Hee Teak Shin1, Junichi Kaneko1 and Makoto Sugamata1
1Department of Mechanical Engineering, College of Industrial Technology, Nihon University, Narashino
Precipitation hardening of a supersaturated solid solution of extended solubility obtained by rapid solidification has been studied on an Al-8%Mn-2%Cr alloy with or without addition of Zr or Ni. Rapidly solidified flakes were produced by using an apparatus combining gas-atomization and water-cooled copper single roll. P/M materials were consolidated from the flakes by cold pressing, vacuum degassing and hot extrusion. Precipitation hardening behavior was examined for both rapidly solidified flakes and P/M materials.
In age-hardening at 673 K, a higher peak hardness was attained and softening due to overaging was observed for a Zr-added alloy. TEM obsevation and X-ray diffraction revealed that the hardening due to ZrAl3 precipitation was superimposed on that due to ternary G-phase ［(Mn, Cr)Al12］. Nickel addition caused a significant delay of precipitation hardening due to the formation of a ternary compound Al16Mn3Ni. Both Ni and Zr additions increased the tensile strength as well as the elongation of as-extruded materials. However, the fully precipitation hardened materials showed extremely poor tensile ductility at room temperature.
rapid solidification, precipitation hardening, aluminum-manganese-chromium alloy, powder metallurgy, mechanical property, zirconium addition, nickel addition
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