Effect of multi-pass friction stir processing on microstructure and mechanical properties of cast Al-7Fe-5Ni alloy

The mechanical behavior and microstructure of aluminum alloys for high temperature applications, prepared by rapid solidification and powder metallurgy techniques, have been observed. These alloys contain high concentrations of transition elements which form thermally stable precipitates. Tensile tests were performed at room temperature, at 77 K and at high temperature. The microstructure is described in terms of precipitation and dislocation structure. Samples deformed at different temperatures were observed. The behavior of alloys of this type is discussed, introducing the effect of an internal stress. Special attention is devoted to the ductility dip frequently observed in such alloys.

Mechanical properties and microstructure of AlFeX alloys

Hydrogen effect on high temperature ductility of a powder metallurgy AlFe alloy

\n Due to the limited solid-solubility of Fe and Ni in Al, coarse brittle intermetallics rich in Fe and/or Ni are inevitably formed in the as-cast microstructure of Al-Fe-Ni alloys. Upon formation, Fe(Ni)-rich intermetallics significantly deteriorate the properties and restrict the application of alloy in as-cast condition. The purpose of this study was to investigate the effect of friction stir processing (FSP) on microstructure and tribological properties of cast Al-7Fe-5Ni alloy. The dry sliding wear tests were done by using a pin-on-disk type machine under the applied pressures of 1, 2, and 3 MPa, sliding distance of 1000 m, at room temperature. According to the results, FSP (1250 rpm and 8 mm/min) effectively refined the microstructure, especially the coarse primary Al9FeNi intermetallics and eliminated the alloy casting-related defects. FSP also converted the large columnar grains of the cast alloys to the ultrafine equiaxed grains. These microstructural changes enhanced the substrate mechanical properties thereby increased its resistance against sliding-induced plastic flow, leading to the higher tribolayer stability on the surface, and accordingly, higher wear resistance. The results showed that applying 1-pass FSP reduced the wear by 13% and 53% under applied pressures of 1 and 3 MPa, respectively. The friction results also revealed that, compared with the as-cast sample, FSPed samples exhibited lower friction coefficient and friction coefficient fluctuations.

Improving the Tribological Properties of Al-7Fe-5Ni Alloys via Friction Stir Processing

The preparation of an Al–3·8Fe–3·6Ni–3·8Co engineering material from atomized powders is described. The production route involves cold compaction followed by extrusion at 400–600°C. It is shown that products having acceptable surface finishes may be produced and that the properties of the products are related to the extrusion parameters. The structure is considerably modified during the deformation processing and is much coarser than that existing in the individual powder particles. The properties of the product are superior at room temperature to those of existing non-heat treatable Al alloys and the material maintains its considerable strength at elevated temperatures. PM/0284

T. Sheppard

Papers

Production structure and properties of Al-Fe-Ni-Co alloy prepared from atomized powder