Mechanical and Microstructural Response of Elevated Temperature PM (Powder Metal) Aluminum-Titanium Alloys.

摘要

In order to extend the useful temperature range of aluminum alloys to 200-300 C. a novel processing scheme was formulated where prealloyed gas atomized powders were mechanically alloyed in the presence of a carbon bearing process control agent to produce an alloy with a fine dispersion of aluminides, carbides, and oxides. Titanium was selected as the prime alloying element since it forms a thermally stable Al(3)Ti dispersoid and has the potential to form a stable carbide, i.e., TiC. Also, the low diffusivity and solid state solubility of titanium in aluminum indicated that Al(3)Ti should resist coarsening and curtail property degradation. The objective of the study was to investigate the microstructural and mechanical behavior and develop a model account for the ambient and elevated temperature deformation behavior. Helium gas atomized (AT), mechanically alloyed (MA), and atomized plus mechanically alloyed (AM) aluminum 4 and 6 wt.% Ti alloy powders were vacuum hot pressed and extruded into 22mm diameter round rod. The alloy microstructure was fully characterized using optical and electron microscopy, x-ray and electron diffraction; and image analysis. Ambient and elevated temperature mechanical tests were performed in order to assess alloy strength, ductility, notch toughness, and creep resistance. Keywords: Powder metallurgy; Aluminum carbide; High temperature aluminum dispersion strengthened aluminum oxide. (sdw)