Structures and Mechanical Properties of Multilayer Friction Surfaced Aluminum Alloys

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1 ISSN Report of the Research Institute of Industrial Technology, Nihon University Number 78, 2005 Structures and Mechanical Properties of Multilayer Friction Surfaced Aluminum Alloys Hiroshi TOKISUE*, Kazuyoshi KATOH*, Toshikatsu ASAHINA* and Toshio USHIYAMA** ( Received January 20, 2005 ) Abstract 5052 aluminum alloy plate used for substrate and both 5052 and 2017 aluminum alloys bar for coating material, multilayer friction surfacing were done. Effects of phase value and phase direction of coating consumable rod (coating material) on the structures and mechanical properties of multilayer surfaced material were investigated. The second layer deposit of the surfaced material tended to incline toward the first layer deposit side regardless of the direction of phase. And, the incomplete welded part of the edge in the first layer deposit was disappeared by the second layer surfacing. Microstructure of deposit became finer than those of the coating material and substrat regardless of the coating material. The surfacing efficiency of the second layer deposit of the 5052 alloy surfaced material showed almost equal to that of the first layer deposit. In case of using the 2017 alloy as a coating material, the surfacing efficiency of the second layer deposit showed higher value than that of the first layer deposit. When the phase is given to the advancing side 15 mm showed the highest surfacing efficiency of about 53%, and it s showed remarkably higher than that of the 5052 alloy surfaced material. Hardness of deposit of the 5052 alloy surfaced material was same value of substrate. But the hardness of deposit of the 2017 alloy surfaced material showed a higher value than that of the substrate. The width of the softening zone of all the surfaced materials was proportional to the total width of coating consumable rod. Both tensile strength and elongation of the 5052 alloy surfaced material showed same value to those of the substrate. Tensile strength of 2017 alloy surfaced material showed higher than that of the substrate, but the elongation was inferior to the substrate. The elongation remarkably recognized the effect of phase further than the tensile strength. 1. Introduction One type of the surface modification method that allows highly functional materials to be adhered onto the surface of the plate for enhanced functionality is friction surfacing 1), which is yet to be commercialized but achieves hard deposits with relatively simple equipment. The authors examined friction surfacing of both 5052 and 2017 aluminum alloys onto the surface of the 5052 aluminum alloy plate which observed the shape and structure of the deposit and the mechanical properties 2), 3). As the results, the friction surfaced material * Professor, Department of Mechanical Engineering, College of Industrial Technology, Nihon University ** Master s Course, Mechanical Engineering, Graduate School of Industrial Technology, Nihon University

2 Hiroshi TOKISUE, Kazuyoshi KATOH, Toshikatsu ASAHINA and Toshio USHIYAMA using 5052 aluminum alloy bar was capable of forming a deposit with the fine structure. The elongation of surfaced material was obtained higher than that of the substrate, but since the softening zone was found on the substrate near the deposit, the tensile strength of the surfaced material was reduced to about 90% of the substrate. This means friction surfacing using this material has no effectiveness in terms of strength. Therefore, considering the known advantages of friction surfacing and the industrial significance of surface modification, it is apparent that a type of material which can produce added value, such as high hardness of the surface of the substrate or enhanced strength of the surfaced material, should be used as a coating material. According to research on some aluminum alloys used for friction welding, a similar technique to friction surfacing, based on the effective use of frictional heat 4) -7), the maximum temperature of the friction welding process is slightly higher than that of the friction surfacing, although its heat cycle is similar to that of the friction surfacing. For a friction welded 2017 aluminum alloy joint 4), when left at room temperature after welding, the hardness of the softening zone is generally improved by natural aging to a level of the base metal. This suggests that use of 2017 aluminum alloy as a coating material may be able to ensure sufficient strength in friction surfaced material even if no post heat treatment is performed. It is concluded that the 2017 aluminum alloy is a raw material suited for coating material, also for save energy. To realize improved functionality of the material surface, which is one of the purposes of friction surfacing, wider deposits are often necessary to achieve that purpose from the surface efficiency. It would appear at first glance that increasing the diameter of the coating material would increase the surface area of the deposit; however, it actually results in an increase in frictional force during surfacing process, which is detrimental to the equipment employed. Another method that has potential is multilayer friction surfacing; a technique that involves repeated friction surfacing. However, there are currently almost no reports on this type of surfacing technique. In this study, the multilayer friction surfacing was conducted with 5052 aluminum alloy plate as a substrate and both 5052 and 2017 aluminum alloys bar which has different compositions as a coating material, and examined the surfacing conditions, particularly focusing on the effects of phase applied to the coating material on the structures and mechanical properties of the multilayer friction surfaced materials. 2. Materials and Experimental Procedure 5052P-H34 aluminum alloy plate of 5mm thickness as a substrate was machined by cutting down to 50mm in width and 150mm in length. And, as coating rod which is a coating material, both 5052 BDS-F and 2017BE-T4 aluminum alloys bar of 20mm in diameter were used machining it down to 100mm in length. These friction surfaced materials made from their coating rods are hereinafter respectively referred to as 5052 alloy surfaced material and 2017 alloy surfaced material. The chemical compositions and mechanical properties of these base metals are shown in Table 1 and Table 2, respectively. The friction surfacing was conducted by restricting the length of the coating rod (i.e., the surfacing operation was terminated when 30 mm of the coating rod had been consumed) 2),3). The friction surfacing was performed under the surfacing conditions shown in Table 3, using a surfacing device equipped on the pressure part of numerically controlled full automatic friction welding machine. The schematic illustration of friction Table 1 Chemical compositions of base metals. (mass %) Materials Si Fe Cu Mn Mg Cr Zn Al A5052 plate bal. A5052 rod bal. A2017 rod bal.

