Experimental Alloys Research Articles

Effect of substituting Mo for W on γ/γ′ partitioning behaviors of alloying elements in heat-treated second generation Ni based single crystal superalloys: An atom probe tomography study

The effect of substituting Mo for W on γ/γ′ partitioning behaviors of alloying elements in heat-treated second generation Ni based single crystal superalloys was investigated via atom probe tomography technique. Re, Cr, Co and Mo elements tended to distribute in γ phase, while Al, Ta and W elements tended to distribute in γ′ phase, and significant interfacial segregation was not found in experimental alloys. Moreover, substituting Mo for W obviously increased Re content in γ phase. Meanwhile, Re content in γ phase increased with increasing Mo + Cr content in single crystal superalloy, while Re content in γ′ phase decreased with increasing W + Ta content in single crystal superalloy. In addition, partitioning ratios of both W and Mo elements were positively correlated with Ta content in single crystal superalloy, and partitioning ratio of Ta element was inversely correlated with Ta/Al ratio in single crystal superalloy. Furthermore, substituting Mo for W increased the solid solution strength of γ phase but decreased the solid solution strength of γ′ phase.

Development of technology for modification of heat-resistant nickel alloy ЖС3ДК-ВІ with titanium carbonitride ultrafine powders

Purpose. To study the effect of modification by the titanium carbonitride Ti(C, N) ultrafine particles additives in the form of powder and briquettes on the structure and physical-mechanical properties of the ЖС3ДК-ВІ alloy used for the manufacture of aircraft engine turbines cast rotor blades.
 Research methods. Preliminary high-temperature treatment of the melt was carried out on a VIP-10 installation.
 On the UPPF-3M installation with the alkaline melting pot, the ЖС3ДК-ВІ alloy was modified with ultrafine particles of titanium carbonitride Ti(C,N) in an amount of 60...80 g in the form of briquettes or powder wrapped in nickel foil.
 The samples were subjected to homogenization at a temperature of 1210 °C with a holding time of 3.5 hours and air cooling.
 The chemical composition of investigated alloys was determined. The macrostructure was studied on plates ~ 4 mm thick after chemical etching. The microstructure was evaluated on microsections before and after etching in the Marble reagent.
 Microhardness, ultimate strength, elongation and contraction, impact strength were determined at room temperature. Long-term strength tests were carried out at 850 °C under a load of 350 MPa. The bending test of the blades was carried out on a manual screw press in accordance with GOST 14019-80.
 Results. The microstructure of Ti+TiCN briquettes has been studied by optical and electron microscopy. X-ray microanalysis of specimen fractures confirmed a fairly uniform distribution of titanium carbonitride in the volume of briquettes.
 The chemical composition, macro- and microstructure of the experimental alloy have been studied. A fracto-graphic study of the samples fracture structure was carried out.
 The modifying effect of titanium carbonitride ultrafine particles on the dendritic structure, distribution and change in the morphology of primary carbides, the number and distribution of carbonitride particles has been established.
 A comparative analysis of the mechanical and heat-resistant properties of the ЖС3ДК-ВІ alloy of standard composition and modified with ultradispersed Ti(C,N) particles has been carried out. Bending tests of turbine rotor blades were carried out.
 Scientific novelty. It is shown that the use of ultrafine titanium carbonitride powders for bulk modification of the heat-resistant nickel alloy ЖС3ДК-ВІ makes it possible to increase the mechanical and heat-resistant properties of the material. Increasing the amount of modifier promotes grain refinement.
 More stable properties and favorable structure are provided by melt modification with ultrafine Ti(C,N) particles in the form of briquettes. It was found that modification with powdered Ti(C,N) leads to a decrease in the impact toughness values due to the formation of boundary microporosity.
 Practical value. The technology of the heat-resistant nickel alloy ЖС3ДК-ВІ, used for the manufacture of cast rotor blades of gas turbine engines, modification with additives of titanium carbonitride Ti(C,N) ultrafine particles, providing an increased level of performance properties of finished products, has been developed.

