In recent years, there has been a significant thrust toward the development of novel implant alloys based on β-Ti with low Young’s modulus to prevent stress shielding. In this study, porous Ti–Nb–Ta–Zr alloys with porosity of <55% and macro-pore size of 100–400 μm for biomedical applications were successfully fabricated by a space-holder method. The microstructure and compressive behavior were studied. The results show that the micro-pore size of porous Ti–Nb–Ta–Zr alloys decreases with an increase in the amount of the process control agent (PCA), which has no obvious effect on the porosity and the macro-pore size formed by the space holder. Porous Ti–Nb–Ta–Zr alloys fail mainly because of the cleavage and ductile fracture with some dimples in compression. The compressive modulus increases from 0.6 to 6.5 GPa with the increase in the PCA and decrease of the space holder. The influence mechanism has been analyzed by the finite element calculation and the Gibson–Ashby model.

This paper aims at understanding the texture evolution in extruded oxide dispersion strengthened 18Cr ferritic steel during high-temperature uniaxial compression testing at 1,423 K at a strain rate of 0.01/s based on extensive electron back scatter diffraction characterization. The α-fiber texture is observed along the extrusion direction (ED) in the initial microstructure. The flow curves generated during uniaxial compression test are used to determine the associated hardening parameters. In addition, the degree of texture evolution after deformation along the ED and the transverse direction (TD) with respect to the initial condition has been predicted using VPSC-5 constitutive model. The prediction shows that the deformation along the ED produces a dominant γ-fiber texture in contrast to the TD. This is in agreement with the experimental results where γ-fiber texture is observed, due to enhanced dynamic recrystallization at high-temperature deformation.

Flat products of carbon nanotubes (CNTs) reinforced Al matrix composites were fabricated using flake powder metallurgy via shift-speed ball milling and hot-rolling. The evolution of CNTs during preparation and the final distribution in the Al matrix were investigated, and the effect of CNT content on mechanical properties were discussed. Due to the combined effect of uniform dispersion of CNTs, structural integrity, interfacial bonding and directional alignment, the balance between high strength and ductility was successfully achieved in the annealed rolled composites with 1.5 wt% CNT addition, with the value of 382.6 MPa in tensile strength and 9.8% in fracture ductility. The load transfer strengthening was the main mechanism of the strength enhancement with CNTs addition. In addition, a strong rotated cube {001}〈110〉 texture was found in the final flat product of rolled composites. This study provides an effective route to produce and improve the mechanical properties of CNT/Al flat products.

At GE Research, we are combining “physics” with artificial intelligence and machine learning to advance manufacturing design, processing, and inspection, turning innovative technologies into real products and solutions across our industrial portfolio. This article provides a snapshot of how this physical plus digital transformation is evolving at GE.

A homogeneous structured CoCrNi medium-entropy alloy was synthesized by gas atomization and spark plasma sintering (SPS). The mechanical properties, corrosion resistance, and magnetic properties were reported in this study. The as-atomized CoCrNi MEA powder, with a spherical morphology in shape and a mean particle diameter of 61 μm, consisted of a single face-centered cubic (FCC) phase with homogeneous distributions of Co, Cr, and Ni elements. Also, the cross-sectional microstructure of powder particles gradually transformed from fully cellular structure into equiaxed-type structure with increasing particle size. After being sintered by SPS, the CoCrNi MEA consisted of a single FCC phase with a mean grain size of 20.8 μm. Meanwhile, the CoCrNi MEA can capable of offering an ultimate tensile strength of 799 MPa, yield strength of 352 MPa, elongation of 53.6%, and hardness of 195.3 HV. In addition, this MEA showed superior corrosion resistance to that of 304 SS (stainless steel) in both 0.5 mol/L HCl and 1 mol/L NaOH solutions. The magnetization loop indicated that this MEA has good soft magnetic properties.

In this study, a rapid powder consolidation method combining powder compact hot pressing and extrusion was utilized to consolidate relatively cheap, high impurity blended powder mixture Ti–6Al–4V alloy. The purpose of this work was to investigate whether a suitable microstructure deriving from a particular heat treatment balance out or compensate for the presence of high interstitial impurity contents. From mechanical property data attained, it was clear that annealing in high α–β region gave a much better combination of mechanical properties: impact toughness (14 J), yield strength (878 MPa), ultimate tensile strength (1092 MPa), and ductility/plastic strain (6.2%) compared to as-extruded material despite the presence of 0.44 wt% oxygen. Therefore, it can be concluded that optimization of microstructures provides improvement to the fracture related properties and Ti–6Al–4V produced in this way is suitable for less demanding applications. For further enhancement in properties, utilization of low oxygen starting powders is vital.

