Features of phase and structure formation in a titanium matrix composites reinforced with a multicomponent alloy of the Ti-Fe-Mn-Si-C(B) system

The practice of building in difficult geological and hydrogeological conditions found wide use grout mixes used to fill old mine workings or large underground cavities. However, the traditional oil well cementing cementing solutions causes a large flow rate of the solution in the absorbing horizons and its erosion under the influence of the tributaries of the water. A problem arises, which is associated with insufficient provision of guaranteed strength and durability fixed soil or structures, as well as in environmental and health safety used injectable compositions. A promising direction in the construction material science is the approach to the directed structure formation of composites that are initiated by the introduction of nanomodifiers, having ultra-small dimensions in super small quantities.The aim of this work is to develop new cement compositions with improved processing characteristics, based on the comparison of the effect of additives aluminosilicate nanotubes (ANT) and boehmite on the structure formation of cement composites. The main components of the composite solution were: bentonite Π2T2A, ANT, bemit, cement and liquid glass.Performed x - ray phase analysis of boehmite and ANT. Studied the structure formation of composite systems. It is established that the highest rate of structure formation is achieved at a concentration of boehmite 0.208% by weight of cement. Relative to the control sample, the rate of structure formation increases 1.3 times. With the introduction of additives ANT the greatest strength of the composite solutions was achieved with the introduction of 0.125% by weight of cement. It was found that cement compositions based on ANT after 28 days of storage the strength of the compositions is increased almost 2 times compared to the composite solution with additives boehmite. It is established that a promising direction for obtaining of composite systems is the modification due to the introduction of environmentally friendly aluminosilicate nanotubes based on natural mineral.

Surface phenomena during the early stages of sintering in steels modified with Fe–Mn–Si–C master alloys

Preparation of porous-structured LiFePO4/C composite by vacuum sintering for lithium-ion battery

For the synthesis of composites based on the MAX-phase TiSiC, different approaches based on heat treatment and consolidation of powder mixtures 3Ti/1.8SiC/0.8C, 2Ti/1.2SiC/1.8TiC are considered. The first approach consists in powder heat treatment by vacuum sintering at 1400°C for 1 h and spark plasma sintering at 1350°C and a pressure of 50 MPa. The second approach consists in two-stage heat treatment, including additional consolidation by spark plasma sintering of vacuum-sintered composites. For each of the approaches, the influence of temperature and holding time during spark plasma sintering on the phase composition, density and porosity of the obtained composites has been determined. It is found that the consolidation of TiSiC–TiC–TiSi–TiSi and TiSiC–TiC composites obtained by vacuum sintering by spark plasma sintering with the addition of 5 wt. % SiC leads to the formation of high-density Ti3SiC2–TiC–TiSi2 composites with an open porosity index of up to 0.3% and MAX-phase content from 9 to 33 vol. % depending on the sintering temperature (1300–1400°C). It is shown that the microstructure of the composite surfaces synthesized by spark plasma is represented by agglomerates of MAX-phase grains of TiSiC, TiC and inclusions of secondary phases (SiC, TiSi — depending on the sintered composition).

The purpose of this work was to investigate physicochemical conditions of formation and features of structure formation of molybdenum-base composites and, in particular, to study the adhesion characteristics and features of contact interaction in Mo-Cu-Ni(Co) systems, to investigate the distribution of the basic elements and impurities, the phase composition, the structure, and certain properties of the materials and parts. A combination of methods was used including x-ray spectral microanalysis, Auger spectroscopy, x-ray diffraction phase and structure analysis, microhardness and hot hardness methods, scanning electron microscopy, and metallography by optical microscopy. The influence of hot hardness of the composite was selected as the criterion of evaluation and it was found that increases in hot hardness and in high-temperature oxidation increased the life and service properties of electrodes used for spot welding and brazing in production.

In the process of production of Ti-6Al-4V alloy, which consists of blending of extra-low-chlorine T i and 60mass%Al-40mass%V master alloy, cold compaction, vacuum sintering and hot forging, the influence of compaction stress and sintering conditions on the density of sintered compacts and various forging characteristics of the sintered compacts were investigated.The increasing rate of the compact density during heating up to sintering temperature depends on density of the green compact and heating time, with which it has a linear correlation. The increasing rate of the compact density during holding at sintering temperature is in proportion to the power of the holding time. The empirical equation of the density change during sintering was derived from these findings, and confirmed to coincide well with experimental values.The density after forging is strongly influenced by pressure and plastic deformation during forging. Tile holes in the compact can be rejected completely by suitable forging condition, except the surface area of the compact where the temperature reduces rapidly compared with that of the inner part of the compact.

Effects of aluminum content and sintering temperature on microstructures of TiCp/Al master alloy were investigated. The DSC results showed that reaction temperatures of the Al-Ti-C system were influenced by aluminum content. The average grain size of TiCp in the master alloy was 0.5～1μm with 40wt% Al content at 750°C sintering temperature. TiCp/AZ91 composites were fabricated through remelting TiCp/Al master alloy in magnesium alloy. Microstructural characterization of the TiCp/AZ91 composites showed relatively uniform distribution of TiC particulates in the matrix material and the hardness of the composites was improved significantly.

