Abstract

The measurement of absorptance is important for the analysis and modeling of laser–material interactions. Unfortunately, most of the absorptance data currently available consider only polished pure metals rather than the commercially available (unpolished, oxidized) alloys that are actually being processed in manufacturing. We present the results of absorptance measurements carried out at room temperature on as-received engineering grade nonferrous metals (Al, Cu, and Zn alloys). The measurements were made using an integrating sphere with a Nd:YLF laser at two wavelengths (1053 and 527  nm, which means that the results are also valid for Nd:YAG radiation at 1064 and 532   nm). The absorptance results obtained differ considerably from the existing data for polished, pure metals and should help improve the accuracy of laser–material interaction models. Some clear trends were identified. For all 22 cases studied the absorptance was higher than for ideal pure, polished metals. For all Al and Cu samples the absorptance was higher for the green than it was for the infrared wavelength, while for all Zn coatings this trend was reversed. No clear correlation between absorptance and surface roughness was found at low roughness values (Sa 0.15–0.60), but one rougher set of samples (Sa 2.34) indicated a roughness–absorptance correlation at higher roughness levels.

© 2007 Optical Society of America

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References

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  1. D. Bergström and A. Kaplan, "Mathematical modelling of laser absorption mechanisms in metals: A review," in Proceedings of the 16th Meeting on Mathematical Modelling of Materials Processing with Lasers, D.Schuöcker, A.Kaplan, and A.Kratky, eds. (Igls, Austria, 2003), CD-ROM.
  2. K. Blidegn, "The interaction between laser light and metal," Ph.D. dissertation (Technical University of Denmark, 1997).
  3. D. J. Price, "The temperature variations of the emissivity of metals in the near infrared," Proc. Phys. Soc. London 47, 131-138 (1947).
  4. D. Bergström, D. A. Kaplan, and J. Powell, "Laser absorptance measurements in opaque solids," in Proceedings of the Tenth Nordic Laser Materials Processing Conference, A.Kaplan, ed. (Piteå, Sweden, 2005), pp. 91-115.
  5. F. J. J. Clarke and J. A. Compton, "Correction methods for integrating sphere measurements of hemispherical reflectance," Color Res. Appl. 11, 253-262 (1986).
    [CrossRef]
  6. Labsphere Application Note 01, "Methods for single beam substitution error for integrating sphere spectroscopy accessories," http://www.labsphere.com.
  7. A. Seifter, K. Boboridis, and A. W. Obst, "Emissivity measurements on metallic surfaces with various degrees of roughness: a comparison of laser polarimetry and integrating sphere reflectometry," in Proceedings of the 15th Symposium on Thermophysical Properties (Boulder, Colorado, 2003), pp. 547-560.
  8. A. Roos, C. G. Ribbing, and M. Bergkvist, "Anomalies in integrating sphere measurements on structured samples," Appl. Opt. 27, 3828-3832 (1988).
    [CrossRef] [PubMed]
  9. CRC Handbook of Chemistry and Physics, 73rd ed. (CRC Press, 1989).
  10. J. H. Weaver, D. W. Lynch, and R. Rosei, "Optical properties of single-crystal Zinc," Phys. Rev. B 8, 2829-2835 (1972).
    [CrossRef]

1988 (1)

1986 (1)

F. J. J. Clarke and J. A. Compton, "Correction methods for integrating sphere measurements of hemispherical reflectance," Color Res. Appl. 11, 253-262 (1986).
[CrossRef]

1972 (1)

J. H. Weaver, D. W. Lynch, and R. Rosei, "Optical properties of single-crystal Zinc," Phys. Rev. B 8, 2829-2835 (1972).
[CrossRef]

1947 (1)

D. J. Price, "The temperature variations of the emissivity of metals in the near infrared," Proc. Phys. Soc. London 47, 131-138 (1947).

Bergkvist, M.

Bergström, D.

D. Bergström, D. A. Kaplan, and J. Powell, "Laser absorptance measurements in opaque solids," in Proceedings of the Tenth Nordic Laser Materials Processing Conference, A.Kaplan, ed. (Piteå, Sweden, 2005), pp. 91-115.

