mass% fabricated by hot-extrusion from rapidly solidified powders The present TMT consisted of aging at 498 K for precipitation of T phase (Mg<sub>32</sub>(Zn, Al)<sub>49</sub>) and subsequent warm rolling at the same temperature. Due to aging up to 7.2 ks at 498 K, extremely fine T phase precipitated homogeneously in the matrix. At the next warm rolling step, those fine precipitates contributed to form the uniform dislocation cell structure with high number density. The microstructure analysis by means of XRD and TEM made clear that their dislocation cell structure recrystallized continuously and transformed to very fine (sub-) grain structure with average size of 0.45 μm at the tensile testing temperature of 718 K. The fine grain structure was stabilized by the distribution of fine Al<sub>3</sub>Zr particles. Thus the high strain rate superplastic behavior realized for the warm rolled specimens after aging at 498 K for about 7.2 ks. On the other hand, the warm rolled specimens after aging at 498 K for the longer time than 18 ks formed a very coarse grain structure and resulted in a poor superplasticity. The reason has been discussed on the basis of discontinuous recrystallization theorem.
軽金属 49(8), 389-394, 1999-08-30
The Japan Institute of Light Metals