Thermal Stability Of Alloy Research Articles

Stress relief heat treatment and mechanical properties of laser powder bed fusion built 21-6-9 stainless steel

In this work, the effectiveness of residual stress relief annealing on a laser powder bed fusion (L-PBF) manufactured austenitic stainless steel, alloy 21-6-9 was investigated. Residual stress levels were gauged using geometrical distortion and relaxation testing results. In the investigated temperature interval (600–850 °C), shape stability was reached after subjecting the as-built material to an annealing temperature of 850 °C for 1 h. Microstructural characterization and tensile testing were also performed for each annealing temperature to evaluate the alloy's thermal stability and the resulting tensile properties. In the as-built state, a yield strength (YS) of 640 MPa, ultimate tensile strength (UTS) of 810 MPa and 4D elongation of 47% were measured. Annealing at 850 °C for 1 h had little measurable effect on ductility (48% 4D elongation) while still having a softening effect (UTS = 775 MPa, YS = 540 MPa). From the microstructural characterization, cell-like features were observed sporadically in the annealed condition and appeared stable up until 800 °C after which gradual dissolution began, with the last remnants disappearing after subjecting the material to 900 °C for 1 h.

Effects of phosphorus substitution on amorphous formation, crystallization behavior and magnetic properties of FeSiBCuNb alloys

Fe-Si-B-Cu-Nb nanocrystalline alloys exhibit excellent soft magnetic properties and have been increasingly applied in high frequencies ranging from several kHz to several hundred kHz, but the magnetic permeability needs further to design to meet the magnetic components under different frequencies. In the present work, the influences of phosphorus substitution on amorphous forming, crystallization behavior and soft magnetic properties of silicon-rich Fe-Si-B-Cu-Nb alloys were systematically investigated. It was found that the suitable addition of 1 at.% of P in Fe-Si-B-Cu-Nb alloy can significantly improve the amorphous forming ability, reduce the coercivity (Hc) of the annealed alloys and elevate the effective magnetic permeability (μe) at frequencies ranging from 1 to 30 kHz in spite of having fractional detriment to the alloy's thermal stability but still remaining a relatively broad annealing temperature region. Besides, the μe in high P-containing alloys becomes insensitive to frequencies at high frequencies region, which can attain frequencies-dependent constant magnetic permeability induced by composition design.

Towards applicable photoacoustic micro-fluidic pumps: Tunable excitation wavelength and improved stability by fabrication of Ag-Au alloying nanoparticles

Photoacoustic micro-fluidic pumps (PMPs) based on localized surface plasmon resonance (LSPR) of nanoparticles (NPs) can convert photo energy into kinetic energy of fluidic jetting therefore attracted considerable attentions in microfluidics and optofluidics. In this work, PMPs are fabricated using Ag-Au alloy NPs. Through solid-state-dewetting, alloy NPs are prepared of variable component ratios for tunable LSPR absorption between 440 and 530 nm. The relationship between NP morphology and optical properties are studied with the assistant of finite-difference time-domain (FDTD) simulation. Photoacoustic jets are observed through the excitation of both 450 and 532 nm lasers. Noticeably, with 450 nm laser, long lasting jets over 1 h are excited on Ag0.9Au0.1, which sharply contrast to the duration within 1 min on Ag0.2Au0.8 NPs with 532 nm laser, indicating the importance of material selection in performance improvement. Further investigation on jetting stability is performed according to the morphological evolution by laser striking, suggesting the enhanced stability can be related to the increased melting-point and thermal-stability of alloys.