D. Bergström and A. Kaplan, "Mathematical modelling of laser absorption mechanisms in metals: A review," in Proceedings of the 16th Meeting on Mathematical Modelling of Materials Processing with Lasers, D.Schuöcker, A.Kaplan, and A.Kratky, eds. (Igls, Austria, 2003), CD-ROM.

Blidegn, K.

K. Blidegn, "The interaction between laser light and metal," Ph.D. dissertation (Technical University of Denmark, 1997).

Boboridis, K.

A. Seifter, K. Boboridis, and A. W. Obst, "Emissivity measurements on metallic surfaces with various degrees of roughness: a comparison of laser polarimetry and integrating sphere reflectometry," in Proceedings of the 15th Symposium on Thermophysical Properties (Boulder, Colorado, 2003), pp. 547-560.

Clarke, F. J. J.

F. J. J. Clarke and J. A. Compton, "Correction methods for integrating sphere measurements of hemispherical reflectance," Color Res. Appl. 11, 253-262 (1986).
[CrossRef]

Compton, J. A.

F. J. J. Clarke and J. A. Compton, "Correction methods for integrating sphere measurements of hemispherical reflectance," Color Res. Appl. 11, 253-262 (1986).
[CrossRef]

Kaplan, A.

D. Bergström and A. Kaplan, "Mathematical modelling of laser absorption mechanisms in metals: A review," in Proceedings of the 16th Meeting on Mathematical Modelling of Materials Processing with Lasers, D.Schuöcker, A.Kaplan, and A.Kratky, eds. (Igls, Austria, 2003), CD-ROM.

Kaplan, D. A.

D. Bergström, D. A. Kaplan, and J. Powell, "Laser absorptance measurements in opaque solids," in Proceedings of the Tenth Nordic Laser Materials Processing Conference, A.Kaplan, ed. (Piteå, Sweden, 2005), pp. 91-115.

Lynch, D. W.

J. H. Weaver, D. W. Lynch, and R. Rosei, "Optical properties of single-crystal Zinc," Phys. Rev. B 8, 2829-2835 (1972).
[CrossRef]

Obst, A. W.

A. Seifter, K. Boboridis, and A. W. Obst, "Emissivity measurements on metallic surfaces with various degrees of roughness: a comparison of laser polarimetry and integrating sphere reflectometry," in Proceedings of the 15th Symposium on Thermophysical Properties (Boulder, Colorado, 2003), pp. 547-560.

Powell, J.

D. Bergström, D. A. Kaplan, and J. Powell, "Laser absorptance measurements in opaque solids," in Proceedings of the Tenth Nordic Laser Materials Processing Conference, A.Kaplan, ed. (Piteå, Sweden, 2005), pp. 91-115.

Price, D. J.

D. J. Price, "The temperature variations of the emissivity of metals in the near infrared," Proc. Phys. Soc. London 47, 131-138 (1947).

Ribbing, C. G.

Roos, A.

Rosei, R.

J. H. Weaver, D. W. Lynch, and R. Rosei, "Optical properties of single-crystal Zinc," Phys. Rev. B 8, 2829-2835 (1972).
[CrossRef]

Seifter, A.

A. Seifter, K. Boboridis, and A. W. Obst, "Emissivity measurements on metallic surfaces with various degrees of roughness: a comparison of laser polarimetry and integrating sphere reflectometry," in Proceedings of the 15th Symposium on Thermophysical Properties (Boulder, Colorado, 2003), pp. 547-560.

Weaver, J. H.

J. H. Weaver, D. W. Lynch, and R. Rosei, "Optical properties of single-crystal Zinc," Phys. Rev. B 8, 2829-2835 (1972).
[CrossRef]

Appl. Opt. (1)

Color Res. Appl. (1)

F. J. J. Clarke and J. A. Compton, "Correction methods for integrating sphere measurements of hemispherical reflectance," Color Res. Appl. 11, 253-262 (1986).
[CrossRef]

Phys. Rev. B (1)

J. H. Weaver, D. W. Lynch, and R. Rosei, "Optical properties of single-crystal Zinc," Phys. Rev. B 8, 2829-2835 (1972).
[CrossRef]

Proc. Phys. Soc. London (1)

D. J. Price, "The temperature variations of the emissivity of metals in the near infrared," Proc. Phys. Soc. London 47, 131-138 (1947).