AlCoCrFeNi is among the promising high-entropy alloys (HEAs) that possess high strength with considerable ductility. Powder sintering is one of the competitive routes for the production of HEA powders. However, sintering of HEA powders under a pressureless condition is difficult. The present work aims to produce high-density components from mechanically alloyed AlCoCrFeNi HEA powders through the pressureless sintering method. Nearly full density was achieved at 1275 °C. Sintering was performed in the presence of a viscous phase in the temperature range of 1200–1250 °C, which was confirmed through differential scanning calorimetry and dilatometric measurements. This viscous phase was found have a Cr-rich composition, detected by interrupting the sintering and quenching of the sample. The powder initially contained the BCC phase with a small fraction of FCC and other phases. During sintering, a significant fraction of the FCC phase and nanosized B2 phase were formed. Sintered sample had a hardness of 679 ± 20 Hv.

Nanocrystalline (NC) and ultrafine-grained (UFG) CoCrCuFeNi high-entropy alloy (HEA) with grain size ranging between 59 and 386 nm was produced via powder metallurgy and heat treatment. The as-sintered HEA exhibited two face-centered cubic (FCC) phases (CoCrFeNi-rich and Cu-rich phases) and a small grain size (59 nm), whereas the alloy after heat treatment at 1000 °C exhibited a CoCuFeNi-rich phase with FCC structure and relatively larger grain size (386 nm). Moreover, the yield strength decreased from 1930 to 883 MPa, and plastic strain to failure increased by 8–32%. In terms of microstructural evolution, grain boundary strengthening coupled with lattice distortion was the dominant strengthening mechanism for NC HEAs. Furthermore, the coefficient for boundary strengthening was higher in the HEAs than in the corresponding pure elemental metals with FCC structure, possibly because of significant lattice distortion. The UFG HEAs exhibited high strength and good ductility because of the activation of dislocation.

The constant search for the improvement of the performance of materials of industrial application, evaluated under aspects of weight reduction, greater resistance, greater resistance to wear and better thermal stability, among others, associated with the search for the development of ecologically viable products, that convert the context of environmental degradation in preservation and sustainability, reflects the need to conduct research that results in new materials. The objective of this work is to obtain composites of the AA6061 aluminum alloy reinforced with different contents of coke coal blast-furnace slag by powder metallurgy. The processing of these materials was done by sieving, mixing and compacting powders of reinforced aluminum alloy with 5, 10 and 15% of blast-furnace slag. The cold uniaxial compaction was realized at a pressure of 500MPa. The obtained materials were sintered at 580°C for 3h under inert atmosphere. Unreinforced aluminum alloy samples were also produced. The characterization of the materials was realized by density and hardness measurements and three-point bending tests. The analysis of its microstructure was realized by scanning electron microscopy. As results, the composites presented a homogeneous distribution of the reinforcing particles and also a progressive improvement of the hardness and the bending strength with the increase of the slag content, producing an increase of 79% in hardness and 128% in flexural strength, when compared to the material without reinforcement obtained by the same process. Such results give the coke coal blast-furnace slag a new possibility of exploitation in the metal-mechanical sector, besides contributing with the environmental issue.

This paper presents a novel way to obtain reinforced pores by the dissociation of mixed carbides during sintering. Porous materials have a wide range of applications such as dampeners, light structures, etc. But usually pores act as points of stress concentration and crack nucleation, harming the mechanical properties of these materials. Methods have been developed to control the shape and size of pores but, until now, there are no techniques that allow reinforcing the material around the pores. To address this, steels were prepared by adding 1, 3 and 5 wt.% of Mo1.5Cr0.5C mixed carbide particles to a iron matrix by metal injection moulding. The results showed that during sintering, the dissociation of the carbide followed by the dissolution of the elements in the matrix generated rounded secondary pores with a reinforced vicinity, which increased the mechanical strength of the materials. The presence of rounded pores encircled by an enriched vicinity can allow the production of porous materials with exceptional fatigue strength and fracture toughness.

