Influence of different Ni coatings on the long-term behavior of ultrasonic welded EN AW 1370 cable/EN CW 004A arrestor d
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RESEARCH PAPER
Influence of different Ni coatings on the long-term behavior of ultrasonic welded EN AW 1370 cable/EN CW 004A arrestor dissimilar joints Tobias Köhler 1
&
Michael Grätzel 1 & Jean Pierre Bergmann 1
Received: 30 September 2020 / Accepted: 6 November 2020 # The Author(s) 2020
Abstract The increasing demand for energy-efficient vehicles requires suitable methods for cost and weight reduction. This can be achieved by the replacement of copper by aluminum, in particular for the on-board power systems. However, the complete substitution is restricted by the mechanical and physical material properties of aluminum as well as challenges in the aluminum copper interface. The challenges concern the corrosion vulnerability and the occurrence of brittle intermetallic compounds (IMC) which can negatively influence the mechanical properties and the electrical conductivity. Therefore, current investigations focus on the one hand on the realization of dissimilar aluminum copper joints by suitable joining technologies, like ultrasonic welding, and on the other hand on the assurance of a sufficient prevention against harmful corrosion effects. In cases where the joint cannot be protected against corrosion by sealing, nickel coatings can be used to protect the joint. In the present study, the influence of electroless, electroplated, and sulfamate nickel coatings was investigated regarding the long-term stability. The joints were performed as industry-related arrester connections, consisting of EN AW 1370 cables and EN CW 004A terminals. The samples were exposed to corrosive as well as electrical, thermal, and mechanical stress tests according to current standards and regulations. Keywords Ultrasonic welding . Aluminum . Copper . Eutectic phase . Long-term behavior
1 Introduction In order to fulfill the current demands for reducing CO2 emissions, energy-efficient vehicles must be realized through approaches such as lightweight construction. By using electrically conductive materials with a lower density compared to the most commonly used material, copper, weight can be reduced. One approach is the substitution of copper by aluminum. Aluminum has a density which is about 70% lower than copper [1]. Since the conductivity of aluminum is lower than that of copper, the cross section of aluminum conductors must be increased by approximately 60%. Despite the increase in the conductor cross section, it is possible to achieve a theoretical weight saving up to 50% [2]. Due to the properties of Recommended for publication by Commission III - Resistance Welding, Solid State Welding, and Allied Joining Process * Jean Pierre Bergmann [email protected]; [email protected] 1
Technische Universität Ilmenau, Ilmenau, Germany
aluminum, such as the creep behavior and its oxide layer, the substitution can only be partial. The contacts provided for consumers and energy suppliers remain made of copper. Therefore, there is a need for the production of mixed aluminum/copper compounds. Due to the propertie
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