Effects of constraint and strain path on evolution of ultrafine grained microstructure by multi-axial alternative forging

For the formation of ultrafine grain in Al alloys, various means have been investigated based on a process of continuous recrystallization using a high-strain technique that employs rigorous plastic working. However. utilization for practical application is difficult for small specimens that require constraining. In this study the effects were studied of the use of constraining die walls in the multi-axial alternative forging process (MAF) on the formation of ultrafine grams and microstructural homogeneity This technique has possible for scaling up to a practical scale. Our results showed that tensile strength and yield stress in these fabricated materials were tripled over those of the initial materials when strain was applied. The average grain size after strain application was 0.5 mu m. We conclude that a loading technique that uses different applied directions is the key determinant in creating ultrafine grains.