Electron Probe Microscopy Analysis Research Articles

Retention mechanism of cesium in chabazite embedded into metakaolin-based alkali activated materials

Disposal of cesium-137 (Cs-137)-loaded chabazite generated from decontaminating cooling water of the damaged reactor at the Fukushima Daiichi Nuclear Power Station (FDNPS) has become a crucial concern. The potassium aluminosilicate-based alkali activated material (K-AAM) matrix is one of the candidate encapsulation matrices proposed for encapsulating cesium-137. In this study, chabazite loaded with a low Cs concentration (1 mg/g of Cs), embedded into a K-AAM matrix (K-AAM-C), was analysed to determine its capability to immobilise Cs, which was investigated by batch leaching experiments, field emission–electron probe microscopy analysis (FE-EPMA), X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy. The leaching experiments revealed that K-AAM-C efficiently immobilised Cs, with only 3 % of the Cs leached out after 360 days of leaching in deionised water. Characterisation using XRD, TEM, and Raman analysis confirmed that the alkali-activator was responsible for the phase transformation of chabazite. FE-EPMA demonstrated that K entered the chabazite structure. This phenomenon resulted in the breakdown and subsequent reconstruction of the chabazite structure. TEM observation showed that the Cs was concentrated into the aggregates of precipitates, heterogeneously forming a pollucite-like structure in the chabazite after the fabrication process. Thermodynamic calculations indicated that pollucite was preferably stable in an AAM environment. When immersed in water, the amount of nano-pollucite increased over time, leading to the structural re-arrangement of aluminosilicate rings of chabazite according to TEM and Raman analysis. Pollucite is well known as a Cs-bearing natural zeolite, which can encapsulate Cs in its structure. Therefore, Cs retention was achieved in the spent chabazite adsorbent embedded into the K-AAM due to the resultant pollucite structure formed during AAM fabrication.

Chemical and Spectral Variations between Untreated and Heat-Treated Rubies from Mozambique and Madagascar

The chemical composition and spectra of untreated and heat-treated rubies from Mozambique and Madagascar were analyzed by an electron probe microscopy analysis, laser ablation inductively coupled plasma quadrupole mass spectrometry, Fourier transform infrared spectroscopy, Raman spectroscopy and UV-visible spectroscopy. Due to the different content of Fe and different inclusions, rubies from Madagascar belong to alkaline basalt deposit, while rubies from Mozambique belong to amphibole metamorphic rock. The ruby samples were heated to 900 °C to change their color. As Fe and Ti ions can be transferred into different valences and diffused into the interior of rubies, Cr ions in cracks or cleavages entered the crystal lattice during heat treatment and the content of Fe and Ti decreased, while the content of Cr increased in heat-treated rubies. After heating, blue-purple decreased and the red hue increased, while the blue color band disappeared and yellow appeared in the cracks of the samples because of the chemical changes. Compared with untreated rubies, the infrared absorption peaks of 2123 cm−1 and 1990 cm−1 related to inclusions disappeared, and the existence of 3236 cm−1 and 3186 cm−1 absorption peaks was a typical characteristic of heat-treated ruby, which was produced by changes in its inclusion. In addition, due to the weakened charge transfer of Fe2+ and Ti4+ and the increasing reaction of Fe2+ → Fe3+ along with the heat treatment, the UV-visible absorption peak at 400 nm shifted to purple.

Effect of heating processing on the formation of micro-pores during solution treatment of high generation nickel-based single crystal superalloy

With the development of nickel-based single crystal superalloys, the quantity of micro-pores generating in solution treatment has increased, and there is an urgent need to develop a solution treatment design method that takes account of both residual eutectics and micro-pores. Therefore, the effect of heating processing on the formation of micro-pores during solution treatment of a 4th generation nickel-based single crystal superalloy has been investigated using high-resolution transmission X-ray tomography and electron probe microscopic analyzer. In the temperature range below interdendritic γ' phases solvus, decreasing the heating rate can limit the formation of micro-pores significantly. However, heating method (continuous or stepwise), has a little effect on micro-pores formation. The influence of heating processing on micro-pores formation is associated with composition homogenization degree of the alloy before eutectics dissolve. Moreover, it is found that the dissolution of eutectics is most likely the reason for substantial formation of micro-pores. Finally, a designing thinking for heating processing of solution treatment for high generation nickel-based single crystal superalloys is proposed.

