Metamorphic Layer Research Articles

Research on the machined surface integrity under combination of various inclination angles in multi-axis ball end milling

It is well known that the multi-axis machining technology has been developed into a key technique applied in the manufacturing field. The machined surface integrity is one of the most important factors influencing the performance of the produced components. Hence, this research concentrated on the machined surface integrity induced by the multi-axis milling operation with different inclination angle combinations. In this research work, the cutting conditions of the conventional or up-milling process with tool orientations were divided into eight different types, and the machining characteristics corresponding to different cutting strategies were discussed. The varying conditions of surface topography, texture and other machining features induced in machining process which corresponds to different inclination angle combinations were analyzed by geometrical analysis, and the surface roughness and linear profile along specific directions on the machined surface were also investigated. There is a special corresponding relationship between the rotation angle and tool tilt and lead angles. Better surface roughness could be achieved when rotation angles are 0° (positive lead), 60° (combination of positive tilt and positive lead), 90° (positive tilt) and 330° (combination of negative tilt and positive lead). Then, the samples used for study of the metamorphic layer were produced by lapping and polishing process, and the macro hardness (HL) and micro-hardness (HV) of the top machined surface were investigated. According to the measured results of both Leeb hardness and micro-hardness, higher surface hardness could be obtained under rotation angles of 60° (combination of positive tilt and positive lead), 120° (combination of positive tilt and negative lead) and 210° (negative tilt and negative lead). Moreover, the variations of the micro-hardness along the depth direction of the samples were studied. Finally, discussions on the machined surface residual stresses in both feed and cross-feed direction were carried out. Compressive surface residual stress in both feed and cross-feed direction could be generated when rotation angles are 210° (combination of negative tilt angle with smaller value and negative lead angle with larger value) and 330° (combination of negative tilt angle with smaller value and positive lead angle with larger value). Generally, the evaluation indicators of surface integrity are not all very satisfying under one special cutting condition with a certain inclination angle combination, and the optimal cutting parameters should be selected based on the specific application requirements. Finally, the optimal tool orientations and related cutting parameters were recommended, and further studies of the related topics were also presented.

Effects of temperature and substrate miscut on the crystalline quality of metamorphic AlInAs layers grown on GaAs substrate

We have investigated the effects of temperature and substrate miscut on the crystalline quality of metamorphic AlInAs layers grown on a GaAs substrate by metal organic chemical vapor deposition (MOCVD). The AlInAs layers grown at 700°C show a much better crystalline quality than the ones grown at 675°C, because a high temperature can suppress phase separation and enhance the glide velocity of dislocations during the strain relaxation process. Compared with the miscuts of 2° and 7°, the 15° miscut is more effective in suppressing phase separation during the growth of the AlInAs buffers. Theoretical calculations show that the miscut will facilitate the strain relaxation by dislocation gliding. These results indicate that a high growth temperature and a large miscut will improve the quality of the metamorphic AlInAs layers grown on the GaAs substrate by MOCVD.

Effects of cutting parameters on surface residual stress and its mechanism in high-speed milling of TB6

Formation mechanism and influence of cutting parameters on residual stress in flank milling of TB6 are investigated through orthogonal experiments. The thermal–mechanical coupling effect on forming residual stress is studied by analyzing the microstructure of metamorphic layer. Experiment results show that cutting temperature varies between 300 °C and 518 °C under experiment conditions, while residual compressive stress on machined surface is −199.8 to −41.7 MPa. Tensile residual stress occurs on subsurface when increasing milling parameters excessively. When cutting TB6 with parameters of fz = 0.02 mm/z, vc = 60 m/min, ae = 0.2 mm and ap = 10 mm, only the compressive residual stress can be detected, which is good for its fatigue life. The depth of compressive residual stress layer is 10–20 µm.

Growth of metamorphic InGaP layers on GaAs substrates

We report on the growth of InGaP metamorphic layer by gas source molecular-beam epitaxy. After optimization of the growth temperatures of the compositionally graded InGaP layer and the indium content in the top metamorphic InGaP layer, almost fully relaxed metamorphic layer was obtained with surface roughness of only about 2.17nm. Strong photoluminescence signals were measured from both InGaAs quantum well and InAs quantum dots embedded in the metamorphic layer, indicating that the top metamorphic layer had low density of threading dislocations.

