Search

High strength and large ductility of existing Mn-containing brass alloys need to be further improved when used as slippers of friction-pair materials, which could be achieved by tuning alloy composition and thermomechanical treatments appropriately. The present work optimized the amount of minor-alloying elements M (M = Mn, Fe, Si) in Cu-Zn alloy via a cluster formula approach and then investigated the microstructural evolution of the designed alloy with different thermomechanical treatments. As-cast alloy ingots were solid-solutioned at 1093 K (820 °C) for 3 h, hot-rolled at 923 ~ 1023 K (650 ~ 750 °C), and then aged at 673 ~ 723 K (400 ~ 450 °C) for 1 ~ 2 h, respectively. It is found that the alloy matrix consists of the main FCC-α phase plus a small amount of BCC-β and M5Si3 phases, among which the M5Si3 exhibits three types of primary, fine, and nano-scaled particles. The mechanical property varies with the thermomechanical treatments due to diverse microstructures (especially the morphology of M5Si3 particles), in which the high strength (σUTS > 580 MPa) and large ductility (δ = 16.3 ~ 29.4%) could be achieved simultaneously in 673 K (400 °C). The optimal matching of high strength and large ductility makes the current alloy more suitable as an alternative slipper material. The strengthening effect was further discussed in light of various strengthening mechanisms, and the calculated strength increment is well consistent with the experimentally measured yield strength.

High-precision manufactured thin-walled pure copper components are widely adopted in precision physics experiments, which require workpieces with extremely high machining accuracy. Double-sided lapping is an ultra-precision machining method for obtaining high-precision surfaces. However, during double-sided lapping, the residual stress of the components tends to cause deformation, which affects the machining accuracy of the workpiece. Therefore, a model to predict workpiece deformation derived from residual stress in actual manufacturing should be established. To improve the accuracy of the prediction model, a novel method for predicting workpiece deformation by amending the initial residual stress slightly based on the support vector regression (SVR) and genetic algorithm (GA) is proposed. Firstly, a finite element method model is established for double-sided lapping to understand the deformation process. Subsequently, the SVR model is utilized to construct the relationship between residual stress and deformation. Next, the GA is used to determine the best residual stress adjustment value based on the actual deformation of the workpiece. Finally, the method is validated via double-sided lapping experiments.

Back grinding of wafer with outer rim (BGWOR) is a new method for carrier-less thinning of silicon wafers. At present, the effects of process parameters on the grinding force remain debatable. Therefore, a BGWOR normal grinding force model based on grain depth-of-cut was established, and the relationship between grinding parameters (wheel infeed rate, wheel rotational speed, and chuck rotational speed) and normal grinding force was discussed. Further, a series of experiments were performed to verify the BGWOR normal grinding force model. This study proves that the BGWOR normal grinding force is related to the rotational direction of the wheel and chuck, and the effect of grinding mark density on the BGWOR normal grinding force cannot be ignored. Moreover, this study provides methods for reducing the grinding force and optimizing the back thinning process of the silicon wafer.

Mechanisms for removal of materials during the grinding process of monocrystalline silicon have been extensively studied in the past several decades. However, debates over whether the cutting speed significantly affects the surface integrity are ongoing. To address this debate, this study comprehensively investigates the effects of cutting speed on surface roughness, subsurface damage, residual stress, and grinding force for a constant grain depth-of-cut. The results illustrate that the changes in the surface roughness and subsurface damage relative to the grinding speed are less obvious when the material is removed in ductile-mode as opposed to in the brittle-ductile mixed mode. A notable finding is that there is no positive correlation between grinding force and surface integrity. The results of this study could be useful for further investigations on fundamental and technical analysis of the precision grinding of brittle materials.

Milling is one of the main methods for processing titanium alloy. At present, the complex process of milling is usually simulated by finite element method, which often has problems in mesh distortion and mesh reconstruction. Therefore, a meshless three-dimensional milling simulation model was established for TC4 titanium alloy using the smooth particle hydrodynamics (SPH) method. Firstly, the established SPH model was analyzed by the LS-DYNA software, and the stress distribution, temperature field, and cutting force during milling were studied under specific conditions. Subsequently, the cutting force was simulated under different cutting parameters and the effects of these parameters on the cutting force were determined. Finally, based on a series of cutting force experiments, the accuracy of the simulation model was verified. This study proves the feasibility of SPH method in the simulation of titanium alloy milling process and provides novel methods for investigating the processing mechanism and optimizing the processing technology of titanium alloys.

