0
Research Papers: FORMING

Direct Single-Stage Processing of Lightweight Alloys Into Sheet by Hybrid Cutting–Extrusion

[+] Author and Article Information
Dinakar Sagapuram

Center for Materials Processing and Tribology,
Purdue University,
315 N. Grant Street,
West Lafayette, IN 47907
e-mail: dsagapur@purdue.edu

Andrew B. Kustas

Center for Materials Processing and Tribology,
Purdue University,
315 N. Grant Street,
West Lafayette, IN 47907
e-mail: andrew.kustas@gmail.com

W. Dale Compton

Center for Materials Processing and Tribology,
Purdue University,
315 N. Grant Street,
West Lafayette, IN 47907
e-mail: dcompton@ecn.purdue.edu

Kevin P. Tumble

Center for Materials Processing and Tribology,
Purdue University,
315 N. Grant Street,
West Lafayette, IN 47907
e-mail: driscol@ecn.purdue.edu

Srinivasan Chandrasekar

Mem. ASME
Center for Materials Processing and Tribology,
Purdue University,
315 N. Grant Street,
West Lafayette, IN 47907
e-mail: chandy@ecn.purdue.edu

1Corresponding author.

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING. Manuscript received December 22, 2014; final manuscript received June 26, 2015; published online September 4, 2015. Assoc. Editor: Yannis Korkolis.

J. Manuf. Sci. Eng 137(5), 051002 (Sep 04, 2015) (10 pages) Paper No: MANU-14-1705; doi: 10.1115/1.4031022 History: Received December 22, 2014

Widespread application of lightweight magnesium and titanium alloys sheet is limited mainly because of their poor-workability issues, both in primary processing by rolling and secondary sheet forming. This study describes a hybrid cutting–extrusion process, large-strain extrusion machining (LSEM), for producing sheet and foil. By utilizing a constraining edge placed across from the cutting tool edge, the usual cutting process is transformed into continuous shear-deformation process, wherein the thickness of the sheet at its exit from the deformation zone is directly controlled. The confinement of the deformation field in LSEM enables near-adiabatic heating in the deformation zone. Consequently, external workpiece heating, intrinsic to sheet manufacturing by multistage rolling in alloys of poor workability (e.g., hexagonal close packed (hcp) alloys and cast materials), is minimized. Furthermore, the deformation parameters, such as strain, strain rate, and strain path, can be controlled to refine the microstructure and induce shear-type crystallographic textures that enable enhanced sheet mechanical properties (strength and formability). This application of LSEM is demonstrated using magnesium alloy AZ31B as a model system. Since LSEM is a single-stage process for sheet production, it is potentially attractive in terms of production economics and energy. Implications for process scale-up and control of plastic flow localization are briefly discussed.

FIGURES IN THIS ARTICLE
<>
Copyright © 2015 by ASME
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Fig. 1

Flow localization and shear bands (dark regions) in rolled Mg AZ31B sheet. Twinning-dominated deformation is evident in regions between the bands; 65% rolling (thickness) reduction, processing temperature ∼150 °C.

Grahic Jump Location
Fig. 2

Sheet/strip production by LSEM: (a) schematic and (b) experimental setup. A light rolling pass following LSEM is also shown in the setup. CFD, TD, and RFN are the chip (sheet) flow direction, transverse direction, and rake face normal, respectively. V is the workpiece surface velocity.

Grahic Jump Location
Fig. 3

Schematic of the LDH test setup

Grahic Jump Location
Fig. 4

Mg AZ31B alloy: (a) discrete, needlelike chips in conventional cutting and (b) continuous long strip having a homogeneous microstructure in LSEM. Optical micrographs of the cutting chip and LSEM strip microstructure (from thickness cross section) are given in (c) and (d), respectively. Strip dimensions in (b) are 0.175 mm × 6.3 mm × ∼1 m.

Grahic Jump Location
Fig. 5

TEM images of microstructure of Mg AZ31B sheet at different T: (a)-1 T ∼ 165 °C, (b) T ∼ 207 °C, and (c) T ∼ 240 °C; (a)-2 is a higher magnification image taken from the shear-banded region in (a)-1.The strain ε was kept constant at ∼1.1 in this series of experiments. T was varied using V, without preheating (To ∼ 25 °C). Note the different scales in the images.

Grahic Jump Location
Fig. 6

Shear textures in Mg AZ31B sheet processed at λ = 0.7: (a) T ∼ 220 °C (To ∼ 25 °C), (b) T ∼ 400 °C (To = 200 °C), and (c) T ∼ 450 °C (To = 280 °C). The (0002) and (101¯0) pole figures are taken from the CFD-TD cross section (see Fig. 2). The texture intensity is given as mrd units.

Grahic Jump Location
Fig. 7

SEM images of dome samples and associated fracture surfaces (right) of (a) LSEM sheet and (b) conventional rolled sheet, tested for formability using LDH test. Note significantly different fracture morphologies for the two samples. The optical micrograph below the dome sample in (b) shows extensive twinning near the fractured region in the rolled sheet sample.

Grahic Jump Location
Fig. 8

Ti–6Al–4 V alloy: (a) saw-tooth shaped chip typical of conventional cutting and (b) continuous sheet with smooth surfaces and homogeneous microstructure created by LSEM. The inset in (b) shows tightly coiled LSEM strip/sheet. Cutting: α = 0 deg and V = 1 m/s and LSEM: α = 5 deg, λ = 0.6, V = 0.25 m/s, t = 125 μm, and To ∼ 25 °C.

Grahic Jump Location
Fig. 9

TEM images showing UFG microstructures in LSEM processed Ti sheet: (a) Ti–6Al–4 V; α = 5 deg, λ = 0.6, ε ∼ 1.2, V = 0.25 m/s, and To ∼ 25 °C and (b) CP Ti (grade 2); α = 5 deg, λ = 1.4, ε ∼ 1.1, V = 0.25 m/s, and To ∼ 25 °C. Note the more recrystallized microstructure in the CP Ti.

Grahic Jump Location
Fig. 10

LSEM of DC cast Mg AZ31B: (a) dendritic microstructure of the as-received cast ingot (grain size is large ∼2–3 mm) and (b) through-thickness microstructure of the LSEM sheet processed from the ingot. LSEM process conditions: α = 5 deg, λ = 0.9, ε ∼ 1, V = 1 m/s, and T ∼ 380 °C (To = 200 °C).

Grahic Jump Location
Fig. 11

Bright-field TEM images showing UFG microstructure in Mg AZ31B sheet processed from the as-cast ingot; ε ∼ 1 and T ∼ 160 °C. Diffraction pattern taken from the imaged region in (a) shows ringlike pattern, indicative of the submicron cell/domain sizes. The 100–200 nm sized grains (arrows) are clearly seen in a higher magnification image (b).

Grahic Jump Location
Fig. 12

Schematic of the proposed layout for prototype LSEM sheet production. Author's original figure adapted from 2012 DOE Clean Energy Trust Competition

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In