Jiqiang Ma

The Tribological Behavior of a Ti-46Al-2Cr-2Nb Alloy Under Liquid Paraffine Lubrication

The tribological behavior of a Ti-46Al-2Cr-2Nb alloy prepared by hot-pressed sintering was investigated under liquid paraffine lubrication against AISI 52100 steel ball in ambient environment and at varying loads and sliding speeds. For comparison, the tribological behavior of a common Ti-6Al-4V alloy was also examined under the same testing conditions. The worn surfaces of the two alloys were analyzed using a scanning electron microscope. The friction coefficient of the Ti-46Al-2Cr-2Nb alloy in the range of 0.13–0.18 was significantly lower than that of the Ti-6Al-4V alloy (0.4–0.5), but comparable to that under dry sliding, which indicated that TiAl intermetallics could be more effectively lubricated by liquid paraffine than titanium alloys. Applied load and sliding speed have little effect on the friction coefficient of the Ti-46Al-2Cr-2Nb alloy. The wear rate of the Ti-46Al-2Cr-2Nb alloy was about 45–120 times lower than that of Ti-6Al-4V alloy owing to Ti-6Al-4V alloy could not be lubricated effectively. The wear rate of the Ti-46Al-2Cr-2Nb alloy increased with increasing applied load, but decreased slightly at first and then increased with increasing sliding speed. The wear mechanism of the Ti-46Al-2Cr-2Nb intermetallics under liquid paraffine lubrication was dominated by main plowing and slight flaking-off, but that of the Ti-6Al-4V alloy was plastic deformation and severe delamination.

Combustion Synthesis and Characterization of Bulk Nanocrystalline

Bulk nanocrystalline Fe88Si12 alloy is fabricated by a combustion synthesis processing that is convenient, low in cost, and capable of being scaled up. The Fe88Si12 alloy consists of two phases: ¿-Fe(Si) and Fe3Si. It is a composite structure of meshwork dispersed in a matrix. The meshwork is a few micrometers in length and 0.5-1 ¿m in diameter, and the grain size of the matrix is in the range of 5-15 nm. The nanocrystalline Fe88Si12 alloy is yielded at 1760 MPa with a large ductility of 14.6% in compressive test. Moreover, the coercive force of the product is approximately 3.6 A/m and saturation magnetization is about 196 emu/g. The results suggest that the product exhibits good mechanical behavior and soft magnet properties.

{\bf Fe}_{\bf 88} {\bf Si}_{\bf 12}

In this paper, we investigated the effect of counterface of AISI 52100 steel and ceramics of SiC, Al2O3, and Si3N4 on the tribological behavior of Ti3AlC2 at ambient. The results showed that the tribological properties of Ti3AlC2 are strongly dependent on the counterfaces. Under present test conditions, the tribocouple of Ti3AlC2/SiC exhibits lower coefficient of friction (CoF) 0.40, Ti3AlC2/AISI 52100 steel shows a rising CoF from 0.1 to 0.63, both Ti3AlC2/Si3N4 and Ti3AlC2/Al2O3 tribopartners exhibit higher CoF of 1.22 in average. The Ti3AlC2 exhibits the lowest wear rate sliding against AISI 52100 steel, the wear rate of Ti3AlC2 sliding against Al2O3, Si3N4, and SiC are higher and comparable. The morphologies of the worn surfaces of the Ti3AlC2 are observed by scanning electron microscopy, and the element states are analyzed by X-ray photoelectron spectroscopy. The wear mechanisms are discussed.

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.

Effect of Counterface on the Tribological Behavior of Ti3AlC2 at Ambient

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.

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