Improving the Efficiency of Turning Processing of Heat-Resistant Alloys by Introducing Ultrasonic Field Energy into the Cutting Zone

Studies have been carried out to assess the effectiveness of dry processing by the current preparations from the heat-resistant alloy CN45MVTUBR with mineral ceramic incisors with the introduction of the ultrasound-field energy treatment zone. It has been established that the use of ULTRASOUND in the rough treatment of mineral ceramic tools without coolant allows to reduce the depth of the defective layer in 1.5 times.

Plasma FIB Delayering and Nanoprobing with EBIRCH for Localizing Metal Shorts in DRAM

This paper demonstrates how to localize metal-to-metal short failures in DRAM, where defects can occur over a large area including the aluminum layer, by using the means of mechanical grinding, plasma FIB delayering, and EBIRCH (Electron Beam Induced Resistance Change). Our experiments show that a uniform mechanical grinding of an aluminum layer, and DX PFIB delayering, results in a high quality planer surface in the target layer and site, as the slope created during the grinding is compensated by PFIB delayering. This approach has advantages that are conducive to EBIRCH analysis. First, the target layer can be prepared at any given location (site-free). Second, the defective layer can be delayered to a desired depth without damage (layer-free). Last, after delayering, the surface of the device becomes evenly flat enough to allow the electron beam to evenly penetrate the device for EBIRCH analysis (higher-flatness).With the use of more advanced device preparation methods, EBIRCH analysis has a higher chance of successfully localizing metal line/via shorts even in a large region, which includes the aluminum layer.

Electrochemical removal of a defective layer after electroerosive shape forming

The possibilities of electrochemical removal of the defective layer from the surfaces of steel products, including those with a high carbon content, after electroerosion processing are considered. The influence of the processing mode parameters on the dynamics of metal removal and the quality of the resulting surface is investigated. Keywords electrochemical treatment, electroerosive treatment, defective layer, electrolyte composition, processing mode. [email protected]

MAGNESIOCHROMITE (MgCr2O4) SYNTHESIS: EFFECT OF MECHANICAL AND MICROWAVE PRETREATMENT

Magnesiochromite spinel synthesis based on oxides, hydroxides and nitrates of magnesium and chromium was investigated. The precursors reactivity was compared by means of effective rate constants calculated by Ginstling-Brounshtein equation. The possibility of use of this equation was confirmed by the dependences linearity with high linear approximation coefficients. The reactivity of MgO various forms (soft-burned, or caustic magnesite, and dead-burned, or periclase) in the spinel formation was compared. Oxide precursors (especially with the periclase participation) reacted with the substantially less rate in comparison with hydroxides and salts. The influence of a preliminary mechanical activation by impact-and-attrition (planetary mill) and attrition (ball-ring mill) action as well as a microwave treatment (2.45 GHz) was analyzed. The most positive effect of a mechanical treatment in a planetary mill that was associated with an activation of Mg and Cr compounds became apparent in the field of relatively low temperatures (700-1100 °С). For example, MgCr2O4 yield at 1000 °С and the joint impact treatment of oxides was twice as much than under the simple mixing. The subsequent temperature rising lead to some decrease of a pretreatment effect so long as diffusion coefficients in these conditions grew, so the reaction run rapidly even without a preliminary mechanical treatment. It was noticed that an appreciable reduction of MgO reactivity in the spinel formation after a certain attrition in a ball-ring mill linked to the plane sliding in cubic crystals and resulted in the removing of the most disordered and defective layer from grains and the plane surface uncovering. The combined method consisting of a mechanical treatment of magnesium and chromium nitrates mixture in a planetary mill and the subsequent burning in a thermal kiln (1000 °С) was considered as the most effective as it resulted in practically single product. The microwave treatment took up an intermediate position by the effectiveness.

