Microstructure of warm rolling and pearlitic transformation of ultrafine-grained GCr15 steel
- School of Materials Science, State Key Laboratory of Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049 (China)
- State Key Laboratory of Rolling Technology and Automation, Northeastern University, Shenyang 110819 (China)
Pearlitic transformation mechanisms have been investigated in ultra-fine grained GCr15 steel. The ultrafine-grained steel, whose grain size was less than 1 μm, was prepared by thermo-mechanical treatment at 873 K and then annealing at 923 K for 2 h. Pearlitic transformation was conducted by reheating the ultra-fine grained samples at 1073 K and 1123 K for different periods of time and then cooling in air. Scanning electron microscope observation shows that normal lamellar pearlite, instead of granular cementite and ferrite, cannot be formed when the grain size is approximately less than 4(± 0.6) μm, which yields a critical grain size for normal lamellar pearlitic transformations in this chromium alloyed steel. The result confirms that grain size has a great influence on pearlitic transformation by increasing the diffusion rate of carbon atoms in the ultra-fine grained steel, and the addition of chromium element doesn't change this pearlitic phase transformation rule. Meanwhile, the grain growth rate is reduced by chromium alloying, which is beneficial to form fine grains during austenitizing, thus it facilitating pearlitic transformation by divorced eutectoid transformation. Moreover, chromium element can form a relatively high gradient in the frontier of the undissolved carbide, which promotes carbide formation in the frontier of the undissolved carbide, i.e., chromium promotes divorced eutectoid transformation. - Highlights: • Ultrafine-grained GCr15 steel was obtained by warm rolling and annealing technology. • Reduction of grain size makes pearlite morphology from lamellar to granular. • Adding Cr does not change normal pearlitic phase transformation rule in UFG steel. • Cr carbide resists grain growth and facilitates pearlitic transformation by DET.
- OSTI ID:
- 22403556
- Journal Information:
- Materials Characterization, Journal Name: Materials Characterization Vol. 95; ISSN 1044-5803; ISSN MACHEX
- Country of Publication:
- United States
- Language:
- English
Similar Records
MICROSTRUCTURE IN ADIABATIC SHEAR BANDS IN A PEARLITIC ULTRAHIGH CARBON STEEL
First semi-annual progress report on development of superplastic steel processing: A joint R and D effort between industry and a national laboratory: Caterpillar Inc. , Peoria, IL; Ladish Co. , Inc. , Cudahy, WI; North Star Steel Company, Monroe, MI; Lawrence Livermore National Laboratory, Livermore, CA