Among the various types of metal matrix composites, SiC particle-reinforced aluminum matrix composites (SiCp/Al) are finding increasing applications in many industrial fields such as aerospace, automotive, and electronics. However, SiCp/Al composites are considered as difficult-to-cut materials due to the hard ceramic reinforcement, which causes severe machinability degradation by increasing cutting tool wear, cutting force, etc. To improve the machinability of SiCp/Al composites, many techniques including conventional and nonconventional machining processes have been employed. The purpose of this study is to evaluate the machining performance of SiCp/Al composites using conventional machining, i.e., turning, milling, drilling, and grinding, and using nonconventional machining, namely electrical discharge machining (EDM), powder mixed EDM, wire EDM, electrochemical machining, and newly developed high-efficiency machining technologies, e.g., blasting erosion arc machining. This research not only presents an overview of the machining aspects of SiCp/Al composites using various processing technologies but also establishes optimization parameters as reference of industry applications.

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A review on conventional and nonconventional machining of SiC particle-reinforced aluminium matrix composites

Effect of pre-ageing treatment on second nucleating of GPII zones and precipitation kinetics in an ultrafine grained 7075 aluminum alloy

Experimental investigation of thermal performance of the oscillating heat pipe for the grinding wheel

This review paper is devoted to the slide burnishing (SB) of metal components—state-of-the-art, achievements and perspectives. SB belongs to the group of static methods for mechanical surface treatment used largely in aerospace, automotive and other industries. By means of the plastic deformation of the surface layers, the surface integrity (SI) of the respective component is improved greatly in terms of minimum roughness, micro-hardness and introduced residual compressive stresses. As a result, fatigue crack resistance, crack corrosion resistance, wear resistance and corrosion resistance increase dramatically. The main feature of SB is the sliding friction contact between the deforming element and the surface being treated. Using the differential-morphological method, an integrated classification of the static methods is created and the area of SB is outlined. The proposed morphological matrix, which can be expanded and supplemented contains existing burnishing methods as well as combinations of elements and interactions that can be used to synthesize new burnishing methods and tools. In addition, a literature review of the publications devoted to SB has been conducted. Further, an analysis of the published studies on different criteria has been carried out and graphic visualizations of the statistical results have been made. On this basis, relevant conclusions have been made and the directions for future investigations of SB have been outlined.

Slide burnishing—review and prospects

Prior to a critical value of uncut chip thickness (UCT) or the so-called minimum uncut chip thickness (MUCT), the micro milling process is affected by ploughing which causes deterioration of surface quality and reduction of tool life. Stringent surface quality is the major concern during micro milling of P-20 die steel as it has wide application in preparation of micro injection mould. Again, this MUCT value depends upon the workpiece, cutting tool material and its geometry. In this article, we tried to determine MUCT and size effects by considering the variations of surface quality parameters and process signals with the ratio of h/re (UCT (h) to edge radius(re)). MUCT value was determined to be 0.75–1 μm or critical h/re value was found to be in the range of 0.25–0.33. Comprehensive analysis of tool wear and chip morphology with size effect have been instituted those were lacking in the earlier literatures. Curled and helical chips were obtained at feed rate higher than MUCT value, whereas the chips with arbitrary shapes were noticed at feed rates below MUCT. Lamellar structures were observed at the free surface of the chip having both inclined and vertical orientation. Edge rounding, coating delamination and built-up edge formation were observed due to size effect at feed value below MUCT.

Determination of minimum uncut chip thickness and size effects in micro-milling of P-20 die steel using surface quality and process signal parameters

Machining of critical components such as turbine compressor and pump parts is required to generate compressive residual stress on the surface layer in order to obtain high fatigue life. As an effective method to generate and improve the compressive residual stress of machined parts, burnishing has been widely used in industry. Despite its importance, few studies have investigated the mechanism of burnishing on surface residual stress. In this paper, the interference effects due to nearby burnishing points were revealed and investigated in the context of an elastic burnishing tool. The interference effects during the burnishing process help to enhance the compressive residual stress and improve the distribution of compressive residual stress on the burnished surface layer. In order to analyze the mechanism behind the interference effect more clearly, a 2D finite element model of the burnishing process was developed. It was found that the interference effect exists and becomes stronger as the feed rate is decreased. Small feed rates show a more apparent effect on the enhancement of interference effects. The results indicate that the interference effect of the workpiece surface is mainly created by the influence of the preceding burnishing points on the future burnished surface.