Experimental study on cracking behaviors of coarse and fine sandstone containing two flaws under biaxial compression

AbstractIn this paper, the effects of materials and confining pressures on the mechanical properties of flawed coarse and fine sandstone is first analyzed. Then, the evolution processes of spatiotemporal acoustic emission (AE) events of coarse and fine sandstone specimens containing two flaws subjected to biaxial compression are investigated to character the damage characteristics and the fracture mechanism. Third, the ultimate failure modes of coarse sandstone specimens are compared with those of the fine sandstone specimens. Finally, the Electron Probe Microscope Analysis (EPEI) technique is conducted to observe the main macrofracture surfaces of coarse and fine sandstone specimens. Besides, the distribution characteristics of two AE indexes are also employed to qualitatively reveal the failure mechanism of tested specimens. The experimental results can provide new insight into the mechanical responses and the cracking behaviors of flawed rocks in complex stress loading conditions.

Study on deashing and desulphurization of coal with heavy medium in enhanced gravity field

ABSTRACT This study carried out component sulfur composition analysis, electron probe microscopic analysis, and particle size and density composition analysis of coal samples from a coal preparation plant in Liupanshui. The influence of various factors on the indexes of clean coal products under different separation medium conditions by enhanced gravity separation technology, including water medium (WM), magnet powder suspension (MPS), and zinc chloride solution (ZCS), is discussed. The results show that the addition of MPS or ZCS has an obvious improvement on coal deashing and desulfurization compared with the WM separation, especially the separation effect of ZCS, which is better than that of MPS because of better uniformity and stability of ZCS. The addition of MPS or ZCS can help the materials stratify strictly according to the density to enhance the sorting function. The clean coal ash and sulfur content are reduced to 13.24% and 2.51%, while the combustible recovery and desulfurization efficiency are up to 71.46% and 49.27%, respectively, under the optimal condition.

Mineralogy of beach sand in Jumundo, Korea and recovery of heavy minerals using Humphreys spiral concentrator and shaking table followed by magnetic separation process

ABSTRACT The mineralogy of beach sand, which was sampled from an island, Jumundo of South Korea, was investigated and beneficiated using gravity and magnetic separation processes. Ilmenite was determined to be a major heavy mineral and, as minor heavy minerals, zircon, monazite, and sphene were observed. Quartz, biotite, microcline, kaolinite, hornblende, and chlorite were present as gangue minerals. The Ilmenite was concentrated with a Humphrey spiral concentrator and shaking table followed by magnetic separators (drum and cross belt types). As a final product, 18% of the Humphrey spiral system concentrate was recovered, and the grade of final product was determined to be 93% ilmenite. The electron probe microscope analysis indicates that ilmenite was a solid solution of major FeTiO3, minor MgTiO3 (geikielite), and MnTiO3 (pyrophanite).

Phase diagram of the Al–Cu–Fe quasicrystal-forming alloy system

Abstract The microstructures of as-cast and slowly solidified Al– Cu–Fe ternary alloys in the vicinity of the icosahedral phase region have been investigated using light microscopy and scanning electron microscopy. The chemical composition of the different phases present has been determined by energy-dispersive X-ray spectroscopy with a correction of electron probe microscopy analysis. The solidification process was studied by means of the differential thermal analysis and magnetothermal analysis measurements. In contrast to the equilibrium phase diagram, fast cooling leads to the formation of a metastable β′ phase (an ordered cubic structure) rather than to the formation of the φ phase. The nucleation of ω phase is very sluggish during the solidification. The results are presented as solidification paths, superimposed onto the liquidus surface projection to demonstrate the solidification sequences.

