Sliding wear response of a zinc-based alloy compared to a copper-based alloy
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TRODUCTION
THERE has been a continuous search for alternative materials for engineering applications in order to reduce the cost of production without sacrificing the functional requirements of the components made thereof.[1] Zinc-based alloys are of a recent origin in this regard, offering a number of benefits over their conventional counterparts like copper-based alloys (containing lead, tin, etc.) and other ferrous and nonferrous alloys in various engineering applications.[1–6] Interestingly, most of the applications are based on practical experiences.[7] The concept of ‘‘forceful and need-based’’ use of zincbased alloys in place of bronzes/brasses emerged with the start of World War II in Germany, during the period from 1939 to 1943, as a result of the short supply of copper.[7] It may be noted that copper is one of the major constituents of bronzes/brasses. However, as soon as World War II was over and the supply of copper became normal, all the applications of zinc-based alloys were resubstituted with bronze/brass components for the simple reason that not much was known about the new (zinc-based) alloy system.[7] However, experience showed that the zinc-based alloys perform better in some of the applications, especially those involving slow speed of rotation/low-temperature (less than 100 7C) conditions.[1–5,7–12] Seeing the potential of utilizing zinc-based alloys as a cost- and energy-effective substitute for the brasses/bronzes, research and development activities were begun to develop different varieties of the alloy system.[7] One of the major setbacks to the developmental programs was the nonavailability of zinc with a purity level greater than 99.99 pct.[13,14] This, associated with a lack of knowledge about appropriate alloy design, led to the development of a misconception in many parts of the world that zinc-based alloys cannot perform well.[3] The overall influence of these incidents made developmental activities quite slow and ineffective for quite some time. As a result, zinc-based alloys could not make a landmark JAGDISH PRASAD PANDEY, Technical Officer, and BRAJ KISHORE PRASAD, Scientist, are with the Regional Research Laboratory (CSIR), Bhopal-462 026, India. Manuscript submitted June 16, 1997. METALLURGICAL AND MATERIALS TRANSACTIONS A
until the 1970s, when three standard compositions of ‘‘high-strength’’ (zinc-based) alloys containing 8 to 28 pct Al, 1 to 3 pct Cu, and ;0.05 pct Mg came into existence.[8,15] The alloys were designated as ZA8, ZA12, and ZA27, the digits included in the alloy designations representing their approximate aluminum content.[8,15] Other varieties of zinc-based alloys include the ones containing 3 to 5 pct Al, along with Cu and Mg, termed as Zamak 3 and Zamak 5 (the digit in the alloy designation again representing their approximate aluminum content), but they have very limited applications at present and the majority of their applications have been substituted by the ZA series of alloys. Recently, zinc-based alloys with 3 to 5 pct Al, 5 to 10 pct Cu, and ;0.05 pct
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