Additive forging is a newly developed method to manufacture heavy forgings by using multilayer hot-compression bonding. However, the relationship between surface cleaning and bonding performance of bonded samples in the additive forging process is unclear. This paper studies the effect of surface cleaning on interface bonding performance for the first time. A new characterization method of surface cleanliness consisting of water contact angles, relative fluorescence units, and optical observation was proposed to characterize the cleaning effect. The micromorphologies and tensile properties were used to evaluate interface bonding performance. Elemental analysis and morphological analysis were used to infer the hindrance mechanism of contaminants. The results show that the new characterization method can effectively characterize the surface cleanliness of substrates. Moreover, the interfacial bonding performance results indicate that surface cleaning had a great influence on the bonding performance for 316H stainless steel joints manufactured by additive forging. Finally, the hindrance mechanisms of particles, chips, and oil contaminants were attributed to the hindrance effect in a radial direction, along the interface direction, and perpendicular to the interface direction respectively. This research builds a relationship between surface cleaning and bonding performance, which helps achieve high-performance manufacturing of heavy forgings.

The performance of chemical mechanical polishing (CMP) has been found highly dependent on the pad-workpiece contact status, which is far from theoretical understanding. To this end, a physically-based material removal rate (MRR) model is developed under pad-asperity scale. The theoretical predictions agree well with the experimental results no matter the contact spots distribution is dispersed or concentrated. It is found that the deterioration of MRR is attributed to the continuously reduced number of reacted atoms in each individual contact spot and the inadequate time for chemical reaction between successive contact spots. The present model is expected to facilitate the clarification of the effect of contact status on MRR, and further provide a strategy for CMP mechanisms investigation.

Diamond CMP mechanisms have been widely investigated using the CMP experimental methods. However, the experiment could not observe the details of the removal process, it could not explain the mechanism of removal. The atom removal mechanism of chemical mechanical polishing (CMP) process on the diamond surface polished with a silica abrasive in aqueous H2O2/pure H2O was elucidated using ReaxFF molecular dynamics (MD) simulations. The research shows that the oxidation of diamond surface plays a dual role in the removal of C atoms. First, the diamond surface absorbs OH, O or H to form C O, C OH or C H bonds. Then, the C atoms on the oxidized diamond surface are removed under the mechanical action of abrasive in aqueous H2O2. Three types of C atom removal pathway are detected in the CMP process: it can be removed in the form of CO, CO2 or C chain and C atom removal occurs on the first layer. However, no C atoms are removed in pure H2O. The friction in pure H2O is less than that in aqueous H2O2 due to the lubrication of pure H2O. In addition, comparing the different pressures applied to the abrasive, it is found that the greater the pressure applied, the more OH adsorbed on the diamond surface so that the more C atoms are removed. This work shows that the removal of C atoms is the result of the combination of chemical and mechanical effects, which helps understand the removal process of C atoms at the atomic scale in the CMP process and provide an effective method to choose the CMP slurry.

Molecular dynamics simulations using ReaxFF reactive force field are employed to study the process of the silica abrasive particle sliding on the Cu(1 0 0) substrate in the aqueous H2O2 in order to clarify the atomistic mechanisms of the Cu chemical mechanical polishing process. Results reveal that there are mainly Cu H2O, OH Cu OH, Cu OH Cu, Cu OH H2O, O Cu OH etc on the substrate, among them, the number of Cu H2O is the most. And a part of H2O and OH in the above product come from H2O, some from H2O2, and the other are from the recombination of these two types molecule. Under the mechanical sliding effects, Cu atoms are mainly removed in the form of clusters by fracturing of Cu Cu bonds and Cu O bonds on the Cu substrate. When the polishing pressure is different, the more Cu atoms are removed, the greater the friction force between the abrasive particles and the substrate and the more H2O molecules are decomposed as the polishing pressure increases. Besides, H2O plays a dual effect by oxidizing the Cu substrate surface as well as by the effect of lubrication. Our results may shed light on the removal mechanism of Cu atoms in the CMP process at the atomic level and help to further understand the CMP of Cu.

