Microstructural evolution in Al-Zn-Mg-Cu-Sc-Zr alloys during short-time homogenization

Abstract

Microstructural evolution in a new kind of aluminum (Al) alloy with the chemical composition of Al-8.82Zn-2.08Mg-0.80Cu-0.31Sc-0.3Zr was investigated. It is found that the secondary phase MgZn₂ is completely dissolved into the matrix during a short homogenization treatment (470°C, 1 h), while the primary phase Al₃(Sc,Zr) remains stable. This is due to Sc and Zr additions into the Al alloy, high Zn/Mg mass ratio, and low Cu content. The experimental findings fit well with the results calculated by the homogenization diffusion kinetics equation. The alloy shows an excellent mechanical performance after the short homogenization process followed by hot-extrusion and T6 treatment. Consequently, a good combination of low energy consumption and favorable mechanical properties is obtained.

Keywords

aluminum alloys / microstructural evolution / short-time / homogenization / grain refinement

References

[1] Godinho H.A., Beletati A.L.R., Giordano E.J., Bolfarini C. Microstructure and mechanical properties of a spray formed and extruded AA7050 recycled alloy. J. Alloys Compd., 2014, 586(S1): S139.

[2] Rogal L., Dutkiewicz J., Atkinson H., Litynska-Dobrzynska L., Czeppe T., Modigell M. Characterization of semi-solid processing of aluminium alloy 7075 with Sc and Zr additions. Mater. Sci. Eng. A, 2013, 580, 362.

[3] Li W.B., Pan Q.L., Xiao Y.P., He Y.B., Liu X.Y. Microstructural evolution of ultra-high strength Al-Zn-Cu-Mg-Zr alloy containing Sc during homogenization. Trans. Nonferrous Met. Soc. China, 2011, 21(10): 2127.

[4] Chen S.Y., Chen K.H., Peng G.S., Chen X.H., Ceng Q.H. Effect of heat treatment on hot deformation behavior and microstructure evolution of 7085 aluminum alloy. J. Alloys Compd., 2012, 537, 338.

[5] Fan X.G., Jiang D.M., Meng Q.C., Zhong L. The microstructural evolution of an Al-Zn-Mg-Cu alloy during homogenization. Mater. Lett., 2006, 60(12): 1475.

[6] Wu L.M., Wang W.H., Hsu Y.F., Trong S. Effects of homogenization treatment on recrystallization behavior and dispersoid distribution in an Al-Zn-Mg-Sc-Zr alloy. J. Alloys Compd., 2008, 456(1–2): 163.

[7] Deng Y.L., Zhang Y.Y., Wan L., Zhu A.A., Zhang X.M. Three-stage homogenization of Al-Zn-Mg-Cu alloys containing trace Zr. Metall. Mater. Trans. A, 2013, 44(6): 2470.

[8] Li H., Cao D.H., Wang Z.X., Zheng Z.Q. High-pressure homogenization treatment of Al-Zn-Mg-Cu aluminum alloy. J. Mater. Sci., 2008, 43(5): 1583.

[9] Norman A.F., Prangnell P.B., McEwen R.S. The solidification behaviour of dilute aluminium–scandium alloys. Acta Mater., 1998, 46(16): 5715.

[10] Brodova I.G., Bashlikov D.V., Polents I.V. Influence of heat time melt treatment on the structure and the properties of rapidly solidified aluminum alloys with transition metals. Mater. Sci. Forum, 1998, 269–272, 589.

[11] Golubev S., Korzhavina O., Popel P., Kononenko V., Brodova I., Polents I., Shubina T. Effect of viscosity and electrical-resistance of the structural state of Al-Sc melts and the structure of the cast metal. Russ. Metall., 1991, 1, 44.

[12] Marquis E.A., Seidman D.N. Coarsening kinetics of nanoscale Al₃Sc precipitates in an Al-Mg-Sc alloy. Acta Mater., 2005, 53(15): 4259.

[13] Robson J.D., Prangnell P.B. Modelling Al₃Sc dispersoid precipitation in multicomponent aluminium alloys. Mater. Sci. Eng. A, 2003, 352(1–2): 240.

[14] Blake N., Hopkins M. Constitution and age hardening of Al-Sc alloys. J. Mater. Sci., 1985, 20(8): 2861.

[15] Jones M.J., Humphreys F.J. Interaction of recrystallization and precipitation: the effect of Al₃Sc on the recrystallization behaviour of deformed aluminium. Acta Mater., 2003, 51(8): 2149.

[16] Seidman D.N., Marquis E.A., Dunand D.C. Precipitation strengthening at ambient and elevated temperatures of heat-treatable Al (Sc) alloys. Acta Mater., 2002, 50(16): 4021.

[17] Deng Y., Yin Z.M., Zhao K., Duan J.Q., He Z.B. Effects of Sc and Zr microalloying additions on the microstructure and mechanical properties of new Al-Zn-Mg alloys. J. Alloys Compd., 2012, 530, 71.

[18] Hyde K.B., Norman A.F., Prangnell P.B. The effect of cooling rate on the morphology of primary Al₃Sc intermetallic particles in Al-Sc alloys. Acta Mater., 2001, 49(8): 1327.

[19] Røyset J., Ryum N. Scandium in aluminium alloys. Int. Mater. Rev., 2005, 50(1): 19.

[20] Deng Y., Yin Z.M., Cong F.G. Intermetallic phase evolution of 7050 aluminum alloy during homogenization. Intermetallics, 2012, 26, 114.

[21] Li X.M., Yu J.J. Modeling the effects of Cu variations on the precipitated phases and properties of Al-Zn-Mg-Cu alloys. J. Mater. Eng. Perform., 2013, 22(10): 2970.

[22] Maloney S.K., Hono K., Polmear I.J., Ringer S.P. The chemistry of precipitates in an aged Al-2.1Zn-1.7Mg at.% alloy. Scripta Mater., 1999, 41(10): 1031.

[23] Clinch M. R., Harris S. J., Hepples W., Holroyd N. J. H., Lawday M. J., Noble B. Influence of zinc to magnesium ratio and total solute content on the strength and toughness of 7xxx series alloys. Mater. Sci. Forum, 2006, 519, 339.

[24] Wang H.J., Xu J., Kang Y.L., Tang M.G., Zhang Z.F. Study on inhomogeneous characteristics and optimize homogenization treatment parameter for large size DC ingots of Al-Zn-Mg-Cu alloys. J. Alloys Compd., 2014, 585, 19.

[25] Senkov O.N., Bhat R.B., Senkova S.V., Schloz J.D. Microstructure and properties of cast ingots of Al-Zn-Mg-Cu alloys modified with Sc and Zr. Metall. Mater. Trans. A, 2005, 36(8): 2115.