Microstructure and Mechanical Properties of TC4 Titanium Alloy Formed by Selective Laser Melting After Heat Treatment

Fig. 4. Microstructure of TC4 titanium alloy after 840 ℃/2 h/AC annealing treatment. (a) OM photo (light part is α phase and dark part is β phase); (b) SEM photo

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Fig. 5. Microstructure of TC4 titanium alloy after 940 ℃/1 h/WQ solution hardening. (a) OM photo(light part is α phase and dark part is β phase); (b) SEM photo

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Fig. 6. Microstructure of TC4 titanium alloy after 940 ℃/1 h/WQ+540 ℃/4 h/AC solution and aging treatment. (a) OM photo (light part is α phase and dark part is β phase); (b) SEM photo

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Fig. 7. XRD patterns of TC4 titanium alloy samples produced by SLM after different heat treatment processes

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Fig. 8. Fracture morphologies of samples after different heat treatment processes. (a) Untreated; (b) 840 ℃/2 h/AC; (c) 940 ℃/1 h/WQ; (d) 940 ℃/1 h/WQ+540 ℃/4 h/AC

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Fig. 9. Schematic of residual stress measurement points on TC4 titanium alloy sample

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Fig. 10. Stress simulation of TC4 titanium alloy samples after different heat treatment processes. (a) Untreated; (b) 840 ℃/2 h/AC; (c) 940 ℃/1 h/WQ; (d) 940 ℃/1 h/WQ+540 ℃/4 h/AC

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Table 1. Chemical compositions of Ti6Al4V power (mass fraction, %)
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Table 1. Chemical compositions of Ti6Al4V power (mass fraction, %)
Element Al V Fe C O N H Mo Mn Cu Sn Y Zr Ti
Content 5.500-6.750 3.500-4.500 0.140 0.007 0.130 0.007 0.002 <0.050 <0.050 <0.050 <0.050 <0.050 <0.050 Bal.

Table 2. Parameters of TC4 titanium alloy formed by SLM
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Table 2. Parameters of TC4 titanium alloy formed by SLM
Parameter Laser power /W Scanning speed /(mm·s ^-1 ) Layer thickness /μm
Value 180 1250 30

Table 3. Heat treatment conditions for TC4 titanium alloy formed by SLM
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Table 3. Heat treatment conditions for TC4 titanium alloy formed by SLM
Heat treatment mode Heat treatment condition
Annealing 840 ℃/2 h/AC
Solution hardening 940 ℃/1 h/WQ
Solution and aging treatment 940 ℃/1 h/WQ+540 ℃/4 h/AC

Table 4. Mechanical properties of TC4 titanium alloy samples formed by SLM after different heat treatment processes

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Table 4. Mechanical properties of TC4 titanium alloy samples formed by SLM after different heat treatment processes

Heat treatment mode	Tensile strength /MPa	Yield strength /MPa	Elongation /%	Reduction of area /%
No heat treatment	1130.55	1079.44	12.73	22.49
840 ℃/2 h/AC	954.84	927.16	18.95	31.44
940 ℃/1 h/WQ	880.67	841.37	15.95	15.36
940 ℃/1 h/WQ+540 ℃/4 h/AC	901.93	890.31	15.35	10.89

Table 5. Measured and simulated residual stresses of TC4 titanium alloy samples formed by SLM after different heat treatment processes

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Table 5. Measured and simulated residual stresses of TC4 titanium alloy samples formed by SLM after different heat treatment processes

Heat treatment mode	Measured point	Residual stress /MPa
Heat treatment mode	Measured point	Measured	Simulated
	Point 1	175.5	183
	Point 2	258.4	260
Untreated	Point 3	113.3	127
	Point 4	106.1	115
	Point 1	58.6	59
	Point 2	72.0	76
840 ℃/2 h/AC	Point 3	68.9	72
	Point 4	59.3	55
	Point 1	83.0	77
	Point 2	94.3	95
940 ℃/1 h/WQ	Point 3	82.6	91
	Point 4	73.1	71
	Point 1	47.1	41
	Point 2	59.9	55
940 ℃/1 h/WQ +540 ℃/4 h/AC	Point 3	49.5	51
	Point 4	41.0	40

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Xiao Zhennan, Liu Tingting, Liao Wenhe, Zhang Changdong, Yang Tao. Microstructure and Mechanical Properties of TC4 Titanium Alloy Formed by Selective Laser Melting After Heat Treatment[J]. Chinese Journal of Lasers, 2017, 44(9): 902001

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