Investigation of interference effects on the burnishing process

In this study, cryogenic temperature large strain extrusion machining (CT-LSEM) as a severe plastic deformation (SPD) method is applied to fabricate chips with ultra-fine grained (UFG) structure. The chip morphology, microstructure evolution, aging behavior, as well as micro-hardness characteristics of a solution treated (ST) Al 7075 alloy subjected to CT-LSEM and room temperature (RT) LSEM are investigated. It is observed that the processing temperature has a great influence on the chip morphology, i.e., the chips produced by CT-LSEM have better surface quality than that by RT-LSEM. The SPD process of LSEM, especially under CT, can accelerate the aging kinetics of the alloy. Much more deformation energy stored in the CT-LSEM sample could promote the dynamic recrystallization. A higher dislocation density exists in the CT-LSEM samples due to effective suppression of dynamic recovery. The optimized hardness for all samples is obtained at an aging temperature of 120 °C. The hardness of CT and RT LSEM samples after peak aging (PA) have increased from 102 Hv to 201 Hv and 192 Hv respectively. A large number of fine and closely spaced ηʹ and η precipitates are present in the LSEM samples after PA treatment, accounting for the further enhancement of hardness. The ST Al 7075 samples subjected to LSEM are severely deformed. The mean grain/sub-grain size of PA samples has hardly changed as compared with the initial LSEM samples. It is feasible to realize simultaneous hardening including grain refinement, dislocation and precipitation in the Al 7075 alloy via application of CT-LSEM and subsequent aging.

Ultrafine grained Al 7075 alloy fabricated by cryogenic temperature large strain extrusion machining combined with aging treatment

Analytical model and experimental verification of Poisson burr formation in ductile metal machining

Large strain extrusion machining (LSEM) emerges as an innovative severe plastic deformation method of fabricating ultrafine grained materials However, substantial heat generated during LSEM would sacrifice the mechanical properties of materials Cryogenic temperature (CT) LSEM is put forward to overcome this shortcoming The Al 7075 was processed by cryogenic and room temperature (RT) LSEM to investigate their comparative effects on mechanical and microstructural properties Results indicate that the chip morphology of CT LSEM is featured with better integrity Grains are refined to less than 200 nm by CT LSEM A more complicated microstructure with high dislocation density is observed in the CT LSEM specimens The hardness of cryogenic and RT LSEM specimens increases with the compression ratio and reaches the highest values of 187HV and 170HV, respectively Dislocation strengthening is the main contributor, accounting for the higher hardness of CT LSEM specimens

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Development of ultrafine grained Al 7075 by cryogenic temperature large strain extrusion machining

Large strain extrusion machining (LSEM) is a typical process for preparing ultrafine or nanocrystalline strips. It is based on large plastic deformation. The processing parameters of LSEM in this study were optimized by experiments and simulations. Using the orthogonal array, signal-to-noise ratio, and analysis of variance, the influence and contribution of processing parameters on response variables were analyzed. Because of the difference in processing parameters between optimizing the average grain size and the maximum temperature, the response variables analyzed must be correctly selected. Furthermore, the optimal processing parameters for obtaining the minimum average grain size and the lowest maximum temperature are analyzed. The results show that the tool rake angle is the most important factor. However, the level of this factor required to achieve the minimum average grain size is different from that required to obtain the lowest maximum temperature. The validity of the method is verified through experiments and simulations.

Jiayang Zhang

Papers

Investigation of interference effects on the burnishing process

Ultrafine grained Al 7075 alloy fabricated by cryogenic temperature large strain extrusion machining combined with aging treatment

Analytical model and experimental verification of Poisson burr formation in ductile metal machining

Development of ultrafine grained Al 7075 by cryogenic temperature large strain extrusion machining

Towards understanding the microstructure and temperature rule in large strain extrusion machining