《947_A-two-step-SPD-processing-of-ultrafine-grained-titanium》.pdf

NanoStructured Materials, Vol. 11, No. 7, pp. 947–954, 1999 Published by Elsevier Science Ltd Pergamon Printed in the USA. All rights reserved. 0965-9773/99/$–see front matter PII S0965-9773(99)00384-0 A TWO STEP SPD PROCESSING OF ULTRAFINE-GRAINED TITANIUM † † V.V. Stolyarov*, Y.T. Zhu , T.C. Lowe , R.K. Islamgaliev* and R.Z. Valiev* *Institute of Physics of Advanced Materials, Ufa State Aviation Technical University, Ufa 450000, K. Marksa 12, Russia †Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA (Received August 10, 1999) (Accepted August 30, 1999) Abstract—Equal channel angular pressing (ECAP) and high pressure torsion (HPT) are two severe plastic deforma- tion (SPD) processes that have been used to process ultrafine-grained (UFG) materials. In this investigation, we have attempted to combine these two processes to refine the grain size of coarse-grained pure titanium. ECAP processing was first carried out at 500–450 °C to refine the grain size to about 300 nm. Further processing by HPT resulted in finer grain size and higher dislocation density. The second step, HPT processing, also increased the microhardness, ultimate strength, yielding strength and ductility of th