The thermomechanical processing of titanium and Ti-6Al-4V thin gage sheet and plate

Rivard, John D. K.; Blue, Craig A.; Harper, D. C.; Kiggans, Jim; A, Menchhofer, Paul; Mayotte, J.R.; Jacobsen, Lance; Kogut, D. M.

doi:10.1007/s11837-005-0029-x

Cited by 18 publications

(6 citation statements)

References 3 publications

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“…2b. Prior to laser melting, we see three clear α-Ti peaks ((100), (002), and (101)), and a small (110) β-Ti peak between the (002) and (101) α-Ti reflections, indicating that the unprocessed sample comprises a mix of α and β phases as expected for conventionally produced Ti-64 at room temperature [33][34][35][36] . About 4 ms after the laser passes the probed volume ( Fig.…”

Section: Resultsmentioning

confidence: 75%

“…Significant computational effort is being directed at modeling the AM process, but experimental results describing the dynamic processes involved have derived mostly from optical approaches that are largely insensitive to subsurface effects 4,[30][31][32] . Consequently, these methods cannot track the subsurface thermal evolution which is critical to understand the spatial evolution of microstructure in additively manufactured metals [33][34][35][36] . While optical pyrometry and thermal emission imaging can track temperatures, they are only sensitive to the surface, and thus, bulk temperatures must be inferred from models 19,[37][38][39][40][41][42][43][44][45] .…”

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confidence: 99%

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Subsurface Cooling Rates and Microstructural Response during Laser Based Metal Additive Manufacturing

Thampy

Fong

Calta

et al. 2020

Sci Rep

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Laser powder bed fusion (LpBf) is a method of additive manufacturing characterized by the rapid scanning of a high powered laser over a thin bed of metallic powder to create a single layer, which may then be built upon to form larger structures. Much of the melting, resolidification, and subsequent cooling take place at much higher rates and with much higher thermal gradients than in traditional metallurgical processes, with much of this occurring below the surface. We have used in situ high speed X-ray diffraction to extract subsurface cooling rates following resolidification from the melt and above the β-transus in titanium alloy Ti-6Al-4V. We observe an inverse relationship with laser power and bulk cooling rates. the measured cooling rates are seen to correlate to the level of residual strain borne by the minority β-ti phase with increased strain at slower cooling rates. the α-ti phase shows a lattice contraction which is invariant with cooling rate. We also observe a broadening of the diffraction peaks which is greater for the β-ti phase at slower cooling rates and a change in the relative phase fraction following LpBf. these results provide a direct measure of the subsurface thermal history and demonstrate its importance to the ultimate quality of additively manufactured materials. In LPBF, a common metal additive manufacturing (AM) process, a thin layer of precursor powder is selectively melted by tracing a high power laser to create a single, solid layer, followed by the spread of the next layer of powder for melting, and so on to build a part layer-by-layer 1-14. This approach offers a number of distinct advantages over conventional metal fabrication, including rapid prototyping, efficient material utilization, fabrication of complex geometries incompatible with machining or molding techniques, and applicability to materials which may exhibit machining difficulties, such as titanium 4,8-12,14. However, unlike conventional manufacturing techniques, the LPBF process is characterized by rapid melting and resolidification of small volumes of material that results in large thermal gradients both temporally and spatially, and consequently cooling rates that can be orders of magnitude higher than in conventional casting 10,15,16. Such large localized heating and cooling rates largely control the resulting microstructure, grain size and orientation, can lead to large residual stresses in some materials, and may also result in compositional segregation or formation of non-equilibrium trapped phases 4,17-20. Therefore quantifying these cooling rates and correlating them to the characteristics of the final build is an important step towards informing theoretical and process models that can predict and potentially control such stresses and inhomogeneities that are generally undesirable, especially in critical components. For this study, we focused on Ti-6Al-4V (Ti-64, 90%Ti, 6% Al, 4%V-by weight) as our material system. The high strength, light weight, and excellent corrosion resistance inherent to titanium and its ...

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Section: Resultsmentioning

confidence: 75%

mentioning

confidence: 99%

Subsurface Cooling Rates and Microstructural Response during Laser Based Metal Additive Manufacturing

Thampy

Fong

Calta

et al. 2020

Sci Rep

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“…Since the cost of the extraction process is a greater contributor to the total extraction cost than the cost of the metal ore itself, recent work has been pointed in the direction of reducing this cost by increasing the level of automation of the extraction process and by lowering the high energy requirements. The Armstrong Process, a hybrid of the standard Knoll Process, has recently been experimented with to increase the efficiency by making the Knoll Process semi-continuous [6][7][8]. However, it is unclear if this new process has caught on to a large scale production at the moment.…”

Section: Challenges For Incorporating Titanium Into Automobilesmentioning

confidence: 99%

Investigation of the Machining of Titanium Components for Lightweight Vehicles

Kuttolamadom¹,

Jones²,

Mears³

et al. 2010

SAE Technical Paper Series

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Due to titanium's excellent strength-to-weight ratio and high corrosion resistance, titanium and its alloys have great potential to reduce energy usage in vehicles through a reduction in vehicle mass. The mass of a road vehicle is directly related to its energy consumption through inertial requirements and tire rolling resistance losses. However, when considering the manufacture of titanium automotive components, the machinability is poor, thus increasing processing cost through a trade-off between extended cycle time (labor cost) or increased tool wear (tooling cost). This fact has classified titanium as a "difficult-to-machine" material and consequently, titanium has been traditionally used for application areas having a comparatively higher end product cost such as in aerospace applications, the automotive racing segment, etc., as opposed to the consumer automotive segment. Herein, the problems associated with processing titanium are discussed, and a review of cutting tool technologies is presented that contributes to improving the machinability of titanium alloys. Additionally, nonconventional machining techniques such as High Speed Machining and Ultrasonic Machining are also reviewed. Additional factors specific to machining titanium alloys are also discussed, a crucial one being its non-conformity with standard tool wear models. Subsequently, the results of a controlled milling experiment on Ti-6Al-4V are presented, to evaluate the relationship between tool preparation/process parameters and tool wear and for a comparison with traditional wear models.

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“…The Defense Advanced Research Projects Agency (DARPA) has made substantial investments in low-cost production of titanium and titanium alloys, focused primarily on non-melt processing. These non-melt processes, which include vacuum hot pressing and roll compaction processing, 17 open the way to new alloys with unique properties, while eliminating the post-processing typical of the conventional ingot approach (which accounts for roughly half the cost of titanium plate and sheet). Future work is likely to center on intermetallics based on TiAl and SiC-reinforced composites of titanium alloys.…”

Section: Structural Materials: Advances and Enabling Technologymentioning

confidence: 99%

The evolution of technology for structural materials over the last 50 years

Wadsworth

2007

JOM

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The thermomechanical processing of titanium and Ti-6Al-4V thin gage sheet and plate

Cited by 18 publications

References 3 publications

Subsurface Cooling Rates and Microstructural Response during Laser Based Metal Additive Manufacturing

Subsurface Cooling Rates and Microstructural Response during Laser Based Metal Additive Manufacturing

Investigation of the Machining of Titanium Components for Lightweight Vehicles

The evolution of technology for structural materials over the last 50 years

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