Al89.5Ni8Zr2.5 and Al88.5Ni8Ti3.5 alloys extruded from their rapidly solidified powders have tensile strength more than 800 MPa and Young＇s modulus about 100 GPa. The extruded Al89.5Ni8Zr2.5 alloy is composed of alpha-Al, Al3Ni and a metastable tetragonal Al3Zr, and the extruded Al88.5Ni8Ti3.5 alloy consists of alpha-Al, Al3Ni and equilibrium Al3Ti. Through investigation on microstructure change of rapidly solidified Al89.5Ni8Zr2.5 and Al88.5Ni8Ti3.5 alloys with temperature, it is found that a new tetragonal Al3Zr phase, together with alpha-Al and Al3Ni precipitates from the supersaturated alpha-Al phase in the rapidly solidified Al89.5Ni8Zr2.5 alloy at around 603 K and an equilibrium Al3Ti, together with alpha-Al and Al3Ni forms from the supersaturated alpha-Al phase in the rapidly solidified Al88.5Ni8Ti3.5 alloy at about 523 K. The lattice parameters of the new metastable tetragonal Al3Zr phase were calculated to be a = 0.3986 nm and c = 0.9006 nm and nm. Both the metastable tetragonal Al3Zr and equilibrium Al3Ti phases keep a nano grain size, less than 50 nm even at 773 K. The existence of the nano scale Al3Zr, Al3Ti phases and fine grains of alpha-Al, Al3Ni phases is the reason that Al89.5Ni8Zr2.5 and Al88.5Ni8Ti3.5 alloys have the high strength.