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Effect of Surface Pre-Treatment on the Peel Strength of Warm Roll Bonded Aluminum Sheets
Saeed Mousa
Department of Mechanical Engineering, Jazan University, Jazan, Saudi Arabia [email protected]
Abstract.In this work, the effects of a mechanically pre-treating the surface structure of warm roll- bonding of aluminum 1100 alloys was investigated. Sandblasting with Al2O3 was used to pre-treat the metal surface. The parameters that were investigated are blasting time (3 s and 9 s) and the distance between the nozzle and the substrate (300 mm and 500 mm). A 3D profilometer was used to confirm the results of the efforts to increase surface roughness. The adhesion of sandblasting Al alloy 1100 strips characterized by measuring the peel strength. The results show that sandblasting time has a major effect on the peel strength, while distance induced only a minor effect.
Keywords: Warm rolling, Peel strength, Sandblasting, Pre-treatment, Aluminum alloy 1100.
1. Introduction
Roll bonding is a solid state welding process whereby the bonding is established by the joining of the metals to be bonded via plastic deformation. Bonding is achieved when the surface expansion causes the surfaces of the virgin metals to be exposed, or when the pressure reaches a value large enough to extrude the virgin material through the cracks of the fracture layer, resulting in the establishment of the contact and bonding between opposing virgin surfaces [1]. The roll bonding process can be applied to a two pieces composed of the same material, or to different materials that possess widely varying mechanical and metallurgical properties [2].
Metal surfaces are typically rough, and when two clean surfaces are pressed together, bonding is expected. In general, metal surfaces are covered with contamination and layers of oxidation. Consequently, the surface conditions and structure are very important factors
influencing the bond strength in the roll bonding process [3].
Various pre-treatment processes can be applied to the surfaces to ensure proper surface cleaning before attempting to establish bonding. The pre-treatment processes can be classified as mechanical, chemical, or electrical. Mechanical processes include grinding and sandblasting, whereas etching and wet-chemical surface modification are typical examples of chemical processes. Electrical pre- treatment processes including atmospheric and low-pressure plasma treatment [4].
It has been believed that sandblasting removes unfavorable oxides and contaminants, while increasing surface roughness, thereby increasing surface energy and the surface area available for bonding [5]. From the literature review, however, it appears that there haven’t been any studies that investigated the effects of sandblasting pre-treatment process parameters
on roll-bonding of commercially pure aluminum 1100 alloy.
The objective of this study is to investigate the effects of the surface structure that is generated by sandblasting pre-treatment, and the parameters of the pre-treatment, which include sandblasting time and distance (from the nozzle of the blaster to the substrate) on the bond strength of roll bonded Al alloy 1100 alloy.
2. Experimental Procedure
A schematic of the roll bonding process employed in our study is shown in Fig. 1. A commercially pure aluminum (Al alloy 1100) strip was used in this study. The strip was cut into smaller strips having dimensions of 60 mm × 20 mm × 1 mm. The specification of the Al alloy 1100 strips is summarized in Table 1. The stress- strain curve for Al alloy 1100 is shown in Fig. 2.
The preheating of Al alloy 1100 samples was accomplished using a heat plate (Cimarek) set at 250°C for 15 min. Then, the samples were joined by a rolling mill (Durston-DRM 130) with a roll diameter of 65 mm as shown in Fig. 3.
In order to produce a satisfactory bond in roll bonding, it is important to remove the contaminated layers on the surfaces of the strips. The sample surfaces were first degreased with ethanol, followed by sandblasting of the surface, and degreased with ethanol after sandblasting as well. Sandblasting with various
settings were used to investigate the effects on the bond strength. Surface roughness values were measured by a 3D profilometer (Zygo, NewView 7100). The bonding took place immediately after degreasing and sanding to avoid surface oxidation. The sandblasting process parameters and their settings are shown in Table 2. The sandblasting room that was used in the experiments is shown in Fig. 4.
2.1 Adhesion Test
The T-peel test is a method that is convenient for comparing the parameters (surface topography, and number of cycles) that affect the bond strength. The adhesion between the metal sheets was investigated by a T-peel test according to the DIN53282 standard. The T-peel test was performed to determine the resistance of metals bonds to peeling forces, and it is primarily used for the comparative assessments of adhesives and adhesive bonds.
