Abstract
This paper will summarize the strengthening and toughening behaviors of α+β and β alloys at room temperature. In addition, some considerations on the strengthening capacity and some relationships between microstructures and mechanical properties will be presented.
The strength of α+β alloys can be improved by increasing the volume fraction of the β phase and using an ultra refinement of an equiaxed α structure. On the other hand, the toughness can be improved by adjusting an acicular α structure. The strength of β alloys can be increased by the homogeneous and fine precipitation of the α phase and by the β grain refinement. The toughness of β alloys is usually superior to that of α+β alloys at given strength levels. This is mainly due to the disappearance of the coarse primary α phase in β alloys.
Increases in the strength of smooth, notched and precracked specimens are limited by ductility, notched tensile strength and fracture toughness, respectively. As a result, there is a critical value for strengthening for each specimen. Finally, some guidelines for microstructural modification for optimization of the strength-ductility and strength-toughness balance will be presented.
