Effect of Hot Extrusion and Heat Treatment on the Microstructure and Tensile Properties of Network Structured TiBw/TC18 Composites
CHEN Run, WANG Shuai(), AN Qi, ZHANG Rui, LIU Wenqi, HUANG Lujun, GENG Lin
School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
Cite this article:
CHEN Run, WANG Shuai, AN Qi, ZHANG Rui, LIU Wenqi, HUANG Lujun, GENG Lin. Effect of Hot Extrusion and Heat Treatment on the Microstructure and Tensile Properties of Network Structured TiBw/TC18 Composites. Acta Metall Sin, 2022, 58(11): 1478-1488.
To improve the comprehensive performance of Ti matrix composites for defense applications such as aviation and aerospace, as-sintered TiBw/TC18 composites with different reinforcement contents were hot extruded and heat-treated. The composites were characterized and analyzed by OM, SEM, and TEM. The mechanical properties of the composites were measured using an electronic universal testing machine. By extruding in the β single-phase region, the β grain size of TiBw/TC18 was reduced from 70 μm to about 40 μm. After the subsequent triple-annealing or solution aging heat treatment, α phase with different sizes was precipitated and distributed in the β phase. The elongation of the as-extruded composites significantly showed improvement, but the strength decreased by about 17%. After applying the triple-annealing heat treatment, the tensile strength and elongation of 2.0%TiBw/TC18 (volume fraction) reached 1200 MPa and 21.7%, which are higher by 5.5% and 189%, respectively, than those in the sintered state. Moreover, after applying the solution aging heat treatment, the as-extruded 2.0%TiBw/TC18 exhibited tensile strength and elongation of 1389 MPa and 9.9%, which are higher by 22.2% and 32%, respectively, than those exhibited by as-sintered 2.0%TiBw/TC18. Consequently, the hot extrusion can effectively reduce the grain size of as-sintered TiBw/TC18, and the tensile properties of the extruded TiBw/TC18 can be modified to meet the requirements of different service conditions through different subsequent heat treatments.
Fund: National Key Research and Development Program of China(2021YFB3701203);National Natural Science Foundation of China(52171137);National Natural Science Foundation of China(52071116);Natural Science Foundation of Heilongjiang Province(TD2020E001);Heilongjiang Postdoctoral Fund(LBH-Z20058)
Fig.1 OM image of as-sintered 2.0%TiBw/TC18 composites (a), schematic illustrating samples' locations of as-extruded 1.0%TiBw/TC18 for EBSD analysis (b), schematics of solution aging (c) and triple-annealing (d) treatments for as-extruded alloy and composites (AC—air cooling, FC—furnace cooling)
Fig.2 EBSD grain orientation maps (a1-d1), frequency distributions of grain size (a2-d2), inverse pole figures (IPFs) (a3-d3), and pole figures (PFs) (a4-d4) of samples A (a1-a4), B (b1-b4), C (c1-c4), and D (d1-d4) in as-extruded 1.0%TiBw/TC18 composites (ED—extrusion direction)
Fig.3 OM images of TiBw/TC18 composites with different reinforcement volume fractions (a) as-extruded TC18 and enlarged SEM image of the marked area (inset) (b) as-extruded 0.5%TiBw/TC18 (c) as-extruded 1.0%TiBw/TC18, and SEM image and phase map (insets) (d) as-extruded 2.0%TiBw/TC18 (e) as-sintered 0.5%TiBw/TC18 solution at 1100oC followed by water quench, and the area circled by the line is the area where the grains grow
Fig.4 OM (a-d) and SEM (e, f) images of the TC18 alloy (a, b), 0.5%TiBw/TC18 (c, d), and 2.0%TiBw/TC18 (e, f) composites after triple-annealing (a, c, e) and solution aging (b, d, f) heat treatments (Insets show the high magnified images. GBα—grain boungry α, αc—coarse α, αf—fine α, α2—Ti3Al)
Fig.5 Bright field TEM (a, b) and HRTEM (c, d) images of 2.0%TiBw/TC18 composites after triple-annealing, and fast Fourier transformation (FFT) patterns taken from Figs.5c (e) and d (f)
Fig.6 Tensile stress-strain curves of TiBw/TC18 composites with different states
State
V / %
σ0.2 / MPa
σb / MPa
δ / %
As-sintered[21]
0
1082 ± 17.6
1151 ± 10
0.6 ± 0.5
0.5
1052 ± 4.4
1171 ± 6.2
15.6 ± 0.5
1.0
1023 ± 9.8
1140 ± 3.2
13.5 ± 1.0
2.0
1041 ± 7.3
1137 ± 2.5
7.5 ± 1.1
As-extruded
0
804 ± 19
890 ± 18.5
6.5 ± 3.5
0.5
786 ± 8
881 ± 9.5
19.4 ± 3.4
1.0
853 ± 7
925 ± 1
29.7 ± 0.3
2.0
876 ± 4
946 ± 3.5
26 ± 0.1
Triple-annealing state
0
1040 ± 13
1139 ± 13.5
22.6 ± 0.7
0.5
1073 ± 1
1175 ± 3
19.7 ± 0.5
1.0
1093 ± 3.5
1191 ± 4
24.5 ± 0.9
2.0
1097 ± 2.5
1200 ± 7.5
21.7 ± 1.9
Solution aging state
0
1208 ± 3
1310 ± 14.5
9 ± 0.1
0.5
1263 ± 19
1337 ± 7
6.4 ± 0.5
1.0
1280 ± 8
1374 ± 10
12 ± 0.1
2.0
1296 ± 18
1389 ± 7
9.9 ± 0.6
Table 1 Tensile properties of the TiBw/TC18 composites with different states
Fig.7 Low (a, c) and high (b, d) magnified SEM images of tensile fracture (a, b) and fracture side surface (c, d) of as-extruded 1.0%TiBw/TC18 (Inset in Fig.7d shows the enlarged view)
Fig.8 Low (a, c) and high (b, d-f) magnified SEM images of tensile fracture (a, b) and fracture side surface (c-f) of as-extruded 1.0%TiBw/TC18 after triple-annealing (Insets in Figs.8e and f show the enlarged views)
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