Secondary machining of Carbon Fibre-Reinforced Polymer (CFRP) is crucial for achieving precise dimensions and high-quality finishes in manufacturing. However, CFRP's anisotropic and heterogeneous properties present challenges, including delamination, high thrust forces, and excessive tool wear, which can compromise the final products' mechanical integrity and durability. Optimizing machining processes to minimize these issues and enhance tool life is a significant area of research. This study focuses on CFRP drilling operations, investigating the effects of varying feed rates and spindle speeds on critical machining parameters such as delamination factors. Experiments utilize CFRP made of TRH50 fibre and NCT 301 resin, with a solid carbide-tip and diamond-coated tool featuring a stainless-steel body. The research aims to provide insights into the interactions between machining parameters and CFRP properties, contributing to the development of optimized machining strategies for improved performance and product quality. Preliminary findings revealed visible exit and entry delamination during the drilling operation.

Additive manufacturing techniques, particularly Selective Laser Melting (SLM), allow fabrication of intricate metal components; however, their surface condition in the as-built state remains a major limitation for functional applications. This study evaluates the influence of finish turning parameters on improving the surface characteristics of a tapered 316L stainless steel component fabricated through SLM. A structured experimental methodology involving twenty machining trials was employed, where spindle speed, feed rate, and coolant application were systematically varied across two taper geometries. Surface roughness, chip formation, tool wear, and material removal rate (MRR) were examined to establish process–performance relationships. The results indicate a substantial refinement in surface finish, with roughness decreasing from approximately 10 µm to a minimum of 0.437 µm, demonstrating a reduction exceeding 95%. Additionally, the geometric orientation of the taper relative to the SLM build layers significantly influenced the final surface condition. An optimal compromise between productivity and surface quality was achieved at 1000 rpm with a feed rate close to 0.3 mm/rev, yielding roughness values near 2 µm. The outcomes confirm that finish turning is a practical post-processing method for complex SLM parts and provide valuable guidance for selecting machining conditions in industrial environments.

This study aims to evaluate how T6 heat treatment influences the microstructure and microhardness of both cast and additively manufactured (AM) AlSi10Mg. Furthermore, effect of microstructure and microhardness on the machinability of AlSi10Mg was assessed considering the chip morphology, cutting force, machining temperature, and surface roughness. Initially, untreated cast and AM AlSi10Mg exhibited distinctly different microstructures. T6 heat treatment caused substantial alterations in both the microstructure and microhardness of the materials. In both material variants, silicon (Si) experienced fragmentation, followed by spheroidization and subsequent coarsening. However, the heat-treated AM specimens exhibited finer and more uniformly spheroidized Si particles than their cast counterparts. The untreated AM AlSi10Mg showed substantially higher microhardness than the cast alloy. Upon heat treatment, the AM material experienced softening and reduced hardness, whereas the cast material exhibited a notable increase in hardness. Machining the untreated AM alloy generated higher machining temperatures and cutting forces relative to the cast alloy. Post heat treatment, the AM alloy decreased both cutting force and temperature, while the cast alloy exhibited an increase in both parameters. Surface finish was consistently superior in AM specimens compared to cast ones in untreated and heat-treated conditions. Chip morphology also varied significantly: longer chips were produced when milling cast specimens, whereas shorter chips were observed with the AM material. Heat treatment reduced chip size for the cast alloy, while chip morphology remained largely unchanged for the AM material.

