Zhi Ming Zhou

Synthesis and Physical Properties of Graphene Nanosheets Reinforced Copper Composites

Cu/graphene nanosheets composites were fabricated at 800°C by the hot-pressing method using Cu and graphene as initial materials. Graphene content was 1 wt. %-5 wt. %. The fracture morphology and physical properties of the composites were investigated. It was found that the relative density increased with the increment of graphene content from 1 wt% to 5 wt. % with reaching its highest level (96.68%) at 5wt. %. The composites have the anisotropic property which is vertical to the direction of pressure is higher than parallel to the direction of pressure. With the increasing of graphene content, the thermal conductivity property and the electronic conductivity decrease first and then increase with the minimum thermal conductivity and electric conductivity at 3wt%~4wt%.

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.

The Numerical Simulation of Multi-Directional Forging EQ153 Steering Knuckle

This paper centers on EQ153 steering knuckle multi-directional forging forming, and applying Deform-3D to simulation the deformation process. According to temperature, effective strain, load prediction and final forging shape to illustrate in such a process a near-net-shape forming with no flash and little draft angle and lower pressure is been formed.

Influences of Surface Nanocrystallization Induced by High-Energy Spot Peening on Microstructure and Properties of Magnesium Alloy

As relatively new structure materials, magnesium and its alloys demonstrated significant potential for applications in many industries. However, magnesium alloys were easy to be corroded which greatly limited their development. AZ31B and AZ91D, two widely used commercial magnesium alloys in various industries, were chosen to be produced nanostructure on the surface layer, called Surface Nanocrystallization (SNC) by High Energy Spot Peening (HESP). The microstructure was characterized by Scan Electronic Microscopy (SEM) and X-ray diffraction (XRD) in this paper. Microhardness and corrosion resistance were measured by microhardness tester and electrochemical measurement system respectively. Experimental results showed that after HESP the grain sizes in the surface layer were obviously reduced into nanoscale; microhardness was greatly increased in the treated surface, about two times as much as that of original and corrosion current density in polarization curve was evidently raised while corrosion potential changed little.

Study and Practice of Bilingual Teaching Course in Major of Materials Forming and Control Engineering

According to the require of national characteristic specialized construction education for the students and combinating the practice of bilingual teaching in major of materials forming and control engineering, this paper studied the modularization bilingual teaching reform in the curriculum teaching process in the local colleges or universities. The significance of bilingual teaching in major of materials forming and control engineering is clarified. The multimedia bilingual teaching is carried out in the course of foundation of materials forming and technology. The results prove that it is practical and fruitful to conduct bilingual teaching based on excellent original english teaching materials, multimedia methods, scientific organization and modularization teaching.

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.

Solidification Behavior of Undercooled Cu98Cr2 Alloys

The solidification behavior of undercooled Cu98Cr2 alloys was investigated under different rapid solidification methods. The results shown that whole lamellar (α+β) eutectics appeared in melt spun alloys for the sample undercooled into the coupled zone. The microstructure of arc melted Cu98Cr2 alloys consisted of primary β(Cr) particles distributes on α(Cu) matrix and (α+β) eutectics set in cellular α (Cu) phase. However, due to the different thickness and different solidification rate, the microstructure of splat quenched Cu98Cr2 alloys shown that only cellular supersaturated α solid solution occurred for thin flake and primary β(Cr) particles and (α+β) eutectics occurred for thicker flakes.

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.