Microstructural evolution and mechanical properties in Zr–Cu–Al–Nb bulk metallic glass composites prepared by laser metal deposition

In this work, laser metal deposition (LMD), a direct energy deposition (DED) additive manufacturing technology, is used to prepare Zr59.3Cu28.8Al10.4Nb1.5 bulk metallic glass composites (BMGCs). Phase constitutions and thermal behavior of LMD-processed Zr–Cu–Al–Nb samples are examined using X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The microstructure evolution parallel to the build direction is characterized in detail utilizing scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron probe microscopy analysis (EPMA) and electron backscatter diffraction (EBSD). Young's modulus and hardness in typical microstructures are evaluated employing nanoindentation. Within each deposited layer, a periodic microstructure, exhibiting crystalline features of three distinctly different morphologies, is observed, depending on the location within that layer. Along the build direction, the dominating microstructure of the melt pool evolves from a nearly featureless amorphous state over fine nanocrystals to coarse nanocrystals while the morphology of most micro-scale dendritic crystals changes from flower-shaped to columnar, simultaneously a coarse microstructure appearing in upper layers. The fine Al-rich phases gradually coarsen directionally parallel to the build direction. Furthermore, the correlation between microstructure and mechanical properties is investigated. This work enhances our knowledge about microstructural characteristics and mechanical properties of BMGCs in-situ fabricated by DED additive manufacturing.

Insight into effect of alloy elements on corrosion extension of defective coating/AH32 steel system in short-term immersion

The service life of vessels is closely dependent on the corrosion resistance of coated hull steel systems due to the harsh marine environment. In this work, the three-dimensional corrosion extension law of a defective epoxy coating/AH32 steel system in the initial stage was investigated by using micro-Raman spectrum, electron probe microscopic analysis, and X-ray photoelectron spectroscopy. Q235 steel was utilized as a contrast sample. The chemical composition of the AH32 steel was 0.183C, 0.199Si, 1.33Mn, 0.0896Cr, 0.007Mo, 0.0078Al, 0.005Cu, 0.0428P, 0.0258S, and Fe and that of Q235 steel was 0.0692C, 0.0981Si, 0.163Mn, 0.0219Cr, 0.001Mo, 0.0176Al, 0.008Cu, 0.0318P, 0.0318S, and Fe. Results showed that when the electrolyte solution reached the coating/metal interface through the defect, the corrosion of the AH32 steel substrate preferentially developed in the lateral direction. By contrast, the corrosion extension of the Q235 steel showed increased severity in the depth direction. This difference could be attributed to the protectiveness of the corrosion products that had formed at the defect. The oxidation of the Mn element in AH32 accelerated the formation of the protective rust layer of α-FeOOH, which retarded the further vertical penetration of the electrolyte solution into the steel. Therefore, corrosion initially occurred at the under-film area near the defect.

A study on wettability and formation of intermetallic phase between Co–Cr–Mo alloy and Sn-Solder used as a potential under bump metallization for flip-chip packages

The wettability and formation of intermetallic compounds (IMCs) formed between a Co–Cr–Mo-based alloy and Sn-solder metal were investigated using the reflow soldering method. Soldering was conducted in an electric furnace in separate experiments at temperatures of 533, 553, 573, 623, and 673 K for 600 s. The morphology of the intermetallic layer formed at the Co–Cr–Mo-based/Sn-solder interface was characterized by scanning electron microscopy (SEM). The chemical composition and phase of the formed intermetallic layer were analyzed by electron probe microscopic analysis (EPMA) and X-ray diffraction analysis. Wettability analysis indicated that the soldering temperature influenced the wettability. With increasing soldering temperatures, the spreading factor increased, whereas the contact angle decreased. The intermetallic layers were found in triples in the intermediate zone between the solidified Sn-solder and the Co–Cr–Mo-based substrate. The thickness of the intermetallic layers increased in proportion with increasing soldering temperature. The EPMA analysis indicated only two IMCs formed at the interface of the joint at all of the investigated soldering temperatures, although three interfacial layers were observed by SEM analysis. The Sn-richer phase, Co(Cr,Mo)Sn2, formed adjacent to the Sn-solder matrix, whereas the Co(Cr,Mo)Sn was found near the Co–Cr–Mo-based substrate. The nanoindentation measurement revealed that the formed Co(Cr,Mo)Sn2 and Co(Cr,Mo)Sn IMCs possessed lower hardness values compared to the Sn–Cu intermetallic systems.

