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Imai H.,Osaka University | Li S.,Osaka University | Kondoh K.,Osaka University | Kosaka Y.,SAN ETSU METALS Co. | And 4 more authors.
Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy | Year: 2012

In this study, microstructure and mechanical properties of Cu-40Zn brass alloy with 0.5mass%Cr additive produced by powder metallurgy (P/M) were investigated. Cu-40Zn-0.5Cr and Cu-40Zn brass powder were made by water-atomization process, and used as raw materials. These powder compacts were consolidated by hot extrusion at various temperatures. Yield stress of Cu-40Zn-0.5Cr extruded at 773 K was 514.6 MPa, while that of the conventional Cu-40Zn extruded at the same temperature was 332.6 MPa. Solid solution of chromium in the Cu-40Zn-0.5Cr brass alloy extruded at 773 K was about twice as that in the same brass alloy extruded at 873 K. The ratio of solid solution strengthening by chromium additives was 130MPa/mass%[Cr], The grain size of extruded materials increased with increasing the extrusion temperature.


Li S.,Osaka University | Imai H.,Osaka University | Kojima A.,San Etsu Metals Co. | Kosaka Y.,San Etsu Metals Co. | And 4 more authors.
Advanced Materials Research | Year: 2011

The effect of heat treatment on phase transformation, precipitation behavior and microhardness response of Cu40Zn-1.0Ti brass was investigated via powder metallurgy method. The volume fraction of α phase increased with elevated temperature, equaled to that of β phase at 400 °C, and reached to a maximum value of 55.9% at 500 °C. The solid solubility of Ti in Cu40Zn brass matrix decreased with elevated heat treatment temperature, showed high chemical potential for precipitates reaction in Cu40Zn brass. The micro-hardness of the BS40-1.0Ti brass was primarily dependent on the solid solubility of Ti, but also dependent on the phase ratio of α and β phase. © (2011) Trans Tech Publications, Switzerland.


Imai H.,Joining and Welding Research Institute | Imai H.,Xi'an University of Technology | Li S.,Xi'an University of Technology | Kondoh K.,Joining and Welding Research Institute | And 5 more authors.
Materials Transactions | Year: 2014

In this study, the microstructure and mechanical properties of Cu40Zn brass alloy with 0.5 mass% Cr additives produced by powder metallurgy (P/M) process were investigated. Cu40Zn0.5Cr and Cu40Zn brass powders were made by water-atomization process, and used as raw materials. These powders were consolidated by hot extrusion at various temperatures by considering the precipitation behavior of phase and Cr. Yield stress of Cu40Zn0.5Cr extruded at 773K was 514.6 MPa, while that of the monolithic Cu40Zn extruded at the same temperature was 332.6 MPa. Solid solution of chromium in the Cu40Zn0.5Cr brass alloy extruded at 773K was about twice as that of the same brass alloy extruded at 873 K. The strength impact of Cr solid solution was much effective compared to Cr precipitation strengthening. The ratio of solid solution strengthening by chromium additive was 130 MPa/mass%[Cr]. The grain size of extruded materials increased with increasing the extrusion temperature. © 2013 The Japan Institute of Metals and Materials.


Li S.,Osaka University | Imai H.,Osaka University | Kondoh K.,Osaka University | Kojima A.,San Etsu Metals Co. | And 3 more authors.
Materials Chemistry and Physics | Year: 2012

Effect of Ti and Sn alloying elements on microstructure and mechanical properties of 60/40 brass has been studied via the powder metallurgy (P/M) route. The water-atomized BS40-0.6Sn1.0Ti (Cu40wt%Zn-0.6wt%Sn1.0wt%Ti) pre-alloyed powder was consolidated at various temperatures within range of 400-600°C using spark plasma sintering (SPS) and hot extrusion was carried out at 500°C. Effects of extrusion temperature on microstructure and tensile strength were investigated by employing SEM-EDS/EBSD, TEM, XRD and tensile test. Results indicated that super-saturated solid solution Ti and Sn elements created high chemical potential for a precipitate reaction in rapidly solidified brass powder, which showed significant strengthening effects on the extruded sample consolidated at lower temperature. Solid solubility of Ti in brass matrix decreased with increasing of sintering temperature, thus resulted in degradation of mechanical properties. Consequently, lower hot processing temperature is necessary to obtain excellent mechanical properties for BS40-0.6Sn1.0Ti during sintering and extrusion. An yield strength of 398 MPa and ultimate tensile strength of 615 MPa were achieved, they respectively showed 31.3% and 22.9% higher values than those of extruded Cu40Zn brass. © 2012 Elsevier B.V. All rights reserved.


Li S.,Osaka University | Imai H.,Osaka University | Kondoh K.,Osaka University | Kojima A.,San Etsu Metals Co. | And 3 more authors.
Materials Science and Engineering A | Year: 2012

Effect of extrusion temperature on the microstructure and mechanical properties of the powder metallurgy Cu40Zn-CrFeTiSn alloy were investigated, through analysis on the solid solution of alloying elements, phase transformation and precipitation behavior. The extrusion was carried out between 500 °C and 650 °C using an extrusion ratio of 37:1. After extrusion, the microstructure was found consisting of the dual α+Β phase structure and precipitates dispersing uniformly in the matrix. The tensile strength gradually decreased when the extrusion preheating temperature was increased. Solid solubility of Ti and Cr decreased steadily and grain coarsening occurred with increase in the extrusion temperature. Consequently, the lower extrusion preheating temperature was necessary to obtain excellent final mechanical properties, thus the extrusion temperature of 500 °C was enough to produce good ductility while maintaining the promising values of mechanical properties after extrusion. © 2012 Elsevier B.V.


Li S.,Osaka University | Imai H.,Osaka University | Atsumi H.,Osaka University | Kondoh K.,Osaka University | And 4 more authors.
Materials Science and Engineering A | Year: 2012

The effects of Ti and Sn alloying elements on the microstructural and mechanical properties of 60/40 brass were studied by powder metallurgy processing. The super-saturated solid solution of Ti creates a high precipitation reaction chemical potential in water-atomized BS40-1.0Ti brass powder. Consequently, BS40-1.0Ti brass was remarkably strengthened by the addition of Ti. However, Ti readily segregated in the primary particle boundaries at elevated temperatures, which detrimentally affected the mechanical properties of BS40-1.0Ti brass. Accordingly, Sn was proposed as an additive to BS40-0.6Sn1.0Ti to inhibit the segregation of Ti. Consequently, the Ti precipitate was retained in the form of CuSn 3Ti 5 in the interior of grains and grain boundaries rather than in the primary particle boundaries. This result demonstrates that the addition of Sn can effectively hinder Ti segregation in the primary particle boundaries. Sn addition produced significant grain refinement and mechanical strengthening effects in BS40-0.6Sn1.0Ti brass. As a result, outstanding strengthening effects were observed for BS40-0.6Sn1.0Ti sintered at 600°C, which exhibited a yield strength of 315MPa, an ultimate tensile strength of 598MPa, and a Vickers micro-hardness of 216Hv. These values represent increases of 27.5%, 20.1% and 45.6%, over those of extruded BS40-1.0Ti brass. © 2011 Elsevier B.V.

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