アモルファスおよび準結晶急速凝固粉末の利用による高比強度Ａｌ基合金の開発

Abstract

Recent progress and present situation of high specific-sterngth Al-based alloys by the use of nonperiodic structure such as amorphous and quasicrystalline phases have been reviewed. Amorphous alloys with high tensile strength (σf) above 1000 MPa were obtained in Al-Ln-TM and Al-ETM-LTM (Ln=lanthanide metal, ETM= IV to VI group transition metal, LTM= VII and VIII group transition metal) systems by melt spinning and gas atomization. The warm extrusion of atomized amorphous powders caused the formation of bulk nanostructure (NS) alloys consisting of compounds (Al11Ln3 and Al3Ni) with a size of 50 nm embedded in fcc-Al phase with a grain size of 100 to 200 nm and the NS alloys exhibit high σf of 700 to 1000 MPa, elongation of 1 to 8 %, high fatigue strength of 300 to 350 MPa and high elevated-temperature strength of 300 MPa at 573 K. The Al-based NS alloys have been used in some application fields which require high specific strength. Bisides, bulk nanoquasicrystalline (NQ) alloys consisting of nanoscale icosahedral particles with a size of 20 to 70 nm surrounded by fcc-Al phase with a spacing of about 10 nm were produced by warm extrusion of atomized powder in Al-Mn-Ce, Al-Cr-Ce-TM, Al-Mn-TM and Al-Cr-TM systems. The NQ alloys also exhibited good combined mechanical properties, i. e., high σf of 500 to 800 MPa, large elongations of 5 to 35 %, high impact fracture energies reaching 180 kJ/m2 and high elevated temperature strength of 260 MPa at 573 K. These properties are much superior to those for conventional Al-based alloys and hence the NQ alloys are also expected to develop as a new type of high specific-strength material.