Structures and Mechanical Properties of P/M Materials of Rapidly Solidified A.1-8 percentY Based Alloys Containing Transition Metals

摘要

The mechanical properties and microstructures of rapidly solidified P/M materials of Al-8 mass percent Y based alloys containing 4 mass percent Fe, Mn, Cr or Ni have been studied. Rapidly solidified flakes of these alloys were prepared by atomizing the alloy melt and subsequently splat quenching onto a single copper roll. These flakes were consolidated by cold pressing, vacuum degassing and hot extrusion. Metallographic structures and constituent phases were studied in both flakes and P/M materials by X-ray diffraction and transmission electron microscopy. Mechanical properties of P/M materials were examined by tensile tests at room and elevated temperatures. The fine dendritic cell microstructures consisting of alpha-Al surrounded by eutectic compounds are observed in rapidly solidified flakes of the Al-8 mass percent Y alloy and ternary alloys containing Fe, Mn or Ni. In contrast, the globular compound particles are observed in the Cr-bearing alloy. The as-rapidly solidified Al-8 mass percent Y alloy contains alpha-Al_3Y and a metastable phase (Al-Y compound), however alpha-A1_3Y is replaced by beta-Al_3Y after annealing at 773 K for 7.2 ks. The hardness of as-extruded P/M materials of the ternary alloys is greater than that of the binary alloy, and the Cr-bearing alloy shows the highest hardness. As-extruded P/M materials of the ternary alloys contain finer distribution of intermetallic compounds with a higher volume fraction than the binary alloy. Tensile strength of the ternary alloys ranges from 420 to 524 MPa at room temperature, and is higher than that of the binary alloy. The Cr-bearing alloy shows the highest tensile strength, 524 MPa at room temperature, 370 MPa at 473 K and 218 MPa at 573 K. All P/M materials have good ductility with elongation of above 12 percent at room temperature.