The Microstructural Revolution of Ti-6Al-4V Specimens Fabricated by Selective Laser Sintering of Pre-alloyed Powders

Selective laser sintering (SLS) is known as a cutting-edge technique to manufacture complex geometry products. Among various kinds of materials, Ti-6Al-4V is one of the most popular materials for the SLS process. The as-built Ti-6Al-4V products were widely applied in many applications such as aerospace, automobile, and especially in medical and implant parts. The purpose of this research is to investigate the microstructure and other properties of Ti6Al4V pre-alloyed powders produced by selective laser sintering technique. Through this research, the direct fabrication of Ti6Al4V metal object by SLS machine has been carried out using MetalSys250 machine. Different parameters of the SLS process were used to produce 1cm x1cmx1cm cubic samples and then microstructure, as well as mechanical properties of the as-built samples were investigated. Powder particles are fully dense, possess a spherical shape and are composed of acicular α phase. The as-build sample shows the oriented acicular martensitic phase with the defined columnar grain structures

Linear Approximation and Asymptotic Expansion of Solutions for a Nonlinear Carrier Wave Equation in an Annular Membrane with Robin-Dirichlet Conditions

This paper is devoted to the study of a nonlinear Carrier wave equation in an annular membrane associated with Robin-Dirichlet conditions. Existence and uniqueness of a weak solution are proved by using the linearization method for nonlinear terms combined with the Faedo-Galerkin method and the weak compact method. Furthermore, an asymptotic expansion of a weak solution of high order in a small parameter is established

Phase Structure and Magnetic Properties of Intermetallic Cu-Ni Alloy Nanopowders Synthesized by the Electrical Explosion of Wire

Cu-Ni composite nanoparticles were successfully synthesized by electrical explosion of wire (EEW) method. Cu-Ni alloy and twisted wires with various Ni contents were used as the feeding material for a 3 kV charging voltage EEW machine in an ethanol ambient chamber. The phase structure and magnetic properties of the as-fabricated samples were studied. It was established that the prepared powders after drying have a spherical form with the particle size is under 100 nm. XRD analysis indicated that the nanopowders consisted of binary Cu-Ni phases. Only pure phases of the intermetallic compound Cu-Ni (Cu0.81Ni0.19 and Cu3.8Ni) were observed in the XRD patterns of the samples. The synthesized intermetallic Cu-Ni alloy nanopowders reveal magnetic behaviors, however, the lower Ni content samples exhibited paramagnetic behaviors, meanwhile, the higher Ni content samples exposed ferromagnetic properties

Mineralogical Characterization of Di Linh Bentonite, Vietnam : A Methodological Approach of X-ray Diffraction and Transmission Electron Microscopy

Vietnam has decided to establish nuclear power as further energy option. In order to develop a Vietnamese reference bentonite as potential barrier in a final repository for high radioactive waste, a detailed mineralogical investigation of Di Linh bentonite (Lam Dong province), lacustrine clay, was carried out by different methods especially transmission electron microscopy (TEM) linked with energy-dispersive X-ray (EDX). From a sample homogenized from 5 tones of the bentonite, mineral formulae of clay particles was calculated The calculation also focuses on randomly interstratifications of two and three members. The fraction <2 μm of Di Linh bentonite is composed mainly by montmorillonite (Ca0.06Mg0.03Na0.09K0.03Al1.39Fe0.25Mg0.26(OH)2 Si3.96Al0.04O10) and regular ordering (R1) illite-smectite interstratifications with K- and charge-deficiency (Ca0.04Mg0.07Na0.18K0.16Al1.76Fe0.08Mg0.16(OH)2Si3.62Al0.38O10). Additionally, Fe-poor kaolinite-smectite-vermiculite interstratifications and trace of Fe-rich chloritesmectite- vermiculite interstatifications were identified. TEM-investigations showed analytical proofs of the sedimentary character of smectite formation in the Di Linh deposit. Parent muscovite was weathered in several steps in two different environments: (i) K-leaching and layer-wise alteration into kaolinite; (ii) further edge- controlled alteration of mica into lathlike montmorillonite particles under dissolution of kaolinite layers from former kaolinite-mica intergrowths. Mineralogical composition of the Di Linh bentonite with mainly montmorillonite and illite-rich illite-smectite interstratifications shows that the Di Linh bentonite can be a suitable barrier candidate in final repositories.Godkänd; 2014; 20150212 (svek

Pellet feed improvements through vitamin c supplementation for snakehead, channa striata (Bloch 1793), culture

Vitamin C, or ascorbic acid (AA), is important in growth and physiological functions of fish. Six soybean meal-based (SBM) diets containing 0, 125, 250, 500, 1000 and 2000 mg.kg-1 of AA were fed to snakehead, Channa striata (Bloch 1793) (initial weight 6.63 + 0.16 g) for 8 weeks in the laboratory. Survival of snakehead in the 250 and 500 mg.kg-1 treatments was significantly higher (P \u3c 0.05) than the control, but not in the other treatments. Final weight and specific growth rate (SGR) of fish in all the AA-supplemented diet treatments were significantly higher (P \u3c 0.05) than the control. Feed intake (FI), feed conversion ratio (FCR), and protein efficiency ratio (PER) also differed significantly, but not in a clearly dose-dependent manner. The requirement of AA for snakehead was calculated to be 277 mg.kg-1. No vertebral anomalies were observed. Erythrocyte count was significantly (P \u3c 0.05) higher at 1000 and 2000 mg.kg-1 than at 0 and 125 mg.kg-1. Fish in 250 mg.kg-1 had significantly (P \u3c 0.05) higher leukocyte count than those in 0, 1000, and 2000 mg.kg-1. A bacterial challenge test with Aeromonas hydrophila revealed that 500 and 1000 mg.kg-1 had the lowest cumulative mortality. In an on-farm trial, SBM-based and commercial diets augmented with 0, 500, 750, or 1000 mg.kg-1 AA were fed to C. striata for 23 weeks. All AA-supplemented SBM-based diets provided significantly (P \u3c 0.05) higher final weights and overall yield than did all the AA-supplemented commercial diets. Maximum survival (85.3 %), final fish weight (573.5 g), yield (293.3 kg.hapa-1) and profit (0.38 USD.kg fish-1), as well as minimum FCR (1.16), production cost (1.12 USD.kg fish-1) and feed cost (0.98 USD.kg fish-1) were obtained with the 500 mg.kg-1 SBM diet