Development of Processing Maps for Hot Deformation: Algorithm and Common Errors
- PDF / 1,699,947 Bytes
- 5 Pages / 593.972 x 792 pts Page_size
- 98 Downloads / 291 Views
converted to viscoplastic heat or lattice defects, and the dissipator co-content J relates to power dissipation through metallurgical processes or internal changes such as dynamic recovery (DRV), dynamic recrystallization (DRX), void formation, etc. They can be expressed as follows. G¼
and P. CHAKRAVARTHY
The development of processing maps using the dynamic materials modeling (DMM) approach is a widely used method for choosing the appropriate process parameters for the thermomechanical processing of any material. This paper highlights the correct algorithm for developing the processing map by calculating the metallurgical power dissipation efficiency (g) and the newly proposed binary instability parameter (b). Further, common errors that can arise during the computations, and their consequences are also highlighted. https://doi.org/10.1007/s11661-020-05817-x Ó The Minerals, Metals & Materials Society and ASM International 2020
The mechanical behavior of a material undergoing deformation is characterized by its flow stress (r) which can be related to the process parameters: strain (e), strain rate ð_eÞ, and temperature (T). Being a complex thermomechanical process, only certain combinations of the process parameters would result in an efficient deformation path leading to a defect-free product. The dynamic materials modeling (DMM) approach proposed by Prasad et al.[1] is a widely accepted and useful approach for quantifying the material behavior during hot deformation and obtaining its manufacturing feasibility windows using processing maps. It is based on the principles of continuum mechanics by Zeigler,[2] physical systems modeling by Wellstead[3] and irreversible thermodynamics by Malvern et al.[4,5] According to this model, a material undergoing hot deformation is an energy dissipator with the constitutive property P ¼ r_e, where P is the power dissipated per unit volume. The model further partitions P as P ¼ G þ J, where the dissipator content G relates to power dissipation through plastic work, which is
N. NEETHU and P. CHAKRAVARTHY are with the Department of Aerospace Engineering, Indian Institute of Space Science and Technology, Trivandrum, 695547, India. Contact e-mail: [email protected] Manuscript submitted December 30, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
Z e_ rd_e
½1
e_ dr
½2
0
J¼
Zr 0
The power-partitioning factor between G and J is the parameter m, called strain rate sensitivity which is defined as m¼
@J @ log r ¼ @G @ log e_
½3
For a linear power dissipator, m ¼ 1 leading to power being dissipated in equal parts as J ¼ G ¼ P=2. In this situation, J reaches its maximum, Jmax. Further details are described elsewhere.[1,6,7] The processing map of a material is obtained by superimposing two contour plots called the power dissipation map and the instability map. It provides the best feasible combinations of the process parameters that can be used for the safe processing of the material. The power dissipation map is a contour plot of the metallurgical power dissipation efficien
Data Loading...