MICROSTRUCTURE AND PROPERTIES OF METAMOR-PHIC LAYER FORMED ON Mg-RE ALLOY IN MICRO-EDM PROCESS

In this work,the Mg-RE alloy metamorphic layer was formed in the micro-EDM process in different process parameters.The morphology and composition of the metamorphic layer were detected by SEM and XPS,the hardness of the metamorphic layer was measured by a nanoindentor, the corrosion resistance property was investigated by using a potentiodynamic polarization test. The results show that there are microcracks on the surface of metamorphic layer,the microcracks can be reduced by decreasing processing voltage and current,and it can be further eliminated by increasing pulse wide and pulse interval.The oxidation caused on the surface of metamorphic layers in the micro-EDM process in three different dielectrics among which there was significantly electrochemical corrosion on the surface in deionized water.The hardness of metamorphic layer is enhanced compared to the substrate of Mg-RE alloy,and its maximum value is about 1.664 GPa.The potentiodynamic polarization test shows that the corrosion resistance of the Mg-RE alloy was improved significantly due to the existence of the metamorphic layer.

Research on WEDM Process Optimization for PCD Micro Milling Tool

An initial study on WEDM process optimization for PCD micro milling tool has been carried out. With a orthogonal design of roughing and finishing condition experiment of PCD, a largest difference of WEDM parameter is obtained to calculate the influence of those parameter on cutting speed for roughing operation and surface roughness Ra and metamorphic layer thickness for finishing operation. For roughing operation, peak current and voltage pulse width are the dominant WEDM parameters; while for finishing operation, Peak current, peak voltage are the largest influence of parameters on cutting speed. With WEDM optimized parameters, a quadrilateral PCD micro milling tool is fabricated with CTB002 PCD material. Tool edge radius is 6.7 m.

Performance evolution process of machined surface of monocrystalline silicon micro/nanostructures

The machined workpiece has high mechanical storage energy because of the defect structures formed in nanocutting and their evolution from high energy state to the low energy state by adjusting atom positions automatically is called surface-energy aging. The effect of surface-energy aging on the surface properties of monocrystalline silicon workpiece is analyzed by Monte Carlo simulations of machined surface. It is shown that the surface-energy aging effect can increase the surface roughness and the degree of order of damaged layer, however reduce the residual stress and the average potential energy of workpiece. Amorphous silicon structure in metamorphic layer decreases and recrystallization phenomenon occurs in the surface-energy aging process. It is found that some β-Si phase structures and BCT5-si phase structures transform into the diamond cubic structure of Si in the surface-energy aging process. Surface-energy aging effect has a great influence on the surface properties of the machined surface of monocrystalline silicon workpiece, and can improve the mechanical properties of micro/nanostructures.

Energy states and carrier transport processes in metamorphic InAs quantum dots

Photoluminescence excitation spectroscopy is used to probe energy states and carrier transport in InAs quantum dot structures grown on InGaAs metamorphic layers, designed for room temperature emission at 1.3, 1.4, or 1.5 μm. The dominant spectral feature is shown to arise from the partially relaxed InGaAs confining layer. In structures with a low indium composition or thin InGaAs layer, a clear wetting layer feature is observed which acts as the dominant reservoir for carriers thermally excited from the quantum dots. Structures with high indium composition and/or thick InGaAs lack a wetting layer and carriers escape directly to the InGaAs layers.

Localized and chaotic folding: the role of axial plane structures

Most natural fold systems are not sinusoidal in profile. A widely held view is that such irregularity derives solely from inherited initial geometrical perturbations. Although, undoubtedly, initial perturbations can contribute to irregularity, we explore a different (but complementary) view in which the irregular geometry results from some material or system softening process. This arises because the buckling response of a layer (or layers) embedded in a weaker matrix is controlled in a sensitive manner by the nature of the reaction forces exerted by the deforming matrix on the layer. In many theoretical treatments of the folding problem, this reaction force is assumed to be a linear function of some measure of the deformation or deformation rate. This paper is concerned with the influence of nonlinear reaction forces such as arise from nonlinear elasticity or viscosity. Localized folds arising from nonlinearity form in a fundamentally different way than the Biot wavelength selection process. As a particular example of nonlinear behaviour, we examine the influence of axial plane structures made up of layers of different mineralogy formed by chemical differentiation processes accompanying the deformation; they are referred to as metamorphic layering. The alternating mineralogical composition in the metamorphic layers means that the embedding matrix exerts a reaction force on the folded layers that varies not only with the deflection or the velocity of deflection of the layer, but also in a periodic manner along the length of the folded layers. The influence of this spatially periodic reaction force on the development of localized and chaotic folding is explored numerically.