Ultrasonic assisted grinding (UAG) has been demonstrated to be effective for processing hard and brittle materials. In some of the current UAG models, the high efficiency of UAG was attributed to the great maximum momentary force brought by ultrasonic vibration. However, the models were built based on multi-grains behavior which lacks of necessary support by single-grain models and experiments. In this paper, a model for ultrasonic assisted scratching (UAS) was proposed to investigate the cutting behavior of single-grains. The experiments with and without ultrasonic assistance were both conducted on a reaction-bonded silicon carbide specimen to verify the developed model. Results showed that even with the same maximum momentary force, the material removal rate increased greatly with ultrasonic assistance. The factor kL and kH did not remain constants as in the original indentation fracture mechanics models, and were highly related to the amplitude of the ultrasonic vibration.

Back Grinding of Wafer with Outer Rim (BGWOR) is a new method for carrier-less thinning of silicon wafers. There are few studies on the shape of wafer in BGWOR. In this paper, the mathematical models of three-dimensional grinding marks, surface shape and radial thickness of wafer in BGWOR were developed. With this model, the pattern of grinding marks and the radial thickness of the wafer under different inclination angles of grinding wheel were simulated by Matlab, then the relationship between the angle of grinding wheel shaft and the grinding marks, surface shape, radial thickness, total thickness variation (TTV) of wafer in BGWOR was also discussed. The inclination angles of grinding wheel have great influence on the surface shape and radial thickness distribution of wafer. Finally, the pilot experiments were conducted to verify the theoretical model of radial thickness of wafer in BGWOR. The study results will provide helpful instruction for improving the flatness of ground wafer.

In this study, the deformation mechanism of gallium-faces (Ga-faces) and nitrogen-faces (N-faces) gallium nitride (GaN) during nanogrinding were investigated by molecular dynamics (MD). The differences between the two were analyzed from force, temperature, potential energy, surface/subsurface damage, and material removal rate (MRR). The results show that N-faces GaN withstand lower grinding force, higher temperature, potential energy, and MRR. Meanwhile, the total length of dislocations and the number of zinc blende phase atoms are also greater than those in Ga-faces. Further research found that the difference in edge dislocation with b = 1/3 〈11–20〉 is the main reason that causes the dislocations in N-faces longer than that in Ga-faces, which can reach about 3 times. However, the Shockley incomplete dislocation with b = 1/3 〈1–100〉 and other dislocations are slightly smaller than those in Ga-faces. This study innovatively researched the difference in the processing properties of the two GaN at the nano-scale, which provide a theoretical basis for guiding GaN in the processing of ultra-precision.

The deformation of single-crystal beta-phase gallium oxide (or β-Ga2O3) micro-pillars under compression was investigated with the aid of transmission electron microscopy. High-density stacking faults were the dominant deformation defects in the plastically deformed micro-pillars. Micro-cracks were found along (200), (001) and (010) lattice planes and fracture occurred along (200) lattice plane when compressive strain was sufficiently great. Lattice bending was also observed in the fractured pillar. The average fracture stress and strain of β-Ga2O3 being measured are 7.25 ± 1.11 GPa and 3.80 ± 0.57%, respectively, which have never been reported previously.

Surface and deformation characteristics of single crystal β-Ga2O3 under nanogrinding were investigated using nanoindentation and transmission electron microscopy. Nanocrystals, stacking faults, twins and dislocations were the main deformation patterns found in the grinding of this semiconductor crystal. An amorphous phase was found when the specific grinding energy was significantly high, which was initiated behind the occurrence of other defects. The occurrence sequence of defects is somehow different from that of other semiconductors such as silicon, germanium and gallium arsenide. The hardness of grinding-induced deformed layer was higher than that of the perfect β-Ga2O3 crystal. The thickness and hardness of the defect layer were both reduced when a finer grit size was used. The mechanism responsible for deformation was found to be related to the intrinsic stacking fault energy of β-Ga2O3 and the specific grinding energy being used.

Nano-scale Al2O3-ZrO2 eutectic ceramic structures with shapes of thin-wall and cylinder were prepared by ultrasonic-assisted laser engineered net shaping. In the preparation process, the power of ultrasonic was adjusted in real-time on the molten pool. The generation of refining grain by ultrasonic were discussed based on the principle of crystallography. Two methods to improve the fracture toughness were analyzed. The average eutectic spacing was 60–70 nm, and the fracture toughness was 7.67 MPa·m1/2.

