Heat Treatment of a Slurry Squeeze-Cast ZA-27 Alloy at 150 °C

Abstract:

This work reports the result of heat treatment on microstructures and mechanical property of ZA-27 zinc alloy gear part produced by a slurry squeeze casting process. The Gas Induced Semi-Solid (GISS) technique was employed for preparation of the alloy slurry. The microstructures and mechanical property of the alloy were studied by X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM) and HRB hardness testing. The specimens were solid solution heat treated at 365 °C for 1 h and artificially aged at 150 °C for 0.5, 1, 3, 6, 12 and 24 h. The as-cast microstructures of the alloy mainly consist of globular primary α phase surrounded by β, η and ε phases. After solution treatment the primary α and η phases were dissolved and transformed to the supersaturated β phase. At the early stage of ageing (0.5 – 3 h) the β phase decomposed to α and η phases. After a long period of ageing (6 – 24 h) α and ε phases decomposed through the transformation reaction: α + ε → T’+η. The hardness of specimens was increased after ageing for 0.5 h and gradually decreased with increasing ageing time. The peak hardness was 82 HRB at 0.5 h ageing. The hardness decreased to 62 HRB after ageing for 24 h.

• Periodical: Materials Science Forum (Volume 867)
• Pages: 14-18
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.867.14
• Online since: August 2016
• Authors: Supakit Vongcharoenpon, Somjai Janudom, Thawatchai Plookphol*
• Keywords: GISS, Heat Treatment, Semi-Solid, Squeeze Casting, ZA-27, Zinc Alloy

References

[1] K. H. W. Seah, S. C. Sharma, B. M. Girish Mechanical properties of as-cast and heat-treated ZA-27/graphite particulate composites [J]. Composites Part A, 1997, 28: 51−256.

DOI: 10.1016/s1359-835x(96)00117-0

[2] L. Run-xia, L. Rong-de, B. Yan-hua, Q. Ying-dong, Y. Xiao-guang, Effect of specific pressure on microstructure and mechanical properties of squeeze casting ZA27 alloy, Trans. Nonferrous Met. Soc. China 20(2010) 59-63.

DOI: 10.1016/s1003-6326(09)60097-2

[3] M. Gao, F. G.H. He, F. Yang, J.D. Guo, Z.X. Yuan, B.L. Zhou, Effect of electric current pulse on tensile strength and elongation of casting ZA-27 alloy, Mater Sci Eng A, 2002, 337 : 110-114.

DOI: 10.1016/s0921-5093(02)00026-6

[4] M.T. Abou El-Khair, A. Lotfy, A. Daoud, A.M. El-Sheikh. Microstructure thermal behavior and mechanical properties of squeeze cast SiC, ZrO2 or C reinforced ZA27 composites [J]. Mater Sci Eng A, 2011, 528: 2353−2362.

DOI: 10.1016/j.msea.2010.11.060

[5] T. J. Chen, Y. Hao, Y.D. Li. Effects of processing parameters on microstructure of thixoformed ZA27 alloy [J]. Mater Des, 2007, 28: 1279−1287.

DOI: 10.1016/j.matdes.2005.12.010

[6] J.R. Morton, J. Barlow, Squeezecasting: from a theory to profit and a future, Foundryman J. Inst. Brit. Foundryman, Part 1 87 (1994) 23–28.

[7] G.A. Chadwick, T.M. Yue, Principles and applications of squeeze casting, Met. Mater. 5 (1) (1989) 6–12.

[8] J.L. Jorstad, Q.Y. Pan, D. Apelian,. Solidification microstructure affecting ductility in semi-solid-cast products. Mater. Sci. Eng. A, 2005, 413–414, 186–191.

DOI: 10.1016/j.msea.2005.09.026

[9] J. Wannasin, R.A. Martinez, M.C. Flemings. A novel technique to produce metal slurries for semi-solid metal processing [J]. Solid State Phenomena, 2006, 116: 366−369.

DOI: 10.4028/www.scientific.net/ssp.116-117.366

[10] J. Wannasin, R.A. Martinez, M.C. Flemings,. Grain refinement of an aluminum alloy by introduction gas bubbles during solidification. Scripta Materialia. 55, 2006, 115-118.

DOI: 10.1016/j.scriptamat.2006.04.003

[11] J. Wannasin, S. Janudom, T. Rattanochaikul, M.C. Flemings. Development of the gas induced semi-solid metal process for aluminum die casting application [J]. Solid State Phenomena, 2008, 141−143: 97−102.

DOI: 10.4028/www.scientific.net/ssp.141-143.97

[12] S. Thanabumrungkul, S. Janudom, R. Burapa, P. Dulyapraphant, J. Wannasin, Industrial development of gas induced semi-solid process. Trans. Nonferrous Met. Soc. China 20(2010) 1016-s1021.

DOI: 10.1016/s1003-6326(10)60623-1

[13] Y.H. Zhu, W.B. Lee, S. To. Ageing characteristics of cast Zn-Al based alloy (ZnAl7Cu3) [J]. J Mater Sci, 2003, 38: 1945-(1952).

[14] Y.H. Zhu. Decomposition reactions in a quench, aged eutectoid alloy AlZn75Cu3Si2 [J]. J Mater Sci Technol, 1990, 6: 125−131.

[15] Y. Liu, H. Li, H. Jiang, X. Lu. Effects of heat treatment on microstructure and mechanical properties of ZA-27 alloy, Trans. Nonferrous Met. Soc. China 23(2013) 642-649.

DOI: 10.1016/s1003-6326(13)62511-x