Properties of Pulsed Electric Current Sintered Copper and Copper Composites

Riina Ritasalo

    Research output: ThesisDoctoral ThesisCollection of Articles

    Abstract

    This work focuses on the processing and properties of Cu-based materials by the non-conventional and innovative method of pulsed electric current sintering (PECS), also known as spark plasma sintering (SPS). In particular, the aim is to produce materials with fine microstructures and determine the relationships between the manufacturing and the resulting properties of the bulk compacts. This includes process optimization to provide dense samples with controlled microstructures, in terms of grain size and reinforcement distribution, as well as an investigation on the properties of the final materials. The mechanical, nanomechanical, thermal, electrical, and tribological properties are of main interest. The experimental studies employed commercial and experimental powders and their mixtures as the starting materials for consolidation. The PECS process optimization yielded highly dense Cu and Cu-composite samples, mostly ranging between 97.0 and 99.7% of theoretical density (T.D.). Overall, the studied additives, their size, amount, and distribution in Cu matrixes resulted in a variety of influences on their properties. It was found that all the dispersoids decreased the tendency of grain growth during PECS process. Furthermore, a linear relationship between Cu and Cu2O grain growth was observed. Cu2O prevented grain growth of Cu, the effectiveness increasing up to about 20 vol% Cu2O remaining at the same level beyond that. The hindrance of Cu grain growth by Cu2O could be described by the cluster model of Flores. All of the reinforcements in the present study, such as Cu2O, Al2O3, TiB2 and nano/submicron-sized diamond (ND/SMD), were found to noticeably improve the micro-hardness compared to plain sm-Cu (submicron-sized copper). Large amount of small size reinforcements is the most effective. At best, these composites also resulted in improved thermal properties, moderate electrical conductivity, lower CoFs (coefficient of friction) and a reduced wear rate as compared to plain Cu. However, the properties greatly depended on the composite type and do not as such present general rules. The comparison between the PECS and HIP processes and the accompanied properties verified that the shorter time needed for proper densification by PECS resulted in finer grain structure and improved mechanical properties as compared to HIP. Overall, this study shows that PECS can be used to produce high quality Cu-composites with superior properties when compared to those of sm-Cu. On the whole, this research is supportive of the development of new alternative Cu-based materials for various applications, where enhanced thermal properties together with excellent mechanical properties are desired.
    Translated title of the contributionPECS menetelmällä kiinteytettyjen kuparin ja kuparikomposiittien ominaisuudet
    Original languageEnglish
    QualificationDoctor's degree
    Awarding Institution
    • Aalto University
    Supervisors/Advisors
    • Hannula, Simo-Pekka, Supervising Professor
    • Hannula, Simo-Pekka, Thesis Advisor
    Publisher
    Print ISBNs978-952-60-5654-8
    Electronic ISBNs978-952-60-5655-5
    Publication statusPublished - 2014
    MoE publication typeG5 Doctoral dissertation (article)

    Keywords

    • pulsed electric current sintering
    • copper
    • metallic matrix composites
    • microstructure
    • dispersion strengthening
    • mechanical properties
    • thermal properties
    • tribological properties
    • electrical properties

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