scholarly journals Eliminating continuous grain boundary α phase in laser melting deposited near β titanium alloys by heat treatment

2019 ◽  
Vol 563 ◽  
pp. 022025
Author(s):  
Penglin Li ◽  
Changmeng Liu ◽  
Jie Wang ◽  
Jiping Lu ◽  
Shuyuan Ma ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Grain Boundary ◽  
Titanium Alloys ◽  
Laser Melting ◽  
Α Phase

Microstructure and Mechanical Properties of Ti-6Al-4V Alloy Samples Fabricated by Selective Laser Melting

2018 ◽  
Vol 770 ◽  
pp. 179-186 ◽  
Author(s):  
Jing Bo Gao ◽  
Xiao Li Zhao ◽  
Ju Kun Yue ◽  
Meng Chao Qi ◽  
De Liang Zhang
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Crystal Growth ◽  
Yield Strength ◽  
Selective Laser Melting ◽  
Lamellar Structure ◽  
Growth Direction ◽  
Laser Melting ◽  
Α Phase ◽  
Dog Bone

Ti-6Al-4V (wt%) alloy samples with dog-bone and box shapes respectively were fabricated by selective laser melting (SLM). The microstructures and mechanical properties of the 3D printed Ti-6Al-4V samples with and without heat treatment were characterized and tested. The microstructures of the as-fabricated dog-bone shaped samples were mainly composed of acicular α’ phase. After annealing at 700°C, the acicular α’ phase changed into an α/β lamellar structure. After solution treatment at 955°C, water quenching and aging at 550°C, the microstructure was mainly composed of primary α phase and α/β lamellar structure. The optimum heat treatment is annealing, and the mechanical properties of the annealed sample are as follows: yield strength: 1015 MPa, ultimate tensile strength (UTS): 1083 MPa and elongation to fracture: 7.9%. The microstructures of the box-shaped samples after annealing mainly consist of α phase and α/β lamellar structure. When stretched along the direction parallel to the crystal growth direction, the yield strength and UTS of the sample are 1054 and 1090 MPa，and its elongation to fracture is 6.3%. When stretched along the direction perpendicular to the crystal growth direction, the yield strength and UTS of the sample are 1019 and 1068 MPa respectively, and its elongation to fracture is 8.7%.

scholarly journals The Heat Treatment Influence on the Microstructure and Hardness of TC4 Titanium Alloy Manufactured via Selective Laser Melting

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1318 ◽  
Author(s):  
Zhan-Yong Zhao ◽  
Liang Li ◽  
Pei-Kang Bai ◽  
Yang Jin ◽  
Li-Yun Wu ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Titanium Alloy ◽  
Critical Temperature ◽  
Selective Laser Melting ◽  
Heat Treatment Temperature ◽  
Treatment Temperature ◽  
Laser Melting ◽  
Β Phase ◽  
Α Phase ◽  
Increasing Temperature

In this research, the effect of several heat treatments on the microstructure and microhardness of TC4 (Ti6Al4V) titanium alloy processed by selective laser melting (SLM) is studied. The results showed that the original acicular martensite α′-phase in the TC4 alloy formed by SLM is converted into a lamellar mixture of α + β for heat treatment temperatures below the critical temperature (T0 at approximately 893 °C). With the increase of heat treatment temperature, the size of the lamellar mixture structure inside of the TC4 part gradually grows. When the heat treatment temperature is above T0, because the cooling rate is relatively steep, the β-phase recrystallization transforms into a compact secondary α-phase, and a basketweave structure can be found because the primary α-phase develop and connect or cross each other with different orientations. The residence time for TC4 SLM parts when the treatment temperature is below the critical temperature has little influence: both the α-phase and the β-phase will tend to coarsen but hinder each other, thereby limiting grain growth. The microhardness gradually decreases with increasing temperature when the TC4 SLM part is treated below the critical temperature. Conversely, the microhardness increases significantly with increasing temperature when the TC4 SLM part is treated above the critical temperature.