Preparation of Fe-Co-B-Si-Nb bulk metallic glasses by laser powder bed fusion: Microstructure and properties

In this work, laser powder bed fusion (LPBF) was employed for the preparation of {(Fe0.6Co0.4)0.75B0.2Si0.05}96Nb4 bulk metallic glasses (BMGs). Microstructural evolution, thermal stability and mechanical properties of LPBF-processed samples using different laser power and scanning speed were systematically investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe microscopy analysis (EPMA), electron backscatter diffraction (EBSD), differential scanning calorimetry (DSC) and nanoindentation. The results show that low area energy input facilitates the formation of Fe-Co-B-Si-Nb BMGs with a large amorphous fraction. LPBF-processed sample with an area energy density of 1.25 J/mm2 (at a laser power of 60 W and a scanning speed of 600 mm/s) exhibits a nearly fully glassy microstructure with an amorphous fraction of approximately 99%, meanwhile possessing almost identical characteristic temperatures and enthalpy of crystallization as the as-atomized powder. The microstructure and mechanical properties of LPBF-processed samples are correlated with the processing parameters during LPBF. This work demonstrates that LPBF is a promising method to prepare fully amorphous Fe-Co-B-Si-Nb BMGs. The results provide key insights for the fabrication of BMGs and BMGs composites with the desired microstructure and properties by additive manufacturing.

Microstructure and mechanical properties of welded joints of L415/316L bimetal composite pipe using post internal-welding process

In order to reduce the welding cost and improve welding quality, L415/316L bimetal mechanical lined pipes were welded using the post internal-welding process in which the outer carbon layer is welded prior to the inner stainless layer. The mechanical property tests, such as tensile, bending and hardness tests, of the welded joints were carried out. Microstructure and the chemical compositions of the welded joints were analyzed by optical microscope (OM), scanning electron microscope (SEM), electron backscattered diffraction (EBSD) and electron probe microscope analysis (EPMA). In addition, the pitting corrosion resistance of the welded joints was evaluated. The results show that the mechanical properties of the welded joints do meet the standard requirements. The cracks on the bending specimens are closely related to the martensite formed at ER309 L/ER70S-6 or ER309 L/L415 interface. In addition, pitting holes are found in the ferric chloride solution showing that ER309MoL welding wire is not suitable for welding 316L layer. From the perspective of mechanical properties, it is advisable to use the post internal-welding process for the welding of bimetal composite pipes.

Mineral chemistry of the Xiasai Ag–Pb–Zn deposit in the central Yidun Terrane, SW China: Insight into Ni–Ag–Bi mineralization and formation conditions

