Al-base amorphous/nanocrystalline bulk alloy rods composed of Al–10Ni–6Ce (numbers indicate at.%) matrix alloy and Al–4Fe–0.6Mo–1.1V–0.3Zr alloy particles (volume fraction = 0.3) were fabricated by a powder forging process. The starting materials were rapidly quenched, powder-shaped amorphous Al–10Ni–6Ce alloy and nanocrystalline Al–4Fe–0.6Mo–1.1V–0.3Zr alloy. The amorphous alloy powders were prepared by the pulverization of melt-spun ribbons, and the nanocrystalline alloy powders were fabricated by using a gas atomization technique. The powder forging process involved pre-compaction of the amorphous/crystalline powder mixtures by cold pressing and subsequent forging at temperatures ranging from 623 to 773 K with a pressure of 0.66 GPa and a strain rate of 10 −2  s −1 to produce the rod-shaped bulk hybrid alloys having a diameter of 10 mm. Bulk monolithic Al–10Ni–6Ce alloys having the same shape were also fabricated by using a similar process to that used for the hybrid ones. Fully dense bulk rods with a porosity of less than 2% were achieved for all of the forged monolithic and hybrid alloys. A remarkably high compressive strength of about 1.2 GPa along with a compressive plastic strain of 1% was obtained at room temperature for the bulk hybrid specimen forged at 648–673 K. In contrast, the bulk monolithic specimen forged at 648–723 K did not exhibit any compressive plastic strain, although it possessed a very high compressive strength of approximately 1.34 GPa.

Microstructure and compressive behavior of Al-base amorphous/nanocrystalline alloys fabricated by powder forging

The rod-shaped bulk composites consisting of Al-10Ni-6Ce and Al-4Fe-0.6Mo-1.1V- 0.3Zr alloy (mixing ratio; 0.7:0.3, 0.5:0.5 and 0.3:0.7) and corresponding monolithic alloys were produced to a full density via powder forging process. The process involved pre-compaction of rapidly solidified alloy powders and subsequent isothermal forging at 673K. The forged Al-10Ni- 6Ce alloy exhibited nano-scaled crystalline particles, such as fcc-Al, Al3Ni, Al4Ce and Al11Ce3 phase, coexisting with an amorphous phase. In the case of the forged Al-4Fe-0.6Mo-1.1V-0.3Zr alloy, an equiaxed grain structure was observed to exist with uniformly distributed nano-scaled Al- Fe based intermetallics. The monolithic Al-10Ni-6Ce alloy had a considerably high maximum compressive strength (MCS) of 1.35 GPa without showing any compressive plastic strain (CPS). In contrast, the monolithic Al-4Fe-0.6Mo-1.1V-0.3Zr alloy possessed noticeably high CPS of 25% with the MCS of 0.71GPa. The composites acquired the CPS varying from 1 to 5.8 % and the MCS from 1.26 to 0.74 GPa, with increment of the volume fraction of Al-4Fe-0.6Mo-1.1V-0.3Zr alloy from 0.3 to 0.7.

Synthesis and Properties of Bulk Amorphous/Nanocrystalline Aluminum Alloy Composites

Effect of warm-rolling temperature on the microstructural evolution and mechanical properties of large 2219 Al-Cu alloy rings

Mechanical properties of a nano-structured Al-8Fe-2Mo-2V-1Zr alloy produced by spray forming and subsequent hot-extrusion at 420°C were investigated in terms of tensile test as a function of temperature. Warm rolling was adapted as an additional process to expect further refinement in microstructure. Well-defined equiaxed grain structure and finely distributed dispersoids with nano-scale in particle size were observed in the spray formed and hot extruded sample (as-received sample). The average grain size and particle size were measured to 500 nm and 50 nm, respectively. While it was found that warm rolling gives rise to precipitate fine dispersoids less than 10 nm without influencing the grain size of matrix phase, in the temperature range of RT∼150°C, distinguishable changes in ultimate tensile strength were not found between the as-received and warm-rolled samples. At elevated temperatures ranging from 350 to 550°C, warm-rolled sample showed a higher value of elongation than as-received one although similar values of elongation were observed between two samples at temperatures lower than 350°C.

Jae Sung Park

Papers

Effect of Warm Rolling on Microstructure and High Temperature Mechanical Behavior of a Nano-Structured Al-8Fe-2Mo-2V-1Zr Alloy