November 2020 Volume 2

FORGING RESEARCH AND TECHNOLOGY

Acknowledgments.....................................................................................................................................................................................iii 1.0. Introduction.......................................................................................................................................................................................4 2.0. Materials and Methods......................................................................................................................................................................4 3.0. Results and Discussion.......................................................................................................................................................................7 3.1. As-received Microstructure and Austenite Grain Coarsening.....................................................................................................7 3.2. CCT Diagrams. .........................................................................................................................................................................11 3.3. Microstructural Analysis after Dilatometry................................................................................................................................14 3.3.1. SLM 4340 Steel................................................................................................................................................................14 3.3.2. Wrought 4340 Steel.........................................................................................................................................................15 3.4. Advanced Microstructural Analysis (EBSD-IQ) after Dilatometry............................................................................................17 3.4.1. SLM 4340 UniformContinuous Cooling........................................................................................................................17 3.4.2. Wrought 4340 UniformContinuous Cooling.................................................................................................................19 3.4.3. Reconstruction of Prior Austenite Grain Size (PAGS)......................................................................................................21 3.5. Microstructural Analysis after Hot Compression........................................................................................................................22 3.6. Advanced Microstructural Analysis after Hot Compression.......................................................................................................25 3.6.1. Water Quenched Condition Prior to Deformation...........................................................................................................25 3.6.2. Water Quenched Condition After Deformation..............................................................................................................27 3.6.3. Sv Measurements and KAM factor..................................................................................................................................28 3.6.4. Continuous Cooling Condition after Deformation.........................................................................................................31 4.0. Conclusions........................................................................................................................................................................................35 References.................................................................................................................................................................................................36 Acknowledgments The authors would like to thank Dr. Raymundo Ordonez (Ellwood Materials Technologies), Dr. Graham McIntosh (Universal Stainless), and Dr. Chris Schade (GKN Powder Metallurgy) for their technical support and providing the steels for this study. In addition, special thanks to all the undergraduate students in the Ferrous Physical Metallurgy Group at the Swanson School of Engineering, University of Pittsburgh for their contributions to this work.

FIA MAGAZINE | NOVEMBER 2020 83