Magnetic structure of Co–25%Sm sintered magnets after electrical discharge machining

Scanning electron microscopy and magnetic force microscopy were used to conduct the metallographic study of the surface microstructure of KS25 grade Co–25%Sm sintered rare-earth magnets after Electrical Discharge Machining (EDM). The chemical composition of the studied samples: Sm – 25 wt.%; Fe – 18 wt.%; Cu – 5 wt.%; Zr – 3 wt.%; Co – the rest. One of the sample surfaces was subjected to EDM in various ways with changes in such EDM parameters as the straight-line processing speed and offset. The microstructure of magnets contains four coexisting phases: SmCo5, Sm2Co17, Zr5Co3FeSm and Sm2O3. The grain size is 10–50 μm. Crystals of the Zr5Co3FeSm intermetallic compound are 1–5 μm in size, and globular inclusions of Sm2O3 samarium oxide are 2–10 μm. EDM affected the thickness and chemical composition of the defective layer. In general, the chemical composition varies slightly in the direction from the defective layer inward the sample: the content of Sm, Cu, O, and Zr decreases; the content of Fe and Co increases. At a distance of 500 μm from the defective layer inwards the sample, the grain size increases by 40–50 %, while the porosity decreases. At the same time, the size of Sm2O3 oxides slightly increases. The study of the magnetic structure on surfaces perpendicular to the axis of magnetization by means of magnetic force microscopy revealed the presence of a complex domain structure of grains in the form of a labyrinth with a domain size of ~3÷5 μm. Separate singledomain grains ~30÷50 μm in size were also found. Due to the material heating and oxidation, EDM promotes the domain structure of grains appearing in the form of a labyrinth instead of single-domain grains, and the SmCo5 → Sm2Co17 phase transition, which causes a decrease in coercive force.

Formation of the Properties of the Surface Layer during Multi-Stage Milling

The paper provides the results of experimental studies of changes in the depth of the defective layer during milling of various structural materials; shows the convergence of the experimental results with the data published in open-access publishing; substantiates a logical change in the depth of the defective layer at various stages of multi-stage machining; and builds probabilistic tables of milling accuracy.

Removal of Defective Layer after Electrical Discharge Machining

This study investigates the possibility of electrochemical removal of the defective layer formed on the surface of the product after its electrical discharge machining. A set of experiments was conducted in different electrolytes based on aqueous and aqueous-organic solvents. The experiments were to trace the influence of such settings of electrochemical machining as current density, electrolyte pumping speed, electrolyte temperature, and an electrode gap upon both the dynamics of metal removal and surface quality. Morphology of the obtained surface was examined by an Olympus BX-51Microscope. The dynamics of removing material (stock) from the work piece was inspected. Appropriate adjustments were made to the machining parameters during the machining of 65G steels, and a preferred composition was selected for the working medium. A sufficient design for production tools was proposed. Pitting corrosion was discovered on the surface of the samples in all studied modes of electrolysis. It was observed that switching from aqueous electrolyte to aqueous-organic electrolyte gave lower material removal rate and longer machining time accordingly. At the same time, a reduction in surface roughness was visualized, together with smaller pits and lower density of their distribution. The obtained results may be applied in operation design for electrochemical machining of steels with relatively high carbon contents.

Formation of a Defective Layer when Machining Brittle Materials

Parts made of modern brittle materials with high quality finish are widely used in manufacturing of optical and electronic devices as well as crucial assemblies in mechanical engineering products. Diamond machining enables generation of geometry without affecting the functional surface layers by heat. At the same time, brittle material cutting is accompanied by the formation of a defective layer on the machined surface due to the structural disturbances in the material caused by the applied cutting force. The paper discusses causes and the mechanism of the defective layer formation on the machined surface during non-free cutting of brittle materials and examines ways of reducing the size of the defective layer. Theoretical and computer-aided analysis is performed to determine the impact of the local stresses field in the zone of concentrated pressing force acting on the brittle plate surface. Using experimental methods, a defective layer formed after cutting notches on a silicon plate by a diamond tool is studied.

Study of the Efficiency of Ultrasonic Turning of Heat-Resistant Alloys with Tools from Mineral Ceramics

The results of the study of the effectiveness of high-speed ultrasonic turning of billets from heat-resistant nickel alloys without coolant are given. It was established that the introduction of ultrasonic field energy into the shaping zone reduces the contact temperature by 10–15% and the cutting force by 20–30%. However, this does not cause a decrease in metal removal performance due to a significant loss of strength and ease of cutting at temperatures above 800 C. As follows from the results, ultrasound helps to reduce the thickness of the defective layer, the formation of which is caused by thermal processes and phase transformations with the appearance of tensile residual stresses in the surface layer.