Research Papers

Effect of Thermal Softening on Anisotropy and Ductile Mode Cutting of Sapphire Using Micro-Laser Assisted Machining

[+] Author and Article Information
Hossein Mohammadi

Mechanical and Aerospace Engineering,
Western Michigan University,
4601 Campus Dr.,
F-232 Floyd Hall
Kalamazoo, MI 49008
e-mail: hossein.mohammadi@wmich.edu

John A. Patten

Industrial and Entrepreneurial Engineering
and Engineering Management,
Western Michigan University,
E-205 Floyd Hall, Mail Stop 5336,
Kalamazoo, MI 49008
e-mail: john.patten@wmich.edu

1Corresponding author.

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MICRO- AND NANO-MANUFACTURING. Manuscript received October 4, 2016; final manuscript received November 26, 2016; published online January 10, 2017. Editor: Jian Cao.

J. Micro Nano-Manuf 5(1), 011007 (Jan 10, 2017) (7 pages) Paper No: JMNM-16-1060; doi: 10.1115/1.4035397 History: Received October 04, 2016; Revised November 26, 2016

Ceramics and semiconductors have many applications in optics, micro-electro-mechanical systems, and electronic industries due to their desirable properties. In most of these applications, these materials should have a smooth surface without any surface and subsurface damages. Avoiding these damages yet achieving high material removal rate in the machining of them is very challenging as they are extremely hard and brittle. Materials such as single crystal silicon and sapphire have a crystal orientation or anisotropy effect. Because of this characteristic, their mechanical properties vary significantly by orientation that makes their machining even more difficult. In previous works, it has been shown that it is possible to machine brittle materials in ductile mode. In the present study, scratch tests were accomplished on the monocrystal sapphire in four different perpendicular directions. A laser is transmitted to a diamond cutting tool to heat and soften the material to either enhance the ductility, resulting in a deeper cut, or reducing brittleness leading to decreased fracture damage. Results such as depth of cut and also nature of cut (ductile or brittle) for different directions, laser powers, and cutting loads are compared. Also, influence of thermal softening on ductile response and its correlation to the anisotropy properties of sapphire is investigated. The effect of thermal softening on cuts is studied by analyzing the image of cuts and verifying the depth of cuts which were made by using varying thrust load and laser power. Macroscopic plastic deformation (chips and surface) occurring under high contract pressures and high temperatures is presented.

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Fig. 1

Schematic of the μ-LAM technique

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Fig. 2

Monocrystal sapphire C-plane wafer and test directions

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Fig. 3

μ-LAM experimental setup

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Fig. 4

Technique used to measure depth of cut

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Fig. 5

Depth of cut of [1¯1¯20] direction

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Fig. 6

Microscopic image and 3D profile of cutting nature of [1¯1¯20] direction with 200 mN: (a) 11.8 W and (b) 16.8 W

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Fig. 7

Depth of cut of [11¯00] direction

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Fig. 8

Cutting nature of [11¯00] direction with 300 mN and laser power of: (a) 11.8 W and (b) 16.8 W

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Fig. 10

Three-dimensional profile of 300 mN load cut: (a) No laser, (b) 1.6 W, and (c) 6.75 W laser powers, [112¯0] direction

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Fig. 11

Cutting nature of [112¯0] direction with 11.8 W laser power and: (a) 200 mN and (b) 300 mN load

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Fig. 9

Depth of cut of [112¯0] direction

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Fig. 20

DBT depth of cut of [112¯0] direction

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Fig. 19

DBT depth of cut of [11¯00] direction

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Fig. 18

DBT depth of cut of [1¯1¯20] direction

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Fig. 17

(a) DBT depth measurement of cross section of a cut and (b) 3D profile of a DBT test

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Fig. 16

Diamond turning of brittle materials: (a) cross section of the chip during the process and (b) laser heating is enhancing the ductile response

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Fig. 15

Depth of cuts for 16.8 W for different directions

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Fig. 14

Depth of cuts for no laser for different directions

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Fig. 21

DBT depth of cut of [1¯100] direction

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Fig. 13

Cutting nature of [1¯100] direction with 300 mN: (a) 1.6 W and (b) 6.75 W with fractured chips

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Fig. 12

Depth of cut for [1¯100] direction




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