Yonghai Kang

Combustion synthesis of large bulk nanostructured Ni 65 Al 21 Cr 14 alloy

A large bulk nanostructured Ni65Al21Cr14 alloy with dimensions of Φ 100mm × 6mm was produced by combustion synthesis technique followed with rapid solidification. The Ni65Al21Cr14 alloy was composed of γ′-Ni3Al/γ-Ni(Al, Cr) eutectic matrix and γ-Ni(Al, Cr) dendrite. The eutectic matrix consisted of 80-150nm cuboidal γ′-Ni3Al and 2-5 nm γ-Ni(Al, Cr) boundary. The dentrite was comprised of high-density growth twins with about 3-20 nm in width. The nanostructured Ni65Al21Cr14 alloy exhibited simultaneously high fracture strength of 2200MPa and good ductility of 26% in compression test.

Combustion synthesis and characterization of Fe-Ni alloys

A simple and inexpensive method for combustion synthesis of the series of Fe-x%Ni martensite alloys (x = 15, 20, 23, 25 at %) was developed. XRD, SEM, and TEM examinations showed that all the products were composed of lath martensite and retained austenite. With increasing nickel content, the hardness and yield strength decreased gradually, which originated from the differences in phase compositions and micro structural characteristics. All the products exhibited high strength and good ductility, especially the Fe-15%Ni alloy which exhibited (in compression tests) high yield strength (up to 1300 MPa) at a good ductility (∼30%).

Tribological behavior of Fe3Al-60 wt.% Fe3AlC0.5 composite under air and vacuum conditions

Abstract The tribological behavior of Fe3Al composite with 60 wt.% Fe3AlC0.5 under air and vacuum was studied. The composite exhibited a lower wear rate but somewhat higher friction coefficient under air than vacuum. The wear rates increased and the friction coefficients decreased with increasing the applied load under both conditions. The sub-layer of the worn surface under vacuum suffered from severe plastic deformation. This was not the case under air due to protection by surface oxide films. The dominant wear mechanisms were plastic deformation and adhesion under vacuum and oxidative wear and slight delamination under air.

Tribological behavior of Fe70Ni30 alloy with nanoscale twins under liquid paraffin lubrication

Fe70Ni30 alloy with nanoscale twins was obtained by deep cryogenic treatment (DCT) of coarse grained Fe70Ni30 alloy (CG-Fe70Ni30) at liquid nitrogen temperature. The tribological behavior of DCT-Fe70Ni30 alloy was investigated under liquid paraffin oil lubrication compared with that of CG-Fe70Ni30 alloy. The experimental results showed that the wear resistance of DCT-Fe70Ni30 alloy was improved significantly after the introduction of nanoscale twins, and DCT-Fe70Ni30 alloy also showed a little lower friction coefficient relative to CG-Fe70Ni30 alloy. The results indicated that twins play a positive role in the materials friction-reduction and anti-wear properties, which is attributed to the better oil-adsorption ability and enhanced hardness of DCT-Fe70Ni30 alloy caused by structural refinement. Wear mechanisms were discussed.

Friction and wear behavior of nanoeutectic Fe1.87C0.13 under air and vacuum conditions

In this paper, the tribological behavior of nanoeutectic Fe1.87C0.13 alloy and its coarse-grained-eutectic counterpart under air and vacuum was investigated. The results showed that the wear rate of both alloys was lower in air than in vacuum, and their friction coefficient was related to applied load and testing atmosphere. The nanoeutectic Fe1.87C0.13 alloy exhibited lower wear rate than the coarse grained counterpart in both environments. The wear rate of both alloys increased but the friction coefficient decreased with increasing applied load under both air and vacuum. The dominant wear mechanisms were adhesion wear in vacuum but oxidation wear along with slight delamination in air.

Combustion synthesis and characterization of bulk nanostructured Ni50Al17Fe33 alloy

Abstract A bulk nanostructured Ni50Al17Fe33 alloy was produced by combustion synthesis associated with rapid solidification. The microstructure and mechanical properties of the as-fabricated material were investigated by means of scanning electron microscopy, X-ray diffraction, and mechanical tests. The Ni50Al17Fe33 alloy was composed of eutectic matrix and precipitated phase. The eutectic matrix consisted of 30–50 nm globular γ′-(Ni,Fe)3Al and 5–10 nm γ-Ni(Fe) boundary. The precipitate was comprised of 100–150 nm γ′-(Ni,Fe)3Al, γ-Fe, and α-Fe solid solution phases. The nanostructured Ni50Al17Fe33 alloy exhibited simultaneously high yield stress (about 900 MPa), high fracture strength (over 3860 MPa), and good ductility (over 75%) in compression.