tailieunhanh - RECRYSTALLIZATION_2

Recrystallization and related phenomena that occur during thermomechanical processing of all types of crystalline materials are areas of intensive research. However, particular subject matters of research differ depending on scientific discipline. In geology, recrystallization is a process that occurs during natural deformation of rocks and minerals subjected to high temperature and pressure. Grains, atoms or molecules can be packed closer together. Under the influence of these metamorphic processes, new mineral grains can be created in crystalline form. Analysis of the consequences of these processes is often used for quantification in geochronology | 9 Mathematical Modeling of Single Peak Dynamic Recrystallization Flow Stress Curves in Metallic Alloys R. Ebrahimi and E. Shafiei Department of Materials Science and Engineering School of Engineering Shiraz University Shiraz Iran 1. Introduction Deformation of metals and alloys at temperatures above Tm is a complex process in which mechanical working interacts with various metallurgical processes such as dynamic restoration including recovery and recrystallization and phase transformation for polymorphous materials. The understanding of these processes however enables the behavior of the metals and alloys. Recent developments have been described in several review papers. These reviews were in agreement that metals and alloys having relatively low values of stacking fault energy SFE could recrystallize dynamically whereas those of high SFE including bcc metals and alloys which behave in a manner similar to fcc metals of high SFE recovered dynamically only during high temperature deformation. So that according to microstructural evolutions material response can principally be divided into two categories in hot deformation dynamic recovery DRV type and dynamic recrystallization DRX type. The process of recrystallization of plastically deformed metals and alloys is of central importance in the processing of metallic alloys for two main reasons. The first is to soften and restore the ductility of material hardened by low temperature deformation that occurring below about 50 of the absolute melting temperature which leads to lower forces. The second is to control the microstructure and mechanical properties of the final product. The analysis of metal forming process such as hot rolling forging and extrusion has been dependent on various parameters including constitutive relation which contributes to stressstrain curves at high temperatures shape of workpiece and product shapes of tools friction temperature forming speed etc. In such parameters the constitutive .