The Anisotropy of Serrated Flow Behavior of Al-Cu-Li (AA2198) Alloy
- PDF / 4,909,277 Bytes
- 13 Pages / 593.972 x 792 pts Page_size
- 58 Downloads / 191 Views
N
THE occurrence of serrations in stress–strain curves is a characteristic feature of plastic instability, and it has been observed in many alloys during plastic deformation over a synchronized combination of strain rates and temperatures.[1,2] Macroscopically, this effect establishes itself in the form of oscillations in the flow curves. Specifically, during tensile tests at constant strain rate, they appear as stress drops with a characteristic range of frequency and amplitudes.[3] This phenomenon is commonly known as the Portevin–Le Chatelier (PLC) effect, named after Albert Portevin and Franc¸ois Le Chatelier,
NIRAJ NAYAN is with the Materials and Mechanical Entity, Vikram Sarabhai Space Centre, Indian Space Research Organization, Trivandrum 695 022, India and also with the Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai 400 076, India. S.V.S. NARAYANA MURTY is with the Materials and Mechanical Entity, Vikram Sarabhai Space Centre, Indian Space Research Organization. Contact e-mail: [email protected]. RAJDEEP SARKAR and A.K. MUKHOPADHYAY are with the Defence Metallurgical Research Laboratory, Hyderabad 500 058, India. SARITA AHLAWAT and S.K. SARKAR are with Glass and Advanced Materials Division, Bhabha Atomic Research Centre, Mumbai 400 085, India. M.J.N.V. PRASAD and I. SAMAJDAR are with the Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay Manuscript submitted October 4, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
who first reported this phenomenon.[3] The instabilities, in general, and PLC, in particular, are influenced by chemical composition,[4] crystallography, solute concentration and its size[5] and phases,[6] dislocation density and effective grain size.[7] There are elements that are referred to as strain aging agents in solid solution of aluminum and its alloys, viz. Mg, Cu, Li and Zn. The increase in the concentration of these alloying elements makes the effect more pronounced. The other factors that also contribute to strain aging, to a lesser extent, are grain boundaries[8] and anisotropy.[9] A number of common extrinsic factors that affect this phenomenon are the surface finish of the specimens,[10] mode of straining (example: load controlled/displacement controlled[11]), rate of straining[12,13] and temperature.[1] It is to be noted that the most prominent factors reported to influence the plastic instability are the alloy composition, strain rate and temperature. PLC bands have been categorized as A, B and C types depending upon the type of serrations in flow curves during quasi-static tensile testing of the polycrystalline material. The appearance of these serrations is controlled by the strain rate and temperature combination. Type A serrations, which generally start at one end of the gauge length, are generated because of repetitive uninterrupted propagation of deformation bands. Type B serrations, which generally appear during tensile testing at medium strain rates, refer to prop
Data Loading...
