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20 6 2010 6 Vol.20 No.6 The Chinese Journal of Nonferrous Metals June 2010 1004-0609(2010)06-1095-07 7150 ( 100088) OM SEM X DSC 7150 480 475 2 h (475 2 h) + (120 24 h) 650 MPa 600 MPa 13.5% 7150 TG113 TG146.2 A Effect of solution treatment on microstructures and mechanical properties of 7150 aluminum alloy HAN Xiao-lei, XIONG Bai-qing, ZHANG Yong-an, LI Zhi-hui, ZHU Bao-hong, WANG Feng, LIU Hong-wei (State Key Laboratory of Nonferrous Metals and Processes, General Research Institute for Nonferrous Metals, Beijing 100088, China) Abstract: The effects of solution treatment on the microstructures and mechanical properties of 7150 aluminum alloy extrusion plate were studied by OM, SEM, XRD, DSC and room temperature tensile test. The results show that the coarse second phase dissolves more adequately when the alloy is solution treated at higher temperature for longer time. The overheated structure appears in alloys when quenched at 480, and the temperature at which overheated structure appears cannot be enhanced by two-stage solution. The trend of microstructure coarsening and recrystallization appears with prolongating the solution time. The suited solution of the alloy is single-stage solution of 475, 2 h. After solution and peak aging of (475, 2 h)+(120, 24 h), the ultimate tensile strength, yield strength and elongation are 650 MPa, 600 MPa and 13.5%, respectively. Key words: 7150 Al alloy; solution treatment; microstructure; mechanical properties Al-Zn-Mg-Cu [1] 7150 7050 Zn Mg Cu Fe Si [2] 1991 Alcoa T77 7150 T6 [3 5] 7150-T77(25 mm ) 614 MPa 7150-T77 [6] [7] ( ) (2007BAE38B06) 2009-08-25 2009-11-22 010-82241165 E-mail zhangyongan@grinm.com

1096 2010 6 [8] [9 10] 7150 7150 7150 5~30 µm [11 12] XRD MgZn 2 1 Al-6.33Zn-2.35Mg-2.39Cu-0.12Zr Al Zn Mg Al-Cu Al-Zr (440 12 h)+(475 24 h) 100 mm 25 mm 1 12.6 470 475 480 1 2 4 h 450 460 475 480 485 1 h 1 h SX2 12 10 2 (Axiocert200MAT) (HITACHI S4800) Keller X CuK α (2θ) 10 ~90 DSC NETZSCH STA 409C/CD 10 K/min MTS 810, 1 mm/min L 2 2.1 1 7150 1(a) 1(b) 1 7150 Fig.1 Three-dimensional metallograph of as-extruded 7150 alloy: (a) Lower-magnification; (b) High-magnification 2 7150 a Al 2 CuMg b Al 2 CuMg 1 Cu Al 2 Cu Al 2 CuMg Cu Mg Cu Al 2 CuMg Cu c Fe Al 7 Cu 2 Fe Fe Fe SEM Fe [13] d Zn 3 XRD 3 Al MgZn 2 Al 2 CuMg 4 DSC 4

20 6 7150 1097 2 7150 Fig.2 Microstructure of as-extruded 7150 alloy 1 2 Table 1 EDS analyses results of phases in Fig.2 Phase Mole fraction/% Al Zn Mg Cu Fe Mn a 50.60 1.99 24.32 23.09 b 72.98 1.17 3.06 22.79 c 81.07 0.94 1.09 11.75 4.83 0.32 d 76.56 10.53 9.25 3.66 3 7150 X Fig.3 XRD patterns of as-extruded 7150 alloy 487.3 465 MPa 305 MPa 10.5% 2.2 5 7150 1 h 5 470 475 470 1 h 4 7150 DSC Fig.4 DSC curves of as-extruded 7150 alloy 1 µm MgZn 2 Al 2 CuMg 475 1 h MgZn 2 Al 2 CuMg 480 1 h DSC DSC 6 7150 475 6 [14] Al 2 CuMg MgZn 2 [15] [16 17] 7 475 2 h 2 7 e f 2 e Al 2 CuMg f Cu Mg Cu Al 2 CuMg Cu 8 1 h 120 24 h 8

1098 2010 6 5 7150 1 h Fig.5 Metallographs of 7150 alloy after solution treatment for 1 h at different temperatures: (a) 470, transverse section; (b) 470, longitudinal section; (c) 475, transverse section; (d) 475, longitudinal section; (e) 480, transverse section; (f) 480, longitudinal section 6 7150 475 Fig.6 Metallographs of transverse section of 7150 alloy after solution treatments at 475 for different times: (a) 1 h; (b) 2 h; (c) 4 h

20 6 7150 1099 7 475 2 h Fig.7 Microstructure of coarse second phase of alloy after 475, 2 h solution treatment 2 7 Table 2 Chemical composition of phases in Fig.7 Phase Mole fraction/% Al Zn Mg Cu e 54.85 1.69 23.22 20.24 f 40.27 2.30 8.25 49.19 9 7150 Fig.9 Effect of solution time on tensile properties of 7150 alloy aged 120 for 24 h after solution at 475 475 2 h (475 2 h)+(120 24 h) R m R p0.2 A 650 MPa 600 MPa 13.5% 8 7150 Fig.8 Effect of solution temperature on tensile properties of 7150 alloy (aging at 120, 24 h after solution for 1 h) 475 (475 1 h)+(120 24 h) R m R p0.2 A 645 MPa 600 MPa 13.0% 480 9 475 120 24 h 9 2.3 10 10 480 485 11 12 120 24 h 11 12 450 485 R m R p0.2 645 MPa 595 MPa 460 480 R m R p0.2 A 645 MPa 595 MPa 17% (450 1 h)+ 1 h+(475 1 h) + (120 24 h) (460 1 h)+ 1 h+(475 1 h)+ (120 24 h) 3

1100 2010 6 12 460 Fig.12 Effect of second stage solution temperature on tensile properties of alloy at first stage solution temperature of 460 3 Table 3 Comparison of tensile properties of alloy after single-stage solution and two-stage solution Solution treatment R m /MPa R p0.2 /MPa A/% (475, 2 h)+(120, 24 h) 650 600 13.5 10 Fig.10 Metallographs of alloys with different two-stage solution treatments: (a) (450, 1 h)+(heating up for 1 h)+ (475, 1 h); (b) (450, 1 h)+(heating up for 1 h)+(480, 1 h); (c) (450, 1 h)+(heating up for 1 h)+(485, 1 h) (450, 1 h)+(heating up for 640 595 13.5 1 h)+(475, 1 h)+(120, 24 h) (460, 1 h)+(heating up for 645 600 13.0 1 h)+(475, 1 h)+(120, 24 h) 475 475 2 h 3 11 450 Fig.11 Effect of second stage solution temperature on tensile properties of alloy at first stage solution temperature of 450 1) 7150 480 Al 2 CuMg Cu 475 2 h MgZn 2 Al 2 CuMg Cu 2)

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