Interaction between Al and other alloying atoms in α-Ti for designing high temperature titanium alloy

Increasing the solubility of Al and inhibiting the growth of Ti3Al precipitates in high temperature titanium alloy improve both the thermal strength and thermal stability of the alloy. In principle, this may be achieved by adding some other alloying atoms which attract Al so as to serve as traps for Al in the alloy. In the present work, the interaction energies between Al and alloying atoms X with X covering all the transition metal (TM) and noble metal (NM) elements in the Chemical Elemental Period Table (CEPT) are calculated by using a first principles method in order to screen the traps for Al. The effects of temperature (taking Mo-Al interaction as an example) as well as the newly found off-center site-occupation of alloying atoms (Acta Mater. 197, 2020, 91) on the interaction energies are considered. We show that the interactions between Al and the TM alloying atoms early in the CEPT are weak. The middle TM alloying atoms attract but the late TM and NM ones repel Al. At finite temperature, the lattice vibration enhances whereas the configurational entropy weakens the Mo-Al attraction. Both effects become stronger with increasing temperature. The physical origins underlying the X-Al interactions are revealed by analyzing the electronic density of states and bonding charge density. Alloying atoms such as Mo, Tc, Ru, W, Re, and Os are identified to benefit the strength and thermal stability of high temperature titanium alloys. This work is helpful to the rational design of high temperature titanium alloys.

Effect of residual nanocrystals on thermal stability and mechanical properties of metalloid-containing amorphous alloys

Herein we present the amorphization, thermal stability, crystallization behavior, and mechanical properties of (Ni60Nb40)100-x-ySixBy (x = 0, 5 and 10 at.%, y = 0, 5 at.%) alloys with six distinct compositions. We investigated the influence of the nanocrystals formed by the addition of Si and B on the thermal stability and mechanical properties of the (Ni60Nb40)100-x-ySixBy (x = 0, 5 and 10 at.%, y = 0, 5 at.%) alloys. The phase and thermal stabilities of the alloys were studied using X-ray diffraction, high-resolution transmission electron microscopy, and differential scanning calorimetry and the mechanical properties were characterized by nanoindentation testing. It was found that single-step crystallization occurred in B-free alloys, whereas double step crystallization occurred in B-containing alloys. B-free (Ni60Nb40)90Si10 alloy exhibited the highest onset temperature of 714 °C, and B-containing (Ni60Nb40)95B5 alloy shows the lowest onset temperature at 642 °C. The microstructure of B-containing amorphous alloys consists of nano-sized metallic crystals with a size of less than 5 nm embedded in an amorphous phase. The existence of residual nanocrystals facilitates heterogeneous nucleation during crystallization of the amorphous phase, weakening the thermal stability of amorphous alloys. Crystallization of the amorphous phase remarkably enhances the mechanical properties of (Ni60Nb40)100-x-ySixBy (x = 0, 5 and 10 at.%, y = 0, 5 at.%) alloys, with a 40–60% increase in hardness and 19–88% increase in elastic modulus. An increase in mechanical properties after crystallization is lower in B-containing alloys because of the lower nano-intermetallic phases formation after crystallization, due to the presence of the residual nanocrystals.

Coupled segregation mechanisms of Sc, Zr and Mn at [formula omitted] interfaces enhances the strength and thermal stability of Al-Cu alloys

The refinement and thermal stability of intermediate theta-prime (θ′) precipitates are critical in the development of new high strength 2xxx series aluminium-copper (Al-Cu) alloys for high temperature applications. In this work, we use trace additions of Sc, Zr and Mn in an Al-6.5 wt.% Cu alloy to refine and stabilise the θ′ precipitates. The formation of Al3(Sc, Zr) core/shell dispersoids significantly refine the θ′ precipitates by acting as preferential nucleation sites during artificial ageing. Adding Mn results in a significant increase of hardness during ageing at 190 °C. Hardness is maintained during thermal exposure at 280 °C for up to 24 h. Transmission electron microscopy (TEM) reveals that the addition of Mn leads to a finer and denser distribution of θ′ precipitates, and greatly slows the growth and coarsening of the θ′ precipitates at elevated temperatures. Differential scanning calorimetry (DSC) shows that this can be attributed to an enhanced nucleation and improved coarsening resistance of the θ′ precipitates in the presence of Mn. Atom probe tomography (APT) reveals that the enhanced age-hardening kinetics and thermal stability arise from the independent segregation mechanisms of Mn, Sc and Zr at the semi-coherent and coherent interfaces of the θ′ precipitates. The segregation is quantified by calculating the Gibbsian interfacial excess and corresponding reduction in interfacial energy. These calculations reveal that while Sc and Zr play a significant role in the refinement of the θ′ precipitates, Mn not only refines the θ′ precipitates, but also greatly enhances their coarsening resistance and corresponding alloy's thermal stability.

