Origins and Impact of Defects in Aluminum Wire: A Multi Process Perspective

The global aluminum wire market, valued at USD 63.3 billion in 2023, is expanding rapidly driven by increasing demand from the automotive and electrical infrastructure sectors, and by high tech industries seeking lightweight power transmission alternatives. As a major producer of aluminum rod, Rio Tinto plays a key role in supplying this market, where a significant share of production is dedicated to rod and conductor wire applications. Despite technological advances, aluminum wire quality may be subject to challenges associated with casting conditions, rolling mill processes, and environmental or operational constraints. Defects originating in the liquid state, such as segregation, porosity, shrinkage piping, inclusions, and hot tearing, as well as solid state issues like cracks, surface defects, residual stresses, or embrittlement, can severely affect wire performance. Mechanical interactions during drawing and stranding operations further contribute to deformation and surface damag. Fractographic analyses over several years reveal that the primary cause of aluminum wire fractures is the presence of second phase particles, typically oxide inclusions (Al₂O₃, Al₄C₃, and mixed oxide clusters). These inclusions are often pulled out during drawing, initiating cracking. Additionally, transition metal impurities (V, Ti, Zr, Cr) negatively impact electrical conductivity. Their removal through boron treatment occurs via a two stage kinetic process, with faster removal of V and Ti compared to Zr and Cr. Understanding the origins, mechanisms, and impacts of these defects is essential to improving wire reliability and optimizing production parameters across the casting, rolling, and downstream processing stages.