Wei Jiu Huang

Phase Selection in Undercooled Cu85Cr15 Composites

Phase selection of undercooled Cu85Cr15 composites was analyzed by using different solidification conditions. The results revealed that the arc melted composites generally have non-uniform Cr-rich dendrites distributes on Cu-rich matrix. Due to strong electromagnetic stirring, uniform Cr-rich dendrites distributes on Cu-rich matrix for electromagnetic levitation melted composites. Both fine Cr-rich dendrites and Cr-rich particles coexisted in Cu-rich matrix for splat quenched composites, which means liquid phase separation occurred for the high cooling rate.

Microstructure Evolution of Hypereutectic Cu98Cr2 Alloys

Hypereutectic Cu98Cr2 alloys were prepared by vacuum arc melting and electromagnetic levitationing method. The microstructure evolution was investigated during the solidification process. It is shown that for the arc melted hypereutectic Cu98Cr2 alloy, the general microstructures consist of primary β(Cr) grains distributes on α(Cu) matrix and (α+β) eutectics set in cellular α (Cu) phase. However, due to the different solidification rate, the primary β(Cr) phase, (α+β) eutectics and α(Cu) phase coexist for the electromagnetic levitated hypereutectic Cu98Cr2 alloy. The reason for the different microstructure and evolution for the hypereutectic Cu98Cr2 alloy is studied in this paper.

Simulation of Compound Cold Extrusion Al-Zn-Mg-Cu Alumium Alloys

Al-Zn-Mg-Cu super-high strength aluminum alloy is widely used in the aerospace and automotive industry. However, the extrudability of Al-Zn-Mg-Cu aluminum alloy is relatively poor compared with other series of aluminum alloys. The simulation of compound cold extrusion process of Al-Zn-Mg-Cu aluminum alloy was studied for the production of a double-cup workpiece with a deep wobbler hole in this paper. The effective strain and stress distribution of the alloy during cold extrusion were studied by Deform-3D simulation. The results show that the maximum stress was concentrated at the bottom of the deep hole. Cracks were easily to be occured near the bottom of deep-hole. Based on the experimental results, the processing route of the two steps with compound cold extrusion is more suitable than one cold extrusion for the production.

Effect of Cooling Rate on the Microstructure of Cu80Cr20 Alloys

The effect of cooling rate on the microstructure of Cu80Cr20 alloys was studied by using vacuum non-consumable arc melting, vacuum induction melting, electromagnetic levitation and splat quenching. The microstructure evolution of the Cr-rich were analyzed by scanning electron microscopy (SEM) and optical microscopy. The results showed that nonuniform Cr-rich dendrite distributes on Cu-rich matrix for arc melted alloys and uniform Cr-rich dendrite distributes on Cu-rich matrix for electromagnetic levitation melted alloys and vacuum induction melted alloys. However, the Cr-rich phase show both dendrites and spheroids for splat quenched alloys. This means liquid phase separation occurred during rapid solidification.

Numerical Simulation on Rapidly Solidified Melt Spinning CuFe10 Alloys

The numerical simulation model of single roller rapid solidification melt-spinning CuFe10 alloys was built in this paper. The vacuum chamber, cooling roller and sample were taken into account as a holistic heat system. Based on the heat transfer theory and liquid solidification theory, the heat transfer during the rapids solidification process of CuFe10 ribbons prepared by melt spinning can be approximately modeled by one-dimensional heat conduction equation, so that the temperature distribution and the cooling rate of the ribbon can be determined by the integration of this equation. The simulative results are coincident very well with the microstructure of rapid solidification melt spinnng CuFe10 alloys at three different wheel speeds 4, 12 and 36 m/s.

Microstructure of Cu75Cr25 Alloys under Different Conditions

The microstructure of Cu75Cr25 alloys was investigated by using vacuum non-consumable arc melting, electromagnetic levitation and splat quenching. The microstructure and solidification behavior of the Cr-rich were investigated by scanning electron microscopy (SEM). The results showed that inhomogeneous Cr-rich dendrite distributes on Cu-rich matrix for arc melted alloys. The microstructure consisting of a fine dispersion of Cr-rich dendrite in a Cu-rich matrix for electromagnetic levitated alloys. However, the morphology and size of the Cr-rich phase vary greatly with the cooling rate for splat quenched alloys. The Cr-rich phase show both dendrites and spheroids, this means liquid phase separation occurred during rapid solidification.

Microstructure Study of Undercooled Hypereutectic Cu95Cr5 Alloys

Microstructure of Cr-rich phase in undercooled hypereutectic Cu95Cr5 alloys was studied by using arc melting, electromagntic levitation melting and splat quenching. The results showed that the alloys generally have a microstructure consisting of a fine Cr-rich dendrites in a Cu-rich matrix. Even there existed strong electromagnetic stirring during solidification process, the nonhomogeneous Cr-rich dendrites were observed in electromagnetic levitation melted alloys. However, fine homogenous primary Cr-rich particles or equiaxed Cr-rich grains distributed in the Cu-rich matrix in splat quenched alloys.

Comparative Study on Tribological Behaviour between AZ71E and AZ91D Alloys under Ambient and Elevated Temperature

The tribological properties of AZ71E and AZ91D magnesium alloys were comparatively investigated at ambient and elevated temperature. The results indicated that the wear rates of both alloys increased with increasing load, whereas the friction coefficients decreased with increasing load. The wear resistance of AZ71E alloy was significantly superior to that of AZ91D at higher loads and elevated temperature. At ambient temperature, abrasive wear is the predominant wear mechanism for AZ71E, whereas the wear mechanism for AZ91D transfers from abrasive wear to delaminative wear. At elevated temperature, the predominant wear mechanism of both alloys changed from mild wear regime to severe wear regime.