Fatigue Behavior of Ultrafine-Grained Medium Carbon Steel with Different Carbide Morphologies Processed by High Pressure Torsion

Metals

Christoph Ruffing¹  Aaron Kobler²  Eglantine Courtois-Manara²  Robby Prang²  Christian Kﲾl²  Yulia Ivanisenko²  Eberhard Kerscher¹ 

[1] Materials Testing, University Kaiserslautern, Gottlieb-Daimler-Straße, 67663 Kaiserslautern, Germany; E-Mail:;Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany; E-Mails:

关键词: severe plastic deformation;    high pressure torsion;    fatigue;    carbide morphology;    shear bands;    high strength steels;    microstructure;    fracture surface;   

DOI  :  10.3390/met5020891

来源: mdpi

【 摘 要 】

The increased attention ultrafine grained (UFG) materials have received over the last decade has been inspired by their high strength in combination with a remarkable ductility, which is a promising combination for good fatigue properties. In this paper, we focus on the effect of different carbide morphologies in the initial microstructure on the fatigue behavior after high pressure torsion (HPT) treatment of SAE 1045 steels. The two initial carbide morphologies are spheroidized as well as tempered states. The HPT processing increased the hardness of the spheroidized and tempered states from 169 HV and 388 HV to a maximum of 511 HV and 758 HV, respectively. The endurance limit increased linearly with hardness up to about 500 HV independent of the carbide morphology. The fracture surfaces revealed mostly flat fatigue fracture surfaces with crack initiation at the surface or, more often, at non-metallic inclusions. Morphology and crack initiation mechanisms were changed by the severe plastic deformation. The residual fracture surface of specimens with spheroidal initial microstructures showed well-defined dimple structures also after HPT at high fatigue limits and high hardness values. In contrast, the specimens with a tempered initial microstructure showed rather brittle and rough residual fracture surfaces after HPT.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.