A fully fundamental understanding of the roles of the glassy phase (GP) in Glass-Ceramics (GCs) during the cascade collisions remains elusive. In this work, an efficient Molecular dynamics (MD) model with continuous controlled melting and quenching procedures is proposed to mimic the cascade collisions considering the electron stopping effect. Then, the details of both structure evolution and the primary knock-on atom (PKA) behavior induced by the cascade collisions as well as thermal peak effect are observed. The results show that the roles of the GP layer during the cascade collisions can be defined as role I and role II according to the behavior of the PKA. The kinetic energy of the PKA decreases sharply when the PKA passes through the role I. However, the energy exchange between the PKA and the atoms in the GP layer is relatively less and smoother under the role II. Combined with the electron stopping effect and the high energy distorted atoms, the cascade collisions induce a large amount of energy loss in the GP layer. Besides, the distribution of kinetic energy is in good agreement with that of the Frenkel pairs. The mechanism behind the roles of the GP layer is the interaction between the high/low energy distortion atom group and the PKA.

An effective molecular dynamics model to describe heterogeneous materials like glass-ceramics is proposed. Based on the model, we find that the velocity direction of the primary knock-on atom (PKA) is more prone to deflect sharply in glassy phases (GP) than that in crystalline phases (CP). And the high-stress region in CP is more concentrated, while the distribution of the high-stress region in GP is relatively discrete. Typical topologies of the Frenkel pairs (FPs) show that the direction of FPs propagation has an obviously turn at the boundary. In the hot peak period, the off-site atoms induced by the cascade collisions in CP could rearrange to avoid the number of defects coming to a high point. However, once the distorted clusters form in GP, the dislocated atoms of the distorted clusters are hard to move back to their site due to the high energy barriers. The annihilation of defects is also blocked in GP. The derived results could help to further understand the evolution mechanism of the heterostructure and defects at the nanoscale. And the method of model construction could contribute to more exciting simulations.

Molecular Dynamics simulations were carried out to study the formation mechanism of subsurface damage during the process of nano-grinding of gallium nitride (GaN). The effects of grinding depths and speeds on the temperature, the radial distribution function, phase transition, dislocation and the damage layer were systematically investigated. The results showed that quantities of interstitial atom, vacancy defects, atomic clusters, “U"-shaped half dislocation loops and Phase transition atoms exist in the subsurface layer. Additionally, the temperature, dislocation density and the number of phase transition atoms are positively related with the grinding depths, and then resulting in the quality of subsurface decreases with the increase of grinding depths. Although the damage layer is more sensitive to the grinding depth, when the speed increases from 25 m/s to 50 m/s, the above parameters also increase slightly, thus the subsurface quality decreases. As the speed continues to grow, these parameters gradually decrease due to the sharp decrease in processing time, and the quality of subsurface layer improves. This study provides an insight into the subsurface damage mechanism for the low-damage processing of GaN.

Mirror milling is a new efficient and green technology of aircraft skin processing. Currently, the support head of mirror milling system is mostly a metallic sphere and the support area is smaller ...

A new soft abrasive grinding wheel (SAGW) used in chemo-mechanical grinding (CMG) was developed for machining silicon wafers. The wheel consisted of magnesia (MgO) soft abrasives, calcium carbonate (CaCO 3 ) additives and magnesium oxychloride bond. Surface topography, roughness and subsurface damage of the silicon wafers ground using the new SAGW were comprehensively investigated. The results showed that the grinding with the new SAGW produced a surface roughness of about 0.5 nm in R a and a subsurface damage layer of about 10 nm in thickness, which is comparable to that produced by chemo-mechanical polishing. This study also revealed that the chemical reactions between MgO abrasive, CaCO 3 additives and silicon material did occur during grinding, thereby generating a soft reactant layer on the ground surface. The reactant layer was easily removed during the grinding process.

