Nano grained Ti–Nb micro alloy steel achieved by Accumulative Roll Bonding (ARB) process

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Nano grainedTi–Nb micro alloy steel achieved by Accumulative Roll Bonding (ARB)process
A.A.Tohidi n, M.Ketabchi,A.Hasannia
Mining and Metallurgical Engineering Department , Amir kabir University of Technology,Tehran,Iran

چکیده مقاله

Over the last decade,nano crystalline and ultra-fine grained(UFG)materials with grain size less than1 μm
have aroused considerable interest due to their superior mechanical properties compared to convention-
ally grained materials.In this work Ti–Nb micro alloy steel was processed by the severe plastic deformation
(SPD)technique called Accumulative Roll Bonding (ARB)in order to produce an ultra-fine grained
micro structure and improve the mechanical properties.After initial preparation to achieve good sheet
bonding,8cycles of ARB at 550 1C were successfully performed.Observation of optical microstructure,
scanning electron microscopy(SEM) micrographs ,and X-Ray Diffraction(XRD) peak broadening analysis
were used for the characterization of grainstructure of the ARB processed sample.The mechanical
attributes after rolling and cooling were examined.It was calculated that metal’s yield and tensile strength
increasedby334%and215%respectively,whiletheductilitydroppedfromas-receivedvalueof34%to2.9%.
Micro hardness of the material was studied at room temperature.There was a continuous enhancement of
hardness by increasing the pass number of the ARB process.At the 8th pass,the hardness values increased
by 230%The rolling process was stopped at 8th cycle when cracking of the edge became pronounced.

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