Energy-Based Inelastic Hardness of Soda-Lime Silicate Glass

Transcription

1 Energy-Based Inelastic Hardness of Soda-Lime Silicate Glass Satoshi YOSHIDA 1, 2, Hiroshi SAWASATO 1, 2, Masanori YOSHIKAWA 1, Jun MATSUOKA 1, 2 1 Department of Materials Science,, Hikone, Shiga, JAPAN 2 Center for Glass Science and Technology,, Hikone, Shiga, JAPAN

2 Contents 1. Background Indentation impression of glass What is a permanent deformation of glass? Densification and Shear flow of glass 2. Experimental procedure 3. Results and Discussion 4. Summary > Energy based hardness depends on a shape of indenter. > Energy required to create a unit volume of indentation varies with contribution of densification.

3 1. Background Permanent deformation of glass 2. Experimental procedure 3. Results and Discussion 4. Summary

4 1. Background Indentation impression of glass Peter (1970) Plastic flow or Densification? Ball indentation on soda-lime glass (radius = 80 µm, load = 1100 gf) Shear lines! Ball indentation on soda-lime glass (radius = 20 µm, load = 100 gf) The contrast arises from an increase in refractive index. Densification!

5 1. Background Indentation impression of glass Silica glass : After unloading (Vickers indentation) Intensity (a.u.) 492 cm -1 Center of indentation 0.1 MPa 430 cm -1 Outside Wavenumber (cm 1 ) Raman spectra of silica glass. (Indentation load = 1 N) Quenched from ~ 30GPa Raman spectra of silica glass under high hydrostatic pressures Hemley et al.(1986)

6 1. Background Indentation impression of glass Discrimination of densified volume from total indentation volume Mackenzie(1969), Yoshida (2001, 2005) Indentation profile Annealing Tg 0.9, 2 h Densified volume µm 02 0 Relaxation time for viscous flow is long enough. µm µm µm 2 4

7 1. Background Indentation impression of glass Silica glass : before annealing after annealing (at T g X 0.9) 492 cm -1 Center of indentation Center of indentation Intensity (a.u.) 430 cm -1 Outside Intensity (a.u.) Wavenumber (cm 1 ) Outside Raman spectra of silica glass. (Indentation load = 1 N) Wavenumber (cm 1 )

8 1. Background Indentation impression of glass The previous work Yoshida, Sangleboeuf, Rouxel (2005), J. Mater. Res. 20, p Volume ratio of recovery, V R (%)100 Densification cannot be ignored for oxide glasses. Silica Soda-lime glass YBC Poisson's ratio BMG 1. Various kinds of glasses, including silica, oxynitride(ybc6), metallic glass(bmg), undergo densification under an indenter. 2. Volume recovery (densified volume) decreases with increasing Poisson s ratio of glass. 3. The indentation volume provides important information on inelastic deformation of glass.

9 Objectives of this work In order to get insight into inelastic deformation of glass 1. With different indenters, depth-sensing indentation experiments (Load-unload tests) are performed for soda-lime silicate glass. 2. Energy-based hardness, which is calculated from the inelastic work of indentation and the residual indentation volume by using an SPM, is obtained.

10 1. Background 2. Experimental procedure 3. Results and Discussion 4. Summary

11 2. Experimental procedure 2-1. Depth-sensing indentation Denpth-sensing indenter: Shimadzu DUH-201 Diamond indenter: Vickers, Berkovich, Cube-corner Indentation load : 50 mn ~ 400 mn Loading and unloading rates : 14 mn/s Sample: Soda-lime glass(matsunami S-0050) U r U e U r : Inelastic hysteresis loop energy, U e : Elastic stored energy, U t (=U r +U e ): Total energy to create an indentation impression at P max

12 2. Experimental procedure 2-2. Measurement of residual impression volume Scanning probe microscope(spm): Veeco Nanoscope E µm 02 Conditions of Image aquisition: Contact mode Scan area 5 µm 2 ~ 15 µm µm V V V + : Pile-up volume V : Indentation volume