Microstructural stability and tensile properties of a new γ′-hardened Ni-Fe-base superalloy

The microstructure and tensile properties of a new γ′-hardened Ni-Fe-base superalloy HT700T in solutionized state are investigated after thermal exposure at 800 °C for different durations. Within the grain interior, the average size of γ′ precipitates increases from 28.3 to 274.1 nm with increasing aging time from 8 to 10,033 h, but its volume fraction and morphology remain unchanged with time. At grain boundaries, MC carbide and M23C6 carbide also coarsen with time, but the distribution of these carbides is always discontinuous in the most region of the alloy. Tensile tests on the experimental alloy at 650 °C reveal that its yield strength and ultimate tensile strength decrease with aging time, whereas the elongation to fracture increases after thermal exposure for 3053 h and then remains unchanged with increasing time. Transmission electron microscope observations on the slightly deformed specimens disclose that the dominant deformation mechanism in the experimental alloy transits from strongly-coupled dislocation pairs shearing through γ′ precipitates to Orowan looping with time. Based on these experimental observations, it is deemed that the microstructural evolution during thermal aging accounts for the evolution of the operative deformation and fracture mechanisms and therefore the tensile properties of the experimental alloy.

Preageing of magnesium alloys

Abstract Certain magnesium alloy systems can obtain superior mechanical strength through age hardening. However, conventional ageing heat treatments for these alloys are rarely more complex than a single isothermal hold – especially when compared to those of aluminium alloys – so age hardenable magnesium alloys may not be achieving their full strengthening potential. The use of preageing, where a lower temperature heat treatment is utilised before a hotter secondary ageing step, has proven successful in boosting the strength of magnesium alloys previously, but these trials are few in number, and the testing conditions are limited. In this work, a wide range of preageing temperatures and times were trialled on commercial and experimental magnesium alloys to determine the effectiveness of the strengthening technique. The results showed that preageing can produce a significant boost in hardness, can reduce total ageing times, and can provide a degree of mechanical property customisation through control of precipitate habit plane and morphology. However, the effectiveness of the technique is alloy-system dependent, where the fundamental precipitate nucleation and phase evolution is a key contributor to the success of preageing; as is the energy barrier to nucleation in an alloy system, whether that be controlled by alloy chemistry or thermomechanical processing. The results are discussed in the context of alloy design and industrial processing.

Effect of Cu Addition on the Precipitation Hardening and Mechanical Properties of Al-Mg Based Cast Alloys.

This study examines the formation of different phases of Al-6 mass% Mg-xCu (x = 1 and 3 mass%) alloys in as-cast condition. Further, it investigates the dissolution of these phases upon solution heat treatment (SHT) and studies the precipitation behavior of these ternary alloys. Scanning electron microscopy with energy-dispersive spectrometry and high resolution X-ray diffraction analyses show the presence of the second phases of Al₃Mg₂ (β), Al6CuMg₄ (T), and Al₂CuMg (S) in Alloy I (Al-6Mg-1Cu), whereas Alloy II (Al-6Mg-3Cu) had only T and S second phases (with a much higher number of S phases). Upon SHT, a significant number of eutectic phases were dissolved in Alloy I, whereas in Alloy II, the number of undissolved S phases was relatively high. A differential scanning calorimetry (DSC) analysis of experimental alloys in as-quenched states reveals two exothermic peaks related to the formation of nanoclusters and S″ or S' metastable phases. Both alloys undergo a rapid hardening stage during the aging process, in which approximately 50%-60% of total hardness was achieved. This is attributed to the formation of nanoclusters. The maximum yield strength achieved at the peak hardness condition was approximately 200 MPa for Alloy I, whereas it was approximately 160 MPa for alloy II. Alloy I took a long time to reach peak hardness, which is correlated with the stability of nanoclusters for a longer time. Earlier peak hardness in Alloy II, despite having nanoclusters, is correlated with undissolved eutectic phases acting as heterogeneous nucleation sites for the formation of S″ or S' metastable phases.

