On enhancing the mechanical properties of aluminum P/M alloys

Sintered aluminum alloys are an attractive material for the automobile indu stry, both because of the low specific gravity and high strength-to-weight ratio of aluminum itself, and the fabrication advantages associated with a powder metallurgy process. However, properties such as impact. stiffness, c orrosion and wear resistance are often poor, thereby restricting the widesp read use of these materials. Recent work by the authors has shown that hard ness, wear resistance and tensile properties of a P/M Al-Cu-Mg ternary mast er alloy can be improved using a novel diffusion/supersolidus liquid phase sintering process. Improvements were due to in-situ microalloying during si ntering, in particular, the influence of Ag and Sn. To complement this work , the present investigation addresses the response of a commercial alloy, A A2014, to the microalloying process. Results show that sintered densities f or the commercial alloy were relatively unaffected by the presence of eithe r AE or Sn, and were superior to the ternary master alloy. Hardness and ten sile properties were also improved relative to those obtained for the terna ry, and were comparable to wrought 2014. Examination of final microstructur e of Ag modified AA2014 using TEM showed the presence of Omega as the princ ipal precipitate, but only after extended sintering times. This particular precipitate is believed to contribute to enhanced hardness. The apparent ab sence of Omega for short sintering times was due to the presence of silicon in the commercial product. However, the corrosion behavior of the P/M AA20 14 was superior to the wrought product and thus the process is presented as a potential P/M alternative to using ingot metallurgy techniques for micro alloying. (C) 2000 Elsevier Science S.A. All rights reserved.