Direct Thermal Method of Aluminium 7075


Article Preview

The evolution of microstructure affect from different pouring temperatures and holding times using a direct thermal method is presented in this paper. The direct thermal method is one of the thermal techniques which are used to produce semi-solid metal feedstock. In this experimental work, aluminium 7075 alloy was used. The experiments were carried out by processing a sample with a 0.7 °C/s cooling rate to evaluate the formation of the microstructure. In direct thermal method experiment, a molten 7075 was poured into a cylindrical copper mould at different pouring temperatures of 680 °C and 660 °C meanwhile the holding time of 20 s, 40 s and 60 s before quenched into room temperature water. The sample processed by the cooling rate of 0.7 °C/s produced a large microstructure. The formation of a spheroidal microstructure was obtained with the combination of a suitable pouring temperature and holding time. The pouring temperature of 665 °C and the holding time of 60 s produced a finer and uniform microstructure that is suitable for semi-solid feedstock.



Edited by:

Zone-Ching Lin, You-Min Huang and Liang-Kuang Chen




A. H. Ahmad et al., "Direct Thermal Method of Aluminium 7075", Advanced Materials Research, Vol. 939, pp. 400-408, 2014

Online since:

May 2014




* - Corresponding Author

[1] Kirkwood H, Semisolid metal processing, International Materials Reviews (1994) 39, 173-189.

[2] Kopp R, Some current development trends in metal-forming technology, J. Mater. Process. Technol. (1996) 60, 1-9.

[3] McLelland ARA, Henderson NG, Atkinson HV, Kirkwood DH, Anomalous rheological behaviour of semi-solid alloy slurries at low shear rates, Materials Science and Engineering: A (1997) 232, 110-118.


[4] Chinesta F, Cueto El, Atkinson H, Current Status of Semi-Solid Processing of Metallic Materials, Advances in Material Forming, Springer, Paris, 2007, pp.81-98.


[5] Brabazon D, Browne DJ, Carr AJ, Mechanical stir casting of aluminium alloys from the mushy state: process, microstructure and mechanical properties, Materials Science and Engineering A (2002) A326, 370-381.


[6] Naher S, Brabazon D, Looney L, Development and assessment of a new quick quench stir caster design for the production of metal matrix composites, J. Mater. Process. Technol. (2005) 166, 430-439.


[7] Neag Adriana, Favier Véronique, Bigot Régis, Pop Mariana, Microstructure and flow behaviour during backward extrusion of semi-solid 7075 aluminium alloy, Journal of Material Processing Technology (2012) 212, 1472-1480.


[8] Chayong S, Atkinson HV, Kapranos P, Thixoforming 7075 aluminium alloys, Materials Science and Engineering A (2005) A390, 3-12.


[9] Bo X, Yuandong L, Ma Y, Yuan H, Effect of novel self-inoculation method on microstructure of AM60 alloy, China Foundry (2011) 8 (1), 121-126.

[10] Hussey MJ, Browne DJ, Brabazon D, Car AJ, In A direct thermal method of attaining globular morphology in the primary phase of alloys, Proceedings of the 7th International Conference on Semi-Solid Processing of Alloys and Composites, (2002).

[11] Browne DJ, Hussey MJ, Carr AJ, Brabazon D, Direct thermal method: new process for development of globular alloy microstructure, International Journal of Cast Metals Research (2003) 16, 418-426.


[12] O. Lashkari and R. Ghomashchi, The implication of rheology in semi-solid metal processes: An overview, Journal of Materials Processing Technology (2007)182, 229-240.


[13] Hallstedt B, Balitchev E, Shimahara H, Neuschütz D, Semi-solid Processing of Alloys: Principles, Thermodynamic Selection Criteria, Applicability, ISIJ International (2006) 46, 1852-1857.


[14] Vaneetveld G, Rassili A, Pierret JC, Lecomte-Beckers J, Conception of tooling adapted to thixoforging of high solid fraction hot-crack-sensitive aluminium alloys, Transactions of Nonferrous Metals Society of China (2010) 20, 1712-1718.


[15] ASM International. Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, USA, 1992, Vol. 2.

[16] Adriana Neag, Veronique Favier, Mariana Pop, Eric Becker, Regis Bigot, Effect of experimental conditions on 7075 aluminium response during thixoextrusion, Key Engineering Materials (2012) 504-506, 345-350.


[17] Mohammadi H, Ketabchi M, Kalaki A, Microstructural evolution and mechanical properties of back-extruded Al 7075 alloy in the semi-solid state, International Journal of Material Forming (2012) 5, 109-119.


[18] Browne DJ, Hussey MJ, Carr AJ, In Towards optimisation of the direct thermal method of rheocasting, 8th International Conference on Semi-Solid Processing of Alloys and Composites, (2004).

[19] Asnul Ahmad, Sumsun Naher, Dermot Brabazon, In Effects of direct thermal method temperature and time on A35 microstructure; 15th International conference on advances materials and processing technology, 23-26 September (2012).


[20] Carr AJ, Browne DJ, Hussey MJ, Lumsden N, Scanlan M, Modelling and experimental development of the direct thermal method of rheocasting, International Journal of Cast Metals Research (2007) 20, 325-332.


[21] Metals Handbook, Vol. 2 - Properties and Selection: Nonferrous Alloys and Special-Purpose Materials. ASM International: (1990).

[22] A.H. Ahmad, S. Naher, D. Brabazon, Thermal profiles and fraction solid of aluminium 7075 at different cooling rate conditions. Key Engineering Materials (2013) 554-557, 582-595.


[23] Gonzalez G, Lara-Rodriguez G, Sandoval-Jiménez A, Saikaly W, Charai A, The influence of cooling rate on the microstructure of an Al–Ni hypereutectic alloy, Mater Characterization (2008) 59, 1607-1612.


[24] Mukherjee M, Ramamurty U, Garcia-Moreno F, Banhart J, The effect of cooling rate on the structure and properties of closed-cell aluminium foams, Acta Materialia (2010) 58, 5031-5042.


[25] Zeer G, Pervukhin M, Zelenkova E, Effect of cooling rate on microstructure formation during crystallization of aluminum alloy 1417M, Metal Science and Heat Treatment (2011) 53, 210-212.


[26] Gowri S and Samuel F, Effect of cooling rate on the solidification behavior of Al-7 Pct Si-SiCp metal-matrix composites, Metallurgical and Materials Transactions A (1992) 23, 3369-3376.


Fetching data from Crossref.
This may take some time to load.