Awaiting Activation edited begin_itemize_The_other_process__.tex  over 8 years ago

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\begin{itemize}  The other process is when $\alpha$ forms around the boundary of $\beta$. This process occurs when $\beta$ is slowly cooled. However this process also contribute to yield stress of titanium , though to a smaller extent. this is because the formation of $\alpha$ around boundary are large particles and are prone to plastic deformation and subsequent cracking. This kind of $\alpha$ formation only provides boundary hardening but does not prevent dislocation from moving through the grains. This mechanism can be used to control the toughness after precipitation hardening described above. A two stage annealing process can be used to nucleate $\alpha$ particle on the boundaries of $\beta$ matrix and the second stage can be used to increase grain size until desired hardenability is obtained.  \begin{itemize}  \itemProcess: \item Process:  Obtaining $\alpha$ by Slow Cooling In order to obtain $\alpha$ phase titanium is heated above the $\beta$ transus temperature and slowly cooled to the $(\alpha +\beta )$ phase field. During this transition the $\alpha$ phase forms around the grain boundaries of the $\beta$ phase creating a continuous layer of $\alpha$ around $\beta$ grains. When cooled the $\alpha$ either continue forming the plate or grow into $\beta$ grain as parallel plates until meeting another $\alpha$ colony.