Phase formation and evolution during transient liquid phase sintering of MIM418 superalloy with master alloy addition

Evolution of aluminum particle-involved phase transformation and pore structure in an elemental Fe–Mn–Al–C powder compact during vacuum sintering

DEVELOPMENTS IN VACUUM SINTERING FURNACES

A new Al–5Ti–0.75B–0.2C master alloy was successfully prepared by self-propagating high-temperature (SHS) reaction from an Al–Ti–B4C system with molten Al. Microstructure and phase characterization of the prepared Al–5Ti–0.75B–0.2C master alloy show that the nearly spherical TiC particles, hexagonal or rectangular TiB2 particles, and block-like TiAl3 particles distribute uniformly in the aluminum matrix. Grain refining test on commercial pure aluminum indicates that Al–5Ti–0.75B–0.2C master alloy exhibits a better grain refining performance than Al–5Ti–1B master alloy. By addition of 0.2 wt% Al–5Ti–0.75B–0.2C master alloy, the average grain size of α-Al can be effectively refined to 160 ± 5 μm from about 3000 μm, and the tensile strength and elongation are increased by about 20% and 14.1% due to the grain refinement.

Nearly dense Ti–6Al–4V/TiB composites manufactured via hydrogen assisted BEPM

High speed steels processed by Powder Metallurgy (PM) techniques present better mechanical properties when compared with similar steels obtained by the conventional process of cast to ingot and hot working. PM techniques produce improved microstructures with smaller and better distribution of carbides. Liquid phase sintering high speed steel seems to be a cheaper processing route in the manufacturing of tool steels if compared to the well-known and expansive hot isostatic pressing high speed steels. The introduction of niobium as alloying element began with the object of replacing elements like vanadium (V) and tungsten (W). Phase liquid sintering consists in a manufacturing technique to process high speed steels by powder metallurgy. The aim of this work of research is to process and obtain AISI M2 and M3:2 with and without the addition of niobium carbide by high energy milling, cold uniaxial compaction and vacuum sintering in the presence of a liquid phase. The powders of the AISI M2 and M3:2 were processed by high energy milling adding a small quantity of niobium carbide (6% in mass), then the powders were characterized by means of X-ray diffraction (XRD) and scanning electron Microscopy (SEM) plus energy dispersion spectroscopy (EDS) in order to evaluate the milling process. The powders of the AISI M2 and M3:2 with the addition of niobium carbide (NbC) were uniaxially cold compacted and then submitted to vacuum sintering. The sintered samples had their microstructure, porosity and carbide distribution observed and evaluated by means of Scanning Electron Microscopy (SEM) and the mechanical property of hardness was investigated by means of Vickers hardness tests. At least five samples of each steel were investigated.

Nowadays, aluminum alloys with silicon are the most widespread construction materials. To increase the mechanical properties of aluminum alloys, modifying by Sr, Ti, and B are used. However, in the foundries, when using scrap and secondary aluminum alloys, the modifying elements are accumulated in alloys in the form of intermetallic particles that decrease castability. This is because of the modifiers have a short time effect and are not activated when remelting. Hence it is necessary to add the modifiers without reference to intermetallic particles that are exactly presented in the melt. This work investigated the effect of Sr, Ti, and B additions on A356.2 aluminum alloy fluidity obtained by vacuum fluidity test. It was shown that when AlSr10 and AlTi5B1 commercial master alloys are used (up to 0.3 wt.% Sr and 0.5 wt.%Ti), no fluidity decrease is observed. However, adding the same quantity of Ti with the homemade AlTi4 master alloy leads to a considerable fluidity decrease. With the help of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), the microstructure and phase composition of master alloys and A356.2 alloy after the addition of mentioned master alloys were investigated. Additionally, Thermo- Calc software evaluated the influence of modifier additions on alloy phase composition and phase transition temperatures. It was established that the influence of the modifier additions on the fluidity of the A356.2 alloy is connected with the shape and size of crystals that contained modifier elements in the structure of the master alloy. When the coarse crystals of that phases are present, these crystals’ incomplete dissolution is possible, inhibiting the free melt flow.

In PM steels, alloying through master alloy (MA) addition enables the introduction of oxygen-sensitive elements such as Cr, Mn, and Si. These elements offer cost-effective and sustainable alternatives to Cu and Ni, enhancing hardenability and performance. This study investigates the atomisation of Fe-Cr-Mn-Si-C MA powders using three different techniques: water atomisation, gas atomisation, and gas atomisation-water cooling. The MA powders were sieved into two size fractions and mixed with Fe – 0.85 wt.% Mo pre-alloyed base powder and graphite. MA powder characterisation, compressibility, and dilatometry-sintering experiments were performed to evaluate the different atomisation techniques, and liquid phase formation at various sintering temperatures. Additionally, industrial sintering trials were conducted, and mechanical properties were assessed to understand the behaviour of sintered samples. The results indicate that MA addition improves the hardenability and performance, especially after sintering above 1200°C, once the MA melting and alloy homogenisation have occurred.