Effects of B Addition on Precipitation Behavior of β Phase in Al–Mn–Mg–B Alloys

Abstract

In order to investigate the effect of boron on the precipitation behavior of β phase in Al–Mn–Mg–B alloy used as a material for cask baskets, 1.00 × 10⁴ hours aging treatment was carried out focusing on the temperature history in the cask as in the previous report, and the Time-temperature-precipitation diagram and Supersaturation-diffusion length-precipitation diagram were evaluated using the change tendency of the specific resistance obtained. In the Al–Mn–Mg–B alloy, although grain refinement by AlB₂ was confirmed, the effect of boron addition on the precipitation rate of β phase was hardly recognized. That is to say, it was confirmed that the grain boundary and the interface between B compounds and matrix phase hardly contributed as nucleation sites of β phase. In conclusion, it is considered that the reduction of the solid solution Mg content in the Al–Mn–Mg–B alloy does not occur even after 60 years if the Mg content is 1.0 mass% as in the Al–Mn–Mg alloy.

 

This Paper was Originally Published in Japanese in J. Japan Inst. Light Metals 72 (2022) 691–701.

Fig. 12 SLP diagram. The double-dotted lines indicate the standard lines for 60 years as hypothetical conditions of the thermal history in the casks which were calculated at constant temperatures. The filled circles indicate the representative conditions from 50 to 125°C (in steps of 25°C).