3 surfacing is shown in Fig. 1. The surfacing conditions in multilayer surfacing may vary depending on the correlation between the rotational direction of the coating rod and the surfacing direction. Thus, the rotational Table 2 Mechanical properties of base metals. Materials A5052 plate A5052 rod A2017 rod Coating material Friction pressure Tensile strength (MPa) P(MPa) Rotational speed N(s -1 ) Traverse speed Elongation (%) Table 3 Friction surfacing conditions. f(mm/s) Phase of 2nd layer G(mm) 5052 rod , 5, 10, 15 Hardness (HV0.1) rod center of the coating rod for the second layer was phase to the rotational center of the coating rod for the first layer by the distance shown in Table 3, in the same direction as the rotational direction of the coating rod and the surfacing direction (advancing side; AS) and in the direction opposite to them (retreating side; RS). Hereinafter, the phase is shown as a combination of direction and distance, as in AS10 or RS10. The friction surfacing was performed by maintaining contact between substrate and coating rod for 1 second and then moving substrate. For multilayer friction surfacing, after surfacing the first layer, the surfaced material was cooled down to room temperature, after which surfacing of the second layer was conducted. Observation of the outside appearance and structures, hardness measurement and tensile tests of the deposit and surfaced material were conducted at the room temperature. For the 2017 alloy surfaced material, these tests were applied to the monolayer friction surfaced material 3) on the 14th days after surfacing when no further change in hardness was observed. The tensile test specimen, which were taken from the gauge part at the position of the surfaced material shown in Fig. 2 in the same shape as that described in previous report 2), 3.5mm in thickness, 10mm in width and 40mm in length. The Fig. 1 Schematic illustration of friction surfacing. Fig. 2 Sampling position of tensile test specimen.

4 Hiroshi TOKISUE, Kazuyoshi KATOH, Toshikatsu ASAHINA and Toshio USHIYAMA surfaced material was machined such that the proportion of the deposit to the thickness of the gauge part was 40% of the plate thickness. 3. Experiment Results and Discussion 3.1 Observation of the deposit The appearances of the multilayer friction surfaced material are shown in Fig. 3. For the 5052 alloy surfaced material, circularly patterns made by rotation of the coating rod were clearly seen on the surface of the second layer, regardless of both degree and direction of the phase. These patterns are similar to those that appeared on the surface of the monolayer friction surfaced material, combining 5052 alloy plate and bar 2) or friction surfaced mild steel 8). Regardless of the direction of the phase applied to the coating rod, however, some parts could be observed where the width of the second layer changes irregularly. These width changes were particularly noticeable in cases with AS phase. This phenomenon, which was also observed for the monolayer friction surfaced material 2), it believe to be caused by the deposit being more likely to be located towards the AS and to be pushed toward the first layer side due to the presence of the first layer. Generally the second layer is prone to be moved more to the first layer side, and this tendency is greater Fig. 3 Appearances of multilayer deposit. : Center of 1st coating rod, : Center of 2nd coating rod