Grinding Process Parameters Optimization and Surface Performance Analysis of Spiral Bevel Gear Based on the Orthogonal Test

Based on the experimental conditions of generation grinding of spiral bevel gear, the grinding orthogonal test design of L16(45) is made, and the results of grinding orthogonal test are obtained. On this basis, the range and variance analyses are carried out by using an integrated balance method, and the optimizing configuration of grinding process parameters of spiral bevel gear is obtained. The test regression models of three grinding evaluating indicators of spiral bevel gear, such as the grinding surface roughness Ra, metamorphic layer depth h and removal rate Zw, are set up by using a method of multivariate nonlinear least square. The maximal absolute value of relative error between computing values and testing ones is 18.41 percent by test validation, and this shows that the regression models are more effective. Through the test optimization of grinding surface performance, the value of grinding surface roughness Ra is more less 0.1μm than one of the normal grinding process, and other comprehensive performances are better. The pre-control measures of grinding process optimization of spiral bevel gear are also put forward. These provide a basis for the improvement of grinding surface quality of spiral bevel gear.

Experiment Study on Micro-Hardness and Structure of NC Grinding Surface Layer of Spiral Bevel Gears

Through the analyses of experiment,mechanism of dislocation and coupling of grinding temperature and deformation field,many conclusions are gotten.Firstly,a tempering metamorphic layer of lower hardness is formed in hardening zones of grinding layer of spiral bevel gear. Secondly,the microstructure of grinding tooth surface is acicular martensite+residual austenite+ a small amount of carbides,and it’s outside to the inside presents the variation of "fine→coarser→finer".Thirdly, the critical condition of grinding burns is obtained,that is when grinding temperature is above 600°C,metamorphic layer depth is greater than 0.2mm or more. The formation characteristics of grinding cracks is also revealed. These provide a basis for the NC grinding quality control of spiral bevel gears.

Study on Kaiser Effect of Edge Chipping for Engineering Ceramics during their Failure Process

An edge chipping experiment under static load is adopted to study the Kaiser Effect during the failure process for engineering ceramics. The mechanisms inducing Kaiser Effect are discussed. Some AE signals during the course of Kaiser Effect are analyzed. The results show that there’s obvious Kaiser Effect during the failure process of edge chipping; count, energy and amplitude can be well used to describe the Kaiser Effect. The surface metamorphic layer remained on the ceramic surface during the course of machining is the main factor for Kaiser Effect. Edge distance and mechanics characteristic are the important factors for Kaiser Effect. The study on Kaiser Effect of edge chipping has provided some guidance to prevent edge chipping of engineering ceramics.

Research on Workpiece Surface Temperature and Surface Quality in High-Speed Cylindrical Grinding and its Inspiration

The temperature in cylindrical grinding contact zone is difficult for measurement. Relative to the fixed workpiece in surface grinding, the workpiece rotation in cylindrical grinding brings challenges to the temperature measurement. In grinding titanium alloy, more heat will be generated, and due to the poor thermal conductivity of this material, it is easy to make the high temperature rise in the grinding zone. The high surface temperature and its distribution along the depth of the workpiece have great impacts on the grinding burn, metamorphic layer and residual stress. In order to improve the surface quality of machined parts, based on the undeformed chip thickness, this paper proposed a quadratic curve heat flux distribution model to predict the surface temperature distribution in the grinding of titanium alloy (TC4). Experimental results showed that the quadratic curve model under the condition of the measured grinding power, can predict the temperature distribution in the cylindrical grinding zone. Meanwhile, it specifically discussed the impact of the wheel speed on the TC4 surface roughness and the stress distribution, and found the "high-speed" definition in high-speed grinding should be distinguished from the traditional way only judged by the wheel speed, different workpiece materials should be with different "speed" ranges for acquisition of better machining quality.

Analysis of optical properties of InGaSb PIN photdiodes

This paper represents the optical characteristics of InGaSb PIN photodiodes, grown on metamorphic layers of InGaSb, through the modeling of responsivity, quantum efficiency and detectivity. The modeling is based on the wavelength dependent models of absorption coefficient and reflectivity. Theoretical results are fitted with experimental data obtained for these photodiodes. The cut-off wavelength is found to be 2271nm, which is within ?5nm of the experimentally obtained data. The detectivity of the photodiodes is found to be 1.5(?0.1)×10 9 cmHz 1/2 W -1 and quantum efficiency 28?3% through the analysis. Such modeling can be used to optimize the detection performance of InGaSb PIN photodiodes. Full Text: PDF

