Microstructure Appearance of TC4 Titanium Alloy Welded Join by Pulsed Electron Beam

Study on microstructure appearance of 3 mm thick TC4 titanium alloy welded join by common electron beam and pulsed electron beam were carried out. Experimental results show that pulsed electron beam improved grain size and decreased the cooling velocity of weld metal by oscillation and fast cooling effect, the acicular martensite decomposes β phase and transforms to finer and more α′ phase, which shows an interwoven pattern.

CRYSTALLIZATION HEAT OF HIGH HEAT CONDUCTING POLYMER COMPOSITES BASED ON POLYETHYLENE FILLED WITH COPPER MICROPARTICLES

The results of experimental studies of the specific heat of crystallization of polymer composites based on polyethylene filled with copper microparticles are presented. Data concerning the effects on the crystallization heat of the studied composites on such factors as the mass fraction of the filler and the cooling rate of the composites from the melt are presented. The corresponding studies were performed with a change in the mass fraction of the filler from 0.3% to 4.0% and the cooling velocity of the microcomposite from the melt from 1 K/min to 20 K/min. It is shown that the specific heat of crystallization decreases significantly with increasing speed VT and the mass fraction of the filler ω. The results of the comparison of the values of the specific heat of crystallization of polymer microcomposite, obtained by a method based on the mixing of components in a dry form and in a polymer melt, are presented. It was established that the first of the indicated methods correspond to large values of the heat of crystallization.

MODELISATION DE L'INFLUENCE DU TRAITEMENT THERMIQUE SUR LES PROPRIETES MECANIQUES DES ALLIAGES ALUMINIUM-CUIVRE (Al-Cu)

In order to master and improve the quality and properties of the final products, the major industrial challenge lies in the possibility of controlling the morphology, size of microstructures that reside within the molded pieces, as well as their defects; this is the fundamental reason according to which we are more and more interested in mastering the growth and germination of such alloys, as well as the developing structures, at the time of solidification process. The modeling reveals as a valuable aid in the mastery of the formation of such heterogeneousness: segregation cells that are incompatible with industrial requirements.  The whole work focuses upon the modeling of the segregation phenomenon of the four hypoeutectic alloys, Al1%Cu, Al2%Cu, Al3%Cu et Al4%Cu, as well as the copper effect upon certain mechanical properties of aluminum. Usually, the microstructure and mechanical behavior of such alloys as Al-Cu are directly influenced by some parameters such as composition, cooling velocity and homogenization process.

MODELING OF THE INFLUENCE OF THERMIC TREATMENT UPON THE MECHANICAL PROPERTIES OF ALUMINUM-TIN ALLOYS

In order to master and improve the quality and properties of the final products, the major industrial challenge lies in the possibility of controlling the morphology, size of microstructures that reside within the molded pieces, as well as their defects; this is the fundamental reason according to which we are more and more interested in mastering the growth and germination of such alloys, as well as the developing structures, at the time of solidification process. The modeling reveals as a valuable aid in the mastery of the formation of such heterogeneousness: segregation cells that are incompatible with industrial requirements. The whole work focuses upon the modeling of the segregation phenomenon of the four hypoeutectic alloys, Al1%Sn, Al2%Sn, Al3%Sn and Al4%Sn, as well as the tin effect upon certain mechanical properties of aluminum. Usually, the microstructure and mechanical  behavior of such alloys as Al-Sn are directly influenced by some parameters such as composition, cooling velocity and homogenization process.

Effects of Melt Cyclical Superheating Conditions on the Microstructure of FeSi2 Alloy

In order to avoid coarse primary-precipitated ε phase which prolong α+ε→β phase transition time in FeSi2 material prepared by conventional casting, a cyclical superheating process of melt for preparing FeSi2 with complete α+ε eutectic structure was proposed. The effects of melt superheating conditions on the microstructure of FeSi2 were investigated. The results showed that, with the increase of the superheating temperature, the superheating time, the recycling times and the cooling velocity, the size and quantity of the ε phase reduced. Meanwhile, the number of the fine eutectic structure increased. FeSi2 sample with uniform and complete α+ε eutectic structure was successfully prepared in the conditions of melt superheating temperature at 1550°C, superheating time for 10mins, recycling 3 times,melt cooling rate of 30°C/s.

Effect of Cooling Velocity and Casting Temperature on Solidification Microstructure of Pure Al Refinement under Al-5Ti-B Alloy

The texture feature and grain refinement effect of Al-5Ti-B alloy on pure aluminum were analyzed and by adjusting the cooling velocity and casting temperature of molten aluminum,the influence of Al-5Ti-B alloy on solidification microstructure of pure aluminum was studied by using X-ray diffraction (XRD), scanning electron microscopy (SEM), optical microscopy (OM) and other experimental methods. The results show that: Al-5Ti-B alloy is composed of Al, TiAl3 and TiB2. under the same solidified velocity,with the increase of the mass fraction of Al-5Ti-B alloy among the aluminum melt, solidification structure of pure aluminum equiaxed dendrite size small. But at the same additives of Al-5Ti-B alloy, the cooling rate and casting temperature have significant effects on the number and size of equiaxial crystal. Faster cooling rate and lower casting temperature of molten aluminum are favorable for the formation of thin equiaxial crystal of solidification microstructure.

Martensite Phase Transform during Nitrogen-Spray Water Jet Quenching

Nitrogen-spray water jet quenching is a new kind of quenching, whose cooling velocity can be controlled. Thus different phase can be achieved according requirement, which can improve the characteristic of material. 9SiCr alloy steel was tested during Nitrogen-spray water jet quenching. The continuous cooling curves of 9SiCr under mixture of Nitrogen-spray water quenching for different pressure and mixture ratio of Nitrogen and spray water are obtained. After quenching, the metallographic structures were investigated, in which the uniform martensite was obtained after quenching.

Study of Casting Self-Colored Liquid Crystalline Solid Films of Hydroxypropyl Cellulose

Solutions of lyotropic cholesteric liquid crystalline hydroxypropyl cellulose (HPC) in water would be self-colored due to the selective reflection of visible light, depending on the solution concentration. Colored coating of the liquid crystalline aqueous HPC solutions was attempted to apply. HPC solid films were found which could cast from the liquid crystalline solutions at different conditions such as solution concentration and different drying temperature. Experiments show that both solution concentration and cooling velocity play an important effect in controlling the color of HPC films.