F. Huang
材料科学技术（英）
Microstructure and hardness were investigated in pure Al samples with different purities (5N: 99.999%, 4N: 99.993%, and 2N: 99.7% in weight) subjected to dynamic plastic deformation at cryogenic temperatures. The saturated sizes of refined grains/subgrains in these samples induced by plastic deformation are about 240 nm without an obvious impurity effect, but the dislocation density in 2N Al is evidently higher than that in other samples. Boundary misorientations for 5N and 4N Al are below 10° with average values of 2-3°, while the average misorientation for 2N Al is obviously larger, being about 14°. Microhardness of LNT-DPD 2N Al is higher than that of 5N and 4N Al, owing to the enhanced dislocation density as their grain/subgrain sizes are almost identical.
关键词:
Aluminum
F. Huang
材料科学技术（英）
Microstructure and hardness were investigated in pure Al samples with different purities (5N: 99.999%, 4N: 99.993%, and 2N: 99.7% in weight) subjected to dynamic plastic deformation at cryogenic temperatures. The saturated sizes of refined grains/subgrains in these samples induced by plastic deformation are about 240 nm without an obvious impurity effect, but the dislocation density in 2N Al is evidently higher than that in other samples. Boundary misorientations for 5N and 4N Al are below 10° with average values of 2-3°, while the average misorientation for 2N Al is obviously larger, being about 14°. Microhardness of LNT-DPD 2N Al is higher than that of 5N and 4N Al, owing to the enhanced dislocation density as their grain/subgrain sizes are almost identical.
关键词:
Aluminum
F. Huang
材料科学技术（英）
The oxidation behavior of alloy 690 exposed to high-temperature and high-pressure steam and water at 280 °C for 1 h was investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). In high-temperature and high-pressure steam, the oxide film is composed of an outermost Ni-rich hydroxides layer, an intermediate layer of hydroxides and oxides enriched in Cr, an inner oxide layer. The film formed in high-temperature water is similar to that in steam, except for missing the Ni-rich hydroxides layer. Samples with different surface finishes (electropolished, mechanically polished, ground, and as-received) were prepared for comparison. A general increase of the oxide thickness with the degree of surface roughness is observed. The equivalent oxide thicknesses lie in the range of 100{200 nm for the as-received samples, 150{250 nm for the samples ground to 400# and 10−20 nm for the samples ground to 1500#, mechanically polished, and electropolished.
关键词:
Alloy 690
