Microstructural and crystallographic response of shock-loaded pure copper
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Nachiketa Ray Department of Materials Engineering, Indian Institute of Science, Bangalore, India
Gopalan Jagadeesh Department of Aerospace Engineering, Indian Institute of Science, Bangalore, India
Satyam Suwasa) Department of Materials Engineering, Indian Institute of Science, Bangalore, India (Received 29 October 2016; accepted 5 January 2017)
Microstructural and crystallographic aspects of high-velocity forming or “rapid” forming of rolled sheets of pure copper have been investigated in this work. Significant changes in crystallographic orientation and microstructure were observed when thin (0.5 mm) metal sheets of annealed copper were subjected to high strain rate deformation in a conventional shock tube at a very low impulse magnitude (;0.2 N s), which is inconceivable in conventional metal forming. Shock-loaded samples show characteristic texture evolution with a high brass {110}h112i component. A significant change in grain orientation spread was observed with increasing amount of effective strain without any drastic change in grain size. The texture after deformation was found to be strain-dependent. The path of texture evolution is dependent on the initial texture. Misorientation was limited to less than 5°. Deformation bands and deformation twins were observed. There was a decrease in twin [R3 coincidence site lattice (CSL)] boundary number fraction with increasing strain due to the change in twin boundary character to high-angle random boundary (HARB) as a result of dislocation pile up. The study shows the probability of a high-velocity shock wave forming pure Cu.
I. INTRODUCTION
Sheet metal forming is a well-known procedure in the processing industry, where plates (t . 6 mm) and sheets (6 mm . t . 0.15 mm) are deformed into coveted shapes by stretching and shrinking the dimensions of all its volume elements in the three principal directions: the rate at which these loads are applied, the range of operating temperatures and pressures, and the material thickness virtually dictating the metal-forming processes. While there are established industrial methods to form metallic plates (;few mm thick) of any material, considerable difficulties are experienced in adapting the conventional technique to deform thin metal sheets/foils (thickness 0.1–1 mm) to the desired shape. High-velocity forming of thin sheets is a popular method of obtaining shapes that are difficult to obtain from conventional manufacturing techniques. High-velocity forming using electric/magnetic fields and explosive gases is used in industry to form thin
Contributing Editor: Jürgen Eckert a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2017.15
sheets. This acts as a frictionless punch and its energy transfer (kinetic energy) is efficient. Hence, considerably less energy is required in this process compared to conventional sheet metal-forming processes. Due to high strain rates involved in such forming processes, the microstructure and textural evolution are likely to be different fr
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