Comparison of the EHLA and LPBF Process in Context of New Alloy Design Methods for LPBF

Additive Manufacturing (AM) processes are becoming more and more important for production of parts with increasing geometrical complexity and functionality. However, to draw on the full potential of AM technologies, alloys that exploit process inherent particularities such as extremely high cooling rates (ca. 106 K/s) have to be developed. One of most important AM-processes is Laser Powder Bed Fusion (LPBF), a batch-wise process. This complicates experimental alloy development and increases the use of powder resources since only one chemical composition can be tested within one test job and the process chamber has to be cleaned carefully in between. The process Extreme High-Speed Laser Material Deposition (EHLA) has been found to have similar cooling rates as LPBF, however it uses an in situ supply of powders which allows an easy switching between materials and has potential for rapid alloy development methods. Since the mechanical properties of materials primarily depend on chemical composition and microstructure, which in turn depends heavily on the cooling rates in the production process, the EHLA-process could be used as a means for an accelerated alloy development for LPBF. However, to explore this possibility, a thorough comparison of the two processes has to be performed.In this work, EHLA and LPBF processes are compared and evaluated regarding the following characteristics: process parameters, laser intensities and volume energy densities, resulting microstructure (primary dendrite arm spacing, DAS), melt pool size and shape. The reference samples were manufactured using one set of LPBF process parameters and EHLA samples were manufactured using three different sets of process parameters.The volume energy densities Ev [J/mm³] of the processes were found to differ by a factor 2.4 with higher Ev observed in LPBF. However, considering that approximately 2 to 3 layers are remelted with each pass of the laser beam, the introduced Ev per pass approximates the Ev introduced in the EHLA process. The melt pool size as seen in a cross section in the EHLA-manufactured samples is approximately 25 times larger than in the LPBF-manufactured samples and its depth to width ratio (d/w ratio) can be attributed to a heat conduction welding process while the d/w ratio observed in the LPBF-manufactured sample suggests a transition process between heat conduction welding and deep welding. The observed DAS is in the same order of magnitude for both processes ranging from 0.55 to 1.15 µm in EHLA-manufactured samples and 0.73 µm in the LPBF-manufactured reference sample. Since the resulting microstructures of samples manufactured with both processes show this common feature and EHLA process parameters can be adjusted to control the cooling rates, the transferability between EHLA- and LPBF-processes is supported in this first investigation. Research for a more efficient alloy development for LPBF using EHLA will be continued by e.g. examining chemical compositions and performing mechanical testing.

Effect of ageing treatment on microstructures, mechanical properties and corrosion behavior of Mg-Zn-RE-Zr alloy micro-alloyed with Ca and Sr

Effects of ageing treatment on the microstructures, mechanical properties and corrosion behavior of the Mg-4.2Zn-1.7RE-0.8Zr-xCa-ySr [x=0, 0.2 (wt.%), y=0, 0.1, 0.2, 0.4 (wt.%)] alloys were investigated. Results showed that Ca or/and Sr additions promoted the precipitation hardening behavior of Mg-4.2Zn-1.7RE-0.8Zr alloy and shortened the time to reaching peak hardness from 13 h to 12 h. The maximum hardness of 77.1±0.6 HV for the peak-aged Mg-4.2Zn-1.7RE-0.8Zr-0.2Ca-0.2Sr alloy was obtained. The microstructures of peak-aged alloys mainly consist of α-Mg phase, Mg51Zn20 phase and ternary T-phase. The Zn-Zr phase is formed within the α-Mg matrix, and the Mg2Ca phase is formed near T-phase due to the enrichment of Ca in front of the solid-liquid interface. Furthermore, fine short rod-shaped β′1 phase is precipitated within the α-Mg matrix in the peak-aged condition. The peak-aged Mg-4.2Zn-1.7RE-0.8Zr-0.2Ca-0.2Sr alloy exhibits optimal mechanical properties with an ultimate tensile strength of 208 MPa, yield strength of 150 MPa and elongation of 3.5%, which is mainly attributed to precipitation strengthening. In addition, corrosion properties of experimental alloys in the 3.5wt.% NaCl solution were studied by the electrochemical tests, weight loss, hydrogen evolution measurement and corrosion morphology observation. The results suggest that peak-aged alloys show reduced corrosion rates compared with the as-cast alloys, and minor additions of Ca and/or Sr improve the corrosion resistance of the Mg-4.2Zn-1.7RE-0.8Zr alloy. The peak-aged Mg-4.2Zn-1.7RE-0.8Zr-0.2Ca-0.2Sr alloy possesses the best corrosion resistance, which is mainly due to the continuous and compact barrier wall constructed by the homogeneous and continuous second phases.