Effect of Ni:Al blending ratio on porous structure of porous nickel aluminides fabricated through reactive synthesis with space holder particles were investigated. Fabricated porous nickel aluminides had large pores derived from NaCl space holder particles and small pores derived from reactions between Ni and Al. Porosity and size of the small pores increased with increasing Al content in the raw powder mixture. Compressive property of porous NiAl are also investigated. porous NiAl exhibited good energy-absorption properties with relatively high plateau stress, high plateau end strain, and relatively flat plateau stress. This study suggests the possibility of intermetallic-based porous materials as high-performance energy absorber.

A homogeneous HfNbTaTiZr high-entropy alloy was successfully processed via powder metallurgy route. For the initial powder feedstock material fabrication, the electrode induction-melting gas atomization procedure was used, resulting in a spherical powder morphology and dual bcc phase composition distinguishable within the individual particles. Spark plasma sintering was then used for the powder compaction at sintering temperatures ranging from 800 to 1600 °C. By the characterization of the compact microstructures, lattice defects (microscopic porosity and vacancy-like misfit defects), and mechanical properties (hardness and three-point bending strength), the sintering conditions were optimized to obtain a fully dense, homogeneous, single-phase bcc material. It was found that such properties are achieved when sintering at 80 MPa pressure for 2 min at temperatures above 1200 °C, where the single bcc phase structure exhibited ductile behavior with considerable flexural strength and ductility at ambient temperature. Positron annihilation spectroscopy was used to characterize the evolution of atomic and mesoscale defects during optimization of the sintering process.

By using electrochemical tests, small signal variations were study by digital signal processing techniques. Electrochemical noise and electrochemical polarization curves were very useful to obtained electrochemical behavior of alloys, but the low signal levels of measurements obtained showed that some of the information was not likely to be measured and, therefore, not being able to identify. Graphene oxides (GO) samples were prepared by ball milling procedure adding Lithium. SIGVIEW software was used for Digital Signal studies. Comparing, the signals obtained by electrochemical techniques and the research by computational tools; it was possible to find out a behavior path of samples. Display devices made by graphene were observed to provide new information about the structure of samples and how nanotechnology area can be improved. The current investigation aimed at maintaining electrochemical stability, since different deformations, as twisting and bending are quite relevant in portable electronics devices.

This research shows the development of alternative Cu-based materials for applications where enhanced thermal properties are desired. Cu/AlN composites were fabricated from mixtures of pure Cu and copper plated AlN-Cu composite powders. The ceramic phase was added in amounts of 10, 20 and 30 vol.% and the mixtures sintered by pulsed electric current sintering process (PECS). The results showed that the AlN particles are homogeneously distributed in the copper matrix and that the true contacts between hard particles are reduced because of the deposited copper on their surfaces, improving the connectivity of the matrix phase and bonding at the metal-ceramic interface. The relative density of the Cu/AlN composites was major than 97% in all cases. Thermal conductivity of the composites was high and decreased with the ceramic content from 359 to 194 W/mK, for 10 and 30% AlN, respectively. The coefficient of thermal expansion followed a lineal behavior with temperature and is also reduced with the ceramic content.

Oxygen is known to have a significant impact on the strength of Ti alloys, whereas it can also reduce the ductility substantially. Thus, the usage of oxygen to strengthen Ti is restricted in the industry. In this study, we rekindled the research of oxygen behavior in Ti with the purpose of developing Ti alloys with high strength and suitable ductility by using no expensive and poisonous element. To this end, experiments of producing high performance commercially pure Ti using only oxygen solid solution were carried out. The oxygen element was introduced into the Ti by two different powder metallurgy methods. The microstructural examination and mechanical test were performed for the samples, which indicated a strong hardening effect of oxygen in spite of the processing routes. Most importantly, the results suggested that a high elongation to failure of over 20% can still be obtained in the samples having yield stress over 800 MPa, up to an oxygen content of 0.8 wt%, which is far beyond the previously recognized limit.

