Thermal Stability of PECS-Compacted Cu-Composites

Abstract:

In this paper pulsed electric current sintering (PECS) is applied for submicron-sized copper (sm-Cu) based composite-powders aiming to produce MMC’s with higher strength and better temperature stability than reference sm-Cu. Incorporation of cuprite (Cu₂O), alumina (Al₂O₃), titaniumdiboride (TiB₂) and nano- and submicronsized diamonds (ND’s and SMD’s) improved noticeably the room temperature mechanical properties and the high-temperature stability of copper the effects becoming more noticeable with smaller dispersion size and higher amount of reinforcement. The hardness increment was at highest, when using ND’s or Al₂O₃. E.g., the microhardness for the reference sm-Cu sample and Cu with 3 vol.% ND’s, 6 vol.% ND’s and 2.5 vol.% Al₂O₃ were 1.02, 1.43, 1.77 and 1.58 GPa, respectively. Similar trend was noted also in the case of thermal stability and CTE. The study shows that Cu-ND, Cu-SMD and Cu-Cu₂O are suitable for use at moderate temperatures around 623 - 673 K, whereas Cu-Al₂O₃ and Cu-TiB₂ are suitable above 1023 K. In conclusion, PECS is suitable method to produce high quality Cu-composites having superior thermal and mechanical properties compared to those of sm-Cu.

• Periodical: Key Engineering Materials (Volume 527)
• Pages: 113-118
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.527.113
• Online since: November 2012
• Authors: Riina Ritasalo, Ulla Kanerva, Simo Pekka Hannula
• Keywords: CTE, Cu-Composite, Microhardness, Microstructure, Spark Plasma Sintering (SPS), Thermal Stability

References

[7] The authors state the Orowan strengthening contributes mainly in the case of nanoparticles less than 300 nm. Nevertheless it is not visible in the Fig.2. Could this be clarified? We have modified the text, changed Fig 1c., and added inserts to Fig 1a ja 1e to make this point more clear.

[8] In Fig.2 one contribution to the strengthening is s0, base strength of copper. This should be part of Hall-Petch strengthening, why is it depicted separately? The base strength of the copper was shown separately to depict its contribution on the total strength. However, since it is similar to all composites we have included it now to the Hall-Petch contribution as proposed.

[9] The figure caption of Fig. 3a. should be changed. In the figure there is no direct measurement of thermal stability. We have modified the figure caption of Fig. 3a as instructed.

[10] Discussion, line 2. Could you explain the meaning of "superior thermal properties" We have modified the text in the discussion to make this point more clear.