Microstructure and microhardness mechanism of selective laser melting Mg-Y-Sm-Zn-Zr alloy

Abstract In this study, a multi-element mixed rare earth magnesium alloy of Mg-3.4Y-3.6Sm-2.6Zn-0.8Zr (wt%) was selected to form selective laser melting (SLM). In addition, an investigation was conducted on the microstructure, precipitated phases and elements segregation of the experimental alloy deposited by SLM. Moreover, the microhardness and nanomechanical properties of the alloy were determined, with its mechanism summarized. As revealed from the results, there were refinement equiaxed grains in the center of the scanning tracks, and the grain size was 1–3 µm; the overlapping area primarily composed columnar crystals. Specific to the precipitated phases of the mentioned two regions, Mg matrix (hcp), eutectic phase ( Mg , Zn ) 3 (Y,Sm) (fcc) distributed in a network along the grain boundary, and the segregation of Y 2 O 3 and Zr elements were largely involved, noticeably inconsistent with the microstructure of as-cast. As corresponds to the mentioned, the microhardness mechanism of SLM deposited samples was mainly grain boundary hardening and solid solution hardening. The cross section exhibited the significantly greater microhardness (105 HV) than the as-cast (81.5 HV).

Microstructural effect and wear performance of high chromium white cast iron modified with high boron contents

The present study discuss the effects systematic additions of boron (up to 1.197 wt%) on the microstructure, bulk hardness and abrasive wear of a 17Cr– 3C–1Ni–1Mo white cast iron. The alloys were melted in an open induction furnace and cast into 25.4 mm × 12.5 mm cross-section bars. Characterization was carried out by optical and electronic microscopy, energy dispersive spectroscopy, and X-ray diffraction in the as-cast conditions and after a destabilization heat treatment. Hardness was also measured in both conditions. The results show that, boron addition produced a considerable increase of the carbide volume fraction from 27.1 to 53.84% (percentage by volume) and promotes the transition from the Cr rich M7C3 eutectic carbides to the lower C and Cr content M23(C,B)6carbide. However, the hardness values of the experimental alloys were not affected by this transition, and thus, the hardness values increased with the boron content due to a higher carbide volume fraction and the strengthening of the iron matrix reaching a maximum value of 767 HV for the higher B content. Likewise, a secondary hardening effect was produced by the destabilization heat treatment, increasing the hardness values of the different alloys. However, as the boron content increased, this hardening effect becomes less significant. Abrasive wear test were consistent with the hardness values in the as-cast condition by decreasing the wear losses with the increase in B for high and low loads. Similarly, for the destabilized irons, which exhibited higher harness values, a decrease in the wear volume losses were observed for B contents up to 0.598 wt% and the wear losses increased with the increase in applied load.In the case of the heat treated 1.197 wt% B added iron, the wear losses were significantly affected by the applied load during the wear tests. For this alloy, a volume lost of 0.639 mm3 was observed for the test with 54 N a load, which corresponds to the lower value obtained for any B content and experimental condition, while in the case of the test performed with 130 N a relatively high volume lost of 1.319 mm3 was measured which is considerably higher compared with the lower boron alloys in the same condition. This behavior was attributed to the massive carbide cracking observed after heat treatment promoting the carbide detachment during the test with 130 N of load.From the author's review of the literature, the effect of such a high boron addition on the microstructure and wear behavior have never been performed or published for high chromium white cast irons. And the based in the experimental results of the present study, the addition up to 1.197%wt boron in the as cast condition represents an effective way to increase the hardness and wear resistance of these kind of alloys in the as-cast condition suppressing the destabilization heat treatment.

Chemical and structural analyze of experimental biodegradable ZnMgY alloy

Beside biocompatible classic metallic materials, biodegradable metals (BMs) like alloys of zinc (Zn-based) present a high potential as an alternative solution for permanent implants elements generally being applied for fractures restorations or other similar medical conditions. An experimental alloy, ZnMgY, was obtained using an induction furnace from high purity materials (Zn: 99,995 and master alloy MgY: 65-35 wt%), in Argon atmosphere. Microstructure of the alloy (after mechanical grinding and polish plus chemical etching) and chemical insights (before chemical etching) were taken using optical microscope (Zeiss+Motic digital camera for image acquisition) scanning electron microscope (SEM VegaTescan LMH II, SE, 30 kV, 16 mm WD) and dispersive energy spectroscopy (EDS Bruker, PB ZAF, Automatic mode of analyze, Point and Mapping features). The experimental alloy was five times re-melted in the induction furnace using a ceramic crucible. The experimental alloys present a good chemical homogenization without porosity, metallic inclusions or segregation.