In this paper, the Die-Sinker Electrical Discharge Texturing (DSEDT) is utilized to machine closed cell titanium foam using pure brass tool electrode. Discharge time, current and discharge voltage were taken as input factors. By varying these input factors, discharge energy generated in between the tool and workpiece gets altered. Therefore, the influence of discharge energy on the average crater diameter, re-solidified layer thickness and chemical alteration of machined surface are analysed. The stochastic nature of DSEDT process is studied using microscopic images and energy dispersive X-ray spectroscopy profiles. Through micrographs it is perceived, increase in the discharge energy from 5.12 J to 10.13 J, leads to an increase in average crater diameter from 29.26 to 66.29 μm respectively. It is observed that combined effect of crater overlap phenomena and re-solidification of material seals the cells in a foam material. A minimum re-solidified layer thickness of 44.29 μm is achieved. The machined surface of closed cell titanium foam shows significant rise in carbon, copper and zinc elements owing to the disintegration of the dielectric liquid and tool electrode during spark erosion. The study on DSEDT of closed cell titanium foam revealed the possibility to create surfaces with uniform crater diameter and establish titanium carbide on the machined surface.

This research examines the effects of post-heat treatments on the thermomechanical characteristics and microstructure of a Ti-6Al-4V Extra Low Interstitials (ELI) alloy produced via Selective Laser Melting (SLM). The study utilized two post-SLM heat treatments to produce different microstructures: Solution Treatment and Aging (STA) for a bimodal microstructure and Beta Annealing (BA) for a Widmanstatten microstructure. Thermomechanical compression tests were conducted at 550 degrees C with strain rates of 0.01 s-1 and 1 s-1 utilizing a Gleeble-3800 thermomechanical simulator. The microstructures were analyzed utilizing Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and X-Ray Diffraction (XRD). The findings indicated that the compressive yield strength (CYS) of the bimodal microstructure reached 724 MPa and 740 MPa at strain rates of 0.01 s-1 and 1 s-1, respectively, representing a 20 % and 12 % increase over the as-printed martensitic microstructure (604 MPa and 662 MPa). In comparison to the Widmanstatten microstructure (422 MPa and 438 MPa), the CYS of the bimodal microstructure was 71 % and 69 % greater at the corresponding strain rates. Adiabatic Shear Bands (ASBs) were present in all microstructures at both strain rates, significantly influencing the failure mechanisms. The martensitic microstructure displayed minimal cracking under compression at both strain rates. The bimodal microstructure showed predominantly intergranular fractures along the grain boundaries of thick primary alpha (alpha p) phases. Conversely, the Widmanstatten microstructure exhibited both intergranular and translamellar fractures. Intergranular cracks originated and advanced along the continuous grain boundary alpha (alpha GB), while translamellar fracture, occurring within the alpha colonies, exhibited cracks traversing across lamellar alpha/(3 interfaces.

The study investigates the post-printing machinability of AlSi10Mg aluminum alloy, with a primary focus on evaluating T6 heat treatment influence on the cutting force and surface quality of additive manufactured material while comparing the outcomes with the cast alloy. Milling experiments were performed on untreated and heat-treated specimens using a range of cutting speeds and feed rates. Results revealed that the surface roughness of as-cast AlSi10Mg alloy was 50.5-532.3% higher than that of the as-printed material. This was attributed to the coarser microstructure and lower microhardness (73.04 HV) of the as-cast alloy, which led to increased plastic deformation during machining, leading to increased surface roughness, especially at lower feed rates. In contrast, the fine cellular microstructure of the as-printed alloy enhanced the microhardness (140.3 HV) and deformation resistance, producing better surface quality. T6 heat treatment significantly affected the surface roughness of the cast and AM aluminum alloy. While heat treatment enhanced the surface finish of cast alloy, it reduced the surface roughness in the printed alloy. T6 heat treatment refined the microstructure of cast and printed alloys, increasing microhardness (126.1 HV) and reducing plastic deformation in cast alloy while reducing the microhardness (78.7 HV) and increasing the ductility of the printed alloy, potentially increasing the surface roughness. Despite the treatment, surface roughness of heat-treated cast alloy remained 19.3-38.2% higher than that of the heat-treated printed material. Cutting force analysis showed that additively manufactured (AM) specimens experienced a 49.5-178.1% increase in cutting force compared to as-cast specimens. However, when heat-treated, the AM specimens exhibited a 16.9-67.1% reduction in cutting force relative to untreated AM parts. In contrast, heat-treated as-cast specimens showed a moderate increase in cutting force, ranging from 17.1 to 56.3%, compared to their untreated counterparts. The findings emphasize the significant influence of material manufacturing route and heat treatment on the machining outcomes. The results show that the section on milling process variables depends on the material fabrication route and heat treatment applied during the post-processing stage.

