Internal friction and impact toughness of structural BCC alloys

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 521; pp. 329 - 334
• Main Authors: Kardashev, B.K., Chernov, V.M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.09.2009
• Subjects: BCC structural alloys; Dislocation amplitude-independent damping; Impact toughness; Logarithmic decrement; Young's modulus; Dislocation amplitude-independent damping; Young's modulus; Logarithmic decrement; Impact toughness; BCC structural alloys
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2008.10.062

The paper deals with acoustic properties (Young's modulus E and logarithmic decrement δ) and impact toughness of the BCC alloys: low activation ferritic–martensitic steel EK-181 (produced in the RF) and V–(4–10)Ti–(4–5)Cr alloys (produced in the RF, USA and Japan). The materials have been investigated in ∼77–300 K temperature range where BCC metals usually become brittle at low temperatures. The acoustic measurements were made by composite oscillator technique mainly in the amplitude-independent damping ( δ i ) range at frequencies of longitudinal vibrations of about 100 kHz. The data have been obtained for annealed, plastically bent and bent-then-straightened specimens. The δ i ( T) dependences for the pre-bent samples show a similar behavior as the impact toughness of the alloys. So, the ductile to brittle transition temperature (DBTT) for the BCC alloys can be determined by an acoustic non-destructive technique. It has been found that the acoustical DBTT depends on microstructure of specimens (internal stresses) and is different for the EK-181 steel of different thermal–mechanical treatments and for the RF, USA and Japan vanadium alloys. A comparison of the δ i ( T) curves for the BCC EK-181 steel and for the FCC austenitic EK-164 steel is shown and discussed as well. A viscous dragging of edge dislocations is found to control the ductile to brittle transition of the BCC alloys.