Alloying behavior and thermal stability of mechanically alloyed nano AlCoCrFeNiTi high-entropy alloy

Abstract

Enhancement of mechanical and electrical properties of Al-RE alloys by optimizing rare-earth concentration and thermo-mechanical treatment

Al-based immiscible systems, such as Al-RE (rare earth), seem to be promising materials for high conductivity conductors as RE alloying elements have zero solubility in Al and thus are less detrimental for electrical conductivity. The intermetallic phases, precipitated as small particles and uniformly distributed in the alloy's volume, may significantly increase the mechanical strength and thermal stability of alloy. However, the immiscible element compound concentration should be controlled as an excessive amount might result in a loss of electrical conductivity. Therefore, the optimization of RE concentration to obtain the best combination of mechanical strength and electrical conductivity is considered in this research. It focuses also on the effect of high-pressure torsion (HPT) and post deformation annealing temperature on mechanical and electrical properties of Al-RE (La + Ce) alloy. Alloys with total Ce and La concentrations of 2.5, 4.5 and 8.5 wt % are subjected to HPT at room temperature and subsequent annealing in the range of temperatures 230–400 °C. The optimal concentration of RE and processing parameters for enhancement of both mechanical strength and electrical conductivity are defined.

Enhanced thermal stability and fracture toughness of TiAlN coatings by Cr, Nb and V-alloying

The effect of metal alloying on mechanical properties including hardness and fracture toughness were investigated in three alloys, Ti~0.33Al0.50(Me)~0.17N (Me = Cr, Nb and V), and compared to Ti0.50Al0.50N, in the as-deposited state and after annealing. All studied alloys display similar as-deposited hardness while the hardness evolution during annealing is found to be connected to phase transformations, related to the alloy's thermal stability. The most pronounced hardening was observed in Ti0.50Al0.50N, while all the coatings with additional metal elements sustain their hardness better and they are harder than Ti0.50Al0.50N after annealing at 1100 °C. Fracture toughness properties were extracted from scratch tests. In all tested conditions, as-deposited and annealed at 900 and 1100 °C, Ti0.33Al0.50Nb0.17N show the least surface and sub-surface damage when scratched despite the differences in decomposition behavior and h-AlN formation. Theoretically estimated ductility of phases existing in the coatings correlates well with their crack resistance. In summary, Ti0.33Al0.50Nb0.17N is the toughest alloy in both as-deposited and post-annealed states.

Influence of Annealing Treatment on Microstructure and Mechanical Properties of Fe-Cu-Si-Al Amorphous Composites

In this study, the bulk amorphous alloys with 3mm in diameter were prepared at different voltages adopting copper mould suction casting method by adding microelement Al to Fe-Cu-Si based amorphous alloy respectively. The microstructures, glass-forming ability, mechanical compressive properties of (Fe0.34Cu0.47Si0.19)95Al5 amorphous composites annealed in different temperature were investigated. The results showed that re-melting of master alloy refined the solidified microstructure and homogenize the composition and microstructure. Moreover, the microstructure was stable with the increase of re-melting times. After relaxation and annealing at low temperature the majority of residual thermal stress was released during annealing at low temperature, with the enlargement of short-range order of amorphous microstructure and the decrease of the most adjacent inter-atomic distance. After proper annealing treatment the hardness and thermal stability of alloy were improved, indicating that the annealing treatment could improve the properties of amorphous alloy.

High Temperature Behavior of the EN AW-2618A Piston Alloy Containing 0.12wt% Zr: Influence of Heat Treatment

This study compares the conventional T6 (“solution-quenching-aging”) treatment with an innovative one, in terms of high temperature response of the EN AW-2618A alloy, containing 0.12wt% Zr. The new treatment is aimed to stimulate Zr-based precipitates with optimal size, shape and distribution, in order to completely take advantage of Zr anti-recrystallization effect. To assess alloy's thermal stability, samples subjected to both heat treatments were soaked at 250°C, up to 50h. Hardness measurements, microstructural characterization and high temperature compression tests have been carried out, giving evidence of significant improvements connected to controlled formation of Zr-based precipitates.

