Relation between Phase Change and Hardness in Cu-Al and Cu-Al-Mn Alloys by Different Cooling Conditions

Abstract

The phases in Cu-Al and Cu-Al-Mn alloys (10.0∼14.5% Al and 0.0∼14.0% Mn) subjected to slow-cooling, air-cooling, oil-quenching and water-quenching have been observed by the use of an optical microscope; and the hardness of the phases tested by Rockwell hardness tester (B scale). The relation between the phase and the hardness in their alloys has been investigated in detail.
The main results obtained are as follows:
(1) The appearance of filamental α phase increases the hardness of the alloys.
(2) The maximum hardness will be reached within the range of appearance of the filament α phase, and migrates to lower Mn content with the increase of Al content.
(3) The maximum migrates to the lower content of Al or Mn, with the increase of the cooling rate.