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. 2018 Mar 2;8(1):3934.
doi: 10.1038/s41598-018-22329-2.

Ductile and brittle transition behavior of titanium alloys in ultra-precision machining

W S Yip  1 , S To  2
Affiliations

Ductile and brittle transition behavior of titanium alloys in ultra-precision machining

W S Yip et al. Sci Rep. .

Abstract

Titanium alloys are extensively applied in biomedical industries due to their excellent material properties. However, they are recognized as difficult to cut materials due to their low thermal conductivity, which induces a complexity to their deformation mechanisms and restricts precise productions. This paper presents a new observation about the removal regime of titanium alloys. The experimental results, including the chip formation, thrust force signal and surface profile, showed that there was a critical cutting distance to achieve better surface integrity of machined surface. The machined areas with better surface roughness were located before the clear transition point, defining as the ductile to brittle transition. The machined area at the brittle region displayed the fracture deformation which showed cracks on the surface edge. The relationship between depth of cut and the ductile to brittle transaction behavior of titanium alloys in ultra-precision machining(UPM) was also revealed in this study, it showed that the ductile to brittle transaction behavior of titanium alloys occurred mainly at relatively small depth of cut. The study firstly defines the ductile to brittle transition behavior of titanium alloys in UPM, contributing the information of ductile machining as an optimal machining condition for precise productions of titanium alloys.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Experimental Setup of diamond cutting for generating a machined groove. The upward movement of diamond tool provided the cutting motion on the machined surface.
Figure 2
Figure 2
(a–f). The chip formations with the indication of brittle and ductile deformation areas at depth of cut 2 μm–7 μm. The letters B and D are the brittle deformation area and the ductile deformation area respectively.
Figure 3
Figure 3
The groove profiles and groove surfaces generated at depth of cut 2 μm–7 μm. The letters X, Y and Z are denoted as the area with “a lower level of material swelling”, “a transition point of lower material swelling to higher material swelling” and “a higher level material swelling”.
Figure 4
Figure 4
Surface roughness of areas X, Y and Z generated at depth of cut 2 μm–7 μm.
Figure 5
Figure 5
The graph of d versus different depth of cut. d is the minimum/critical cutting distance of starting the brittle fracture deformation.
Figure 6
Figure 6
The material recovery percentage of areas X and Z.
Figure 7
Figure 7
The thrust forces of machined grooves generated at depth of cut 2 μm–7 μm.
See this image and copyright information in PMC

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