Criticality Research in the Materials Community

As materials scientists and engineers, the primary focus of our industry is on performance. Whether selecting from existing materials and processes or developing new alloys and processing techniques, it is first and foremost important to meet the functional requirements of any given application. Next, it is often most logical and practical to select the option which minimizes cost while maximizing performance. However, what role do other factors, such as life cycle environmental impacts and supply-chain security, play in this decision-making process? What role should they play, now and in the future? And what is our responsibility, as a community, in leading the way? Historically, the aforementioned issues have been considered ancillary and were largely neglected in major materials design decisions. However, over the past 50 years, several events have forced these concerns into the spotlight. For example, in the 1970s, a small-scale uprising in Zaire (now the Congo) created a short-term supply shortage in cobalt as 40% of global production was mined in that geographic area. This caused massive spikes in the commodity price of cobalt, which resulted in speculation, government stockpiling, and massive disruption to firms in the semiconductor industry. Additionally, the introduction of the Environmental Protection Agency (EPA) and its various policies (Toxic Substances Act, Clean Air Act, Clean Water Act, etc.) changed the way many materials could be used. For example, in light of new evidence as to its extremely high toxicity, substitution of lead became a priority in the 1980s for applications such as gasoline additives and paint pigments. However, because of the lack of substitutes in battery applications, lead use has increased overall. When considered together, these factors begin to form part of the larger picture that is materials criticality. Although it lacks a consistent definition throughout the literature, criticality is generally defined as a dynamic, multidimensional characteristic of materials, which describes the level of inherent vulnerability as well as the risk within their respective supply-chains. This special topic in JOM highlights some articles representing international, industrial, and academic perspectives on the complex and evolving issue of materials criticality. It is the hope that this issue will increase awareness and inspire further developments that help improve our collective understanding of criticality and its impact on the material science field. There will be a criticality plenary session at the upcoming TMS annual meeting in Orlando, Florida, and a future expanded special topic in the June issue of JOM (manuscript deadline of February 15, 2015). The most basic type of criticality research focuses on concerns over physical abundance or scarcity. Concerns over material availability, especially for emerging technologies, are not new and over the last 70 years have sparked debates as well as national policies aimed at securing critical materials. For example, the most recent Department of Defense Strategic and Critical Materials report per the Strategic and Critical Materials Stockpiling Act uses material consumption, production, and projected future demand to determine the severity of material criticality. Similarly, in previous literature the material availability is determined primarily by physical scarcity. Scarcity research calculates static metrics, such as depletion time (a measure of how long known reserves will last, given current levels of extraction); although it is informative and useful, it can provide only limited resolution of the real and complex issues at hand. In reality, criticality is a dynamic characteristic; however, dynamic approaches are challenging and therefore lacking in the literature. However, a few studies have been published in recent years employing dynamic material flow analysis and agent-based modeling. Expanding on physical scarcity is an approach first introduced by the National Research Council’s Gabrielle Gaustad is the guest editor for the Recycling and Environmental Technologies Committee, a joint committee of the TMS Extraction & Processing and the Light Metals divisions, and coordinator of the topic Critical Materials: Strategies for Achieving Sustainability in this issue. JOM, Vol. 66, No. 11, 2014