Sulfides and sulfosalts are major ore minerals for most of Ag–Pb–Zn deposits and can be used to study enrichment and distribution of ore-forming elements and formation conditions. The Xiasai Ag–Pb–Zn deposit (Zn 0.141 Mt @ 4.30%, Pb 0.132 Mt @ 4.03%, Ag 1028 t @ 337.8 g/t, Cu 10058 t @ 0.56%, and Sn 20000 t @ 0.75%) is a hydrothermal vein-type deposit in the central Yindun Terrane, SW China. It consists of proximal quartz-cassiterite veins and distal Ag–Pb–Zn sulfide veins to a Cretaceous monzogranite. Three successive mineralization sub-stages are recognized for Ag–Pb–Zn veins, i.e., arsenopyrite + coarse-grained pyrite (Py1) + pyrrhotite, sphalerite + chalcopyrite + fine-grained pyrite (Py2), and silver-minerals + native bismuth + galena.Nickel-minerals, such as breithauptite and ullmannite were identified as inclusions hosted within pyrrhotite using Energy Dispersive X-ray Spectroscopy (EDS) and Electron probe microscopy (EPM) analysis and mapping. Trace amounts of invisible silver have been detected in chalcopyrite and galena, whereas a significant amount of silver is incorporated in pyrargyrite, freibergite, miargyrite, and electrum as intimate intergrowths with galena or inclusions within galena. A high content of invisible bismuth is detected within galena (0.21–16.95 wt%), as well as numerous grains of native bismuth occur as inclusions in galena. Based on the Bi concentrations determined and the modal composition a large-sized bismuth deposit would be estimated with about 23,800 t of Bi resource. The presence of nickel-minerals and native bismuth, together with Zn/Cd ratios (58–151) of sphalerite, indicate that the ore-forming materials are derived from the Xiasai monzogranite.Based on mineral assemblages and chemical features for sulfides and sulfosalts, the formation of Ag–Pb–Zn ores was triggered by a decrease in temperature, fs2, fO2, and sulfidation. The early episode of arsenopyrite, Py1, pyrrhotite, and nickel-minerals formed at temperature of 320–470°C, lower fs2 and decreasing sulfidation conditions from low alkaline fluids. In contrast, the late episode of silver-minerals, native bismuth, and galena deposited at 160–270 °C with a lower fs2 state and neutral or acidic pH. However, a slight increase of fs2, fO2, and sulfidation (intermediate sulfidation) occurred during precipitation of Zn–Cu.

Effect of varying TiB2 reinforcement and its ageing behaviour on tensile and hardness properties of in-situ Al-4.5%Cu-xTiB2 composite

The objective of this study is to understand the suitability of mixed salt route using stir casting technique to fabricate in-situ Al-4.5%Cu-xTiB2 (x = 3, 6, 9 and 12 wt %) composites. The mechanism behind titanium/boron-based phase evolution in Al-Cu alloy has been enlightened first time, particularly its strong influence over mechanical behaviour was examined. The in-situ TiB2 reinforcement particles were prepared by the exothermic reaction of K2TiF6 and KBF4 salts in melted aluminium copper alloy which improves the hardness, yield, and tensile strengths to the extent of ∼89 VHN, ∼236 MPa and ∼295 MPa, respectively. Preliminary microstructural evolution was analysed and discussed through optical microstructures and proposed mechanism. The composites were characterized carefully with the help of field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) to know the morphological details and TiB2 distribution in the aluminium matrix composite (AMC) microstructure. In support with electron microscopic observations, the X-ray diffraction (XRD) and Electron Probe Microscopic Analysis (EPMA) were also performed. To further enhance the mechanical properties, T6 heat treatment (HT) was done. During the HT process, the composites were solutionized at 540 °C for two hours followed by water quenching. After that, artificial ageing was carried out at 170 °C with varying durations of 5, 10, 15, 20, and 25 h and post-ageing effect on the mechanical properties were recorded. Composites were thermally characterized through differential scanning calorimetry (DSC) to learn the precipitation kinetics and compared with alloy chosen.

