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The aging precipitation behavior of 6061 aluminum alloy that underwent iron casting and water-cooled copper casting and 6061 aluminum with Mn and Zr elements added was studied. Firstly, the hardness curves, tensile properties, and fracture morphology of four aging alloys—6061 (iron mold casting), 6061 (water-cooled copper mold casting), 6061-0.15Mn-0.05Zr (iron mold casting), and 6061-0.15Mn-0.05Zr (water-cooled copper mold casting)—were studied. The results of the aging hardness curve show that the aging precipitated phase of the 6061 alloy cast with a water-cooled copper mold is dispersed. The addition of Mn increases the amount of coarse inclusion α-(AlMnFeSi) in the alloy, resulting in a decrease in the age hardening property. The addition of Zr is related to the nucleation and growth of the G.P. region in the early aging period, mainly changing the formation rate and quantity of the G.P. region, leading to the advancement of peak aging and an increase in hardness. After the G.P. region gradually transforms into the β phase, the hardness of the alloy increases with the increase in the volume fraction of the β phase. When the β″ phase is coarsened to the point where the fault line can be bypassed, the transitional metastable β′ phase begins to precipitate, and the coherent distortion around it weakens, indicating over-aging. Finally, the equilibrium phase Mg2Si is formed. The results of the tensile tests indicate that the tensile strength and yield strength of the 6061-0.15Mn-0.05Zr alloy produced by water-cooled copper casting after aging are 356 Mpa and 230 Mpa, respectively. These values are 80 MPa and 75 MPa higher, respectively, than those of the 6061 aluminum alloy produced via iron casting. However, the elongation is by 5%. The fracture morphology of the tensile sample of the aging alloy shows that dislocation slip in the alloy results in dislocation plugging, stress concentration, and the initiation of crack cleavage on the surface. The fracture of the water-cooled copper mold-casting alloy is a ductile fracture of the microporous aggregation type, and the macroscopic fracture exhibits an obvious "neck shrinkage" phenomenon. The fracture analysis is consistent with the mechanical properties. The DSC curve shows that there is no enrichment process of solute atoms during the heating process, and the aging precipitation process after homogenization is as follows: G.P. zone → β″ phase → β′ phase. The aging precipitation process of the water-cooled copper casting alloy after homogenization treatment is as follows: β″ phase → β′ phase (no precipitation in the G.P. zone was observed). The results of the differential scanning calorimetry (DSC) analysis show that the main strengthening phase in the experimental alloy system is the β″ phase. The activation energies for the β″ phase precipitation were calculated and found to be 147 KJ/mol, 217 KJ/mol, 185 KJ/mol, and 235 KJ/mol, respectively. Additionally, a kinetic equation for the β″ phase precipitation during alloy aging was fitted. [ABSTRACT FROM AUTHOR]

The compressive behavior of closed-cell copper-coated carbon fiber/aluminum composite foam with 1 and 5wt.% fibers was assessed under quasi-static and high-strain-rate loading conditions. The 5wt.% fiber/aluminum foam exhibits higher plastic collapse stress. The failure modes of fibers in the matrix were discussed. A strain-rate effect was demonstrated for fiber/aluminum foam. The strain-rate effect was more apparent at strain rates in the ∼ks−1 range and is attributed to the rate sensitivity of dense fiber/aluminum composite and to the foam structure. [ABSTRACT FROM AUTHOR]

Abstract: The anisotropic compressive behavior of closed-cell Al–Si alloy foams prepared by melt foaming process has been investigated. The results show that the stress drop ratio measured in the longitudinal direction is higher than that in the transverse direction. Moreover, the stress drop ratio decreases with increasing relative density of foamed specimen. The shape anisotropy ratio R increases firstly and decreases afterward with increasing relative density. The Young''s modulus ratio and yield stress ratio for closed-cell Al–Si alloy foams were investigated and compared with G&A model. A linear relationship between Young''s modulus ratio, yield strength ratio and anisotropy ratio has been obtained. The Young''s modulus is more sensitive to cell shape than yield stress. [Copyright &y& Elsevier]

Abstract: Closed-cell aluminum alloy foams with 1.5, 3.0wt.% fly ash particles have been manufactured by molten body transitional foaming process. The room temperature damping properties of fly ash reinforced aluminum alloy foams were measured at different strain amplitude in two directions using the forced vibration mode. The results show that the damping properties of fly ash reinforced aluminum alloy foams increase with FA content. A critical strain amplitude εcrit was observed and εcrit decreases with increasing FA content. Moreover, the damping property in the transverse direction is higher than that in the longitudinal direction. The related mechanism has been discussed. [Copyright &y& Elsevier]

The present study shows a new manufacturing process for improving the quality of Al alloy foams by powder metallurgy method. Foaming process was accelerated by combining the actions of the modification of Al-1%Mg-xSn (x=0, 3 and 5 wt%)/7%SiC precursor and the application of foaming mould providing high heating rate. The liquid Sn filled up the voids in the precursor and helped to capture the liberated H 2 during foaming. The early expansion stage occurred in advance with addition of Sn. Foaming behaviors and the morphologies of the Al foams revealed that the stability and the final cellular structure were improved significantly. [ABSTRACT FROM AUTHOR]

Abstract: The wetting behavior of Al–Ge alloys on TiH2 substrates was investigated by an improved sessile drop method under high vacuum and in a temperature range of 773–818K. Results indicate that the equilibrium contact angles of Al–Ge/TiH2 increase linearly with temperature according to the following formula: θ =0.2882T −85.04, and decrease linearly as the Ge content increases from 25.2% to 36.2% according to the formula: θ =214−200Ge (wt.%). The worst wetting behavior was obtained for a pure Al/TiH2 system at its foaming temperature (973K). TiH2 particles were prone to aggregate and were thus difficult to disperse. This could be one of the reasons for closed-cell aluminum foam products having non-uniform pores. [Copyright &y& Elsevier]