Influence Of The Pressing Temperature:

The pressing temperature is a key factor in use of ECAP because it can be controlled relatively easily. There will be an increase in equilibrium grain size with increasing temperature. Also the fraction of low angle grain boundaries increase with increasing temperature due to the faster rates of recovery at the higher temperature which led to an increasing annihilation of dislocation within the grain and a consequent decrease in the number of dislocations absorbed into the sub grained walls. Although it is easier to press specimens at high temperature, optimum ultra fined grain micro structures will be attained when the pressing is performed at the lowest possible temperature where the pressing operation can be conducted without the introduction of any significant cracking in the billets. By maintaining a low pressing temperature ensures the potential for achieving both the smallest possible equilibrium grain size and the highest fraction of high angle grain boundaries.