Improvement in the Mechanical Behavior of Mechanically Alloyed Aluminum Using Short-Time NH 3 Flow
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IN recent years, lightweight alloys have attracted much interest in the transportation industry due to the weight reduction and the consequent reduction in fuel consumption.[1,2] Aluminum and its alloys are very attractive for a wide range of structural applications, especially in the automotive and aircraft industries, because of their excellent properties, including their lightweight nature.[3,4] However, the properties of such alloys undergo a marked degradation when the temperature is above 373 K (100 °C). Thus, aluminum alloys cannot be used in many applications, hindering, for instance, the application of these low-density alloys to the reduction of fuel consumption of vehicles. Consequently, it is interesting to enhance the mechanical properties of aluminum, both at room temperature and at high temperatures. One way to improve the properties of Al is to reinforce it with a variety of hard ceramic particles.[5] The resulting materials, which are widely used in the industrial sector,[6,7] are generally known as aluminum matrix composites (AMCs). AMCs exhibit very interesting properties, outstanding wear resistance, and specific strength compared with conventional alloys.[8,9] Nevertheless, the development and widespread application of high-performance AMCs are limited due to an inadequate matrix-reinforcement bonding interface. Moreover, high temperatures could promote reactions between the
matrix and the reinforcement, which can adversely affect the bonding strength. In recent years, many studies have been performed to determine which reinforcements produce the best combination of mechanical properties.[10,11] Although Al2O3 and SiC have been predominantly used as reinforcements over recent decades,[12–14] a wide variety of reinforcements have appeared for AMCs, such as AlN, B4C, SiO2, TiB2, TiC, TiO2, and ZrB2. Particulate-reinforced composites can be prepared by accumulative roll bonding (ARB),[15] cross-ARB,[16] stir casting,[17] and powder metallurgy (PM),[18,19] among other methods. This last technique is inexpensive and allows for producing, in general, AMCs with good mechanical properties. In the present work, highly dense Al-based metal matrix composites reinforced by oxides, carbides, and mainly nitrides were obtained by mechanical alloying (MA), pressing, and sintering. Traditionally, Al powder has been reinforced with submicron (0.1 to 1 lm) or nanosized (
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