5 when the phase is applied to the RS. It considered that this phenomenon appears because the correlation between rotational direction of the coating rod and direction of surfacing caused the coating rod to be moved more to the AS, and, in addition, because of the presence of the first layer at the AS. On the deposit of the 2017 alloy surfaced material, circular patterns similar to that on the 5052 alloy surfaced material were clearly seen, and the clear difference was not observed between the first and second layer. From observation of the appearance of deposit, the effect of the second layer deposit on the first layer deposit could not be recognized. Almost no irregular changes in the deposit width of the second layer were observed for the 2017 alloy surfaced material, whereas they had been found for the 5052 alloy surfaced material. Under conditions where phase was applied during surfacing of the second layer, some deviation was observed for the second layer, but the degree of deviation was smaller than in case of the 5052 alloy surfaced material. Regardless of the phase direction of the coating rod, the second layer is shown inclined to be formed closer to the first layer side. Deviation increases in cases where the AS phase was applied, while it becomes smaller when a larger phase is applied. This result may be predicted from the facts that the high temperature strength of the 2017 alloy is greater than that of the 5052 alloy, and that the deviation of deposit using the 2017 alloy 3), is smaller than when 5052 alloy used as the coating material. For the 2017 alloy surfaced material, the degree of phase had almost no influence on the deviation of the deposit when the RS phase was applied. For multilayer friction surfaced material, there was no clear difference visible in the deposit length between the first layer and second layer, regardless of the type of coating material. Therefore, the shape of the deposit was evaluated according to the thickness and width of the deposit. The measurement results are shown in Fig. 4, in which the results are shown as the average of entire deposits. For the 5052 alloy surfaced material, when the AS phase was applied, no difference either in thickness or width of the deposit dependent on the degree of phase was observed. For the RS phase, it was observed that the thickness of deposit was affected by the phase and that the AS part of the second layer tended to be the thickest. The width of the deposit of second layer was almost equal to that of the monolayer surfaced material 2). The width of the deposit is seen to increase with increased phase, regardless of the phase direction. Fig. 4 Relation between phase of 2nd layer and thickness, width of multilayer deposit.

6 Hiroshi TOKISUE, Kazuyoshi KATOH, Toshikatsu ASAHINA and Toshio USHIYAMA The deposit of the 2017 alloy surfaced material tends to be thicker for cases with 5mm and 10 mm phase than without the phase, regardless of the measuring positions, and to be slightly thinner than the 15mm phase. The monolayered part of the second layer deposit become thicker and narrower than that of the monolayer surfaced material 3). 3.2 Surfacing efficiency Regardless of the coating material, the consumed part of the coating rod is not entirely accumulated on the substrate used for friction surfacing: part of the surfacing material is discharged outside in addition to the burrs generated by friction welding 5). Although not illustrated, the coating rod after multilayer friction surfacing showed a similar to that of the monolayer friction surfaced material 2). The relationship between the phase as related to the shape of the deposit and the surfacing efficiency of the second layer (weight ratio of the coating rod before and after surfacing) is shown in Fig. 5. The surfacing efficiency of the second layer of the 5052 alloy surfaced material showed almost equal to that of the monolayer friction surfaced material 2). While the surfacing efficiency was slightly smaller at the phase of 0 and 5 regardless of either AS or RS, it slightly improves as the phase grows. Fig. 5 Effect of friction surfacing conditions on surfacing efficiency. Regardless of the AS or RS phase, the surfacing efficiency of second layer of the 2017 alloy surfaced material increases with increased phase as well as in case of the 5052 alloy surfaced material. And, regardless of the degree of phase, the surfacing efficiency of the 2017 alloy surfaced material is higher than that of the 5052 alloy surfaced material. This is due to the difference in high temperature strength of the coating material used. To be specific, because the high temperature strength of the 5052 alloy is lower than the 2017 alloy, the amount of 5052 alloy discharged as burrs is greater than for the 2017 alloy. The 2017 alloy surfaced material showed the highest surfacing efficiency at the AS15 phase, the value of which is about 53%, and is remarkably high compared with that of the 5052 alloy surfaced material, which is about 33%. This value is higher than the monolayer friction surfaced material under the same conditions 3). 3.3 Observation of Macro- and Microstructures Figure 6 shows the macrostructures of the multilayer friction surfaced material. For the multilayer friction surfaced material, both inside of the deposit and interface between deposit and substrate showed similar to that of the monolayer surfacing 2), 3), regardless of the coating materials. Concerning the multilayer friction surfaced material, at the part where the first layer and second layer overlap, the incomplete welded part of the substrate and coating rod at the edge of the deposit observed on the first layer had been joined by heating and compression by surfacing of the second layer. No voids due to insufficient surfacing were found at the interface between the first and second layer. However, some incomplete welded parts were observed at both ends of the second layer, although very small, as in the case of the single layer alone. The thickness of the deposit of second layer tends to be slightly greater than the first layer. In addition, regardless of the degree of phase, the thickness of the deposit of second layer of the 5052 alloy surfaced material is greater than that of the 2017 alloy surfaced material in case of the AS phase, but thinner in case of the RS phase. Effects of the phase on the microstructures, near the weld interface between the deposit and substrate

