Influence of microstructure on the Young's modulus in a Cu-2Be (wt%) alloy

Abstract

The influence of microstructure on the Young's modulus and hardness in a Cu-2Be (wt%) alloy was analyzed. The material was homogenized at 1113 K and submitted to thermal aging at different times and temperatures between 540 and 680 K. The improvement of the mechanical properties of the material, with an increase of the hardness and Young's modulus is mainly due to the formation of metastable phases in the α matrix. For temperatures up to 623 K, the formation of γ″ precipitates produces an increase of the hardness in an early stage. At 676 K, the maximum hardness is reached for 0.75 h due to the presence of γ′ phase, and further aging times induce a softening of the material. The Young's modulus curves present a similar behavior respect to the hardness curves. However, no significant variation of the modulus was found for aging longer than 1 h at 676 K. Then, only the size and shape and not the change in the orientation of the precipitates would have influence on the value of the modulus. A micromechanical model was applied, and the volume fraction curves of precipitates were estimated from E modulus. For the aging temperature of 676 K and times longer than 1 h, the modulus is almost constant because there is no increase in the fraction of precipitates and their maximum volume fraction is reached.