The remarkable tribological behavior of a novel high-strength, wear-resisting zinc-based alloy, named ZMJ, which is aimed to replace bronze as an engineering material, has been studied. A desirable wear-resisting microstructure was achieved through a specially designed composition and casting procedure. The micro-constituents and microstructures were studied, their relationships with the mechanical, anti-friction and wear-resisting properties having been analyzed both qualitatively and quantitatively. It was found that the microstructure of ZMJ plays a dominant role in providing its superior wear-resisting properties. The composition of ZMJ consists of Zn, Al, Cu, Mg, Mn, Ti, B and rare earth elements. The functions of each of these alloying elements have been explained in detail. This novel alloy's strengthening mechanisms and wear mechanisms have been studied and compared with those of phosphor-tin-bronze ZCuSn10P1 (GB1176-87) and the popular ZA-27 (ASTM B669-82) zinc-based alloy. ZMJ has been proven to be an excellent engineering material by comparing its mechanical properties and friction and wear properties with those of ZCuSnlOP1 and ZA-27. Industrial applications in gears, worm-gears, bearing and bushes etc. have shown that ZMJ brings significant benefits in energy saving and enhances the quality and life expectancy of these machinary parts.

By studying microstructural effects on the mechanical and tribological behaviors of aluminum bronzes, a novel high-strength wear-resisting aluminum bronze (KK) has been developed by optimizing microstructures, modifying, adding special elements and controlling the casting process. The mechanical properties, friction and wear behavior of this alloy have been tested and compared with two other commercial aluminum bronzes of the same class. Experimental results show that the properties of the novel KK bronze are much superior to those of the other bronzes.

Friction and wear characteristics of a Zn-27% Al-2% Cu alloy, modified with Ti and misch metal, with different Mn contents, coupled with steel have been studied. A pin-on-disk tribometer was used to measure the friction coefficient of alloy samples under different loads, speeds and lubricating conditions while the wear volume and temperature rise of the lubricant were measured by a cylinder-on-ring wear tester. Friction and wear characteristics of these Mn-containing alloys were compared with those of ZA-27. Effects of Mn content on the tribological behaviors and microstructures were studied and the relationships between the tribological characteristics and the microstructures of the alloy were also analyzed. Experimental results indicate that the addition of Mn can significantly improve the tribological behaviors of the Zn-27% Al-2% Cu alloy. Finally, an optimum Mn content for the best overall mechanical properties and tribological behaviors was obtained.

Microstructural effects on mechanical and tribological behaviours have been studied for a series of aluminium bronzes with different microstructures. ASTM 1045 and 52100 steels were used as the counterparts in the friction and wear tests. Experimental data show that the coefficients of friction, wear rate and mechanical properties strongly depend on the volume fraction of a-phase present in the alloy and, to a lesser extent, on the average a-grain size. The minimum coefficients of friction and the wear rate correspond to a yield strength of 370 Nmm-2 and a bulk hardness of liB 168. Except for extreme low average a-grain size (corresponding to low volume fraction), both the coefficients of friction and the wear rate show linear relations with the reciprocal of the yield strength of the alloy, but not to the reciprocal of the hardness as expected. Based on these results, a design principle for high strength wear-resistant aluminium bronze has been developed.

The 2024/3003 alumintan gradient alloys are prepared by semi-continuous casting. The influences of throttle bore diameter of embedded nozzle and temperature of internal melt on composition distribution, macrestructure, hardness are analyzed, and the stability of gradient distribution of composition, macmstructure and hardness along the axial direction of the ingot is also studied. The results show that diffe-rent composition profiles can be achieved by adjusting the processing parameters; the volume fraction of inner ahoy in the ingot can be increased by enlarging the threttle bore diameter and elevating the temperature of inner melt; quasi-steady solidification can be realized within 20s during cast processing, and consistent quality ingot is obtained by controlling the casting speed and liquid height of inner melt.

Effects of different sintering temperature and sintering time on the relative density of the sintered compacts were studied to obtain the optimal sintering parameters for the fabrication of NbC patti culate reinforced iron-base compos ire. With optimal sintering temperature of 1280℃ and sintering time of 80min, wear-resisting, high density NbC particulate reinforced iron-base composites can be obtained using warm compaction powder metallurgy. The microstructure, relative density, mechanical properties and tribologieal behaviors of the sintered composites were studied. The results indicate that the mechanical properties of the sintered compacts were closely related to the sintered density. The iron base composite materials with different combinations of mechanical properties and tribological behaviors were developed for different applications. One of the developed composite, which contains 10% NbC, possesses a high strength of 815MPa with a remarkable friction and wear behaviors. The other developed composite, which contains 15% NbC, possesses a lesser strength of 515 MPa but with exeeUent friction and wear behaviors.

he fine NbC particles are embedded on the surface of iron particles and evenly distributed in the mixed powders. Warm compaction was used not only to increase the green density but also to improve the formability of the mixed powder and to improve the compact's green strength to facilitate handling. The influences of fabrication parameters such as ball milling time, annealing temperature and time, warm compaction temperature, sintering temperature and sintering time were studied. Compacts with a relative sintered density of 97% and a tensile strength of more than 800MPa can he obtained by using a ball milling time of 5h, an annealing temperature of 800℃, a compaction pressure of 600MPa, warm compaction temperatore of 120℃, sintering temperature of 1 280℃, and sintering time of 80min. The shrinkage at this sintering condition was approximately 4.3%.

Die wall lubrication was applied on warm compaction powder metallurgy in the hope to reduce the concentration level of the admixed lubricant, since lubricant is harmful to the mechanical properties of the sintered material. Iron-based samples were prepared by die wall lubricated warm compaction at 135 and 175℃, using polytetrafluoroethylene (PTFE) emulsion as the die wall lubricant. Compacting pressures of 700 and 550MPa were used. An admixed lubricant concentration ranging from 0 to 0.6wt.% was used in this study. The results show that in addition to a decrease in ejection forces, the green density of the compacts increased linearly with the decrease in the admixed lubricant content. The mechanical properties of the sintered compacts increase sharply when the admixed lubricant concentration was reduced to 0.125wt.% or less, No scoring was observed in all of the experiments.

Iron-based powder metallurgy material was prepared by warm compaction at 125℃ using a compacting pressure of 700MPa. Sintering temperature ranging from 1100℃ to 1300℃ and sintering time ranging from 40min to 80min were used to study the effects of sintering parameters on the compacts. Die wall lubrication polytetrafluoroethylene (PTFE) emulsion was also applied in combination with warm compaction in hope to increase the compact density and the mechanical properties of the sintered material. Green and sintered density, spring back effect and sinter shrinkage were measured. Mechanical properties of both as-sinter and heat treated samples were also measured. Results show that mechanical properties of the sintered compacts increase with the increase of sintering temperature and sintering time. Sample prepared by die wall lubricated warm compaction always shows higher density and mechanical properties.

AZ31 Mg alloy was prepared through equal channel angular pressing (ECAP) by Bc route in two different dies, in which the intersecting angles between channels are 90