The Range of the Occurrence of α Phase in near β Titanium Alloys

2016 ◽  
Vol 682 ◽  
pp. 77-82
Author(s):  
Janusz Krawczyk ◽  
Łukasz Frocisz ◽  
Robert Dąbrowski ◽  
Edyta Rożniata ◽  
Tomasz Śleboda
Keyword(s):  
Heat Treatment ◽  
Titanium Alloys ◽  
Processing Time ◽  
Casting Process ◽  
Compression Tests ◽  
Phase Precipitation ◽  
Phase Dissolution ◽  
Β Phase ◽  
Α Phase ◽  
Temperature Strain

Two near β titanium alloys (Ti-3Al-8V-6Cr-4Mo-4Zr and Ti-10V-2Fe-3Al) were investigated in his research. Both materials contained disperse precipitations of α phase in β phase matrix. In the case of Ti-3Al-8V-6Cr-4Mo-4Zr alloy clear segregation of alloy constituents, resulting from casting process, were observed. This segregation caused different susceptibility to α phase precipitation in dendritic and interdendritic areas in the microstructure of the investigated alloy. The influence of the temperature, strain and processing time on α phase dissolution was determined. Gleeble compression tests were performed on both of the investigated alloys. The research showed different character of the influence of strain rate and processing time on the temperature of α phase dissolution for each alloy. The effect of heat treatment on α phase dissolution during ageing of the investigated alloys was also determined. The possibility of obtaining homogenous microstructure in these alloys by properly designed heat treatment was also discussed.

Influence of continuous grain boundary α on ductility of laser melting deposited titanium alloys

2016 ◽  
Vol 661 ◽  
pp. 145-151 ◽  
Author(s):  
Changmeng Liu ◽  
Ying Lu ◽  
Xiangjun Tian ◽  
Dong Liu
Keyword(s):  
Grain Boundary ◽  
Titanium Alloys ◽  
Laser Melting

Effects of Aging Heat Treatment on the Microstructure of Ti-Nb and Ti-Nb-Sn Alloys Employed as Biomaterials

2011 ◽  
Vol 324 ◽  
pp. 61-64 ◽  
Author(s):  
Eder S.N. Lopes ◽  
Alessandra Cremasco ◽  
Rodrigo Contieri ◽  
Rubens Caram
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Mechanical Behavior ◽  
Titanium Alloys ◽  
Phase Transformations ◽  
Aging Heat Treatment ◽  
Α Phase ◽  
High Temperature Xrd ◽  
Highly Sensitive ◽  
Effects Of Aging

The mechanical behavior of β titanium alloys applied as orthopedic biomaterials depends directly on their microstructural features, and can be improved by tailoring the microstructure through the control of their phase transformations. The aim of this investigation is to discuss phase transformations during the aging heat treatment of β Ti-30Nb and β Ti-30Nb-2Sn alloys and to correlate microstructure and mechanical behavior. The results of high temperature XRD experiments showed decomposition of orthorhombic α” phase, followed by the precipitation of ω and α phases. The mechanical behavior of Ti-Nb and Ti-Nb-Sn alloys was found to be highly sensitive to the microstructural changes caused by the addition of Sn and by heat treatments.

scholarly journals The Microstructural Difference and Its Influence on the Ballistic Impact Behavior of a Near β-Type Ti5.1Al2.5Cr0.5Fe4.5Mo1.1Sn1.8Zr2.9Zn Titanium Alloy

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4006 ◽  
Author(s):  
Xinjie Zhu ◽  
Qunbo Fan ◽  
Duoduo Wang ◽  
Haichao Gong ◽  
Hong Yu ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Titanium Alloy ◽  
Dislocation Density ◽  
Titanium Alloys ◽  
Impact Behavior ◽  
Alloy Plate ◽  
Α Phase ◽  
Heat Treated ◽  
Hot Rolled ◽  
Titanium Alloy Plate