13 2. Experimental procedure 2-3. Energy-based inelastic hardness Meyer hardness = Load (N) Projected area (m 2 ) Meyer hardness is an Elastoplastic work to create a unit volume of maximum indentation volume. Energy based inelastic hardness = Inelastic loop energy, U (J) Indentation volume, V - r (m 3 ) U r U e V V Energy based inelastic hardness is an Inelastic work to create a unit volume of residual indentation volume. M. Sakai, Acta Metall. Mater., 41, 1751 (1993) N.A. Stilwell and D. Tabor, Proc. Phys. Soc. 78, 169 (1961)

14 1. Background 2. Experimental procedure 3.Results and Discussion 4. Summary

15 3. Results and Discussion Load-depth curves of soda-lime glass using different indenters 400 Vickers Berkovich Cube-corner Load /mn 200 Load /mn 200 Load /mn Depth /µm Depth /µm Depth /µm Elastic recovery of Cube-corner indentation is small as compared with other indentations. Glass behaves like a metal under a Cube-corner, but has some cracks.

16 3. Results and Discussion Load-depth curves of soda-lime glass using different indenters 400 Berkovich The indenter which has the larger face angle, β, shows deeper penetration. Load /mn Vickers Cube Corner Vickers Berkovich Cube-corner Depth /µm β V = 22.0 º β B = 24.7 º β C = 54.7 º cf. Geometrical factors of indenter, g : A pro = g h 2 g V = 24.5, g B = 24.5, g c = 2.6 A pro : Projected area, h : depth

17 3. Results and Discussion SPM image of residual impression Vickers 50 mn Using the maximum depth, h max =0.54 µm, from load-depth curve and the contact depth, h c =0.44 µm, from the diagonal of impression, the surface geometrical factor, γ (= h max /h c ), is estimated to be 1.23.

18 3. Results and Discussion SPM image of residual impression Berkovich 50 mn The surface geometrical factor, γ (= h max /h c ), is 1.29.

19 3. Results and Discussion SPM image of residual impression Cube-corner 50 mn The surface geometrical factor: γ ~ 1 No sinking-in

20 3. Results and Discussion Energy based inelastic hardness Inelastic hardness /GPa Berkovich Cube-corner Vickers Indentation load /mn Inelastic hardness with a Cube-corner is larger than those with other indenters. Inelastic hardness >> Meyer hardness Meyer hardness (from maximum 400 mn ) Vickers: 4.4 GPa Berkovich: 3.3 GPa Cube-corner: 6.8 GPa

21 3. Results and Discussion Annealing recovery (Relaxation of densified volume) Vickers 100 mn Densified volume

22 3. Results and Discussion Annealing recovery (Relaxation of densified volume) Cube-corner 100 mn Sharp indenter: Less recovery Less densification

23 3. Results and Discussion Energy based inelastic hardness Inelastic hardness is an inelastic work to create a unit volume of residual impression. Inelastic hardness: ~ 14GPa > Inelastic hardness: ~ 12GPa (Cube-corner) (Vickers, Berkovich) Shear flow only Shear flow(20%) + Densification(80%) S. Yoshida et al., J. Mater. Res., 20, 3404 (2005) Shear flow is a bond-breakage process. Intrinsic strength of soda-lime glass: ~ 10 GPa (two-point bending of fiber) Pressure onset for hydrostatically densification of soda-lime glass: ~ 8 GPa See Poster Presentation, M. Inoue et al. H. Ji et al., Scrip. Mater., 55, 1159 (2006) The difference of inelastic hardness stems from Shear flow energy > Densification energy

24 4. Summary 1. Hardness is an energy required to create a unit volume of residual indentation impression. 2. Energy-based inelastic hardness depends on a shape of indenter. Hardness (Cube-corner) > Hardness (Vickers or Berkovich) 3. Deformation mechanism changes with a shape of indenter. Shear flow (Sharp indenter) Densification (Blunt indenter) 4. Energy-based inelastic hardness varies with contribution of densification beneath an indenter.