Mechanical properties and thermal stability of Al-23Si-8Fe-1Cr and Al-23Si-8Fe-5Mn alloys prepared by powder metallurgy

Al–23Si–8Fe–1Cr and Al–23Si–8Fe–5Mn (in wt%) alloys were prepared via melt centrifugal atomization following powder compaction by uni-axial pressing at 6GPa and 450°C for 60min. The obtained materials were porosity-free with good particle-to-particle contact. The “composite-like” microstructures were very fine, showing silicon particles distributed in an α-Al matrix and displaying nearly equiaxed intermetallic phases. The intermetallic phases were identified as β-Al5FeSi and α-Al9.3FeMn1.4Si1.8 in the Al–23Si–8Fe–1Cr and Al–23Si–8Fe–5Mn alloys, respectively. The Vickers hardness and compressive yield strength were 182HV5 and 540MPa, respectively, for the Al–23Si–8Fe–1Cr alloy and 197HV5 and 650MPa, respectively, for the Al–23Si–8Fe–5Mn alloy. The thermal stability of the alloys was studied by mechanical testing after long-term annealing at 300–400°C, by compressive testing at 200–300°C and by creep testing at 300°C and 250MPa. The thermal stability of both alloys was significantly better when compared to the “thermally stable” casting Al–12Si–1Cu–1Mg–1Ni alloy that is commonly utilized in the automotive industry for thermally loaded components such as pistons for combustion or diesel engines.

Thermal stability of Al-Ni-Fe-La aluminum amorphous alloys

The thermal stability of aluminum amorphous alloys with various contents of nickel, iron, and lanthanum is studied by differential scanning calorimetry, X-ray diffraction, and electron-microscopic analysis in the initial state and after heat and deformation treatment. The alloys are found to crystallize in two stages. The alloy with the maximum iron content (Al85Ni7Fe4La4) is shown to have the maximum thermal stability. Preliminary annealing at temperatures below the temperature of the onset of crystallization weakly affects this temperature. Preliminary severe plastic deformation increases the thermal stability of the alloys, which is caused by the existence of the first stage of crystallization during deformation. The structural aspects affecting the thermal stability of the alloys are considered.

Investigation of glass forming ability in Ce–Al–Ni alloys

The compositional dependence of the glass forming ability (GFA), the correlation between their GFA and the GFA related parameters, and the thermal stability of the Ce–Al–Ni alloys were investigated. Rapidly quenched Ce65AlxNi35−x (x=2, 5, 10, 17, 20) and Ce70AlxNi30−x (x=2, 5, 10, 15, 20) ribbons were prepared by melt spinning, and their phase transformations were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The experimental results indicated that the GFA of Ce65AlxNi35−x (x=2, 5, 10, 17, 20) and Ce70AlxNi30−x (x=2, 5, 10, 15, 20) alloys increased firstly and then decreased with the increasing of the Al content up to 20at.%, respectively. It was found that only one parameter, F1, in evaluated currently available empirical GFA parameters searching for metallic glasses with a good GFA, can reflect the GFA of the Ce–Al–Ni alloys. It was indicated that the thermal stability of alloy with fully amorphous maybe lower than that of alloy with partial amorphous.

Structure and Properties of Ultrafine-Grained Cu-Cr Alloys after High Pressure Torsion

The effect of chromium content (0.75, 9.85, 27%) and initial state on the thermal stability of copper-chromium alloys after severe plastic deformation has been studied by microhardness and electrical resistivity measurements. The stability of the structures is established to depend on the initial state of the alloys and on the content of chromium phase. In the low-alloy bronze, quenching before HPT substantially increases the thermal stability of the alloy relative to that observed after annealing. The softening temperature increases with increasing chromium phase content and reaches 450°C for the alloy with 27% Cr.