In this work, a near β-type Ti5.1Al2.5Cr0.5Fe4.5Mo1.1Sn1.8Zr2.9Zn alloy was hot-rolled at the temperature of 800–880 °C with a thickness reduction of 87.5% and then heat-treated with the strategy of 880 °C/1 h/air cooling (AC) + 650 °C/3 h/AC. The microstructure difference between the hot-rolled and heat-treated titanium alloys and its influence on the ballistic impact behavior of the hot-rolled and heat-treated titanium alloys were analyzed. The microstructural investigation revealed that the average size of the acicular secondary α phase (αs) dropped from 75 to 42 nm, and the corresponding amount of this phase increased significantly after heat treatment. In addition, the dislocation density of the α and β phases decreased from 0.3340 × 1015/m2 and 4.6746 × 1015/m2 for the hot-rolled titanium alloy plate to 0.2806 × 1015/m2 and 1.8050 × 1015/m2 for the heat-treated one, respectively. The high strength of the heat-treated titanium alloy was maintained, owing to the positive contribution of the acicular secondary α phase. Furthermore, the critical fracture strain increased sharply from 19.9% for the hot-rolled titanium alloy plate to 23.1% for the heat-treated one, thereby overcoming (to some extent) the constraint of the strength–ductility trade-off. This is mainly attributed to the fact that the dislocation density and the difference between the dislocation densities of the α and β phases decreased substantially, and deformation localization was effectively suppressed after heat treatment. Damage to the hot-rolled and heat-treated titanium alloy plates after the penetration of a 7.62 mm ordinary steel core projectile at a distance of 100 m was assessed via industrial computer tomography and microstructure observation. The results revealed that a large crack (volume: 2.55 mm3) occurred on the rear face and propagated toward the interior of the hot-rolled titanium alloy plate. The crack tip was connected to a long adiabatic shear band with a depth of 3 mm along the thickness direction. However, good integrity of the heat-treated titanium alloy plate was maintained, owing to its excellent deformation capability. Ultimately, the failure mechanism of the hot-rolled and heat-treated titanium alloy plates was revealed by determining the crack-forming reasons in these materials.

Cooling Rate Effects on Ti-6A1-4V and Beta III Titanium Alloys

1983 ◽  
Vol 28 ◽  
Author(s):  
T. F. Broderick ◽  
F. H. Froes ◽  
A. G. Jackson
Keyword(s):  
Heat Treatment ◽  
Grain Boundary ◽  
Titanium Alloys ◽  
Cooling Rate ◽  
Solute Redistribution ◽  
Splat Quenching ◽  
Aging Response ◽  
Heat Treated ◽  
Rate Effects ◽  
Order Of Magnitude

ABSTRACTThe titanium alloys Ti-6A1-4V and Ti-11.5Mo-6.0Zr-4.5Sn (Beta III) were produced at cooling rates of 103°C/sec and 105°C/sec using the Rotating Electrode Process (REP), and the Electron Beam Splat Quenching (EBSQ) process, respectively. Material from both alloys examined in the as-produced, heat treated, and vacuum hot pressed (VHP) conditions exhibited an order of magnitude decrease in beta grain size with increasing cooling rate (~135 μm and 7 μm in the Ti-6A1-4V alloy; ~40 μm and 2–4 μm in the Beta III alloy), and a difference in aging response between REP powder and EBSQ flakes. After heat treatment the Ti-6A1-4V developed an alpha morphology which was lenticular in REP powder and equiaxed in EBSQ flakes. Three possible mechanisms are proposed to explain this change involving an increased dislocation density and a tendency for grain boundary allotriomorphic alpha in the EBSQ case. Heat treatment of the Ti-11.5Mo-6.0Zr-4.5Sn materials showed a change in the location of alpha precipitation from interdendritic to grain boundary in going from REP to EBSQ. It is suggested that this change may relate to the decreased solute redistribution which occurs in the more rapidly cooled material.

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