Three‐Dimensional Q Value Tomography for Xiuyan Meteorite Impact Crater

AbstractUntil 2009, 176 meteorite impact craters have been found in the world. Since the 80's of 20th century, Chinese scholars have confirmed, from the geological, geochemical and drilling data, that a circular structure was formed by meteorite impacting in Xiuyan County, Liaoning Province. But the deep structures and the overall characteristics of the crater need still to be confirmed by using the geophysical methods. In this paper, three‐dimensional Q structure has been obtained for the first time by using seismic refraction data in order to have a total understanding of the crater. Q value structure is of great significance for understanding the non‐elastic and nonuniform nature of the crust. Using three‐dimensional Q tomography method based on absorption characteristic time t* the amplitude spectra have been obtained and by fitting the amplitude spectrum, t* values have been obtained, which reflect seismic wave attenuation. The three‐dimensional Q value structure has been obtained by using t* values through three‐dimensional Q tomography method. The results showed that the Q‐value layer from the surface to the depth of 100 m within the crater corresponds to the upper 107 m thick lake sediments, the Q‐value layer from the depth of 100 m to 300 m corresponds to the lower 188 m thick breccia accumulation lens. The Q‐value layer from the depth of 300 m to 700 m corresponds to the broken Lower Proterozoic metamorphic rock layer with less impacting. The wave impedance interface about 250 m deep corresponds to the meteorite impact interface confirmed by geological drilling at the 260 m depth.

Research on Chip Formation Mechanisms of Nano-Composite Ceramics in Two-Dimensional Ultrasonic Grinding

Experimental research on grinding characteristics of nano-composites ceramics were carried out using diamond wheel in two-dimensional ultrasonic vibration grinding (TDUVG) and the topography of the scratched grooves were observed with Transmission Electron Microscope. The surface crack, plastic deformation and brittle-ductile transition during chip formation were analyzed. Subsequently, the grinding model of nano-composites ceramics machining in TDUVG was established based on fracture theory of micro-indentation in fracture region and plastic information mechanism of hard-brittle materials. The metamorphic layer can be divided into three regions: brittle-fracture, non-elastic deformation and residual damage region. Ultrasonic grinding process can be divided into three phase: elastic friction and extrusion, crack growth and crack propagation and chip formation.

CBN Slipstone Super-Accurate Grinding Theoretical Analysis and Application

In this paper, the principle and impact factors for super-accurate grinding are analyzed and discussed. A comparative test is made to investigate the differences between advanced cubic boron nitride (CBN) slipstone and ordinary CBN abrasive corundum in performance such as grinding force, grinding temperature, metal surface metamorphic layer and so on. Based on these results, we design and manufacture a carding Laura slot super-accurate grinding machine. This new grinding machine is standard in system, compact in structure and perfect in appearance. Its fixture has a high positioning accuracy. The surface roughness of the Laura manufactured on the new grinding machine has reduced to Ra0.01μm. The productivity of the new machine increases by 25 times.

Quantum well intermixing of a quantum well structure grown on an InAsP metamorphic pseudosubstrate on InP

InGaAsP quantum well (QW) structures, with ∼1% compressive strain, have been grown on an InAs0.21P0.79 metamorphic substrate layer (MSL) deposited on an InP substrate. For comparison, a similar QW structure is grown directly on InP. A consequence of growth on the MSL is to move the QW and barrier compositions outside the spinodal isotherm resulting in a significant reduction in phase separation. This is shown to increase the photoluminescence wavelength and improve its quality in terms of linewidth and intensity. Thermally induced QW intermixing (QWI) has also been carried out on these structures both with and without a low-temperature InP capping layer. The defects present in the underlying metamorphic buffer layers are shown to have no effect on the QWI process. However, the samples with the MSL are shown to exhibit more intermixing either due to a higher diffusion or greater P–As exchange probability in the different composition QW and barrier layers compared to the QW structure grown without the MSL, and possibly influenced by the large reduction in phase separation.

Extraction of Electron and Hole Ionization Coefficients From Metamorphically Grown InGaSb Diodes

Metamorphic pseudosubstrates of In0.15Ga0.85Sb are grown on p- and n-type GaSb substrates using InxGa1-xSb buffer layers compositionally graded in steps of x=0.03. Extensive material characterization was done on the metamorphic layers to determine the in-plane lattice constant, density of threading and misfit dislocations, and surface roughness by high-resolution X-ray diffraction, cross-sectional and plan-view transmission electron microscopy, and atomic force microscopy. This is followed by a regrowth of p-i-n and n-i-p device layers of InxGa1-xSb (x=0.10), lattice matched with the underlying partially relaxed metamorphic layer. Hole ( beta) and previously unreported electron (alpha) ionization coefficients, at room temperature and 90degC, respectively, were extracted from these structures. The results show that alpha > beta for In0.10Ga0.90Sb. A semianalytic expression was used to extract the temperature-dependent parameters for further investigations on practical avalanche photodiodes.

Trap Density and Charging-Discharging Characteristics of a Metamorphic Layer between GaAs and an Insulator

Trap Density and Charging-Discharging Characteristics of a Metamorphic Layer between GaAs and an Insulator