High‐Strength Porous Copper by Cold‐Extrusion

Abstract

Porous metals have many possible applications such as lightweight structure, energy absorber, heat exchanger, biomaterial, filter, etc. Unidirectional casting of molten metal, [1,2] heat treatment with a bubbling agent [3][4][5] and sintering of powder containing space holder [6,7] are major fabrication processes of porous metals. The porous metals produced by these processes show relatively low strength not only due to the porosity, but also due to the softening during the heat treatments at high temperature. Non-uniformities of porosity, pore size and pore morphology deteriorate the strength further. Thus, specific strength (strength/density) of the porous metals is not so high as that of non-porous commercial wrought metals. Therefore structural applications of porous metals are currently still rather limited.In this study, alternative fabrication method using solidphase bonding in bulk metal forming is proposed. If the deformation and the removal of space holder are conducted at room temperature, high specific-strength porous metals can be obtained. Two types of porous coppers with one-dimensional pores, i.e. lotus-type and honeycomb-type rods, are successfully fabricated by cold extrusion followed by chemical leaching. Both the porous coppers show higher specific yield strength than a conventional porous copper in axial compression test.

Development of Unidirectional Cellular Structure with Multiple Pipe Layers and Characterisation of Its Mechanical Properties

“…The porosity values of the rolled copper [ 21 ] and rolled aluminium [ 27 ] UniPore structures were between 31% and 42% and between 9% and 18%, respectively. The porosity range of the specimens fabricated by cold extrusion bonding was between 14% and 54% [ 22 ].…”

“…Utsunomiya et al [ 22 ] proposed another approach to fabricate a two-dimensional cellular copper structure with a constant cross-section and excellent mechanical properties. This structure was based on cold extrusion (plastic metalworking process with solid-phase bonding [ 23 ]) in three steps: (i) setting up an assembly of copper and aluminium wires, (ii) bonding by extrusion, and (iii) chemical leaching of aluminium.…”

Bending efficiency through property gradients in bamboo, palm, and wood-based composites

“…Matsumoto et al, 2007) or by the removal of a second phase which thus effectively acts as the porogen (e.g. Utsunomiya et al, 2008). A fifth strategy is based on composite design and the introduction of reinforcing fibers, the filling of a shell with a foam, and circumferential and longitudinal stiffeners.…”

Damage behavior of cold-rolled sintered fiber felts

“…In a review, Utsunomiya et al [30] provided insights into studies on conventional forming processes on porous materials and explained their advantages. For example, they explained that work hardening can be achieved through forming processes, which leads to advantageous mechanical properties [31]. Furthermore, an example of cold-rolled porous aluminum was provided.…”