Effect of transition metal addition on microstructure and hardening behavior of two-phase Ni3Al-Ni3V intermetallic alloys

The comprehensive mechanisms for the hardening of two-phase Ni3Al-Ni3V intermetallic alloys by transition metal addition were presented, based on the microstructural observation, alloying behavior and lattice properties of the additives in the constituent phases. The alloys to which 2 at.% Ti, Nb and Ta were added in different substitution manners for Ni, Al and V, respectively were studied by scanning electron microscopy, electron probe microscopic analyzer, X-ray diffraction and hardness test. The alloys in which the additives were substituted for Al exhibited microstructures with finer and cuboidal Ni3Al precipitates. Nb and Ta addition resulted in larger lattice expansion in the two constituent phases than Ti addition. The hardness increase by the Nb and Ta addition was larger than that by the Ti addition. Also, the hardness increase was larger in the substitution manner of the additives for Al than in those for Ni and V. The hardening behavior was explained in terms of solid solution hardening mechanism in which the mixture rule in the volume fraction of the two constituent phases and the atomic size misfit evaluated from the changes of the lattice parameters were incorporated. Consequently, the hardening for the alloys in which the additives were substituted for Ni and V was wholly attributed to solid solution hardening. On the other hand, the hardening for the alloys in which the additives were substituted for Al was attributed to the hardening due to microstructural refining in addition to the solid solution hardening.

Tritium retention characteristics in dust particles in JET with ITER-like wall

A tritium imaging plate technique (TIPT) in combination with an electron-probe microscopic analysis (EPMA) were applied to examine tritium (T) retention characteristics in individual dust particles collected in the Joint European Torus with the ITER-like Wall (JET-ILW) after the first campaign in 2011–2012.A lot of carbon (C)-dominated dust particles were found, which would be pre-existing carbon deposits in the JET-C or released carbon particles from the remaining carbon-fiber components in the JET-ILW. Most of T was retained at the surface of and/or in the C-dominated dust particles. The retention in tungsten, beryllium and other metal-dominated dust particles is relatively lower by a factor of 10–100 in comparison with that in the C-dominated particles.

Garnet composition as an indicator of skarn formation: LA‐ICP‐MS and EPMA studies on oscillatory zoned garnets from the Haobugao skarn deposit, Inner Mongolia, China

Oscillatory zoned garnets are widespread in the Haobugao skarn‐type copper–lead–zinc–iron polymetallic deposit, and they can record garnet growing process in the early stages of metallogenesis. In order to investigate the skarn‐forming process and hydrothermal fluid evolution of the Haobugao deposit, major, trace, and rare earth element (REE) contents of oscillatory zoned garnets were analysed by electron probe microscope analysis (EPMA) and laser‐ablation inductively‐coupled plasma mass spectrometry (LA‐ICP‐MS) techniques. Three distinct generations of garnets were identified: the first generation garnets (Grt I) are Fe‐rich, euhedral, fine‐ to coarse‐grained, isotropic, show characteristic concentric oscillatory zoning, and have light rare earth element (LREE)‐enriched and heavy rare earth element (HREE)‐depleted REE patterns, with strong positive Eu anomalies and low ΣREE concentrations. The second generation garnets (Grt II) are Al‐rich, anhedral to subhedral, anisotropic, with abundant oscillatory zoning alone the growth lines, and have LREE‐depleted and HREE‐enriched REE patterns, with negligible Eu anomalies and relatively higher ΣREE concentrations. The third generation garnets (Grt III) are anhedral, anisotropic and generally occurred at the rim of pre‐existing Grt I or beside fractures that cut through the pre‐existing Grt I crystals. All these three generations garnets show oscillatory zoning under an optical microscope and have different compositions from each other, but there's limited chemical zoning (such as bell‐shaped zoning of major elements) in each individual garnet crystal.The texture and composition characteristics of the garnets indicate that the Grt I is precipitated rapidly from high temperature and oxidized magmatic fluids by advective metasomatism, in a high water/rock ratio condition; the Grt II is precipitated from low temperature residual fluids that were in equilibrium with the host rock by diffusive metasomatism, in a low water/rock ratio condition; and the Grt III is formed by retrograde hydrothermal‐metasomatic alteration of pre‐existing garnets. The incorporation of REE into garnet is controlled by its crystal chemistry and fluid composition, dominated by the YAG (yttrium aluminium garnet) ‐type substitution mechanism .

