Microstructure of Rapidly Solidified Al–V–Ce–M (M=Fe, Co or Ni) High Strength Alloys Containing High Volume Fraction of Fine Icosahedral Precipitation

Abstract

Nanostructure alloys of icosahedral (I) and fcc-Al phases exhibiting good bending ductility and high tensile strength (σ t ) were found to form in rapidly solidified Al 98-x V x Ce 1 M 1 (M=Fe, Co or Ni ; x=3 to 6 at%) and Al 95-x V 4 Ce 1 M x (M = 1 to 2 at%) alloys. The particle size and interparticle spacing of the I phase are 30 to 90 nm and 10 to 40 nm, respectively, for the Al 94 V 4 Ce 1 M 1 alloys and no distinct difference in the nanostructure is seen among the three alloys containing Fe, Co or Ni as the M element. The volume fraction of the I phase (V f ) was measured to be as high as about 80%. However, the deviation of V and M concentrations from 4 at%V and 1 at%M causes the increase in the particle size of the I-phase accompanying the decreases in the thickness of the fcc-Al layer and in V f . The better mechanical properties are obtained for the Al 94 V 4 Ce 1 M 1 alloys with the smallest particle size of the I phase and the highest tensile strength (σ f ) is 1040 MPa for M = Fe, 1120 MPa for M=Co and 1170 MPa for M = Ni. The σ f is the highest for the Ni-containing alloy. The reason for the achievement of the highest σ f is presumably due to the increase in the degree of quenching effect because the eutectic temperature in Al-rich Al-Ni binary system is much lower than those in Al-Fe and Al-Co systems. It is thus to be noticed that the high σ f exceeding 1000 MPa is obtained for the Al-rich alloys containing 94 at%Al.