Role of Elastic Stress on the Precipitate in Al-Cu Alloy and the Corresponding Modeling

There are three variants of precipitate in Al-Cu alloy. Many researchers assumed that the external stress was parallel to or perpendicular to the precipitate; however, the external stress may have a certain angle with the precipitate for some aluminum alloys. Therefore, a new model was proposed in this paper with the consideration of the angle between precipitate and stress, by which we can determine the stress orientation effect of the precipitate. Transmission electronic microscopy (TEM) and scanning transmission electronic microscopy (STEM) were employed to analyze the precipitate in the aged Al-4Cu alloy under applied stress. The results show the stress orientation effect of GP zones and theta " phase are existent. The new model was used to analyze the external stress orientation effect. This model is simple to ascertain whether there is stress orientation effect.