7 are shown in Fig. 7. Regardless of the coating material, the structure of deposit shows a finer lamellar structure than the coating rod or substrate. Even with the largest phase, similar structural patterns resulted, and no major differences were observed in the deposit with different surfacing conditions and coating rod. Regardless of the direction and size of the phase, the thickness of deposit using 5052 alloy coating rod became thicker than that of the 2017 alloy coating rod. In surfacing by fusion welding, it has been reported that the coating material penetrates to inside the substrate 9). The friction surfacing is a novel solid phase surface modification technology; no penetration of the coating rod into the substrate was observed. On the other hand, the mechanically mixed layer has been observed on the weld interface of the dissimilar friction welded 2017/5052 alloys joint 10). However, in this experiments, the mechanically mixed layer was not observed at the weld interface between the substrate and coating rod. Fig. 6 Macrostructures of multilayer deposit. Fig. 7 Effect of phase value and direction of coating rod on the microstructures of multilayer deposit.

8 Hiroshi TOKISUE, Kazuyoshi KATOH, Toshikatsu ASAHINA and Toshio USHIYAMA 3.4 Hardness Distribution The hardness distribution of the multilayer friction surfaced material is shown in Fig. 8. For the 5052 alloy surfaced material, a softening zone was found on the substrate, as seen in case of the monolayer friction surfaced material 2). The width of the softening zone was proportional to the total width of the coating rod that passes the substrate, since the width was influenced by the deposit of first layer and that of second layer. In case of the phase of 0, the hardness of the softening zone was reduced as the coating rod of second layer passed the same position as the first layer. Whereas the hardness of substrate of the 2017 alloy surfaced material showed a similar distribution to that of the 5052 alloy surfaced material, but the hardness of softening zone of the 2017 alloy surfaced material at the phase 0 tends to be slightly higher than the 5052 alloy surfaced material. Concerning hardness distribution in a transverse section of the 5052 alloy surfaced material, the hardness of deposit was slightly higher than that of the phase of 0. When some phase was applied, however, no clear difference was observed hardness between the deposit and substrate. Hardness distribution in the transverse section of the 2017 alloy surfaced material showed similar patterns to those of the monolayer friction surfaced material 3) regardless of whether phase is applied or not. In case of the coating rod with the phase of 0, the hardness of the first layer and second layer were both greater than that of the substrate and equal to the base metal of coating material. For the coating rod with some phase, Fig. 8 Hardness distributions of multilayer deposit.

