Papers by Author: Zhi Qiang Jiang

Abstract: The effects of 2at.% Ga addition on the microstructure and mechanical properties of the TiCu-base nano/ultrafine bimodal structured alloy were investigated systematically through XRD, OM, compressive test and SEM. The results showed that constitutional phases were changed from bcc -Ti(M) to unknown nanostructure + bcc -Ti(M), content of nanostructured matrix is increased, the calculated mean crystalline size was decreased from 12.6 to 11.7nm, and also, the yield and maximum strengths and plasticity were enhanced markedly. The reasons, which caused these phenomenons, were discussed.

Abstract: New bulk nanostructure-dendrite Ti₄₄Cu₄₆Co₄Zr₆ composite with excellent mechanical properties has been fabricated by using copper molder casting through systematic alloy design from binary Ti₅₀Cu₅₀. The results showed that the micro-scaled β-Ti (M) solid solution embedding on the nanostructured matrix, which resulted in the excellent mechanical properties: high fracture strength (σ_f=2278 MPa) and good ductility (ε_p=9.01%) under quasi-static compression.

Abstract: Effect of Minor Si and Ag additions on glass-forming ability (GFA) of the base Ti₄₄Cu_38.9Co₄Zr₆Sn₂Be_5.1 (at. %) alloy are studied. (Ti₄₄Cu_38.9Co₄Zr₆Sn₂Be_5.1)_100-xR_x (R = Si, Ag, x=0, 1, 2, 3 at. %) metallic glasses are formed by splat-quenching and copper mold suction casting. It is found that the minor Si and Ag additions enhance the glass-forming ability of Ti₄₄Cu_38.9Co₄Zr₆Sn₂Be_5.1 greatly. The maximum size of fully amorphous structure is increased from 4 mm for base alloy to be larger than 6 mm for alloys containing 1-2 at. % Si/Ag, while Si/Ag more than 2 at. % additions decrease the GFA.

Abstract: Bulk metallic glass Ti42Cu37.1Co4Zr8Sn2Ag2Be4.9 that can be cast into a fully amorphous rod of more than 6 mm in diameter by copper molder casting has been developed through systematic alloy design. The bulk metallic glass exhibits high fracture strength (f＝2071 MPa) and good ductility (f＝5.83％) under compression.

Abstract: a cold extrusion forming process in die structure of plug extremity is analyzed in this paper, its technological data on the tooling structure design of plug extremity are discussed, and the die architecture design and key technology in the automatic extrusion machine for plug extremity with cold extrusion forming approach were accomplished. This plug extremity equipment developed with cold extrusion forming process technology can not only achieved the process of delivering material, extruding forming and cutting-off material in automatically, but also enhanced the rigidity and intension at two ends of plug. The production efficiency and the material used ratio were increased greatly, the manufacturing cost was decreased obviously, and the plug quality with cold extrusion forming method was ensured.

Abstract: A casting granulated metal equipment by a short flow was developed, which is comprised of pre-heating chamber, heating furnace, ceramic pipe used to transport the molten metal, the holding furnace, the drip nozzle and the cooling tank etc. The equipment can accomplish preheating the ingot, melting, holding temperature and the polluting at the same time. The preheating temperature of ingot is 100-120 °C. After the ingot is melted, the molten metal is transported to the holding furnace from the melting furnace by ceramic pipe, and the temperature in the holding furnace is 25-28 °C above the melting point of meta1. And the dwell time of granulated metal is 10-18 seconds in the cooling water box. Finally the granulated metal is directly delivered to the packing box by the bucket elevator. The granulated metal produced by a short flow has lower energy consumption and higher efficiency, and the energy consumption is 15-20% lower than that of the common flow.

Abstract: The microstructures of B-bearing cast steel containing 0.8-1.2 wt.%B, 0.8-1.2 wt.%Cr, 1.0-1.5 wt.%Mn, 0.6-1.0 wt.%Si and 0.10-0.25 wt.%C have been characterized by means of optical OM, SEM, EPMA and XRD. The solidification structure of B-steel consists of pearlite, ferrite, martensite and boride (Fe2B), while the hardness is 1430-1480 HV. Borides distribute along the grain boundary in the form of eutectic. Fine lath martensite and eutectic Fe2B can be obtained by water quenching at 1223 K-1273 K. The hardness and impact toughness of the B-steel exceed 55 HRC and 150 kJ/m2, respectively. The abrasion resistance determined using a pin abrasion tester is obviously higher than that of the martensitic cast steel and nears to the high chromium white cast iron.

Abstract: High-carbon high-speed steels (HSS) are extremely abrasion resistant materials due to their high hardness MC type carbide and high hardness martensitic matrix. Different microstructures and mechanical behaviours were obtained after the quenching and tempering temperatures of HSS roll were changed. With air cooling and sodium silicate quenching, when the austenitizing temperature reaches 1273K, the metal matrix all transforms into the martensite, Afterwards, the eutectic carbides dissolve ceaselessly into the metal matrix and its continuous network distribution changes into broken network. The peak hardness temperature of high-carbon HSS is around 1323K, and the second hardening temperature is around 793K. No significant change in tensile strength and elongation percentage was observed unless the tempering temperature is beyond 753K. The tensile strength is increased obviously and the elongation percentage is decreased slightly beyond 753K. However, the tensile strength is decreased and the elongation percentage is increased when the temp exceeds 813K. The high-carbon HSS roll presents excellent abrasion resistance at 793K-813K.

Abstract: A study on solidification process of centrifugal cast high-speed steel (HSS) rolls and the crack forming condition is discussed. The result was represented that the crack forming was because of the solidification layer strength of HSS roll was low, and a clearance between the solidification layer and the mould, and the solidification layer of HSS roll could not endure a large centrifugal pressure. In common centrifugal casting, the free solidification constriction of HSS rolls was difficult, which accelerated the crack propagation. The appearance of mesosphere and axial solidification was unfavorable to obtaining the compact roll structures, which accelerated HSS rolls to crack.

Abstract: Influence of quenching temperature and cooling speed on the structures and properties of cast Fe-B-C alloy containing more than 1.0%B and lower than 0.2%C was researched. The results showed that the structures of Fe-B-C cast alloy changed from a great of pearlite + a small of martensite 􀄗 a great of martensite + a small of pearlite 􀄗 martensite and the hardness increased with the increase of quenching cooling speed. In the condition of water cooling, higher or lower quenching temperatures were not advantageous to obtaining single martensite. Quenching at 950~1000oC, cast Fe-B-C alloy could obtain the compound structures of fine lath martensite. The hardness and impact toughness of cast Fe-B-C alloy excelled 55HRC and 15J/cm2 respectively.