Investigation of the Microstructure and Mechanical Properties of Copper-Graphite Composites Reinforced with Single-Crystal α-Al₂O₃ Fibres by Hot Isostatic Pressing.

Single-crystal α-Al2O3 fibres can be utilized as a novel reinforcement in high-temperature composites owing to their high elastic modulus, chemical and thermal stability. Unlike non-oxide fibres and polycrystalline alumina fibres, high-temperature oxidation and polycrystalline particles boundary growth will not occur for single-crystal α-Al2O3 fibres. In this work, single-crystal α-Al2O3 whiskers and Al2O3 particles synergistic reinforced copper-graphite composites were fabricated by mechanical alloying and hot isostatic pressing techniques. The phase compositions, microstructures, and fracture morphologies of the composites were investigated using X-ray diffraction, a scanning electron microscope equipped with an X-ray energy-dispersive spectrometer (EDS), an electron probe microscopic analysis equipped with wavelength-dispersive spectrometer, and a transmission electron microscope equipped with EDS. The mechanical properties have been measured by a micro-hardness tester and electronic universal testing machine. The results show that the reinforcements were unevenly distributed in the matrix with the increase of their content and there were some micro-cracks located at the interface between the reinforcement and the matrix. With the increase of the Al2O3 whisker content, the compressive strength of the composites first increased and then decreased, while the hardness decreased. The fracture and strengthening mechanisms of the composite materials were explored on the basis of the structure and composition of the composites through the formation and function of the interface. The main strengthening mechanism in the composites was fine grain strengthening and solid solution strengthening. The fracture type of the composites was brittle fracture.

Experimental investigation on phase equilibria of Cu–Ti–Hf system and performance of Cu(Ti, Hf)2 phase

Phase relations in Cu–Ti–Hf ternary system have been studied by diffusion triple technique supplemented with typical alloy sampling method. Based on results from electron-probe microscopy analysis and X-ray diffraction, isothermal sections of the Cu–Ti–Hf system at 800 and 700 °C were established, which consist of ten and nine three-phase regions, respectively. It is observed that Ti can completely substitute Hf in the CuHf2 phase, indicating formation of a continuous solid solution Cu(Ti,Hf)2. Hf can substitute about 20% Ti in the phase CuTi, while solubility of Ti in Cu10Hf7 and Cu51Hf14 phases reaches to 14 and 11 at.% at 800 °C, respectively. The Cu8Hf3 phase in existence at 800 °C was proved to be unstable at 700 °C. In addition, the elastic modulus and hardness of solid solution Cu(Ti,Hf)2 were determined by using nano-indentation techniques.

Investigation of the phase equilibria in Ti-Ni-Hf system using diffusion triples and equilibrated alloys

In present work, the phase equilibrium relations in the Ti-Ni-Hf ternary system, which are of great importance for the design of Ti-Ni based high temperature shape memory alloys, were investigated using diffusion triples and sixteen key equilibrated alloys. Based on the experimental results from electron-probe microscopy analysis (EPMA) and X-ray diffraction (XRD) techniques, two isothermal sections were constructed, which consist of 13 and 12 three-phase regions at 900°C and 800°C, respectively. Hf can substitute for Ti in TiNi and Ti2Ni phases increasing from 30, 62at% at 800°C to 36, 64at% at 900°C, respectively. The Hf7Ni10 and Hf9Ni11 phases show wide ternary composition ranges, while the solubility of Ti in HfNi5, Hf2Ni7, and HfNi phases are relatively limited. A new ternary phase of τ was detected for the first time, and the stoichiometry of τ phase is close to Ni:(Hf,Ti) = 11:14, with Ti substituting for Hf from ～5at% to ～22at%. The single-phase region of the τ phase became narrow as the decreasing of annealing temperature. Based on comparison of phase relations at 900°C and 800°C, it is speculated there is an invariant reaction TiNi + τ → HfNi + Ti2Ni at between 900°C and 800°C.