Thermal and Microstructure Study of the Chip Formation During Turning of Ti64 β Lamellar Titanium Structure

Abstract

In recent years, many titanium alloys have emerged, each of them associated with a range of different heat treatments. Thus, several microstructures have been studied to varying degrees. For example, the Ti64 titanium alloy, mostly known for its α + β structure, can display a different state: the structure, inducing nonstandard mechanical behavior. This work presents chip formation in this specific microstructure where a strong heterogeneity is observed and where the shear band formation is a function of the relationship between the shear direction and the microstructure orientation. From these reasons, major differences are found in the chip morphology, within the same cutting condition, in comparison to the bimodal structure where a single chip morphology is obtained for each cutting condition. A section of this paper is devoted to the presentation of the β microstructure where different configurations can be seen within the same chip. Next, the influence of cutting conditions on the chip formation is studied. To highlight the specific chip formation process, a temperature model has been developed and combined with cutting force analysis to understand clearly the specificity of the chip formation for this structure. Finally, the discussion explains the different chip formation scenarios according to the workpiece microstructure to be cut.

Evolution of contact lengths during the turning of treated Ti64 β

“…This initial study thus shows the randomness of chip formation. A study from [10] concerning the influence of cutting conditions on chip formation then shows that adiabatic shear and cracking become regular when the feed rate and therefore the shear forces are high enough to generate them despite the orientation of the colonies. The objective of the next part is then to observe the effect of this particular chip formation on the chip flow length.…”

“…Wagner and al. [10] shows that chip formation during the machining of Ti64 β does not follow the cutting process introduced by [11]. It then appears that chip formation is not constant over time but is a function of the orientation of the structure encountered during the creation of the shear band.…”

Kinematic fields measurement during Ti-6Al-4V chip formation using new high-speed imaging system

“…Understanding the mechanisms of chip formation under complex thermomechanical loads require developing dedicated experimental set-up. In the cutting zone, the material undergoes high plastic deformation and local temperature rise that may induce changes in the material microstructure [1,2] as well as its mechanical and physical properties. Establishing the link between the thermomechanical load and the material microstructure evolution leads to develop physical-based models [3][4][5][6] that are suitable for numerical simulation of the machining processes.…”

Kinematic fields measurement during Ti-6Al-4V chip formation using new high-speed imaging system

“…Understanding the mechanisms of chip formation under complex thermomechanical loads requires developing dedicated experimental set-up. In the cutting zone, the material undergoes high plastic deformation and local temperature rise that may induce changes in the material microstructure Haythem Zouabi haythem.zouabi@u-bordeaux.fr Laboratoire Génie de Production, ENIT-INPT, Université de Toulouse, Toulouse, Tarbes, 65440, France [1,2] as well as its mechanical and physical properties. Establishing the link between the thermomechanical load and the material microstructure evolution leads to develop physical-based models [3][4][5][6] that are suitable for numerical simulation of the machining processes.…”

“…2 NSSD: normalized sum of squared differences 3 NSSD: zero normalized sum of squared differences 4 NCC: normalized cross-correlation 5 ZNCC: zero normalized cross-correlation Inc (incremental)…”