Peel strength is the average peel load per unit width of bond line required to separate bonded materials where the angle of separation is 180 degrees. The relationship between peel strength and interfacial strength depends on the mechanical properties of the interface which affected by the processing parameters [6]. A schematic of the peel test is shown in Fig. 5. A typical force response from the peel test is shown in Fig. 6, where the average load is noted.
Al alloy 1100
Surface preparation and preheating
Roll Bonding
Fig. 1. Schematic illustration of the warm roll bonding process.
Table 1. Specification of Al alloy 1100 materials.
Material Chemical composition (wt. %) Tensile Strength (MPa) Yield Strength (MPa) Elongation (%) Al alloy 1100-O 99.61 Al, 0.11 Si, 0.55 Fe, 0.11
Cu, and 0.07 others
85 33 30
Fig. 2. Stress-Strain curve for Al alloy 1100-0.
Fig. 3. Laboratory rolling mill.
Table 2. Process parameters settings.
Parameter Value
Sandblasting time (seconds) 3 and 9 nozzle-to-substrate distance (mm) 300 and 500 Preheat temperature (°C) 250
Fig. 4. Sandblasting box.
Fig. 5. Schematic illustration of the peel test.
Fig. 6. The peeling force versus peeling distance and the method of calculating the average peeling force.
Moving grip
Fixed grip
Al1100/Al1100
2. Results and Discussion
1.1. Surface Structure After Pre-Treatment The variations of the blasting parameters (time and nozzle-to-substrate distance) result in a significant increase in surface roughness.
Table 3 shows the mean roughness index, Ra, of blasted Al alloy 1100 strips as a function of the blasting parameters. As expected, it is clearly seen that the surface roughness is increased with increased blasting time and with a decreased nozzle-to-substrate-distance. The mean roughness index Ra is approximately nine times higher than the untreated reference sample when the pre-treatment included the longest blasting time and smallest distance. On the other hand, increasing the blasting distance from 300 mm to 500 mm did not show a significant effect on the roughness, as the blasting particles lose only a minor amount of kinetic energy while traveling such short distances through the air.
Table 3. Surface roughness measurements.
Distance (mm) Time (s) Ra (µm)
Reference 0 0.6
300 3 2.76
9 5.3
500 3 1.56
9 3.84
Sandblasting the Al alloy 1100 strips generates a non-uniform surface structure characterized by dimples and furrows. The difference between the untreated and pre- treated surfaces is clearly visible in Fig. 7. The
influence of blasting time and distance is shown in the microscopic images is reflected in the surface roughness measurements. When comparing the untreated specimen to the one that was blasted for nine seconds at a distance of 300 mm, the difference in the surface, and how it completely changed, is easily noted.
Fig.8 shows the influence of the blasting time and distance on the peel strength of bilayer Al alloy 1100 strips. As expected, an increase of the roughness led to interlocking effects at the surface, and consequently to a higher peel strength [7-9]. It would appear that these rough surface layers break up coherently in the roll gap since the relative movement between them is restricted by frictional constraints or the mechanical interlocking [6, 10-13]. It can clearly be seen that blasting time plays a role on the peel strength, while no significant difference observed between the two blasting distances.
The peel strength of blasted samples, even for a 3 s blasting time, is approximately six times higher than the peel strength in untreated samples. An increase in the blasting time, which led to a rougher surface, did not, however, lead to a major further increase of the peel strength.
Figure 9 shows the relationship between the roughnesses that were produced, and the resulting peel strength variations. It can be seen that the effect of the distance and time approach an identical value. The distance produces an effect on the residual compressive strength on the surface of the sample [14]. Distance causes a plastic deformation effect on the surface of the samples.
Fig. 7. Optical microscopic images (left) and the corresponding 3D surface profiles (right) of the Al alloy 1100 roughened with different time and distance: (A) as-received Al alloy 1100 (Ra=0.6 µm), (B) blasting time 9 s at a distance of 300 mm (Ra=5.3 µm).