Structure and Properties of Ca and Zr Containing Heat Resistant Wire Aluminum Alloy Manufactured by Electromagnetic Casting

Experimental aluminum alloy containing 0.8% Ca, 0.5% Zr, 0.5% Fe and 0.25% Si (wt.%), in the form of a long-length rod 12 mm in diameter was manufactured using an electromagnetic casting (EMC) technique. The extremely high cooling rate during alloy solidification (≈104 K/s) caused the formation of a favorable microstructure in the ingot characterized by a small size of the dendritic cells, fine eutectic particles of Ca-containing phases and full dissolution of Zr in Al the solid solution. Due to the microstructure obtained the ingots possess high manufacturability during cold forming (both drawing and rolling). Analysis of the electrical conductivity (EC) and microhardness of the cold rolled strip and cold drawn wire revealed that their temperature dependences are very close. The best combination of hardness and EC in the cold rolled strip was reached after annealing at 450 °C. TEM study of structure evolution revealed that the annealing mode used leads to the formation of L12 type Al3Zr phase precipitates with an average diameter of 10 nm and a high number density. Experimental wire alloy has the best combination of ultimate tensile strength (UTS), electrical conductivity (EC) (200 MPa and 54.8% IACS, respectively) and thermal stability (up to 450 °C) as compared with alloys based on the Al–Zr and Al– rare-earth metal (REM) systems. In addition, it is shown that the presence of calcium in the model alloy increases the electrical conductivity after cold forming operations (both drawing and rolling).

Tensile Creep Behavior and Microstructure Evolution of As‐Cast Mg–9.82Gd–0.38Zr Alloy at 250 °C

Herein the tensile creep behavior and microstructure evolution of an as‐cast Mg–9.82Gd–0.38Zr alloy under different stresses at 250 °C are investigated. The results of creep test show that the creep strain and steady creep rate increase with the creep stress at 250 °C. The fitted stress exponent n value (4.4) and transmission electron microscopy analysis suggest that the steady creep is dominated by the dislocation climb and glide mechanisms together. At the primary stage, due to the segregation of the Gd content, a fine‐strengthening β′ phase precipitates near the α‐Mg grain boundary. Then the transformation of β′ precipitates to a needle‐like β phase, coarsening, and growth of the β phase toward the intragranular direction gradually deteriorate the creep resistance of the experimental alloy. Moreover, two kinds of precipitate‐free zones (PFZs) appear at the end of the secondary creep stage and the PFZs nearly perpendicular to the applied stress direction widen gradually because of the directional diffusion. The nucleation and propagation of creep crack along the cracked eutectic phase and PFZs lead to the greatly rising creep rate at the end of the tertiary creep stage, which eventually results in the intergranular creep fracture of the experimental alloy.

Effects of Ta on microstructural stability and mechanical properties of hot corrosion resistant Ni-based single crystal superalloys during long-term thermal exposure

Abstract The effects of Ta on microstructural stability and mechanical properties of hot corrosion resistant Ni-based single crystal superalloys during long-term thermal exposure at 900 °C were investigated in the present study by comparing two experimental alloys with different content of Ta (6Ta and 6.7Ta). The results indicated that the addition of extra 0.7Ta increased the volume fraction of the γ′ precipitates and accelerated the coarsening rate of γ′ precipitates, facilitated the formation of misfit dislocation and precipitation of σ phases. The 6.7Ta alloy exhibited higher hardness and better stress rupture properties than 6Ta and the variations of stress rupture properties during the exposure for 6Ta and 6.7Ta alloy are significantly different. The effects of γ′ coarsening, formation of σ phases and misfit dislocations were taken into consideration to identify the reasons of variations of mechanical properties during the thermal exposure.