9 the hardness of the deposit of first layer as it approaches the second layer, and the hardness of almost the entire surface of the second layer turned out to be equal to that of the base metal of the coating material. This is probably due to the thermal influence on the first layer by surfacing of the second layer. For the hardness at the center between the rotational centers of coating rod of the first and second layer, the influence of heat during surfacing became smaller as the decrease in phase became greater, suggesting that a reflection of hardness changes according to the degree of phase. 3.5 Tensile test Results of the tensile tests are shown in Fig. 9. For the 5052 alloy surfaced material, there was a small difference in tensile strength depending on the direction and degree of phase, and the tensile strength was equal to that of the substrate. Although the elongation for the RS phase of 10 and 15 was equal to that of the substrate, the other phase conditions was slightly lower than the substrate. Although the tensile strength of the 2017 alloy surfaced material showed higher than that of the substrate, the tensile strength is affected very little by the degree of phase. The elongation decreases in comparison with the substrate regardless of the degree of phase, and it was almost equal to that of the monolayer friction surfaced material 3). Elongation of the 2017 alloy surfaced material with the phase of 0 showed the smallest value, while elongation with some phase decreased with an increase in phase, regardless of the direction of phase. The tensile strength of the 2017 alloy surfaced material, calculated assuming that the strength of the coating material simply follows the rule of mixture, was 319 MPa, but the maximum value of the 2017 alloy surfaced material showed in this experiment was 95.2% of that value. Regardless of the coating material, the peeling of at the interface of substrate and deposit was not recognized at the rupture part of the tensile tested specimen. 4. Conclusion The 5052 aluminum alloy plate was used the substrate, and multilayer friction surfacing was carried out on the substrate with both 5052 and 2017 aluminum alloys for the coating rod. The surfaced materials were studied to investigate the influence on the structures and mechanical properties of surfaced material of phase applied to the coating rod, the following results were obtained. (1) The circular pattern due to the rotation of coating rod was clearly observed on the surface of deposit. The second layer deviated toward the first layer, regardless of phase direction. (2) Regardless of the coating material, the incomplete welded parts of the edge in the first layer deposit were disappeared by the deposition of second layer surfacing. The deposit showed fine lamellar structure, which is finer than that of the coating rod and substrate. Fig. 9 Results of tensile test of multilayer deposits.

10 Hiroshi TOKISUE, Kazuyoshi KATOH, Toshikatsu ASAHINA and Toshio USHIYAMA (3) The surfacing efficiency of the second layer of the 5052 alloy surfaced material, calculated from the weight ratio before and after surfacing of the coating rod, was equal to that of the 5052 monolayer surfaced material. The surfacing efficiency of second layer of the 2017 alloy surfaced material was remarkably higher than that of the 5052 alloy surfaced material, and still higher than that of the 2017 alloy monolayer surfaced material. (4) The hardness of the deposit of both 5052 and 2017 alloy surfaced materials were revealed to be equal to those of the base metals. Softening zones were observed as wide as the coating rod that passed the part of the substrate under deposit. (5) The tensile strength and elongation of the 5052 alloy surfaced material were almost equal to those of the substrate. But the tensile strength of the 2017 alloy surfaced material showed higher value whereas its elongation was lower than that of the substrate. (6) Regardless of the coating material, the influence of phase was observed more clearly on the elongation than the tensile strength. Acknowledgements This research is supported by both the Grant-in- Aid for Scientific Research (c) (grant no ) and the Technology to Special Research Grants for the Development of Characteristic Education from the Ministry of education, Culture, Sport, Science. Authors wish to express our sense of gratitude by making special mention here.

