AbstractsEngineering

Grain refinement is one of the techniques used to improve the newlinemechanical properties of polycrystalline metals Severe plastic deformation newline SPD processes such as equal channel angular pressing ECAP newlineaccumulative roll bonding ARB and high pressure torsion HPT processes newlinehave attracted the attention of the researchers since these processes can reduce newlinethe grain size from microns to several hundred nanometers Ultra fine newlinegrained UFG metals produced by SPD processes show high strength newlineconsistent with the Hall Petch relationship and they also exhibit unusual newlinemechanical properties compared to coarse grained metals for instance a newlinesudden decrease in uniform elongation strain rate sensitivity flow stress and newlineimproved low temperature toughness are improved significantly However newlinethe detailed mechanisms that influence these unusual mechanical properties newlinehave not been fully understood yet newline%%%reference p230-243.