Tham khảo tài liệu 'handbook of workability and process design part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 34 Ị Introduction Temperature F Temperature C Fig. 28 Finished processing map for the nickel-base superalloy Nimonic API. Obtained by superposition of instability regions determined with Eq 59 with contours of percent efficiency of power dissipation. Shaded region corresponds to conditions of flow instability. Source Ref 25 The DMM methodology describes the dynamic path a material element takes in response to an instantaneous change in at a given T and . As such it is a map that graphically describes power dissipation by the material in stable and unstable ways. These boundaries correspond to safe and unsafe regions on a processing map. The use of the DMM methodology is in its infancy but it appears to be a powerful tool for evaluating workability and controlling microstructure by thermomechanical processing in complex alloy systems . see Ref 24 and Chapter 22 Multidisciplinary Process Design and Optimization An Overview in this Handbook . A major compendium of processing maps has been published Ref 25 . Summary The workability of metals is a complicated subject. Workability is both a material attribute and a process characteristic. The two aspects interact in complex ways. The process establishes the state of stress in the material as well as its temperature strain and strain profile. In addition the process imposes frictional conditions that affect the stress state. The material response to the process environment is expressed by the level of stress needed to deform the material the flow stress and by its propensity for fracture. The flow characteristics can be measured by methods described in Chapter 4 Bulk Workability Testing in this Handbook. Also discussed there are tests expressly designed to evaluate fracture. Most commercial metals are complex alloys that undergo a wide range of structural behavior over the range of strain strain rate and temperature common to deformation processing. These mechanisms of fracture and instability must be understood and .