Precipitation of secondary intermetallic phases in aluminium alloy Al7075 sintered by spark plasma sintering method from powders milled at room and cryogenic temperature was studied by X-ray powder diffraction. Deformation energy stored during cryogenic milling influences the precipitation in Al7075 alloy. High temperature X-ray diffraction experiment revealed the potential for further precipitation strengthening of samples prepared by spark plasma sintering of milled powders. It was established that the correction of absorption edge of metal Kβ-line filter used for laboratory sources greatly enhances the precision of quantitative Rietveld analysis as well as the determination of precipitates’ crystallite sizes.

In this work, the high-performance silicon carbide particle SiCp[carbon nanotube (CNT)] hybrid reinforcement is currently explored to develop the advanced metal matrix composites. 17 wt% SiCp(CNT)/Al composites were fabricated by a powder metallurgy technique, in which SiCp(CNT) hybrid reinforcement with various CNT contents (e.g., 3, 6 and 9 wt%) were applied. Effects of CNT content on the morphology of SiCp(CNT) hybrid reinforcement, the microstructural characteristics, and the tensile mechanical behavior of SiCp(CNT)/Al composites were studied as well. Especially, the SiCp(CNT)/Al composites with 6 wt% CNT in SiCp(CNT) hybrid reinforcement exhibited the most significant enhancing effects in the elastic modulus and tensile strength. Meanwhile, the SiCp(CNT)/Al composites produced a synergistic strengthening effect of SiCp and CNT compared to SiCp/Al composites, while the SiCp(CNT)/Al composites with high CNT content in SiCp(CNT) hybrid reinforcement provided weak improvement in the tensile strength and ductility due to the forming agglomeration of CNT in the matrix.

This work presents the effects of sintering temperature and mechanical milling on the weight loss of the powder metallurgical Fe–28Mn–3Si (wt%) alloy. Mechanically milled (MM) and blended elemental (BE) Fe–28Mn–3Si powder mixtures were prepared. Both the MM and BE compacts were sintered in a vacuum furnace for 3 h at various temperatures. It was found that weight loss occurred among all the sintered compacts. The weight loss of the sintered MM compacts was much lower than their BE counterparts sintered at the same temperature. The weight loss of the compacts was mainly caused by the sublimation of Mn in the Mn depletion region. A single α-Fe phase was observed on the surface of all the sintered samples. Predominant γ-austenite and minor ε-martensite were detected in all the sintered compacts at locations beyond the Mn depletion region. Mn3Si phase was found in BE alloys sintered at 1000 °C.

Due to the rapid development of advanced additive manufacturing production routes in recent years, the demand of high-quality alloy powders is significantly increased. We studied gas-atomised spherical powders of several Nb-bearing γ-TiAl based alloys, Ti-45Al-10Nb and Ti-45Al-5Nb-xC in at.% (x = 0, 0.5, 0.75, and 1), which were produced using the plasma melting induction guided gas atomization (PIGA) technique. The phase constitution of different powder fractions was determined by synchrotron high-energy X-ray diffraction at the HEMS beamline DESY (Germany), as well as by SEM, EDX and EBSD measurements. Due to the high cooling rates in the range of 105 K/s, the powder particles mainly consist of hexagonal close packed α-Ti(Al) and body centred cubic β-Ti(Al)-phase. As the cooling rate depends on the particle size, considerable amounts of the β-phase were only found in the small powder fractions (< 45 μm). The total β-phase amount was generally higher in the alloy with a higher Nb content, and also the effect of carbon as a α2-stabilizer was observed. Dendritic cauliflower-like structures are more pronounced in bigger powder particles due to the slower solidification and thus a higher Nb depletion in the remaining melt.

Ni-based bulk metallic glasses and composites with high absolute densities exceeding 11 g/cm3 were synthesized via spark plasma sintering of Ni45Co10Ta25Nb20 powders produced from pulverized, melt-spun amorphous ribbons. Optimizing the synthesis via selection of sintering temperature, uniaxial load pressure, and powder mechanical screening yielded samples with relative densities of nearly 100% and hardness values in excess of 12.5 GPa without cracking. Mechanical testing included Weibull modulus determination for hardness and compression testing at 10-3 s-1 and 103 s-1 strain rates. The capability of using spark plasma sintering to fabricate high hardness, high density, large scale metallic glasses is demonstrated. The mechanical properties of these compacted comminuted melt-spun glass ribbons are presented.