The present work exploits the customized heat treatment, and laser powder bed fusion process to build direction effects on the densification behaviour and microstructural development in Ti6Al4V alloy. Optical microscopy evaluates the porosity and microstructure in different conditions. Further, the porosities are classified as inter-micropores (size < 10 µm) and super-micropores (size > 10 µm). Classification and quantifications of the porosities of laser powder bed fusion processed Ti6Al4V alloy under both directions due to customized heat treatment. The effect of customized heat treatment, the corresponding pore self-healing mechanism, and microstructure refinement on laser powder bed fusion-processed Ti6Al4V alloy were discussed. Moreover, the X-ray diffraction technique was used to analyse the different phases during laser powder bed fusion and customized heat treatment. The elevated customized heat treatment helps to reduce the overall porosity by two times that of as-printed samples due to the sintering self-healing phenomenon. Interestingly, the super micropores observed in as-printed samples are reduced via customized heat treatment ∼ 44% in a horizontal direction and ∼ 46% in a vertical direction, respectively, which is favourable for enhancing mechanical properties. This is because reducing these micropores leads to improved ductility. The ductility of the customized heat treatment executed sample was ∼ 68% in a horizontal orientation and ∼180% in a vertical orientation. The isotropic index for ductility in as-printed Ti6Al4V in the horizontal and vertical directions is 0.61. In contrast, it is 0.97 for customized heat treatment in both orientations showing high isotropy for customized heat treatment samples compared to as-printed samples. This study reveals that the customized heat treatment technique can be beneficial in introducing isotropic microstructure and densifying the distinctive laser powder bed fusion components.
KumarSAPrasadRVS.Chapter 2 – basic principles of additive manufacturing: different additive manufacturing technologies. In: ManjaiahMRaghavendraKBalashanmugamN, et al. (eds) Additive manufacturing. Woodhead Publishing, 2021, pp.17–35.
2.
ButtJ. Exploring the interrelationship between additive manufacturing and industry 4.0. Designs2020; 4: 13.
3.
Nagesha BK, Kumar SA, Vinodh K, et al. A thermo–Mechanical modelling approach on the residual stress prediction of SLM processed HPNGV aeroengine part. Mater Today Proc 2021; 44: 4990–4996.
4.
NageshaBKVinodhKTiggaAK, et al.Influence of post-processing techniques on residual stresses of SLM processed HPNGV. J Manuf Process2021; 66: 189–197.
5.
OttoMPilzSGebertA, et al.Effect of build orientation on the microstructure, mechanical and corrosion properties of a biodegradable high manganese steel processed by laser powder bed fusion. Metals (Basel)2021; 11: 944.
6.
ShrivastavaAAnand KumarSNageshaBK, et al.Electropolishing of Inconel 718 manufactured by laser powder bed fusion: effect of heat treatment on hardness, 3D surface topography and material ratio curve. Opt Laser Technol2021; 144: 107448.
7.
ZhangBLiYBaiQ. Defect formation mechanisms in selective laser melting: a review. Chin J Mech Eng2017; 30: 515–527.
8.
HeemannLMostaghimiFSchobB, et al.Adjustment of mechanical properties of medium manganese steel produced by laser powder bed fusion with a subsequent heat treatment. Materials (Basel)2021; 14: 3081.
9.
MinasyanTHussainovaI. Laser powder-bed fusion of ceramic particulate reinforced aluminum alloys: a review. Materials (Basel)2022; 15: 2467.
10.
ThijsLVerhaegheFCraeghsT, et al.A study of the microstructural evolution during selective laser melting of Ti-6Al-4V. Acta Mater2010; 58: 3303–3312.
11.
ZhongCLiuJZhaoT, et al.Laser metal deposition of Ti6Al4V—a brief review. Applied Sciences2020; 10: 764.
12.
LiZChuzenjiMMizutaniM. Compression and fatigue performance of Ti6Al4V materials with different uniform and gradient porous structures. Mater Sci Eng A2023; 873: 145030.
13.
GongHRafiKGuH, et al.Analysis of defect generation in Ti-6Al-4V parts made using powder bed fusion additive manufacturing processes. Additive Manufacturing2014; 1–4: 87–98.
14.
MaysTJ. A new classification of pore sizes. Stud Surf Sci Catal2007; 160: 57–62.
15.
García-MorenoA-IAlvarado-OrozcoJ-MIbarra-MedinaJ, et al.Ex-situ porosity classification in metallic components by laser metal deposition: a machine learning-based approach. J Manuf Process2021; 62: 523–534.
16.
KarimiJSuryanarayanaCOkulovI, et al.Selective laser melting of Ti6Al4V: effect of laser re-melting. Mater Sci Eng A2021; 805: 140558.
17.
KarimiJXieMSWangZ, et al.Influence of substructures on the selective laser melted Ti-6Al-4V alloy as a function of laser re-melting. J Manuf Process2021; 68: 1387–1394.
18.
LiuJWenP. Metal vaporization and its influence during laser powder bed fusion process. Mater Des2022; 215: 110505.
