Commenced in January 2007
Frequency: Monthly
Edition: International
Paper Count: 31231
Enhancement of Hardness Related Properties of Grey Cast Iron Powder Reinforced AA7075 Metal Matrix Composites through T6 and T8 Heat Treatments

Authors: S. S. Sharma, P. R. Prabhu, K. Jagannath, Achutha Kini U., Gowri Shankar M. C.


In present global scenario, aluminum alloys are coining the attention of many innovators as competing structural materials for automotive and space applications. Comparing to other challenging alloys, especially, 7xxx series aluminum alloys have been studied seriously because of benefits such as moderate strength; better deforming characteristics and affordable cost. It is expected that substitution of aluminum alloys for steels will result in great improvements in energy economy, durability and recyclability. However, it is necessary to improve the strength and the formability levels at low temperatures in aluminum alloys for still better applications. Aluminum–Zinc–Magnesium with or without other wetting agent denoted as 7XXX series alloys are medium strength heat treatable alloys. In addition to Zn, Mg as major alloying additions, Cu, Mn and Si are the other solute elements which contribute for the improvement in mechanical properties by suitable heat treatment process. Subjecting to suitable treatments like age hardening or cold deformation assisted heat treatments; known as low temperature thermomechanical treatments (LTMT) the challenging properties might be incorporated. T6 is the age hardening or precipitation hardening process with artificial aging cycle whereas T8 comprises of LTMT treatment aged artificially with X% cold deformation. When the cold deformation is provided after solution treatment, there is increase in hardness related properties such as wear resistance, yield and ultimate strength, toughness with the expense of ductility. During precipitation hardening both hardness and strength of the samples are increasing. The hardness value may further improve when room temperature deformation is positively supported with age hardening known as thermomechanical treatment. It is intended to perform heat treatment and evaluate hardness, tensile strength, wear resistance and distribution pattern of reinforcement in the matrix. 2 to 2.5 and 3 to 3.5 times increase in hardness is reported in age hardening and LTMT treatments respectively as compared to as-cast composite. There was better distribution of reinforcements in the matrix, nearly two fold increase in strength levels and up to 5 times increase in wear resistance are also observed in the present study.

Keywords: Precipitation, reinforcement, Strain Hardening, thermomechanical, dislocation

Digital Object Identifier (DOI):

Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 1571


[1] Berg L. K, Gjonnes J, Hansen V, Li X. Z, Knutson-wedel, & M, Waterloo G “GP-zones in Al–Zn–Mg alloys and their role in artificial aging” Acta Mater 2001;49:3443–3465.
[2] Song R. G & Zhang Q. Z, “Heat treatment optimization for 7175aluminum alloy by genetic algorithm.” Material Science Engineering, C 2001; 17:133–137.
[3] Tangen Stian, Sjolstad Knut, Nes Erik, Furu Trond & Marthinsen Knut, “The effect of precipitation on the recrystallization behavior of a supersaturated, cold rolled AA3103 aluminium alloy”, Material Science Forum 2002; 469:396–402.
[4] Lee S. H, Saito Y, Sakai T & Utsunomiya H, “Microstructures and mechanical properties of 6061 aluminum alloy processed by accumulative roll-bonding”, Material Science Engineering A, 2002;325:228–235.
[5] Robson J. D, “Optimizing the homogenization of zirconium containing commercial aluminium alloys using a novel process model”, Material Science Engineering A 2002; 338:219–229.
[6] Chen S. P, Kuijpers NCW & Van der Zwaag S, “Effect of microsegregation and dislocations on the nucleation kinetics of precipitation in aluminium alloy AA3003”, Material Science Engineering A, 2003;341:296.
[7] Starink M. J & Wang S. C, “A model for the yield strength of overaged Al–Zn–Mg–Cu alloys”, Acta Mater, 2003; 51:5131–5150.
[8] Chen K. H, Liu H. W, Zhang Z, Li S & Todd R. I, “The improvement of constituent dissolution and mechanical properties of 7055 aluminum alloy by stepped heat treatments”, Journal of Material Process Technology, 2003; 142:190–196.
[9] Dumont D, Deschamps A & Brechet Y, “On the relationship between microstructure, strength and toughness in AA7050aluminum alloy”, Material Science Engineering A 2003; 356: 326–326.
[10] Wang D, Nia D. R & Ma Z. Y, “Effect of pre-strain and two-stepaging on microstructure and stress corrosion cracking of 7050alloy”, Material Science Engineering A, 2008 ; 218-226.
[11] E. Sjolender & S. Seifeddine, “Optimization of solution treatment of cast Al-Si-Cu alloys”, Materials and Design, 2010; 31; 544-549.
[12] Norbert Ponweiser & Klauss W. Richter, “New investigation of phase equilibria in the system Al -Cu-Si”, Alloys and Compounds, 2012; 512; 252-253.
[13] V. C. Yuvaraja & N. Natarajan,”Comparison on Al6061 and Al7075 Alloy with Sic and B4c reinforcement Hybrid Metal Matrix Composites”, Int. Journal of Advanced Research in Tech., 2, , 2012,1- 12.
[14] G. B. Veeresh Kumar, C. S. P. Rao, N. Selvaraj, & M. S. Bhagyashekar ,”Studies on Al6061-SiC and Al7075-Al2O3 Metal Matrix Composites”, Journal of Minerals & Materials Characterization & Engineering, 9, 2010 ;43-55.
[15] Wang H.Q, Sun W.L & Xing Y.Q,” Microstructure Analysis on 6061 Aluminum Alloy after Casting and Diffuses Annealing Process”, Physics Procedia-Elsevier, 2013, 1, 68 – 75.