Titanium alloys are categorized under difficult to machine materials. The machinability of titanium alloy Ti6Al4V using statistical methods such as analysis of variance is investigated in this paper. Titanium alloy Ti6Al4V is the most widely used in aerospace and biomedical application due to its advantageous material properties. However, despite its wide-ranging applications, there is a lack of clarity concerning its ideal machining parameters. This ambiguity primarily stems from titanium alloys’ inherent properties, notably their low thermal conductivity and high chemical reactivity. Understanding and optimizing the machining parameters to get the right combination of speed, feed, depth of cut, and coolant condition are vital. Furthermore, to decipher the collected data and interpret the results, analysis of variance techniques were utilized with the help of software R-programming. The insights garnered can lead to more streamlined machining strategies, ensuring higher productivity and efficiency. By bridging the knowledge gap, this research seeks to make machining titanium alloys simpler, cost-effective, and more efficient for manufacturers. The paper output shows that the mean square values range from nearly zero for cutting speed, feed rate, and depth of cut to around 11.817 for coolant respectively. The paper concludes with the various P-values obtained for the cutting parameters influencing the surface roughness using the analysis of variance technique. The effect of coolant on the surface roughness has been significant with a P-value of 0.000117.

Advances in Additive Manufacturing (AM) technologies have made it possible to reduce the design and prototyping costs to a minimum especially for a low-productivity material like titanium. Titanium alloys are commonly and widely used alloys in the aerospace and biomedical sector due to their advantageous material properties. This paper is an evaluation study of factors affecting the productivity characteristics of Laser Engineered Net Shaping (LENS) titanium alloy (Ti-6Al-4 V) using face milling. Some of the productivity challenges associated with titanium such as rapid tool wear, poor surface finish, and high-power consumption are explored in this paper. All materials processed using AM face the same critical problem that the manufactured part requires a post machining since AM produces relatively poor surface finish. Machining trials are conducted using the combinations of machining parameters such as spindle speed of 800 and 1600 rev/min; feed rate of 50 and 100 mm/min; and a constant depth of cut of 1 mm, respectively. Titanium being a poor thermal conductivity material, the effect of coolant was investigated using wet/dry machining. Data related to the productivity factors and material behavior under a milling trial was recorded and analyzed. The obtained data from the trials include productivity factors such as Metal Removal Rate (MRR), power consumed, and the surface finish for each plate/trial. The power consumed in dry milling was observed to be lower than that in wet milling which is contrary to the observations from conventional wet milling. The paper concludes the trends observed for LENS titanium are opposed to the trends in conventional machining such as increasing cutting speed will result in lower cutting force and power consumed.

Being a difficult-to-cut material, Fiber Metal Laminates (FML) often pose challenges during conventional drilling and require judicious selection of machining parameters to ensure defect-free laminates that can serve reliably during their service lifetime. Helical milling is a promising technique for producing good-quality holes and is preferred over conventional drilling. The paper compares conventional drilling with the helical milling technique for producing holes in carbon fiber-reinforced aluminum laminates. The effect of machining parameters, such as cutting speed and axial feed, on the magnitude of cutting force and the machining temperature during conventional drilling as well as helical milling is studied. It was observed that the thrust force produced during machining reduces considerably during helical milling in comparison to conventional drilling at a constant axial feed rate. The highest machining temperature recorded for helical milling was much lower in comparison to the highest machining temperature measured during conventional drilling. The machining temperatures recorded during helical milling were well below the glass transition temperature of the epoxy used in carbon fiber prepreg, hence protecting the prepreg from thermal degradation during the hole-making process. The surface roughness of the holes produced by both techniques is measured, and the surface morphology of the drilled holes is analyzed using a scanning electron microscope. The surface roughness of the helical-milled holes was lower than that for holes produced by conventional drilling. Scanning electron microscope images provided insights into the interaction of the hole surface with the chips during the chip evacuation stage under different speeds and feed rates. The microhardness of the aluminum layers increased after processing holes using drilling and helical milling operations. The axial feed/axial pitch had minimal influence on the microhardness increase in comparison to the cutting speed.

