Abstract
The effects of isothermal holding process on the microstructure evolution of semi-solid 7075 strength aluminum alloy produced by the recrystallisation and partial remelting (RAP) process were investigated. Tensile mechanical properties of as-received and thixoformed alloys at room temperature were examined. The results show that the microstructure of as-received alloy exhibits remarkable orientation along the deformation direction. With the increase of isothermal holding time, the solid particle grain size continuously increases and the degree of spheroidization also improves. Coalescence mechanism is dominant when reheated at 595 °C and Ostwald ripening mechanism is dominant when reheated at 615 °C in the semi-solid state. A lower coarsening rate is observed for 615 °C (coarsening rate K = 391 μm3·s−1) compared with the coarsening rate for 595 °C (coarsening rate K = 501 μm3·s−1). The RAP 7075 aluminum alloy can be successfully thixoformed and the filling of components is good after thixoforming. The thixoformed components exhibit favorite mechanical properties.
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Guo HM, Yang XJ, Wang JX, Hu B, Zhu GL. Effects of rheoforming on microstructures and mechanical properties of 7075 wrought aluminum alloy. Trans Nonferrous Met Soc China. 2010;20(3):355.
Atkinson HV, Liu D. Microstructural coarsening of semi-solid aluminum alloys. Mater Sci Eng A. 2008;496(1–2):439.
Zhang F, Kang YL, Yang LQ, Ding RH. Taper barrel rheomoulding process for semi-solid slurry preparation and microstructure evolution of A356 aluminum alloy. Trans Nonferrous Met Soc China. 2010;20(9):1677.
Atkinson HV, Burke K, Vaneetveld G. Recrystallisation in the semi-solid state in 7075 aluminum alloy. Mater Sci Eng A. 2008;490(1–2):266.
Chen ZZ. Preparation of semi-solid A356 Al-alloy slurry by introducing grain process. Trans Nonferrous Met Soc China. 2012;22(6):1307.
Chayong S, Atkinson HV, Kapranos P. Thixoforming 7075 aluminum alloys. Mater Sci Eng A. 2005;390(1–2):3.
Luo SJ, Chen Q, Zhao ZD. An investigation of microstructure evolution of RAP processed ZK60 magnesium alloy. Mater Sci Eng A. 2009;501(1–2):146.
Zhao ZD, Chen Q, Hu CK, Tang ZJ. Microstructural evolution and tensile mechanical properties of AM60B magnesium alloy prepared by the SIMA route. J Alloy Compd. 2010;497(1–2):402.
Zhao ZD, Chen Q, Huang SH, Chao HY. Microstructural evolution and tensile mechanical properties of thixoforged ZK60-Y magnesium alloys produced by two different routes. Mater Des. 2010;31(4):1906.
Zhang XM, Guo H, Yin FZ, Fan YM, Zhang YZ. Semisolid microstructure evolution of AZ91D alloy under high shear rate. J Rare Met. 2011;30(1):94.
Sun SC, Yuan B, Liu MP. Effects of moulding sands and wall thickness on microstructure and mechanical properties of Sr-modified A356 aluminum casting alloy. Trans Nonferrous Met Soc China. 2012;22(8):1884.
Li JP, Shen J, Yan XD, Mao BP, Yan LM. Microstructure evolution of 7050 aluminum alloy during hot deformation. Trans Nonferrous Met Soc China. 2010;20(6):935.
Chen J, Wang ZX, Lu S. Effects of electric parameters on microstructure and properties of MAO coating fabricated on ZK60Mg alloy in dual electrolyte. Rare Met. 2012;31(3):172.
Annavarapu S, Doherty RD. Inhibited coarsening of solid-liquid microstructures in spray casting at high volume fractions of solid. Acta Metall Mater. 1995;43(8):3207.
Chen Q, Shu DY, Hu CK, Zhao ZD, Yuan BG. Grain refinement in an as-cast AZ61 magnesium alloy processed by multi-axial forging under the multitemperature processing procedure. Mater Sci Eng A. 2012;541(1–2):98.
Bolouri A, Shahmiri M, Cheshmeh ENH. Microstructural evolution during semisolid state strain induced melt activation process of aluminum 7075 alloy. Trans Nonferrous Met Soc China. 2010;20(9):1663.
Sadough SA, Rahmani MR, Pouyafar V. Rheological behavior, microstructure and hardness of A356 aluminum alloy in semisolid state using backward extrusion process. Trans Nonferrous Met Soc China. 2010;20(Z3):906.
Kori SA, Murty BS, Chakraborty M. Development of an efficient grain refiner for Al–7Si alloy. Mater Sci Eng A. 2000;283(1–2):58.
Tang CY, Xiao ZY, Luo F, Wang J, Ma CY, Zhang W. Structural characteristics and magnetic properties of bulk nanocrystalline Fe84Zr2Nb4B10 alloy prepared by mechanical alloying and spark plasma sintering consolidation. Rare Met. 2012;31(3):255.
Chen Q, Lin J, Shu DY, Hu CK, Zhao ZD, Kang F, Huang SH, Yuan BG. Microstructure development, mechanical properties and formability of Mg–Zn–Y–Zr magnesium alloy. Mater Sci Eng A. 2012;554(1–2):129.
Hu XW, Ai FR, Yan H. Influences of pouring temperature and cooling rate on microstructure and mechanical properties of casting Al–Si–Cu aluminum alloy. Acta Metall Sin. 2012;25(4):272.
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This work was financially supported by the National Natural Science Foundation of China (No. E050802).
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Wang, CP., Tang, ZJ., Mei, HS. et al. Formation of spheroidal microstructure in semi-solid state and thixoforming of 7075 high strength aluminum alloy. Rare Met. 34, 710–716 (2015). https://doi.org/10.1007/s12598-013-0123-0
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DOI: https://doi.org/10.1007/s12598-013-0123-0