Original Research PaperSynthesis and structural control of Fe-based porous layer on Fe substrate for joining with resin parts using combustion reaction
Graphical abstract
Introduction
Weight reduction of vehicle bodies has been intensively studied with a view to reducing CO2 emission and effectively utilizing energy. Multi-material structures have received much attention, in which the most suitable material (e.g., steels, light metals, carbon-fiber-reinforced plastics (CFRPs)) is used for each component of the vehicle [1]. Vehicles then can be designed considering the balance among low cost, high strength, and low weight. Thus, it is essential to establish technologies to join dissimilar materials like metals and resins.
One of the direct joining methods is mechanical interlocking using the anchor effect. Metal and resin can be interlocked by infiltrating resin into dimples formed on the metal surface. The surface structure of the metal is important to obtain high joint strength. Many promising processes to modify and control the structure of metal surfaces, such as laser irradiation, chemical etching, and sandblasting, have been reported [2], [3], [4], [5], [6], [7], [8]. There have been many studies on the shear strength at the joint interface in the case of mechanical interlocking. However, the tensile strength perpendicular to the interface has not been widely investigated.
Recently, Suzuki et al. proposed a novel concept of mechanical interlocking via an “interpenetrating phase layer (IPL)” [9], [10]. Resin is infiltrated into open porous layer formed on the metal surface to interlock the metal/resin three-dimensionally. High bonding strength can be achieved in all directions because of the three-dimensional interlocking in the IPL. Suzuki et al. joined Al with epoxy resin via a porous Al layer fabricated by the space holder method using NaCl [11]. High joint efficiency (87% of resin strength) in the direction normal to the joint interface was achieved [10]. It was also clarified that the fracture mode changes depending on the volume fraction of resin in the IPL. In the present study, we have attempted to synthesize an Fe-based porous layer in order to achieve an Fe/resin joint via the IPL. Processes to fabricate porous Fe include continuous casting [12], [13], the metal hollow sphere (MHS) method [14], [15], metal powder slurry processing [16], [17], and the space holder method using polymethylmethacrylate (PMMA) or polystyrene [18], [19], [20]. Recently, Ito et al. reported that Fe-based porous materials can be synthesized by combustion reactions among Fe, Ti, and B [21]. An open-cell porous Fe/TiB2 composite is synthesized in a very short time by the heat of reaction to form TiB2 from Ti and B. Also, if the reactions are induced on a Fe substrate, it is expected that the large amount of heat will lead to good bonding between the porous layer and substrate. Thus, the combustion reaction of the Fe-Ti-B system is a promising process to synthesize porous layer for joining with resins. In the present study, porous Fe/TiB2 composites were synthesized on an Fe substrate. The effects of Fe particle size and the blending ratio of the raw powder mixture on the porous structure, surface structure of the porous layer, and adhesiveness between the porous layer and substrate were investigated.
Section snippets
Materials and methods
In this study, Fe powders (purity > 99.9%) with various particle sizes (dFe < 53 μm, <150 μm), Ti powder (purity: 99.9%, particle size < 45 μm), and B powder (purity: 99%, particle size < 45 μm) were used as starting materials. Fig. 1 shows secondary electron images (SEIs) of the raw powders used in the present study. These powders were dry blended for 30 min. The molar ratio of Ti and B was fixed at 1:2 to synthesize TiB2. The volume fractions of TiB2 (VTiB2) were set at 40, 50, 60, and 70% on
Results
Fig. 5 shows (a, b) the temperature profiles measured with the thermocouple when Fe powders with (a) dFe < 53 μm and (b) dFe < 150 μm were used and the (c) change in the maximum temperature (TMax) observed during the reaction as a function of VTiB2. When the heating temperature exceeded approximately 1150 °C, the temperature sharply increased. The sharp rise in temperature is due to the combustion reaction among Fe, Ti, and B. Note that the exothermic reaction finished in a very short time
Discussion
In the present study, an Fe-based porous layer was synthesized on an Fe substrate using the combustion reaction of the Fe-Ti-B system. The effects of the volume fraction of TiB2 (VTiB2) and Fe particle size (dFe) on the porous structure and microstructure of the porous layer were investigated. Porous layers in all the samples were composed of Fe/TiB2 composites and exhibited 30% porosity (Figs. 6 and 11(a)). Fe-rich regions without TiB2 were observed when the maximum temperature was below
Conclusion
The effects of the volume fraction of TiB2 (VTiB2) and Fe particle size (dFe) on the porous structure of an Fe-based porous layer synthesized on an Fe substrate by the combustion reaction among Fe, Ti, and B powders was investigated. The main results are as follows.
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The pore size in the porous layer increases with both increasing VTiB2 and dFe while porosity is almost constant.
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The surface roughness of the top surface of the porous layer decreased with both increasing VTiB2 and dFe.
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The bonding
Declaration of Competing Interest
None.
References (28)
- et al.
Laser assisted joining of plastic metal hybrids
Phys. Proc.
(2011) - et al.
Thermal joining of thermoplastic metal hybrids by means of mono- and polychromatic radiation
Phys. Proc.
(2013) - et al.
The effects of grit-blasting on surface properties for adhesion
Int. J. Adhes. Adhes.
(1999) - et al.
Evaluation of mechanical interlock effect on adhesion strength of polymer-metal interfaces using micro-patterned surface topography
Int. J. Adhes. Adhes.
(2010) - et al.
Effects of molding conditions on injection molded direct joining using a metal with nano-structured surface
Prec. Eng.
(2016) - et al.
Effect of layer thickness on bonding strength of Al/epoxy resin joint via interpenetrating phase layer
J. Mater. Process. Tech.
(2018) - et al.
Structural design and bonding strength evaluation of Al/epoxy resin joint via interpenetrating phase layer
J. Mater. Process. Tech.
(2018) - et al.
A novel sintering-dissolution process for manufacturing Al foams
Scripta Mater.
(2001) - et al.
Fabrication of lotus-type porous iron and its mechanical properties
Sci. Technol. Adv. Mater.
(2004) - et al.
Behavior of a random hollow sphere metal foam
Acta Mater.
(2002)
Composite metal foams processed through powder metallurgy
Mater. Des.
Phase diagram calculation: past, present and future
Prog. Mater. Sci.
Calculated phase diagrams of aluminum alloys from binary Al–Cu to multicomponent commercial alloys
J. Alloy. Comp.
Effect of Fe content in Fe-Ti-B system on fabricating TiB2 particulate locally reinforced steel matrix composites
Mater. Sci. Eng.: A
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