Materials and engineering: An evolving landscape
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Introduction
The role of materials in engineering
Starting with stone in prehistoric times followed by copper and then iron and steel by the 19th century, the number of materials available to engineers was perhaps a few hundred. Today, this number stands at about 160,000, most of which were discovered or developed in the past 100 years.1,2 Figure 1 shows an example of this extraordinary growth of materials choice in strength–density space in three Ashby maps.3 The precursors to the discipline of materials engineering were established in the distant past. Metal forming emerged around 3000–4000 BC with the heating of native copper to make tools and other items. In approximately the same period, copper was smelted from its ore in Timna in Israel. The third great innovation, alloying, appears to have occurred between 2000 BC and 3000 BC in Egypt, where the earliest bronzes have been found. Together, this triad of events laid the foundations for the paradigm on which materials science is based: the relationship among composition, processing, structure, and properties. In this article, we explore the impact of the expanding choice of materials and the related processes of making, shaping, and joining; the evolving integration of materials development with the design of products and systems; and attempts to accelerate materials insertion. We also discuss the emerging topography of scarcity and sustainability, which will drive the use of materials in the future.
The relationship between artifacts and materials can be indirect. As Mark Miodownik, the author of one of the articles in this issue, points out in his book Stuff Matters,4 the pyramids could not have been built without copper tools (Figure 2), which resulted from civilizations’ entry into the metal age with the extraction of copper from malachite. Certainly, the emergence of the blast furnace in China in about 200 BC, culminating in large-scale steel production through 1900 AD, laid the platform for the industrial use of materials that have revolutionized the way we travel, produce energy, and inform and interact with each other. The increased capability of commercial aircraft, for example, as measured by range and operating cost, has “shrunk” the world. Figure 3a shows the dramatic decrease in fuel consumption per passenger achieved in air travel over the past few decades. Improvements in the durability and reliability of engines used on commercial aircraft have transformed flight in ways that most of us do not realize. When the Boeing 707, the first large, commercial, jet-powered aircraft, entered service in the late 1950s, the goal was for the engines to stay “on wing” between major maintenance procedures for 500 flight hours. Today, engines used on long-haul commercial aircraft routinely stay on wing for 20,000–25,000 h. Aircraft can now fly nonstop as long as 15–20 h, including long segments over water or other terrain within single-engine
Dipankar Banerjee, Department of Materials Engineering, Indian Institute of Science, India; [email protected]
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