Abstract
The effect of addition of boron or simultaneous additions of boron and titanium on the recrystallization behaviour of cold rolled Al, Al-2%Mg and Al-2%Cu alloys has been studied by means of hardness measurement and microscopy. The results obtained were as follows: (1) The recrystallization temperature in Al and Al-Mg alloy lowered gradually in a slight degree with the increase of the amount of alloying boron till the content reached a certain critical amount, as shown in Table 2. When the content of boron is larger than this critical value, however, the recrystallization temperature becames almost constant. (2) The size of the recrystallized grains become progressively finer with addition of more boron till the content reaches 0.04∼0.05% in Al, Al-Mg and Al-Cu alloys, and also about 0.01% in Al-Ti alloy. In the specimens with boron of more than this content, however, the recrystallized grains are fairly fine and almost constant against the change of final annealing temperature as well as cold-rolling reduction of more than medium degree, also free of influence from the variation of the preliminary annealing temperature. (3) A simultaneous addition of boron and titanium together refines the recrystallized grains of Al more than the addition of boron alone. (4) The recrystallization diagrams for Al-B, Al-Mg-B, Al-Cu-B and Al-Ti-B alloys have been determined, as shown in Fig. 3, Fig. 4, Fig. 5 and Fig. 6.