Erosion of a TiAl intermetallic alloy under conditions simulating plasma disruptions

Radiation erosion and thermal stability of TiAl-based intermetallic alloys produced by vacuum-arc melting, compacting of microcrystal powders with binder and impregnantion by melt, and their brazed joints with bronze have been investigated under irradiation by high-temperature pulsed hydrogen plasma flows (the flow energy density Q = 0.2−0.9 MJ/m 2, the pulse duration 15 μs, the number of pulses 1–21) which simulate the expected plasma disruptions in a fusion reactor. It has been found that the erosion coefficients and thermal stability of alloys are determined by the way of their fabrication, and compacted intermetallides have a higher thermal stability in comparison with the cast ones. The brazed joints of the intermetallic compound with bronze under irradiation by pulsed hydrogen plasma up to the energy density Q = 0.75 MJ/m 2 have a high thermal stability and formation of cracks was not observed.

Enhanced thermal stability of Zr 65Cu 17.5Ni 10Al 7.5 metallic glass at temperature range near glass transition by oxygen impurity

The ‘panoramic effects’ of oxygen impurity on the thermal stability of Zr 65Cu 17.5Ni 10Al 7.5 metallic glass have been investigated by constructing time–temperature-transformation diagram and analyzing the precipitation kinetics of primary phase. It is found that oxygen has contrary effects on the alloy's thermal stability exhibiting in high- and low-temperature ranges because of primary phase selection. The primary phase for Zr 65Cu 17.5Ni 10Al 7.5 glassy alloy depends on its oxygen content as well as the temperature range in which crystallization takes place. For the alloy containing higher oxygen and crystallized at higher temperature, oxygen-induced metastable f.c.c.-Zr 2Ni precipitates as primary phase. However, for the alloy with lower oxygen content, or with higher oxygen content but crystallized at lower temperature, stable b.c.t.-Zr 2Cu forms as initial precipitation phase. Oxygen retards the precipitation of b.c.t.-Zr 2Cu phase and stabilizes glassy matrix, enhanced thermal stability in the temperature range near glass transition is possessed by the alloy with higher oxygen.

A study on the thermal stability of some alloys in the Sb–As–Se glassy system by differential scanning calorimetry

The thermal stability and crystallization of alloys in the Sb–As–Se glassy system have been studied by differential scanning calorimetry (DSC). A comparison of various simple quantitative methods to assess the level of stability of the glassy materials in the above-mentioned system is presented. All of these methods are based on characteristic temperatures, such as the glass transition temperature, T g, the onset temperature of crystallization, T in, the temperature corresponding to the maximum crystallization rate, T p, or the melting temperature, T m. In this paper, the parameter K r( T) is added to the stability criteria. The thermal stability of some ternary compounds of the Sb x As 0.36Se 0.64− x type has been evaluated experimentally and correlated with the activation energies of crystallization by this kinetic criterion and compared with those evaluated by other criteria.

Structure and Properties of Sheets of 1424 Alloy

The weldable, corrosion-resistant 1424 alloy (Al-Mg-Li) with lower density has been developed on basis of Russian 1420 and 1421 alloys for realization of new airbuses fuselage concept using laser beam welding technology [1,2]. The optimization of chemical composition, heat treatment and production technology of wide (2600 mm) sheets ensured the improvment of the damage tolerant behaviour and thermal stability of alloy. In case of an application of 1424 sheets in welded fuselage structures an additional perfomance increase compared not only to the nonweldable 2024T351 alloy, but also to the 6013 / 6056 welded structures can be realized because of the better corrosion resistance and especially of the 8% lower density of 1424.

Effect of boron on the phase composition and thermal stability of a heat-resistant nickel alloy

1. The optimal concentration of boron in alloy VZhL12B for the attainment of phase stability, the formation of a minimum amount of eutectic γ′-phase, and superior properties of 0.05–0.08%. 2. The favorable effect of boron additions is due to formation of the boride M3B2, which prevents the appearance of the embrittling σ-phase in the alloy during use, at locations where chromium and molybdenum accumulate around eutectic γ′-phase. 3. The high thermal stability of the alloy is due to the ability of the boride M3B2 to partially dissolve at high temperatures and stresses, with subsequent interaction of the boron with structural defects at interphase boundaries.