Al-Zr合金の再結晶過程について

抄録

With the object of clarifying the heat resisting mechanism of Al-Zr alloys, the recrystallization process of Al-0.31%Zr alloy was studied by means of the measurements of micro-Vickers hardness, tensile strength, and electric resistivity, and X-ray and electron microscopic observations.
Two typical heat treatments were selected before final cold working; one was quenching after heating at 630°C for 5hrs. (solution heat treatment) and the other was slow cooling after heating at 400°C for 5hrs. (precipitation heat treatment).
The results obtained were as follows.
(1) The recrystallization temperature of the alloy was much improved by the addition of 0.31% of Zr to Al. However, the recrystallization behavior highly depended upon the condition of heat treatment before cold working.
(2) In spite of the precipitation heat treatment at 400°C for 5hrs., most of the soluted Zr atoms were not precipitated in the form of Al₃Zr, but it seemed that their form in the solution state was changed to such as cluster of the atoms or nucleus of Al₃Zr.
(3) The material, which had suffered solution heat treatment, was excellent in thermal stability at lower temperatures below about 300°C, and the material suffered precipitation heat treatment was excellent at higher temperatures.
(4) Solution heat treated material was completely recrystallized with no fine precipitates of Al₃Zr; while, precipitation heat treated material seemed to be extremely resistant to complete recrystallization, owing to subboundary precipitation of Al₃Zr.
Consequently, it may be believed that the heat resisting mechanism of the alloy is attributed to the soluted Zr itself at lower temperatures below about 300°C, and to the precipitates of Al₃Zr at higher temperatures.
(5) The following consideration may be given that the recrystallization process of the alloy is more attributed to the coalescence and growth of subgrains, and the dissipation of subboundaries rather than nucleation and growth mechanism.