The micro-ultrasonic machining (USM) is suitable for machining hard and brittle materials. When a micro hole is drilled deeply using micro-USM, machining speed slows down and the breakage of micro tool may occur. To solve this problem, this paper proposes the application the planetary movement of micro tool in high-aspect ratio micro holes drilling by micro-USM. The micro holes of about 92 μm in diameter with an aspect ratio larger than ten have been machined. The processing efficiency has been improved. The influence of planetary movement parameters on processing efficiency has been investigated

The effects of pressure and sliding velocity on the interface friction behavior during the chemical mechanical polishing process of diamond were investigated utilizing ReaxFF molecular dynamics, with a focus on the subsurface damage, friction force, and atom removal. Simulation results indicate that in the initial stage, the friction force depends on the number of interfacial C-C bonds and C-O-C bonds and shows a positive correlation with the pressure and sliding velocity. Later on, the friction force relies on the number of amorphous carbon atoms, and exhibits a negative correlation with the pressure and sliding velocity. Under low pressure, the carbon atoms are mainly removed along with the formation of C-C single bonds. In contrast, with increasing pressure, the carbon atoms are removed together with the formation of more C-C single and multiple bonds. This accounts for more extensive atom removal, followed by the more severe wear, as well as deeper subsurface damage. This study systematically evaluates the underlying influence mechanism of pressure and sliding velocity on the interface friction behavior from atomistic scale, thus elucidating technological parameters for ultra-precision and low-damage machining of diamond.

Wheel setting is difficult in a grinding process and may directly apply a negative impact on grinding accuracy and efficiency. This study presents a novel method for grinding wheel setting based on acoustic emissions. The method experimentally detects the acoustic emission (AE) signals that come from the touch-down of the grinding wheel with the workpiece. The experimental results show that the measured AE signals monotonically increase with grinding depth and can be used for detection of wheel setting in a grinding process with a detection accuracy better than 0.5μm.

Dressing parameters, which directly affect the flatness of the plate, are very important in planetary double-sided grinding dressing process. In this paper, trajectory and velocity equations of grit are studied. By comparing to the trajectory density of different annular regions, this paper puts forward an evaluation method of the shape of the plate and explores the impact of rotation speed on the shape of the plate. Finally, the experiments are performed by adjusting the rotation speed of the sun wheel and the plate. The results show that the flatness of the plate can be dressed below 0.01 mm, which validates the correctness of the theory.

A new support method used in aircraft skin mirror milling, liquid lubricating support, is proposed in order to solve the problems of scratching aircraft skin surface caused by rolling support or sliding support. The thickness and stiffness of liquid film between skin and support head are obtained with different feed pressure. The effects of thickness and stiffness of liquid film on surface quality and dimensional uniformity of workpiece are analyzed. The surface roughness is better under the condition of liquid film. With better film stiffness, dimensional uniformity is better, and actual axial cutting depth is closer to nominal axial cutting depth.

The molecular dynamic (MD) simulation of monocrystalline silicon under multiple grinding is carried out to study the effect of multiple grinding on the thickness of damage layer. Four grinding processes are conducted on (0 0 1) along 〈−1 0 0〉 direction. The depth of grinding of the first grinding is 20 A. The subsequent grinding is machining on the machined surface with a damage layer left by the first grinding. The second grinding is a spark-out process and the depth of grinding of the third and fourth grinding increases by 5 A compared with the previous grinding. The changes of structures and mechanical properties of the damage layer in the machined surface after the first grinding are investigated by coordination number (CN), the radial distribution functions (RDF) and nanoindentation. The thickness of the damage layer left by the first grinding can be reduced stably in the second and third grinding, but it will increase in the fourth grinding. Therefore, two more grinding steps between the third and fourth grinding are carried out. One is the spark-out process and the depth of grinding of the other increases by 2 A compared with the third grinding. The results show the spark-out process can remove the springback left by the previous grinding and promote the residual compressive stress in the machined surface, which can improve the accuracy and quality of grinding. The thickness of damage layer induced by the first grinding can be reduced without new damage structures generating. However, it cannot be reduced unlimited. When the thickness of damage layer reaches half of the original thickness, a re-grinding will cause new damage structures, and the thickness of damage layer will increase. The depth of grinding is suggested to be less than half of the original damage thickness to reduce the damage layer. The research results can be applied in the ultra-precision grinding of monocrystalline silicon to control the thickness of damage layer and improve the quality of machining.

Grinding force is an important indicator related to processing efficiency and residual strength in the progress of grinding SiC. With the method of ultrasonic assisted grinding (UAG), this paper studied the influence of four parameters on grinding force based on orthogonal experiment, namely vibration amplitude, depth of grinding, feed rate and spindle speed. A series of results with high efficiency and low grinding force were obtained. A regression empirical model under the condition of UAG was established and verified. It was also proved that ultrasonic vibration was conducive to improve the ground surface quality of workpiece.

