Ciência & Tecnologia dos Materiais最新文献

The Mo-rich TCP phases P and μ are susceptible to hot cracking in the alloy C-276. These phases can be reduced by quashing the microsegregation of alloying element Mo in the weldment. The present study investigates the possibility of reducing the microsegregation by post weld heat treatment of the weldments. The joints were fabricated by pulsed current gas tungsten arc welding by employing different filler wires ERNiCrMo-3 and ERNiCrMo-4. The weld joints were characterized with respect to microstructure, Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS), and tensile test. The optical microstructure revealed the fine equiaxed dendrites were observed in the fusion zone. EDS analysis revealed the presence of Mo-rich segregation in the subgrain boundary in the ERNiCrMo-3 and absence in the later. The results show that selection of temperature to dissolve Mo segregation is not sufficient in the case of ERNiCrMo-3. The tensile result shows the improved strength in both weldments compared to base metal.

The present investigation deals with the weldability, structure – property relationship of dissimilar metallurgical joints involving Nickel based superalloy Inconel 718 and ferritic stainless steel AISI 430 using pulsed current gas tungsten welding (PCGTAW) process employing ER2553 and ERNiCrMo-4 filler wires. NDT analysis and macrostructure examination corroborated for defect free weldments. Microstructure studies revealed the presence of unmixed zone at the weld interface of Inconel 718 whereas grain coarsening effect was observed at the heat effected zone (HAZ) of AISI 430. Both cellular and equiaxed dendrites were dominated at the fusion zone of ERNiCrMo-4 weldment; whereas different types of ferrite morphologies such as delta and widmanstätten ferrite were observed at the cap and middle zones of ER2553 fusion zone respectively. It was opined that the tensile failures occurred at the parent metal of AISI 430 for both the fillers. Charpy V-notch studies showed that ERNiCrMo-4 weldment exhibited better impact toughness than ER2553 weldment. Similarly the bend test also recommended the use of ERNiCrMo-4 filler due to the acquaintance of excellent bending strength and soundness. This study also addressed the structure – property relationships of these weldments. The outcomes of the study would be highly beneficial to the nuclear, aerospace and petrochemical industries.

In the present investigation, AlSi17 Aluminum alloy closed-cell foam is fabricated through Melt route process using Calcium powder as thickening agent and Titanium hydride as foaming agent along with the addition of 10wt% Silicon Carbide particles. The effect of pore and pore size on the deformation mechanism under static loading conditions is studied. Also, the fabricated foam properties are analyzed after the completion of the test. The strain rate loading conditions of the compression test conducted on the Al foam lies in the range of 10^-3s^-1 to 10s^-1 and the above investigations are carried out according to the loading conditions. The Artificial Neural Artwork (ANN) approach is employed for predicting the compressive deformation of the fabricated Al alloy foam using simulations. The Plateau stress data is obtained from the compression tests and the neural network functions are successively modeled and later the specific energy absorption (SEA) is calculated from the plateau stress. The simulation results of the ANN are in good agreement with the compression test results and the predictions are performed with highest accuracy.

In this work, CMC was synthesized from cellulose obtained from coir fibres. The obtained CMC yield was about 64.0%. The Degree of Substitution value obtained was 0.44. The spectral pattern and thermogravimetric analysis of the synthesized CMC and cellulose were evaluated using FT-IR, XRD, and TGA/DTG. Characterization of the cellulose and CMC revealed their high crystallinity with cellulose showing a lower crystallinity value due to its lignin content. The CMC also showed a higher degree of crystallinity (56.93%) and hydrogen bonding compared to some earlier literature reports for CMC. The DTG curve revealed that the CMC had a maximum rate of degradation at about 310 °C. The FT-IR spectra of the obtained CMC showed a finger print region characteristic of CMC (1590 cm-1). This work shows that the spectral characteristic and crystallinity of CMC can be related to the synthetic method applied in obtaining the cellulose prior to CMC synthesis.

Titanium and its alloys have been increasingly used since the 1950s, because of its excellent characteristics, such as the specific resistance, corrosion resistance, and biocompatibility, among others. The most employed alloys are the alpha-beta Ti6Al4V (representing 50% of the market), normally used in devices that demand optimized designs and complex technological properties. The manufacture of components in titanium requires dedicated equipment and the combination of different technologies, like electrical discharge machining, five-axis machining, investment casting, additive manufacturing and others. This work presents a literature review of casting, machining and additive manufacturing technologies relative to titanium parts manufacturing, indicating the most common problems and the solutions proposed, with special empahsis to Ti6Al4V, due to its wide industrial use. The goal is presenting a comparative experimental study of the surface finishing, geometric accuracy and microhardness, in a Ti6Al4V impeller manufactured by Investment Casting, Machining and Selective Laser Melting.

The aim of this work is a patent search on cork materials, their manufacture processes and their applications, in the period 2010-2015, using Patenscope (search of international and national patent collections) from the World International Property Organization. 182 patent applications were found. They were classified in three major groups and by origin of application. This is a helpful tool for researchers, students and different professionals in the field of cork.