Cutting fluids are an essential requirement while machining materials like Ti6Al4V alloy exhibiting low thermal conductivity and work hardening behavior. However, the non-biodegradable nature of the oil increases carbon emissions and causes serious health concerns, thus jeopardizing sustainability. In addition, complexity increases when drilling Ti6Al4V alloy due to the temperature build-up, leading to material adhesion and accelerated tool wear. The study, therefore, investigates the utility of helical milling for creating holes in Ti6Al4V alloy. The hole-making operations were appraised considering the chip morphology, microhardness, machining temperature, tool wear, and surface roughness. The findings show that hole-making using helical milling was beneficial since it produced lower thrust force. Measured temperatures during helical milling were significantly lower than in drilling. Helically milled holes displayed superior quality holes with lower surface roughness; however, at higher productivity conditions, chatter marks were noted. The microhardness was lower near the machined surface in the case of conventional drilling, indicating material softening. In comparison, helical milled holes displayed higher microhardness very close to the edge of the hole due to work hardening. The helical milling operation produced short discontinuous chips, which are desirable while machining Ti6Al4V alloy. Furthermore, the examination of the cutting tool showed material adhesion. The severity of tool damage was significantly lower during the helical milling operation. The initial assessment indicates that helical milling is an adept process for making holes in Ti6Al4V alloy.

This paper is based on evaluating, analysing and comparing the secondary machining characteristics of wrought and additive manufactured 316L Stainless Steel. This paper is an attempt to determine the process efficiency and evaluate the machinability factors which effect the service life. Stainless steel is a historic iron carbon alloy reputed for its high corrosive resistance and extensive application base. Threading, tapping, reaming and knurling are the most common secondary machining operations after a primary machining operation to achieve a required surface finish and form. As threading plays a significant role in fastening two components together. Threading is selected as a secondary machining operation in this paper. The research methodology consists of conducting threading operation on a hollow cylinder of 50 mm diameter using a lathe. Threads are cut into the workpiece using variable cutting parameters such as spindle speed; 90 and 180 rpm and coolant condition; on/off. Thread pitch which is also the feed rate (1 mm/rev) and Depth of Cut (0.3 mm) remains constant for all the trails. Statistical data are collected and analysed by qualitative and quantitative evaluation. The outputs under consideration to evaluate the machinability includes the cutting forces, thread profile accuracy (pitch) and tool wear. It has been observed that the cutting force and the tool wear was predominantly high for SLM compared to wrought. The paper concludes to convey the point that wrought components has better machinability characteristics than additive manufactured stainless steel.

This paper presents a novel method to model the metal cutting of 2205 duplex stainless steel alloy. A 2D finite element model was developed to predict the plastic behaviour of two phases of duplex stainless steel, austenite, and ferrite during orthogonal cutting. A mesh based on physical microstructure was created using mapping software OOF2. The finite model was setup on ABAQUS software based on the Lagrangian method. The cutting model allows for tracking of stress and strain on individual phases during chip formation. Simulated and experimental data showed good agreement in comparison of shear angle and cutting strain. Model was created to gain understanding of long-established issues in machining duplex stainless alloys. Future model development required to gain further insight on associated triggering mechanisms.

