Effects of Deformation and Annealing Temperature on the Microstructures and Hardness of Cu-29Zn-0.6Bi Brass

Abstract:

The use of lead-free brass is growing due to the restriction of the lead content in many components. Bismuth replaces lead in the brass alloys and contributes to the machinability and pressure tightness characteristics. However, Bi is immiscible in copper and fills the inter-dendritic spaces during solidication that yields negative impacts on the mechanical properties. This research studied the effects of addition of 0.6 wt. % Bi on the characteristics of Cu-29Zn alloy during cold rolling and subsequent annealing process. The Cu-29Zn-0.6wt.%Bi alloy was produced by gravity casting in a metal mold with the dimension of 110x110x6 mm³. The as-cast plate was homogenized at 800 °C for 2 hours and then cold rolled with the level of deformation of 20, 40 and 70 % in multiple passes. The samples with 70% deformation was annealed at 350, 400 and 450 °C for 15 minutes. Characterization of materials included Vickers hardness measurement and microstructural observation by using optical microscope and SEM. The results showed that addition of Bi reduced the grain size, formed discrete globules in the interdendritic areas and increased the hardness. The globules as dispersoid bismuth deformed and filled intergranular spaces during rolling and promoted the formation of cross slip mechanism at the 20% deformation. At the 40% deformation, the globules led to more closely spaced twin lamellae and increased the twinning density. The phenomena created an inhomogeneous deformation and promoted the formation of shear band. Annealing process dispersed the Bi globules into tight structures along the grain boundaries.The presence of dispersed bismuth increased the rate of recrystallization during annealing due to the increased in potential site for nucleation. In contrast, the dispersed bismuth acted as the pinning agent that inhibited the grain growth and developed smaller grain size which resulted in higher hardness.

• Periodical: Key Engineering Materials (Volume 748)
• Pages: 218-223
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.748.218
• Online since: August 2017
• Authors: Imam Basori, Ruther Gadhu, Bondan Tiara Sofyan*
• Keywords: Twinning, Bismuth, Deformation, Recrystallization, Shear Band

References

[1] A. Reza, A. Lara, E.H. Robert, Physical Metallurgy Principles, Stamford: CT: Cengage Learning, (2009).

[2] ASM, ASM Specialty Handbook: Copper and Copper Alloys, ASM International, (2001).

[3] M.A. Taha, N.A. El-Mahallawy, R.M. Hammouda, T.M. Moussa, M.H. Gheith, Machinability Characteristics of the Lead Free-Silicon Brass Alloys as Correlated with Microstructure and Mechanical Properties, Ain Shams Eng. J. Vol. 3, (2012) pp.383-392.

DOI: 10.1016/j.asej.2012.05.004

[4] M.M. Hernadez, A.J. Hernandez, C.G. Rivera, Bistmuth Segregation and Crack Formation on a Free Lead Yellow Brass Tap, Eng. Failure Anal., Vol. 28, (2013) pp.63-68.

DOI: 10.1016/j.engfailanal.2012.10.002

[5] A. Haruhiko, I. Hisashi, L. Shufeng, K. Katyuyoshi, K. Yoshiharu, K. Akimichi, High Strength, Lead-Free Machinable Alpha-Beta Duplex Phase Brass Cu-40Zn-Cr-Fe-Sn-Bi Alloys, Mat. Sci. Eng. A, Vol. 529C, (2011) pp.275-281.

DOI: 10.1016/j.msea.2011.09.029

[6] N.B. Emelina, A.N. Alabin, N.A. Belov, Influence of Bismuth and Lead on the Formation of the Structure of Experimental Alloys with a Cu–30% Zn Based Composition during Crystallization, Deformation and Thermal Treatment, Russian J. of Non Ferrous Metals, Vol. 51, No. 6, (2010).

DOI: 10.3103/s1067821210060088

[7] S. Suwas, R.K. Ray, Crystallographic Texture of Materials, Springer, London, (2014).

[8] B.T. Sofyan, I. Basori, Effect of Deformation and Annealing Temperature on The Microstructures and Mechanical Properties of Cu-32%Zn Brass, J. ARPN JEAS, Vol. 11, No. 4, (2016) pp: 2741-2745.

[9] H.I. Walker, Grain Size Produzed by Recrystallization and Coalescence in Col Rolled Cartridge Brass, University of Illinois Bulletin, Vol. 43, No. 21, (1945) pp.1-58.

[10] H. Yan, X. Zhao, N. Jia, Y. Zheng, T. He, Influence of Shear Banding on the Formation of Brass-type Textures in Polycrystalline FCC Metals with Low Stacking Fault Energy, J. Mater. Sci. Technol., Vol. 30, No. 4, (2014) pp.408-416.

DOI: 10.1016/j.jmst.2013.11.010

[11] B.J. Duggan, M. Hatherly, W.B. Hutchinson, P.T. Wakefield, Deformation Structures and Textures in Cold-rolled 70: 30 brass, Met. Sci., Vol. 12, No. 8, (1978) pp.343-351.

DOI: 10.1179/030634578790433909

[12] F.J. Humphreys, M. Hatherly, Recrystallization and Related Phenomena, Oxford: Elsevier Ltd, (2004).

[13] C. Feng, S. Clark, Malfunction And Failure Analysis Investigations of C26000 (Cu-30% Zn) Brass Cartridge Cases, Mat. Characterization, Vol. 32, No. 1, (1994) pp.15-23.

DOI: 10.1016/1044-5803(94)90152-x

[14] K. Hajizadeh, M. Tajally, E. Emadoddin, E. Borhani, Study of Texture, Anisotropy and Formability of Cartridge Brass Sheets, J. of Alloy and Comp. Vol. 588, (2014) pp.690-696.

DOI: 10.1016/j.jallcom.2013.11.091