Hot hydrostatic extrusion of Ti/Cu-alloy composite materials.

Abstract

A new hot hydrostatic extrusion process with a visco-plastic pressure medium instead of liquid was developed. A lump of visco-plastic material is introduced into a container just after charging a pre-heated billet, and extrusion is immediately performed. Therefore, the temperature drop of billet is minimized, and at the same time a steady hot extrusion is realized.With this process, co-extrusions of commercially pure titanium and copper alloy were conducted. And favourable extrusion conditions were determined for sound composite bars. For the co-extrusions of titanium and other materials, a heat-treated or axisymmetrically pre-deformed billet of titanium should be used to obtain an uniform deformation.An intermetallic compound was sometimes observed at the interface between titanium and copper alloy when the extrusion temperature was high, or the annealing temperature after extrusion was high. Under a good process condition, no intermetallic compound was observed and the bonding shear strength was as high as 12150MN/m2for the case of a titanium clad copper electrode.

Fabrication and characterization of Ti–Cu clad materials by indirect extrusion

“…4 shows the microstructures and EDS results of interface layer between titanium and copper materials. The difference of thickness on the interface layer with variation of extrusion temperature was attributed to the phase transformation of titanium, which was occurred the phase transformation from HCP structure (␣-Ti) to BCC structure (␤-Ti) at 882 • C. It is found that in the case of extrusion temperature at 900 • C the thickness of interface layer between titanium and copper clad material is drastically increased because titanium material of BCC structure is easily promoted the diffusion comparing to that of HCP structure [5].…”

“…Yamaguchi et al [4] suggested the extrusion limit for variation of the volume fraction of clad material and flow stress ratio with hydrostatic extrusion. Matsushita et al [5] reported * Corresponding author. Tel.…”

Effect of Elevated Temperature and Annealing Time on Mechanical Properties of Ti/Cu Bimetal

“…The first microcracks on the interface appeared after annealing the samples for 90 min at 600 °C ( Figure 13 a), which was not observed at the shorter annealing times. According to Matsuhita [ 16 ], this effect was found after 20 min and for T = 360 °C. A similar fact was also noted in [ 19 , 25 ] on the samples of Ti/Cu bimetals obtained with the explosive method and after post-process annealing at temperatures above 400 °C.…”

“…The secrets of the process of hydrostatic extrusion of bimetal Ti/Cu alloy, where the technique of visco-plastic pressing of a pressure medium was used, are described in the paper of Matsushita et al [ 16 ]. The authors observed the formation of intermetallic compounds at the interface between titanium and copper alloy when the extrusion and annealing temperature after extrusion was high.…”