Modern Aircraft structures use titanium alloys where the processing of holes becomes essential to assemble aerospace parts. Considering the limitations of drilling, the study evaluates the helical milling for hole processing in Ti6Al4V. The experimental evaluation was conducted by considering burr size, surface roughness, machining temperature, and microhardness under coolant-free conditions. The axial feed and cutting speed were varied at three levels, and nine experiments were conducted. The results exhibit a lower machining temperature during helical milling than during drilling. In addition, the helical milling helped to lower the surface roughness and size of the exit burrs. However, helical-milled holes showed higher subsurface microhardness than conventionally drilled holes. The process variables were influential on machining temperature magnitude. The highest recorded temperature of 234.7 °C was observed at 60 m/min of cutting speed and 0.6 mm/rev feed. However, the temperature rise did not affect the microhardness. Strain hardening associated with mechanical deformation was the primary mechanism driving the increase in microhardness. Helical-milled holes exhibited an excellent surface finish at lower axial feeds, while chatter due to tool deformation at higher feeds (0.6 mm/rev) diminished the surface finish. The surface roughness increased by 98% when the cutting speed increased to 60 m/min from 20 m/min, while a moderate increment of 28% was observed when the axial feed increased to 0.6 mm/rev from 0.2 mm/rev. Furthermore, the formation of relatively smaller burrs was noted due to significantly lower thrust load and temperature produced during helical milling.

Titanium alloys are popular and used in a wide range of design applications in aerospace and biomedical industry due to their advantageous material properties. Titanium is categorised into various grades such as Cp Titanium, Titanium5553 and Titanium64. Grade 5 titanium (Ti6Al-4V) is used in this paper. This paper is a preliminary study of machining characteristics of Laser Engineered Net Shaping (LENS) Titanium alloy (Ti-6Al-4V) using face milling. With the advancement in Additive Manufacturing (AM) technologies, components can be easily and efficiently made into various parts with complex geometries that is not possible using traditional manufacturing methods. All materials processed using AM face the same critical problem that the manufactured part requires a post machining since AM produces relatively poor surface finish. This report presents a study of the machining characteristics of a LENS titanium alloy (Ti-6Al-4V) and its behaviour under a milling operation with a set combinations of machining parameters such as cutting speed, feed rate, depth of cut and wet/dry machining. This report also analysed the surface finish of each sample and its correlation to its wrought counterparts. LENS titanium complied with the notion of increasing cutting speed will result in lower cutting force. The cutting force in dry milling is lower than the force in wet milling. The tool wear in dry milling is higher than the wet milling.

Titanium alloy, Ti-6Al-4 V is a popular titanium alloy used in industries such as Biomedical, Aerospace, and Automotive [1]. This is due to its superior mechanical properties such as high tensile strength, corrosion resistance and fracture toughness [2]. The main objective of this research project is to provide insights about the effect of transus based heat treatment on microstructure and mechanical properties of wrought and SLM Ti-6Al-4 V. Selective Laser Melting (SLM) which is a Direct Metal Laser Melting (DMLM) process is used to print samples in this research. Three temperature points near to alpha beta transus zone were selected to determine the effect of heat treatment on the material characterisation. The experimental design consists of heat treating, wrought and SLM Ti-6Al-4 V samples to the selected temperatures, 750 degrees C, 800 degrees C and 900 degrees C and followed up with furnace cooling. Further, the heattreated samples are subjected to metallographic examination, microhardness testing and phase quantification using EBSD. An analysis of changes in microstructure will be conducted to provide a relationship between the effect of heat treatment and the changes in microstructure and corresponding microhardness. Wrought and SLM titanium samples heat treated at 900 degrees C. show maximum transformation to alpha phase against overall phase composition at 92% and 83% respectively. The bulk hardness analysis using Vickers concludes that the wrought sample heat treated at 900 degrees C. and SLM as build sample have almost a similar hardness level at 414 Hv and 407 Hv respectively. The paper concludes that heat treatment effect on SLM microstructure leads to gradual decomposition of martensitic alpha whereas accumulation of alpha into a globular alpha is observed in a wrought sample. Copyright (c) 2022 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the Material TECH 2022 (Second International Conference on Materials and Technologies).