Microstructural, Electrochemical and In Vitro Analysis of Mg-0.5Ca-xGd Biodegradable Alloys

The subject of Mg-based biodegradable materials, used for medical applications, has been extensively studied throughout the years. It is a known fact that alloying Mg with biocompatible and non-toxic elements improves the biodegradability of the alloys that are being used in the field of surgical applications. The aim of this research is to investigate the aspects concerning the microstructure, electrochemical response (corrosion resistance) and in vitro cytocompatibility of a new experimental Mg-based biodegradable alloy—Mg–0.5%Ca with controlled addition of Gd as follows: 0.5, 1.0, 1.5, 2.0 and 3.0 wt.%—in order to establish improved biocompatibility with the human hard and soft tissues at a stable biodegradable rate. For this purpose, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), light microscopy (LM) and X-ray diffraction (XRD) were used for determining the microstructure and chemical composition of the studied alloy and the linear polarization resistance (LPR) method was used to calculate the corrosion rate for the biodegradability rate assessment. The cellular response was evaluated using the 3-(4,5-dimethyltiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) test followed by fluorescence microscopy observation. The research led to the discovery of a dendritic α-Mg solid solution, as well as a lamellar Mg2Ca and a Mg5Gd intermetallic compound. The in vivo tests revealed 73–80% viability of the cells registered at 3 days and between 77 and 100% for 5 days, a fact that leads us to believe that the experimental studied alloys do not have a cytotoxic character and are suitable for medical applications.

Thermoelastic properties and \u03b3\u2019-solvus temperatures of single-crystal Ni-base superalloys

The present work shows that thermal expansion experiments can be used to measure the γʼ-solvus temperatures of four Ni-base single-crystal superalloys (SX), one with Re and three Re-free variants. In the case of CMSX-4, experimental results are in good agreement with numerical thermodynamic results obtained using ThermoCalc. For three experimental Re-free alloys, the experimental and calculated results are close. Transmission electron microscopy shows that the chemical compositions of the γ- and the γʼ-phases can be reasonably well predicted. We also use resonant ultrasound spectroscopy (RUS) to show how elastic coefficients depend on chemical composition and temperature. The results are discussed in the light of previous results reported in the literature. Areas in need of further work are highlighted.Graphical abstract

Effects of Alloying Elements Additions on Ambient Temperature Performance of Al–Si–Cu–Mg Base Alloys

The present study was carried out to investigate the effects of Ni, Mn, Zr, and Sc additions, individually or in combination with other additives, on the microstructure and tensile properties of 354 casting alloy (Al—9wt%Si—1.8wt%Cu—0.5wt%Mg) at room temperature. Tensile tests were carried out in the as-cast, solution heat-treated, and aged conditions using different aging temperatures and times. Six alloys were prepared using the 354 alloy, comprising a) the base 354 alloy (G1) and five other alloys (G6 to G10) containing Ni, Mn, Sc, Zr, added individually or in combination, and comprising one experimental alloy (G7) containing no copper. Among the alloys containing transition element additions (G6 through G10), the highest tensile and yield strength values are obtained with alloy G7 (2wt% Ni and 0.25wt% Zr but no Cu) in the as-cast and solution heat-treated conditions; alloys G8 and G10 also display a significant increase in tensile strength and ductility in the as-cast and solution heat-treated conditions. Solution heat treatment significantly improves strength and quality of these alloys even if they contain higher Fe and Mg levels compared to the base alloy. Holding the tensile samples of T6-treated G1 alloy resulted in a marked increase in the density of precipitated phase in the form of fine spherical particles. Increasing the holding time prior to deformation to 100 h resulted in the change in the morphology of the Al2Cu precipitates into thin platelets distributed in two perpendicular directions.

Interface characteristics and reaction mechanism of steel/Al welds produced by magnetic field assisted laser welding-brazing

In this paper, we describe experimental laser welding-brazing aluminum alloy to galvanized steel using an external magnetic field. The morphology, microstructure and phase transition at interface was carefully investigated using scanning electron microscope, energy diffraction spectrum and X-Ray Diffractometer. The reaction mechanism of steel/Al welds was also discussed. The results showed that the banded structures with zigzag pattern morphology were produced near the steel matrix. The thickness difference at interface was closely associated with characteristics of laser heat source. The introduction of Zn element in filler metals induces the presence of η-Al5Fe2Zn0.4 phase and δ-FeZn10 phase at the steel interface. These non-brittle phases have good ductility, which can effectively reduce the susceptibility of hot cracking of weld metal and improve the behavior of interface bonding. Meanwhile, fine columnar crystals and eutectic structures formed near the Al matrix as the result of dissolution of Al matrix and regulation of the ampere force. In addition, it has been also found that the metallurgical reaction at interface can be mainly divided into three stages: the solute transfer process, the initiation and the growth of non-brittle phases. The driven effect of magnetic field on molten pool can effectively control the size and distribution of non-brittle phases such as Zn-Al eutectic phases, greatly improving the interfacial performance.

