Journal Published Online: 18 June 2019
Volume 8, Issue 5

Hot Workability and Microstructure Control through the Analysis of Stress–Strain Curves during Hot Deformation of M350 Grade Maraging Steel

CODEN: MPCACD

Abstract

The ultrahigh strength (2,400 MPa) 18Ni maraging steel (M350 grade) is widely used for critical structural applications, such as aircraft landing gears, in which the strength–toughness balance is the essential criterion for material selection. Microstructure control during thermomechanical processing is the key to obtain the desired mechanical properties on a repeatable basis in a manufacturing environment. This involves thorough understanding of the hot deformation behavior under a wide range of temperatures and strain rates to map the microstructural evolution as a function of process parameters to obtain defect-free products. Towards achieving this goal of optimization of hot workability with a view to control microstructure for M350 grade maraging steel, hot deformation processing maps have been developed and correlated to the microstructure evolved. Further, analysis of stress–strain curves was carried out to obtain fine prior austenite grain (PAG) size via discontinuous dynamic recrystallization, and the same was verified experimentally by the microstructures evolved through hot isothermal compression tests on cylindrical specimens subjected to different strain levels. A single peak DRX type σ − ε curve was selected for analyses. The theoretically determined critical strain value was verified experimentally for initiation of DRX (DRXI) and transition from DRX dominant region to grain growth dominant region (DRXT). Hot isothermal compression tests have been conducted at T = 950°C and ε˙=0.01s1 and obtained PAG size of 3.14 µm in the specimen deformed to theoretically determined optimum strain of 0.74, thereby validating the used models.

Author Information

Syed Ansari, S.
Department of Materials Science and Engineering, Indian Institute of Technology Gandhinagar, Gujarat, 382355, India
Chakravarthi, K. V. A.
Materials and Metallurgy Group, Vikram Sarabhai Space Center, Kerala, India
Narayana Murty, S. V. S.
Materials and Metallurgy Group, Vikram Sarabhai Space Center, Kerala, India
Nageswara Rao, B.
Department of Mechanical Engineering, Koneru Lakshmaiah Education Foundation, Guntur, Andhra Pradesh, India
Mukhopadhyay, J.
Department of Materials Science and Engineering, Indian Institute of Technology Gandhinagar, Gujarat, India
Pages: 16
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Details
Stock #: MPC20190030
ISSN: 2379-1365
DOI: 10.1520/MPC20190030