During last decade, manufacturing sector has undergone a rapid change with the advent and adaptation of new technologies in a commercial environment. Modern machining, additive and sustainable manufacturing, and process optimization are the latest trends. This chapter discusses the modern machining strategies required for successful processing of difficult-to-machine materials. Some of the materials under consideration are selective laser melted (SLM) titanium Ti6Al4V and super austenitic stainless steel. The machinability of the materials has been evaluated considering the tool wear, cutting force, and surface finish type indicators.

This paper presents a finite element study to assess machinability of AL-6XN alloy by benchmarking against the machinability of Inconel 718 alloy. Johnson-Cook model was used to represent the alloys plastic strain behaviour, at cutting speeds (65 m/min and 94 m/min). Outcomes reveal that percentage increase of the plastic strain at the beginning of cutting, for Inconel 718 alloy was higher by 18% and 4% at speeds of 65 m/min and 94 m/min respectively. The percentage increase in plastic strain for the AL-6XN alloy during the cutting was higher by 36% and 10% at the same cutting speeds. The shear zone temperature percentages of the AL-6XN alloy increased by 31% and 9.5% at 65 m/min and 94 m/min cutting speed respectively when the tool removed chips. Results indicated that the AL-6XN alloy is suitable for industrial applications (due to the alloy elevated ductility) fabricated at elevated cutting speeds.

Titanium is known for its poor machinability characteristics due to its low thermal conductivity and high chemical reactivity. This article explores the machinability characteristics of selective laser melting (SLM) titanium alloy Ti-6Al-4V using wire cut electrical discharge machining (WEDM). For titanium alloys, exploring non-traditional machining operation such as WEDM is critical for a material failure or success in a design application. The research is to study the effect of parameters such as servo voltage, pulse on/off, and machining speed with respect to wire tension and wire feed rate on machinability. The outputs under consideration for evaluating machinability are metal removal rate (MRR) and surface finish under minimal interruption due to wire snaps. The article concludes by identifying the optimal factors responsible to produce an efficient and accurate cut with a minimum downtime.

Titanium alloys are popular and used in a wide range of design applications in aerospace and biomedical industry due to its advantageous material properties.This paper attempts to explore the hole making ability using abrasive waterjet machining.Exploring non-traditional hole making operation such as abrasive water jet machining is an important factor to decide failure or success in a design application.Especially in materials having poor machinability characteristics such as titanium alloys.The main objective of this project is to perform a hole making operation on additive manufactured and wrought titanium alloy, Ti-6Al-4V with standard cutting parameters such as abrasive size, feed rate, traverse speed and standoff distance.A comparative study is carried out in terms of kerf taper angle, Material Removal Rate (MRR) and surface roughness.The paper concludes by identifying the factors responsible to produce a superior hole quality and to evaluate the machinability characteristics.

Stainless steel is an age old and popular alloy known for its high corrosion resistance.This paper is an attempt to explore ways to enhance the fatigue characteristics using heat treatment.The additive manufacturing technique used in this paper is based on Selective Laser Melting (SLM).The material used in this paper is SLM Stainless steel 316L.The specimen printed using SLM technique are subjected to low cycle fatigue tests as per the ASTM standards.Out of the twelve printed specimens, two sets for as-built and heat-treated were separated.A set of six was heat-treated at recrystallisation temperature of 700 o C for 2 hours and air cooled.Two specimen each for the as-built and heat-treated category were reserved for tensile testing to evaluate the yield strength, ultimate tensile strength and strain.The remaining eight printed specimen of as-built and heat-treated were allotted for fatigue testing (four each of as-built and heat-treated).After tensile tests, fatigue tests were conducted on the specimens at mean stress equals to 75%, 70%, 65% and 60% of tensile strength, keeping stress ratio, r = 0.5 and at frequency of 5 Hz.Number of cycles to failure were obtained for each specimen for similar loading conditions to plot the S-N curve.The paper concludes by making an analogy in the fatigue characteristic of as-built and heat-treated specimen.