Investigation on microstructures and mechanical properties of Mg–6Zn–0.5Ce–xMn (x = 0 and 1) wrought magnesium alloys

The microstructure evolution and mechanical properties of Mg–6Zn–0.5Ce– x Mn ( x = 0 and 1 wt.%) wrought magnesium alloys were researched, and the morphologies and role of Mn element in the experimental alloys were analyzed. The research shows that all of Mn elements form the α -Mn pure phases, which do not participate in the formation of other phases, such as the τ-phases. The mechanical properties of Mn-containing alloys in as-extruded and aged states are superior to Mn-free alloys. During the hot extrusion process, the dispersed fine α -Mn particle phase hinders the migration of grain boundaries and inhibits dynamic recrystallization, which mainly takes effect of grain refining and dispersion hardening. During the aging treatments, the dispersed fine α -Mn particle phase not only hinders the growth of the solution-treated grains, but also becomes the nucleation cores of β 1 ′ rod-like precipitate phase, which is conducive to increasing the nucleation rate of the precipitate phase. For the aged alloy, the Mn addition mainly takes effect of grain refining and promoting aging strengthening.

Comparative Study of Superelastic Ti–Zr–Nb and Commercial VT6 Alloy Billets by QForm Simulation

A comparative simulation of hot radial shear rolling (RSR) of billets made of a superelastic Ti–Zr–Nb and a commercial VT6 alloy was performed using the QForm finite element modeling program. Rolling in 48 modes with a variable feed angle and elongation ratio at 4 levels and initial rolling temperature at 3 levels was investigated for each alloy. The Ti–Zr–Nb alloy rheology during hot deformation was determined experimentally by hot upset forging and imported into the QForm program. The presence of maxima on the flow curves at the initial stage of deformation, which are absent in the VT6 alloy, is revealed. Simulation results are presented in the form of fields of the stiffness coefficient, strain rate intensity, cumulative strain degree in the maximum reduction section depending on the rolling mode. General regularities of the Ti–Zr–Nb and VT6 behavior in RSR are similar. The gradient of the fields studied decreases, and the roll pressure and torque increase with an increase in the feed angle and elongation ratio. The initial rolling temperature does not significantly affect the deformation pattern, but it significantly affects the roll pressure and torque. At the same time, the experimental alloy demonstrated the greater tendency to localize deforming forces in the near-contact zone and to increase the gradient of stress-strain state parameters over the billet section. The study of the tightening shape and depth of rolled billet ends showed that the Ti–Zr–Nb alloy has a 3.5–9.6% greater tightening depth. It is shown that experimental alloy rolling requires 1.6–2.4 times higher roll pressure and torque as compared to the commercial alloy.

Hydrogen diffusion in Ni-Cr-Fe system

• Electrochemical permeation test on Ni-base melting-rolling and Inconel alloys. • Mitigation of the hydrogen diffusion coefficient due to the precipitate was found on meting rolling alloys. • The effect of chromium content on the hydrogen effective diffusion coefficient was study. • The interplanar distance does not affect the hydrogen steady state flux and effective diffusion coefficient. Nickel-based superalloys have been widely used in applications that require mechanical and corrosion resistance at high temperatures. Generally, the main problem in some applications such as pressurized water reactors is the hydrogen embrittlement (HE). The HE phenomenon has been extensively studied in several superalloys and other materials. Efforts have focused on improving the performance of Ni based alloys against the main mechanisms associated with HE, developing new strategies such as intergranular precipitation to counteract HE. In the present work the aim was to study the hydrogen diffusion (HD) in Ni-based experimental alloys manufactured by melting and hot rolling processes. Two Inconel commercial and three experimental Ni-based alloys were studied, considering the Cr content (%wt) as the main variable element. The alloys were characterized by optical microscopy (OM), scanning electron microscopy (SEM), Vickers microhardness test and X-ray diffraction (XRD). On the other hand, the effective diffusion coefficient (D eff ) and steady state flux (J ss ) were determined under the ASTM G-148 standard conditions. A slight hydrogen mitigation effect was found due to the Cr content and microstructure. The aforementioned results agree with the literature and a recent proposal for mitigating HD as a function of the irreversible traps density.