MECHANICAL-PROPERTIES OF AN AL88.5NI8MM3.5 (MM, MISCH METAL) ALLOY PRODUCED BY EXTRUSION OF ATOMIZED AMORPHOUS PLUS FCC-AL PHASE POWDERS

A bulky Al88.5Ni8Mm3.5 alloy was produced by extrusion of atomized powders with a mixed structure of amorphous and fcc-Al phases at an extrusion ratio of 10 and at 633 K and was found to exhibit high tensile strengths (sigma(f)) of 940 MPa at room temperature (RT), 700 MPa at 423 K and 520 MPa at 473 K. Similarly, the yield strength (sigma0.2) is also as high as 845 MPa at RT and 420 MPa at 473 K. The high values of sigma(f) and sigma0.2 remain unchanged even after annealing for 100 h at these testing temperatures. The fatigue limit after the cycles of 10(7) is also as high as 330 MPa at 293 K and 220 MPa at 473 K. The fatigue limit at R T is also 1.2 times as high as the highest value for conventional Al-based alloys. The high mechanical strengths and their good heat resistance are presumably due to the formation of a finely mixed structure consisting of Al3Ni and Al11(La, Ce)3 particles with a size of 0.05 mum homogeneously embedded in an Al matrix with a grain size of 0.1 to 0.2 mum. In addition, the Al-Ni-Mm alloy also exhibits a low coefficient of thermal expansion and good wear resistance because of the homogeneous dispersion of a large amount of the intermetallic compounds. The simultaneous achievement of good mechanical and physical properties allows an expectation for practical use of the new type Al-based alloy in various fields.