The origin of drilling force in drilling with twist drill is quite complicated owning to the complex shape of the drill bit cutting edges. In this paper, the drilling experiments both with and without the ultrasonic were designed and conducted on aluminum alloy with pre-drilled hole. The drilling force was tested and the different effects between the cutting edges of the twist drill on the drilling force were analyzed under various drilling parameters including the spindle speed, feed rate and vibration amplitude. The drilling force of conventional drilling (CD) and ultrasonic assisted drilling (UAD) was characterized and the roles of the ultrasonic vibration in drilling were discussed.

In order to improve machining efficiency of sapphire wafer machining using the conventional loose abrasive process, fixed-abrasive diamond plates are investigated in this study for sapphire wafer grinding. Four vitrified bond diamond plates of different grain sizes (40 µm, 20 µm, 7 µm, and 2.5 µm) are developed and evaluated for grinding performance including surface roughness, surface topography, surface and subsurface damage, and material removal rate (MRR) of sapphire wafers. The material removal mechanisms, wafer surface finish, and quality of the diamond plates are also compared and discussed. The experiment results demonstrate that the surface material is removed in brittle mode when sapphire wafers are ground by the diamond plates with a grain size of 40 µm and 20 µm, and in ductile mode when that are ground by the diamond plates of grain sizes of 7 µm and 2.5 µm. The highest MRR value of 145.7 µm/min is acquired with the diamond plate with an abrasive size of 40 µm and the lowest surface roughness...

Chemical mechanical polishing(CMP) is an important method to achieve ultra-precision machining of diamond. However, the friction mechanism during CMP is not well understood due to a lack of information regarding the interface. Here, reactive molecular dynamics simulation was utilized to elucidate the friction behavior under different pressures and flow fates of polishing slurry. Simulation results indicated that pressure could accelerate the passivation of surface, Pauli repulsion between abrasive and substrate could withstand the applied load and prevent the two surfaces from reaching the C–C interaction range. The number of C atoms removed and the subsurface damage of substrate are the function of flow fate and pressure. This provides a theoretical support for the ultra-precision and low-damage machining of diamond.

Mechanical drilling can change the microstructure of the regions near the hole wall, remarkably affecting the working performance of precision parts. The present work investigated the microstructural evolution in the regions from the drilled hole wall to the inner matrix of the soft magnetic 49Fe-49Co-2V alloy after the common drilling experiments were carried out. The microstructures and microhardness in different regions near the hole wall along the radial direction were characterized with OM, SEM, TEM, EBSD and Vickers Microhardness tester. The experimental results show that the nearest region to the hole wall is constituted of nano-sized refined grains. It exhibits a disordered BCC phase due to the rapid cooling from the high temperature during the drilling, different from the dual-phase of BCC and B2 of the matrix. The second-nearest region to the hole wall is distributed by a huge number of dislocations, leading to a maximum in microhardness. The microstructural evolution contributes to the variation of the microhardness, which increases firstly, reaches a maximum, and then decreases to the level of the matrix with the distance increasing from the hole wall. This variation tendency is discussed in light of both refined grain-boundary strengthening and dislocation strengthening mechanisms. Keywords: 49Fe-49Co-2V alloy, Drilling, Microstructural evolution, Microhardness, Strengthening mechanisms

At present, CMP is the only ultra-precision machining technology that can achieve global flattening. Unfortunately, CMP processing efficiency is extremely unsatisfactory. Although the processing efficiency can be improved by increasing the alkaline concentration of CMP slurry, the surface quality will deteriorate rapidly due to excessive concentration. In this study, the removal characteristics of both uncorroded and precorroded Lu2O3 laser crystals were investigated based on nanoscratch tests with edge-forward Berkovich indenter. Further, the elastic deformation model considering both elastic extrusion and elastic recovery deformation was established. The origin of the microcracks was then discussed. The observed responses of surface quality were shown to depend greatly on the extent of elastic deformation prevalent during the nanoscratch and associated material removal processes.

