| Research Abstract |
Recently, aluminum-based light alloys with high strength have attracted great interest because of the increase in the importance of energy and environmental problems. It is well known that ordinary aluminum-based alloys have been developed by the use of the following strengthening mechanisms ; i.e., solid solution, precipitation, grain size refinement, dispersion, work hardening and fiber reinforcement. However, the maximum tensile strength for those alloys is only about 600 MPa. In order to fabricate a new aluminum-based alloy with much higher tensile strength even at high temperatures, amorphous or quasicrystalline particles with high hardness and thermal stability should be used as precipitating particles. Until now, we have carried out the development of aluminum-based alloys with high strength were nanoscale amorphous and quasicrystalline particles are dispersed, we should use amorphous or quasicrystalline particles as precipitates.
In this work, the structure and mechanical proper
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ties are studied for aluminum-based alloys with nanoscale quasicrystalline particles dispersed into fcc-Al phase. The results are summarized as follows.
(1) Structure of melt-quenched Al-Ln-TM (Ln : rare earth element, TM : transition metal) and Al-ETM (ETM : Ti, V, Cr, Mn)-LTM (LTM : Fe, Co, Ni, Cu) alloys with high aluminum concentration changes in order of Al+compound→Al+quasicrystalline→Al+amorphous→amorphous according as decrease of group number of transition metals.
(2) The quasicrystalline particle size in the powder metallurgy (P/M) aluminum alloys is in the range of 200 to 900nm.
(3) Ultamate tensile strength (σ_<UTS>) of P/M aluminum alloys with dispersion quasicrystalline particles ranges from 540 to 670 MPa. The maximum value of σ_<UTS>=670 MPa was obtained for P/M Al_<93>Fe_3Cr_2Ti_2 alloy. This value is more excellent than σUTS=600 MPa of conventional extra super duralumin
(4) Ultamate tensile strength (σ_<UTS>=350 MPa) after holding for 100 hours at 573 K is larger than target 300 MPa for high elevated-temperature strength of aluminum alloy
(5) The high elevated-temperature strength remains unchanged after annealing for 100 hours at 573 K and the good wear resistance against S45C steel is also maintained for the extrued alloy tested at the sliding velocity of 0.5 to 2 m/s. Less
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