Improved method for generation of hot working process maps of metals

ABSTRACT

A process map is an intelligent way of visualizing material deformation behavior under hot working conditions by encompassing the activation and deactivation of different local mechanisms. Process maps are used by engineers to optimize temperature and strain rate conditions appropriate for the highly efficient hot workability of materials. Although the calculation of process maps is well established, the present model for the analysis of instability breaks down at specific points. This study investigates the divergent behavior of the process map instability component by simplified mathematical calculations. In the mathematical model of the instability parameter, the stable transition point and unstable transition point have been defined in this article. A guide to developing the process map is described in detail with suitable numerical software with practical examples of γ-iron and Fe-5Ni. The proposed methodology provides a robust criterion for the identification of different instability regions explained by corresponding physical phenomena.

COEDITOR-IN-CHIEF:

• Hsiau, Shu-San

ASSOCIATE EDITOR:

• Liu, De-Shin

KEYWORDS:

• Hot working conditions
• process maps
• material deformation
• instability

Nomenclature

DMM	=	Dynamic Material Model
D	=	range of divergent region
G (content)	=	dissipation due to conductive entropy
J (co-content)	=	microstructural dissipation
M	=	strain rate sensitivity
MPa	=	Megapascal
P	=	total power dissipation
TRIP	=	Transformation Induced Plasticity
2-D	=	Two Dimensional
3-D	=	Three Dimensional
σ	=	effective stress
$\dot{\epsilon }\hspace{0.17em}$	=	effective strain rate
η	=	efficiency of power dissipation
$\xi \left(\dot{\epsilon }\right)$	=	instability parameter

Acknowledgments

The authors acknowledge the DAAD/MOST scholarship (Sandwich program) for doctoral candidates from Taiwan,110-2927-I-011-505 funding for sponsoring the stay of Shao-Chen Tseng at IMF TU Freiberg.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.