Other (6)

D. Bergström, D. A. Kaplan, and J. Powell, "Laser absorptance measurements in opaque solids," in Proceedings of the Tenth Nordic Laser Materials Processing Conference, A.Kaplan, ed. (Piteå, Sweden, 2005), pp. 91-115.

D. Bergström and A. Kaplan, "Mathematical modelling of laser absorption mechanisms in metals: A review," in Proceedings of the 16th Meeting on Mathematical Modelling of Materials Processing with Lasers, D.Schuöcker, A.Kaplan, and A.Kratky, eds. (Igls, Austria, 2003), CD-ROM.

K. Blidegn, "The interaction between laser light and metal," Ph.D. dissertation (Technical University of Denmark, 1997).

Labsphere Application Note 01, "Methods for single beam substitution error for integrating sphere spectroscopy accessories," http://www.labsphere.com.

A. Seifter, K. Boboridis, and A. W. Obst, "Emissivity measurements on metallic surfaces with various degrees of roughness: a comparison of laser polarimetry and integrating sphere reflectometry," in Proceedings of the 15th Symposium on Thermophysical Properties (Boulder, Colorado, 2003), pp. 547-560.

CRC Handbook of Chemistry and Physics, 73rd ed. (CRC Press, 1989).

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Figures (15)

Fig. 1
Fig. 1

Some of the mechanisms that increase the absorptivity of real engineering surfaces. (a) Typical cross section of an engineering surface, (b) high (Brewster) angle absorptance and multiple reflections due to surface roughness, (c) multiple reflections within an oxide layer.

Fig. 2
Fig. 2

Experimental setup for measuring reflectance.

Fig. 3
Fig. 3

Optical diffusivity can be measured by excluding the specular fraction of the reflected light through an empty port or by fitting a light trap.

Fig. 4
Fig. 4

(Color online) Al1: AA1050, commercially pure aluminium.

Fig. 5
Fig. 5

(Color online) AA5251, AlMg: (a) Al2: AlMg, 3 mm thick, (b) Al3: AlMg, 6 mm thick.

Fig. 6
Fig. 6

(Color online) Al4: AA6082, AlMgSi.

Fig. 7
Fig. 7

(Color online) Cu1: commercially pure copper.

Fig. 8
Fig. 8

(Color online) Brass: (a) Cu2: nonpolished brass, (b) Cu3: polished brass.

Fig. 9
Fig. 9

(Color online) Zn1: Zintec.

Fig. 10
Fig. 10

(Color online) Zn2: Galvatite.

Fig. 11
Fig. 11

(Color online) Hot-dipped galvanized (spangled). (a) Zn3: sample I, (b) Zn4: sample II.

Fig. 12
Fig. 12

Absorptance as a function of the surface roughness for the four aluminium alloy samples studied (reference values in Figs. 4–6).

Fig. 13
Fig. 13

Absorptance as a function of the surface roughness for the three copper alloy samples studied (reference values in Figs. 7, 8).

Fig. 14
Fig. 14

Absorptance as a function of the surface roughness for the four Zn coating samples studied (reference values in Figs. 9–11).

Fig. 15
Fig. 15

Absorptance as a function of the surface roughness (below an Sa value of 0.6 µm) for all Al alloys, Cu alloys, and Zn coatings studied for both wavelengths.

Tables (4)

Tables Icon

Table 1 Laser and Metal Properties of Importance to Absorption a

Tables Icon

Table 2 List of the Alloys Examined in This Survey and Their Chemical Composition

Tables Icon

Table 3 Surface Conditions of the 11 Samples Studied

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Table 4 Summary of the Absorptance and Reflectance Measurements

Equations (4)

Equations on this page are rendered with MathJax. Learn more.

Rs=Ss[(1Ds)Rs,rSs,r+DsRd,rSd,r],
Ds=1Ss,spex/SsSd,spex/Sd,r,
Sa=A|Z(x,y)|dxdy,
Sq=(A(Z(x,y))2 dxdy)1/2.

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