19.
KushwahaASubramaniyanAKBommanahalli KenchappaN, et al.Microstructure, mechanical, and wear properties of thin-walled Ti6Al4V parts produced using laser powder bed fusion technique. Mater Lett2022; 308: 131138.
20.
PathaniaASubramaniyanAKNageshaBK. Influence of post-heat treatments on microstructural and mechanical properties of LPBF-processed Ti6Al4V alloy. Prog Addit Manuf2022; 7: 1323–1343.
21.
GüntherJKrewerthDLippmannT, et al.Fatigue life of additively manufactured Ti-6Al-4V in the very high cycle fatigue regime. Int J Fatigue2017; 94: 236–245.
22.
ZhangBMengWJShaoS, et al.Effect of heat treatments on pore morphology and microstructure of laser additive manufactured parts. Mater Des Process Commun2019; 1: e29.
23.
ZhangBHamKShaoS, et al.Effect of heat treatment and hot isostatic pressing on the morphology and size of pores in additive manufactured Ti-6Al-4V parts. In: 2017 International Solid Freeform Fabrication Symposium. University of Texas at Austin, 2017.
24.
QiuCAdkinsNJEAttallahMM. Microstructure and tensile properties of selectively laser-melted and of HIPed laser-melted Ti-6Al-4V. Mater Sci Eng A2013; 578: 230–239.
25.
Tammas-WilliamsSWithersPJToddI, et al.Porosity regrowth during heat treatment of hot isostatically pressed additively manufactured titanium components. Scr Mater2016; 122: 72–76.
26.
FerrucciMLeachRKGiuscaC, et al.Towards geometrical calibration of x-ray computed tomography systems—a review. Meas Sci Technol2015; 26: 092003.
27.
MugwagwaLDimitrovDMatopeS, et al.A methodology to evaluate the influence of part geometry on residual stresses in selective laser melting. Faculty of Engineering, Department of Industrial Engineering, Stellenbosch University, https://scholar.sun.ac.za:443/handle/10019.1/99209(2016, accessed 27 September 2020).
28.
HuCLiFQuD, et al. 8-Developments in hot pressing (HP) and hot isostatic pressing (HIP) of ceramic matrix composites. In: LowIM (ed) Advances in ceramic matrix composites. 2nd ed. Woodhead Publishing, 2014, pp.177–202.
29.
KahlinMAnsellHMoverareJJ. Fatigue behaviour of notched additive manufactured Ti6Al4V with as-built surfaces. Int J Fatigue2017; 101: 51–60.
30.
KushwahaAKumarSAVeluR. Selective laser melting of titanium alloys: effect of processing parameters on microstructure and mechanical properties. Int J Mechatron Manuf Syst2021; 14: 128–142.
31.
PromoppatumPSrinivasanRQuekSS, et al.Quantification and prediction of lack-of-fusion porosity in the high porosity regime during laser powder bed fusion of Ti-6Al-4V. J Mater Process Technol2022; 300: 117426.
32.
WolffSJLinSFaiersonEJ, et al.A framework to link localized cooling and properties of directed energy deposition (DED)-processed Ti-6Al-4V. Acta Mater2017; 132: 106–117.
33.
TosiRLeungCLATanX, et al.Revealing the microstructural evolution of electron beam powder bed fusion and hot isostatic pressing Ti-6Al-4V in-situ shelling samples using X-ray computed tomography. Additive Manuf2022; 57: 102962.
34.
ZhangX-YFangGLeeflangS, et al.Effect of subtransus heat treatment on the microstructure and mechanical properties of additively manufactured Ti-6Al-4V alloy. J Alloys Compd2018; 735: 1562–1575.
35.
SamesWJListFAPannalaS, et al.The metallurgy and processing science of metal additive manufacturing. Int Mater Rev2016; 61: 315–360.
36.
LiuSShinYC. Additive manufacturing of Ti6Al4V alloy: a review. Mater Des2019; 164: 107552.
37.
Tascioglu E, Karabulut Y, Kaynak Y. Influence of heat treatment temperature on the microstructural, mechanical, and wear behavior of 316L stainless steel fabricated by laser powder bed additive manufacturing. The Int J Adv Manuf Technol 2020; 107: 1947–1956.
38.
JuJZhouYWangK, et al.Tribological investigation of additive manufacturing medical Ti6Al4V alloys against Al2O3 ceramic balls in artificial saliva. J Mech Behav Biomed Mater2020; 104: 103602.
39.
LiHJiaDYangZ, et al.Effect of heat treatment on microstructure evolution and mechanical properties of selective laser melted Ti-6Al-4V and TiB/Ti-6Al-4V composite: a comparative study. Mater Sci Eng A2021; 801: 140415.
40.
PedersonRBabushkinOSkystedtF, et al.Use of high temperature X-ray diffractometry to study phase transitions and thermal expansion properties in Ti-6Al-4V. Mater Sci Technol2003; 19: 1533–1538.
41.