The lapping and grinding induced wafers surface damage layers with the same roughness Ra were compared in terms of surface morphology, surface roughness PV, subsurface damage, material removal mechanism, and material removal rate of later chemical mechanical polishing. The results indicated that surface material on silicon wafer lapped using loose abrasive was removed in brittle mode, and that ground using diamond wheel was removed in both brittle mode and ductile mode. The silicon wafer produced by lapping and grinding had almost the same surface roughness Ra, however, the corresponding surface roughness PV induced by lapping was less than that induced by grinding. When using the chemical mechanical polishing to remove damage layer generated by lapping and grinding, the surface roughness Ra of lapped wafer decreased faster than that of ground wafer, but the material removal rate of lapped wafer was higher than that of ground wafer. Discussion was provided to explore the influence of surface morphology on material removal rate during polishing.

Two types of diamond wheel with a mesh size of 20,000 are developed. A novel approach for mechanical chemical grinding (MCG) is proposed using the diamond wheels developed. A wear layer of 56 nm in thickness is obtained on a silicon wafer, which is ground by the diamond wheel with ceria at a feed rate of 20 μm/min. It consists of an amorphous layer at the top and a damage crystalline layer beneath. The thickness of the wear layer is less than one third those ground using a conventional diamond wheel with a mesh size of 3000. Surface roughness R a and peak-to-valley values keep basically constant at 1 and 9.8 nm, respectively, with increasing feed rates from 5 to 20 μm/min, which is ground by the diamond wheel with ceria. Nanoscale wear layers are obtained on Si wafers ground by MCG in high efficiency, which is different from the traditional diamond grinding with thick wear layers and chemical mechanical grinding with low efficiency. The ground Si wafers are bright and absent of cracks. MCG paves the way for the applications in semiconductor and electronics industries.

The mechanical properties (hardness, elastic modulus) and subsurface damage of quartz glass at high temperature are studied by nanoindentation simulation based on molecular dynamics (MD). By heating the quartz crystal model to 3000[Formula: see text]K and annealing to 300[Formula: see text]K twice, the quartz glass model is prepared. According to the nanoindentation simulation results, the hardness of quartz glass decreases by 53.6% and the elastic modulus increases by 10.9% at 1500[Formula: see text]K compared to those at 300[Formula: see text]K. When the temperature rises from 300[Formula: see text]K to 1500[Formula: see text]K, the critical grinding depth of quartz glass increases from nanoscale to micron-scale. The investigation of subsurface damage shows that the damaged layer thickness decreases slightly with the increase of temperature. The damaged layer extends downward under the indenter at lower temperature and extends along the indenter at higher temperature.

Unidirectionally coherent and boundary-free nanotwinned (nt) mercury cadmium telluride (HgCdTe or MCT) was achieved under plastic deformation of nanoindentation. The hardness of nt-MCT is up to 47.2 GPa, which is two orders magnitude higher than that of monocrystalline MCT. This increased hardness originates from the unique composite nt structure, which exhibits a repeated pattern comprising a lamellar twin >11.5 nm thick, followed by one or several lamellar twins with thicknesses

Nanotwinned (nt) mercury cadmium telluride (HgCdTe or MCT) was prepared using nanoindentations. The hardness of nt-MCT is 100 times higher than that of monocrystalline counterparts. Transmission electron microscopy shows that the twin lamellae of nt-MCT prior to cyclic nanoindentations are distributed along two directions, intersecting at an angle of 76°. The nanotwinned microstructure of nt-MCT is stable after 100 cyclic nanoindentations. The loading–unloading curves of nt-MCT are basically invariable after 50 cycles, and have elastic characteristics.

This article reports a new ultra-precision grinding method for manufacturing wavy-tilt-dam mechanical face seals. It uses a horizontal rotary table, a horizontal swing table, and a vertical linear axis to perform micro-infeed grinding with a slightly inclined cup wheel using line contact kinematics at constant wheel depth of cut. The rotation motion of the rotary table, swing motion of the swing table, and reciprocating motion of the linear axis were numerically controlled so that the grinding contact arc between the cup wheel and the seal ring was a highly accurate approximation of the curves on the wavy-tilted surface bounded by its inner and outer peripheries and the trajectory of the contact arc formed the wavy-tilted surface. The sealing dam was generated when the rotary table rotated about the rotational axis and the swing table was locked in a position where the two end points of the grinding contact arc had the same height. This was expected to be an efficient method to manufacture wavy-tilt-dam m...