Serrated Chips Formation in Micro Orthogonal Cutting of Ti6Al4V Alloys with Equiaxial and Martensitic Microstructures

Abstract

The formation of serrated chips is an important feature during machining of difficult-to-cut materials, such as titanium alloy, nickel based alloy, and some steels. In this study, Ti6Al4V alloys with equiaxial and acicular martensitic microstructures were adopted to analyze the effects of material structures on the formation of serrated chips in straight line micro orthogonal machining. The martensitic alloy was obtained using highly efficient electropulsing treatment (EPT) followed by water quenching. The results showed that serrated chips could be formed on both Ti6Al4V alloys, however the chip features varied with material microstructures. The number of chip segments per unit length of the alloy with martensite was more than that of the equiaxial alloy due to poor ductility. Besides, the average cutting and thrust forces were about 8.41 and 4.53 N, respectively, for the equiaxed Ti6Al4V alloys, which were consistently lower than those with a martensitic structure. The high cutting force of martensitic alloy is because of the large yield stress required to overcome plastic deformation, and this force is also significantly affected by the orientations of the martensite. Power spectral density (PSD) analyses indicated that the characteristic frequency of cutting force variation of the equiaxed alloy ranged from 100 to 200 Hz, while it ranged from 200 to 400 Hz for workpieces with martensites, which was supposedly due to the formation of serrated chips during the machining process.

Mechanics of Grains Size and Orientation on the Machining of AISI S-7 Steel Grade Using Numerical Technique

“…Simulation techniques with finite element codes have been consistently proven and successfully executed on different grades of steel viz. 42CrMo4 Steel, carbide tool, Ti6Al4V Alloys, Al6061-T6 and were found give very promising results [1,2,3,4]. For the understanding of chip morphology and its effect on tool wear, a number of featured models in FEA have been tried, namely Lagrangian formulation: includes nodes formation criterion to predict chip separation, lagrangian description of motion and adaptive remeshing: applied to simulate orthogonal cutting , Finite Element Eulerian formulations: to simulate continuous chip formation at steady state, Finite Element Arbitrary Lagrangian-Eulerian (ALE) the formulation in conjunction with adaptive mesh techniques etc.…”