11 References 1) E. D. Nicholas and W. M. Thomas: Metal Deposition by Friction Welding, Welding Jounal, Vol. 95, No. 8, pp.17-27, ) H. Sakiyama, H. Tokisue and K. Katoh: Mechanical Properties of Friction Surfaced 5052 Aluminum Alloy, Materials Transactions, Vol. 44, No. 12, pp , ) H. Tokisue, K. Katoh, T. Asahina and H. Sakihama: Some Characteristics of Friction Surfaced Deposit using Combined Similar and Dissimilar Aluminum Alloys, Research Report of College of Industrial Technology, Nihon University, Vol. 36, No. 1, pp , ) H. Tokisue and K. Kato: Mechanical properties of friction welded joints of aluminum alloy 2017, Journal of Japan Institute of Light Metals, Vol. 28, No. 9, pp , ) K. Katoh and H. Tokisue: Effect of welding conditions on axial shortening behavior and tensile strength of friction welded joints of 5052 aluminum alloy, Journal of Japan Institute of Light Metals, Vol. 48, No. 8, pp , ) T. Sawai, K. Ogawa, H. Yamaguchi, H. Ochi, Y. Yamamoto and Y. Suga: Effect of heat input on joint performance in 6061 aluminum alloy friction welding, Journal of Japan Institute of Light Metals, Vol. 50, No. 10, pp , ) T. Sawai, K. Ogawa, H. Yamaguchi H. Ochi Y. Yamamoto and Y. Suga: Relationship between diameter of base material and heat input in friction welding 6061 aluminum alloy, Journal of Japan Institute of Light Metals, Vol. 2, No. 1, pp. 7-11, ) K. Fukakusa: Travelling Phenomena of Rotational Plane during Friction Welding Application of Friction Surfacing, Journal of Japan Friction Welding Asociation, Vol. 2, No. 3, pp , ) Y. Kanbe, Y. Nakata, S. Kurihara, H. Koike and S. Miyake: Gas Tungsten Arc Welding Process for Surfacing Aluminum Alloys with Al-Cu Cored Wire, Quarterly Journal of the Japan Welding Society, Vol. 11, No. 2, pp , ) H. Fuwano, K. Katoh and H. Tokisue: Mechanically mixed layer in weld interface and mechanical properties of friction welded 5052/2017 aluminum alloy joints, Journal of Japan Institute of Light Metals, Vol. 50, No. 4, pp , 2000.

12 Hiroshi TOKISUE, Kazuyoshi KATOH, Toshikatsu ASAHINA and Toshio USHIYAMA

13 Biographical Sketches of the Authors Hiroshi Tokisue was born in Okayama, Japan on May 19, He received his B. Eng. degree in Industrial Engineering and D. Eng. degree in Mechanical Engineering from Nihon University, Japan in 1961 and 1982, respectively. He has belonged to the Nihon University from 1961, in 1984 a Professor of the College of Industrial Technology, Nihon University. He is engaged in the study of the metal processing, namely machining, friction welding, friction stir welding and friction surfacing. Dr. Tokisue is a member of the Japan Institute of Light Metals, the Japan Society of Mechanical Engineers, the Japan Welding Society, the Japan Institute of Metals, the Japan Society for Composite Materials, the Japan Friction Welding Association and the Japan Light Metal Welding & Construction. Kazuyoshi Katoh was born in Nagoya, Japan on January 28, He received his B. Eng. degree in Mechanical Engineering from Nihon University in 1969, M. Eng. degree and D. Eng. degree in Mechanical Engineering from Nihon University in 1972 and 1990, respectively. He has belonged to the Nihon University from 1972, in 1995 a Professor of College of Industrial Technology, Nihon University. And he is engaged in the study of the metal processing such as machining, friction welding, friction stir welding and friction spot welding. Dr. Katoh is a member of the Japan Institute of Light Metals, the Japan Welding Society, the Japan Society of Mechanical Engineers, the Japan Society of Precision Engineering, the Japan Institute of Metals and the Japan Light Metal Welding & Construction. Toshikatsu Asahina was born in Tokyo, Japan on March 8, He received his B. Eng. degree and D. Eng. degree in Mechanical Engineering from Nihon University in 1965 and 1998, respectively. He has belonged to the Nihon University from 1965, in 2002 a professor of the College of Industrial Technology, Nihon University. And his present research is laser welding, tungsten inert gas welding, plasma arc welding and resistance spot welding. Dr. Asahina is a member of the Japan Society of Mechanical Engineers, the Japan Institute of Light Metals, the Japan Welding Society, the Japan Light Metal Welding & Construction and the American Welding Society. Toshio Ushiyama was born in Nagano, Japan on August 11, He received his B. Eng. degree in Mechanical Engineering from Nihon University in He is a student of Master Course of Department of Mechanical Engineering, Graduate School of Industrial Technology, Nihon University. And he is a member of the Japan Institute of Light Metals, the Japan Society of Mechanical Engineers and the Japan Welding Society.