A mesoscopic mechanical model based on the Mori-Tanaka method and Eshelby’s inclusion theory was presented to investigate the uniform elastic deformation behavior of Ti6Al4V with β-Ti and α-Ti phases. In particular, elastic mechanics field equations of inclusion and matrix phases were established separately, and several crystal plane diffraction elastic constants were predicted under uniaxial loading in this model. The results demonstrated that diffracted crystal plane elastic constants diversified with the elastic stiffness of the composition phase. In consequence, elastic deformation of one particular phase is related to the constraint of the whole deformation of all the phases constituting the materials. In this work, diffracted crystal plane elastic constants corresponding to different phases exert a substantial role in the determination of stresses by diffraction methods. Several numerical simulation results were compared and discussed.
The CVD diamond film with favorable adhesion and relatively thinner thickness is essential facing for its application on drills for machining carbon fiber reinforced plastics (CFRP), with regard to either the tool lifetime or the machining quality. A 500-nm-thick CrN layer was deposited by the cathode arc technique on slight chemical etched WC–Co 6[Formula: see text]wt.% drill, and nano-crystalline diamond (NCD) is subsequently deposited by the hot filament chemical vapor deposition (HFCVD) technique. The same NCD film is also deposited on the drills pretreated only by the slight chemical etching or the CrN interlayer, which are adopted as comparisons in the present study. The nucleation and growth of diamond film and the cutting performance of the coated drills are systematically studied. The results show that the drill pretreated by the slight chemical etching and CrN interlayer can acquire highest nucleation density (ND) compared to the other pretreatment methods as it sufficiently prevents the Co diffusion. The diamond-coated drill with deep chemical etching was used for comparison to study the machining quality when drilling CFRP. During machining the CFRP, the failure mode of the diamond-coated drill is mainly the delamination and peeling off of the diamond film at areas with stress concentration, while the diamond-coated drill pretreated by slight chemical etching [Formula: see text] CrN interlayer can retard such failure. The exit hole quality of CRFP machined by drill pretreated with slight chemical etching [Formula: see text] CrN interlayer is better than that by drill pretreated with deep chemical etching, which is ascribed to the different cutting edges of the drills.
Recrystallization behavior and microstructure of cold rolling Co41Ni33Al26 alloy were investigated by optical observation and hardness tester.Magnetic properties and martensite transformation were studied by vibrating sample magnetometer(VSM)and differential scanning calorimetry(DSC)respectively.The results show that the cold rolling Co41Ni33Al26 alloy with a high compress reduction about 43.65% recrystallizes below 1000℃.The volume fraction of β phase increases with the increase of quenching temperature.Many micro-cracks exist at the interface of β/γ phases in cold rolling microstructure due to the disaccorded deforming of β/γ two phases and their existing are benefited to plastic deformation.Furthermore those cracks disappeared when quenching above 1200℃,it means that this alloy have a self repairing ability.Both the values of martensite transformation temperature and Curie point are elevated with the increase of quenching temperature and Curie points are always higher than the martensite transformation temperatures at different quenching temperatures,moreover,magnetocrystalline anisotropy of martensitic phase is higher than that of β mother phase,these results suggest that Co41Ni33Al26 alloy is a promising ferromagnetic shape memory alloy.
Hot-deformed Nd-Pr-Fe-B-based nanocomposite magnets with different values of compressive true strain ε were prepared by the die-upset method. The crystallographic texture quantified as the X-ray diffraction intensity ratio of (004) to (220) peaks of the (Nd, Pr) 2 Fe 14 B phase increased from 0.6 for ε = 0 to 2.06 for ε = 2.30, and correspondingly, the magnetic anisotropy was enhanced significantly with ε. The mechanism for texture formation is explained as the preferential growth of the (Nd, Pr) 2 Fe 14 B grains with c-axis closer to the direction of stress in the process of deformation.
Nd2Fe14B and Sm2Co17 particles of submicrometre sizes have been prepared by ball milling in a magnetic field. Structural and magnetic characterization reveal that these submicrometre particles milled in a magnetic field, consisting of nanosize grains, exhibit strong magnetic anisotropy compared with the particles milled without a magnetic field. Based on in situ observations of the field-ball milling in a transparent container, the mechanism of field-induced anisotropy in the nanostructured hard magnetic particles is discussed.
Electrodes made of graphite material are widely used for electro discharge machining. The performance of physical vapor deposition AlTiN and chemical vapor deposition diamond-coated carbide end-milling tools in dry high-speed milling of electro discharge machining graphite was investigated, also adopting an uncoated one as a comparison. The quality of as-deposited diamond film was evaluated by Raman spectroscopy. The adhesion between the coating and the substrate was assessed by indentation test. The tool life and wear mechanism of the milling tools, the cutting forces during tests, as well as the roughness of processed surfaces were systematically studied. It is found that the diamond coating has lower adhesion than the AlTiN coating under the same load. Coating delamination and chipping, irregularly zigzag side flank wear, concave structure on the cutting edge are primary wear patterns for the diamond-coated tool. While different primary wear patterns, including uniform polishing abrasive flank wear and crater rake wear, are observed on the AlTiN-coated tool. Besides, the total cutting force of the diamond-coated tool is larger than that of the AlTiN-coated tool when the diamond-coated tool side flank wear value reaches 0.06 mm, attributed to the different wear patterns. Another notable result is clarified that the chipping of the diamond coating can cause significant increment in the feed force, radial force and worked surface roughness.
To research the effect of severe plastic deformation on the heat-resistant aluminum alloys,Al-Cu-Mg-Ag heat-resistant alloys were prepared by ingot metallurgy technology and equal channel angular pressing(ECAP) tests were carried out.The microstructure and mechanical properties of the alloys were investigated using microscopy,differential scanning calorimetry and hardness tester.It is shown that the ECAP in the solid solution and quenching state with aging treatment was quite effective in refining grains to 2 μm and improving the mechanical properties and heat-resistant properties.The ECAP treatment accelerates the aging hardening process of the extruded alloys,and increases the density of precipitate phase.
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