Fig. 8. Peel strength results with different conditions (n=3).
0.26 1.46
2.2
1.18
1.93
0 0.5 1 1.5 2 2.5
3 9
Peel strength (N/mm)
Blasting time (sec)
As‐received 300 mm 500 mm (A)
(B)
500 µm
500 µm
Fig. 9. Peel strength versus surface roughness produced from time and distance.
4. Conclusions
From the studies that were conducted, some conclusion can be drawn from that as the following:
Experimental results show that the surface roughness is one of the sources of strength of the bilayer Al alloy 1100. The peel strength is increased by the increased surface roughness of the metal substrate.
Mechanical interlocking is enhanced when very rough interfaces are considered; this is due to the fact that a rough topography helps to increase the total area at the interface.
The largest influence creating roughness was the blasting time. A lesser effect was created by varying the blasting distance.
Surface roughness versus peel strength approaches the same level, regardless of whether the roughness was increased by increasing either time or distance.
References
[1] Yan, H. and Lenard, J.G. (2004), A study of warm and cold roll-bonding of an aluminium alloy. Materials Science and Engineering: A, 385(1–2): 419-428.
[2] Jamaati, R. and Toroghinejad, M.R. (2010). Investigation of the parameters of the cold roll bonding (CRB) process.
Materials Science and Engineering: A, 527(9): 2320-2326.
[3] Nezhad, S. A. M. and Ardakani, A. H. (2009) A study of joint quality of aluminum and low carbon steel strips by warm rolling. Materials & Design, 30(4): 1103-1109.
[4] Njuhovic, E., et al. (2013), Influence of the composite surface structure on the peel strength of metallized carbon fibre-reinforced epoxy. Surface and Coatings Technology, 232(1): 319-325.
[5] Milner, J.L., Abu-Farha, F. and Kurfess, T. (2013) The Effect of Warm Accumulative Roll Bonding and Post Process Treatment on Microstructure and Mechanical Behavior of CP-Ti. In: ASME 2013 International Manufacturing Science and Engineering Conference collocated with the 41st North American Manufacturing Research Conference. American Society of Mechanical Engineers.
[6] Danesh Manesh, H. and Karimi Taheri, A. (2004) Study of mechanisms of cold roll welding of aluminium alloy to steel strip. Materials Science and Technology, 20(8): 1064- 1068.
[7] Strano, M., et al. (2014). A Comprehensive Experimental Study on the Effect of Process Parameters in Warm Roll Bonding of Aluminum Sheets. In: ASME 2014 International Manufacturing Science and Engineering Conference collocated with the JSME 2014 International Conference on Materials and Processing and the 42nd North American Manufacturing Research Conference.
American Society of Mechanical Engineers.
[8] Kümmel, F., et al. (2019), High Lightweight Potential of Ultrafine-Grained Aluminum/Steel Laminated Metal Composites Produced by Accumulative Roll Bonding.
Advanced Engineering Materials, 21(1): 180-286.
0 0.5 1 1.5 2 2.5 3
0 1 2 3 4 5 6
Roughness (µm)
Peel strength (N/mm)
Ra from distance Ra from time
[9] Fard, M. N. N., et al. (2017), Accumulative roll bonding of aluminum/stainless steel sheets. Journal of Ultrafine Grained and Nanostructured Materials, 50(1): 1-5.
[10] Bay, N. (1979), Cold Pressure Welding: The Mechanisms Governing Bonding, pp: 121-127.
[11] Yahiro, A., et al. (1991), Development of nonferrous clad plate and sheet by warm rolling with different temperature of materials. ISIJ International, 31(6): 647- 654.
[12] Zhang, W., Bay, N. and Wanheim, T. (1992), Influence of hydrostatic pressure in cold-pressure welding. CIRP Annals, 41(1): 293-297.
[13] Lukaschkin, N., Borissow, A. and Erlikh, A. (1997), The system analysis of metal forming technique in welding processes. Journal of materials processing technology, 66(1-3): 264-269.
[14] Buchner, M., et al. (2008), Investigation of different parameters on roll bonding quality of aluminium and steel sheets. International Journal of Material Forming, 1(1):
1279-1282.
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