125 resultados para INTERMETALLICS


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The effect of Ca addition on the microstructure, physical characteristics (density/porosity), and mechanical properties (tensile and impact strength) has been investigated in an Al-7Si-0.3Mg-xFe (x = 0.2, 0.4, and 0.7) alloy. The size of Al-Fe intermetallic platelets (beta-Al5FeSi) increased with increasing Fe content. The addition of Ca modified the eutectic microstructure and also reduced the size of intermetallic Fe-platelets, causing improved elongation and impact strengths. A low level of Ca addition (39 ppm) reduced the porosity of the alloys. The tensile strength was decreased marginally with Ca addition. However, Ca addition improved the ductility of the alloy by 18.3, 16.7, and 44 pet and the impact strength by 44, 48, and 15.8 pct for Fe contents of 0.2, 0.4, and 0.7 pct, respectively.

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The precipitation of chromium-containing phases, in both the B2 type β-phase coating matrix (nominally NiAl) and the substrate of high-activity-pack-aluminized single crystals of a nickel-base superalloy, is considered in this paper. An ‘edge-on’ transmission electron microscopy (TEM) technique is employed to examine the precipitation of M23X6, σ, α-Cr and other phases after coating and diffusion treatment and subsequent post-coating treatment at 850 and 950 °C. Initial precipitation is dominated by the formation of M23X6 in both the coating and substrate, however, in the case of single-crystal substrates the formation of this carbon-rich phase is not sustained. M23X6 precipitation is superceded by the formation of coherent precipitates of the α-Cr phase which effectively retains the basis but removes the superlattice of the β-matrix. Extensive precipitation of α-Cr has the effect of changing the balance of chromium to molybdenum in solution in the β-phase and further precipitation is dominated by Σ-phase intermetallics and other Cr-Mo-containing phases.

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NASCIMENTO,R.M. et al.Interface microstructure of alumina mechanically metallized with Ti brazed to Fe–Ni–Co using different fillers. Materials Science and Engineering A, v.466, n.1/2, p. 195-200, 2007.

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NASCIMENTO,R.M. et al.Interface microstructure of alumina mechanically metallized with Ti brazed to Fe–Ni–Co using different fillers. Materials Science and Engineering A, v.466, n.1/2, p. 195-200, 2007.