SalarianMAsgariHVlaseaM. Pore space characteristics and corresponding effect on tensile properties of Inconel 625 fabricated via laser powder bed fusion. Mater Sci Eng A2020; 769: 138525.
42.
WangLZhangYChiaHY, et al.Mechanism of keyhole pore formation in metal additive manufacturing. NPJ Comput Mater2022; 8: 1–11.
43.
LalehMHughesAEYangS, et al.Two and three-dimensional characterisation of localised corrosion affected by lack-of-fusion pores in 316L stainless steel produced by selective laser melting. Corros Sci2020; 165: 108394.
44.
SowMCDe TerrisTCastelnauO, et al.Influence of beam diameter on laser powder bed fusion (L-PBF) process. Additive Manufact2020; 36: 101532.
45.
KingWEBarthHDCastilloVM, et al.Observation of keyhole-mode laser melting in laser powder-bed fusion additive manufacturing. J Mater Process Technol2014; 214: 2915–2925.
46.
HannDBIammiJFolkesJ. A simple methodology for predicting laser-weld properties from material and laser parameters. J Phys D: Appl Phys2011; 44: 445401.
47.
FabbroR. Scaling laws for the laser welding process in keyhole mode. J Mater Process Technol2019; 264: 346–351.
48.
KosonenTKakkoKRaitanenN. Evaluation of pore re-opening after HIP in LPBF Ti-6Al-4V. Powder Metall2021; 64: 425–433.
49.
KeshavarzMKSikanFBoutetCE, et al.Impact properties of half stress-relieved and hot isostatic pressed Ti-6Al-4V components fabricated by laser powder bed fusion. Mater Sci Eng A2019; 760: 481–488.
50.
KasperovichGHausmannJ. Improvement of fatigue resistance and ductility of TiAl6V4 processed by selective laser melting. J Mater Process Technol2015; 220: 202–214.
51.
Tammas-WilliamsSWithersPJToddI, et al.The effectiveness of hot isostatic pressing for closing porosity in titanium parts manufactured by selective electron beam melting. Metall Mater Trans A2016; 47: 1939–1946.
52.
UzanNEShneckRYeheskelO, et al.Fatigue of AlSi10Mg specimens fabricated by additive manufacturing selective laser melting (AM-SLM). Mater Sci Eng A2017; 704: 229–237.
53.
YeCZhangCZhaoJ, et al.Effects of post-processing on the surface finish, porosity, residual stresses, and fatigue performance of additive manufactured metals: a review. J Materi Eng Perform2021; 30: 6407–6425.
54.
du PlessisARossouwP. Investigation of porosity changes in cast Ti6Al4V rods after hot isostatic pressing. J Materi Eng Perform2015; 24: 3137–3141.
55.
MajeedAMuzamilMLvJ, et al.Heat treatment influences densification and porosity of AlSi10Mg alloy thin-walled parts manufactured by selective laser melting technique. J Braz Soc Mech Sci Eng2019; 41: 267.
56.
MajeedAZhangYFLvJX, et al.Study the effect of heat treatment on the relative density of SLM built parts of AlSi10Mg alloy. In: Proceedings of the 48th international conference on computers and industrial engineering (CIE 2018), Auckland, New Zealand. 2018, pp.2–5.
57.
SimonelliMTseYYTuckC. Effect of the build orientation on the mechanical properties and fracture modes of SLM Ti-6Al-4V. Mater Sci Eng A2014; 616: 1–11.
58.
CroweTGuraydinA. The effects of heat treatment on area percent porosity and corrosion behavior of high-nickel thermal spray coatings. Mater Eng2011: 1–27. https://digitalcommons.calpoly.edu/matesp/12.
59.
van DijkNvan der ZwaagS. Self-healing phenomena in metals. Adv Mater Interfaces2018; 5: 1800226.
60.
BhagatRPChattorajUSSilSK. Porosity of sinter and its relation with the sintering indices. ISIJ Int2006; 46: 1728–1730.
61.
GibsonIRosenDWStuckerB, et al.Additive manufacturing technologies. Cham, Switzerland: Springer, 2021, 17, pp. 160–186.
ShamirMSyedAKJanikV, et al.The role of microstructure and local crystallographic orientation near porosity defects on the high cycle fatigue life of an additive manufactured Ti-6Al-4V. Mater Charact2020; 169: 110576.
64.
Tammas-WilliamsSWithersPJToddI, et al.The influence of porosity on fatigue crack initiation in additively manufactured titanium components. Sci Rep2017; 7: 1–13.
65.
MurakamiY. Material defects as the basis of fatigue design. Int J Fatigue2012; 41: 2–10.
66.
VranckenBThijsLKruthJ-P, et al.Heat treatment of Ti6Al4V produced by selective laser melting: microstructure and mechanical properties. J Alloys Compd2012; 541: 177–185.
67.
YanXYinSChenC, et al.Effect of heat treatment on the phase transformation and mechanical properties of Ti6Al4V fabricated by selective laser melting. J Alloys Compd2018; 764: 1056–1071.
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