Solid Solution Strength Research Articles

Effect of Al contents on the microstructure and cavitation erosion resistance of TiSiN/NiTiAlxCrCoN nanomultilayer films

Abstract The TiSiN/NiTiAlxCrCoN nanomultilayer films were grown on 304 stainless steels through magnetron sputtering system. The microstructure and cross-sectional and surface images, mechanical and cavitation erosion properties of the prepared films were explored in detail. The results of the study reveal that all TiSiN/NiTiAlxCrCoN nanomultilayer films exhibit a face-centered cubic structure with a preferential orientation in (200) plane. The cross-sectional images of films show the columnar structure. The values of elastic modulus, hardness, and adhesive strength for the TiSiN/NiTiAlxCrCoN nanomultilayer films initially increase and later decrease as the Al content is increased, whereas the mass loss for the TiSiN/NiTiAlxCrCoN nanomultilayer films initially decrease and later increase during the cavitation erosion experiment. The TiSiN/NiTiAl0.8CrCoN nanomultilayer film provides a maximum hardness value equal to 31.3 GPa, a maximum elastic modulus equal to 218.9 GPa, a highest adhesive strength equal to 38.8 N and a least mass loss equal to 0.8 mg. The study showed that the solid solution strength and the alternating stress field enhance the properties of the TiSiN/NiTiAlxCrCoN nanomultilayer films.

Comparison of The Yield Strength of High-Entropy Solid Solutions Based on BCC and FCC Lattices Obtained in the Experiment and Calculation

Based on the literature data, high-entropy alloys based on BCC or FCC phases were selected for which the ultimate strength from 214 to 2863 MPA was determined. Knowing the chemical composition of the selected high-entropy alloys, the average elastic modulus, distortion level, and mixing enthalpy were calculated. The use of formulas that use only their atomic radius and elastic modulus, mixing enthalpy to determine the theoretical level of hardness made it possible to establish the yield strength based on the ratio s0,2=0,3H.

Temperature dependence on γ/γ' partitioning behaviors of alloying elements and γ/γ' interfacial energy of a Mo-rich Ni based single crystal superalloy

Based on three-dimensional atom probe technique and Ardell method, the influences of temperature (850℃∼1150℃) on microstructure, compositions and solid solution strengths of γ and γ′ phases, γ/γ' partitioning behaviors of alloying elements and γ/γ' interfacial energy of a Mo-rich Ni based single crystal superalloy were investigated. After quenching from 1100℃, microstructure was basically similar as heat-treated state. However, after quenching from 1150℃, γ′ phase obviously re-dissolved, and γ channel obviously widened. Meanwhile, with increasing temperature, Co, Cr, Mo and Re contents in γ phase decreased, while Al and Ta contents in γ phase increased. With increasing temperature, Co, Cr and Re contents in γ′ phase slightly decreased, Mo content in γ′ phase significantly decreased, while Al and Ta contents in γ′ phase increased. Meanwhile, with increasing temperature, solid solution strength of γ phase decreased, while solid solution strength of γ′ phase increased. In addition, with increasing temperature, partitioning ratios of Co, Cr and Re elements decreased, partitioning ratios of Mo and Al elements increased, while partitioning ratio of Ta firstly decreased and then increased. Moreover, both γ/γ′ interfacial width and γ/γ′ interfacial energy decreased with increasing temperature.

Influence of Ageing Treatment on Microstructure and Mechanical Properties of GH4169 Alloy Prepared Using Wire Arc Additive Manufacturing

The effects of solid-solution and ageing treatments on the microstructure and mechanical properties of a GH4169 alloy made by wire arc additive manufacturing, micro-casting, and forging were researched. The microstructure, along with the size and type of precipitated phase, were analysed using an optical microscope, scanning electron microscope, and transmission electron microscope. The strength and toughness were tested using a tensile testing machine. The results show that a polygonal austenite microstructure was obtained for the GH4169 alloy prepared through wire arc additive manufacturing, micro-casting, and forging, followed by solid-solution and double-ageing treatments at different times. There were a few twins in the austenite matrix. A large number of nano-sized γ″- and γ′-precipitated phases and a small number of Laves phases and MX phases were found in the matrix. The tensile strength and yield strength of the GH4169 alloy increased first and then decreased with the ageing time. After ageing for 16 h, the maximum yield strength was 1287 ± 22 MPa, the maximum tensile strength was 1447 ± 19 MPa, and the elongation was about 19.5%. The main strength mechanism is precipitated phase strength and solid-solution strength. The fracture exhibited obvious ductile fracture characteristics.

Carbon addition and temperature dependent tensile deformation resistance and capacity of a low-cost 3rd-generation Ni-based single crystal superalloy

A balance between the mechanical performance and castability of Ni-based single crystal superalloys is expected to be achieved by doping with appropriate carbon content. In this study, the influences of carbon content on the tensile properties of a novel low-cost 3rd-generation Ni-based single crystal superalloy at 760 °C and 1120 °C were investigated. Results showed that minor carbon addition could slightly increase the strength and plasticity of the experimental alloy at 760 °C, whereas it led to the decrease of strength and plasticity at an elevated temperature of 1120 °C. This variability was discussed in terms of the microscopic resistance for dislocation movement and the macroscopic deformation capacity associated with damage accumulation. It was found that the solid solution strength and interface strength were enhanced with increasing carbon content, however, the strength at high temperature was compromised by the enormous consumption of refractory elements, even though the precipitation of blocky M6C carbides provided additional hindrance. As for the macroscopic deformation capacity, interdendritic carbides could hinder the extension and/or trigger the activation of slip bands at 760 °C. Nonetheless, the initiation tendency and propagation behavior of microcracks at 1120 °C were facilitated due to the strong stress concentration and severe deformation incompatibility of interdendritic carbides. Overall, future compositional optimization should focus on reducing the formation of Ta-enriched MC carbides to minimize the loss of refractory element reinforcement and the reduction of deformability at high temperatures.

Synthesis, characterization, mechanical and magnetic characteristics of Gd3+ /PO4 3 - substituted zircon for application in hard tissue replacements.

The study reports on the use of sol-gel technique to yield zircon type [Zr(1-0.1-x) GdxTi0.1 ] [(SiO4 )1-x (PO4 )x ] solid solution. Titanium has been used as a mineralizer to trigger zircon formation while equimolar concentrations of Gd3+ and PO4 3- were added to determine their accommodation limits in the zircon structure. The crystallization of t-ZrO2 as a dominant phase alongside the crystallization of m-ZrO2 and zircon were detected at 1200°C while their further annealing revealed the formation of zircon as a major phase at 1300°C. Heat treatment at 1400°C revealed the formation of zircon-type solid solution [Zr(1-0.1-x) Gdx Ti0.1 ][(SiO4 )1-x (PO4 )x ] comprising the accommodation of 10 mol.% of Gd3+ /PO4 3- at the zircon lattice. Beyond 10 mol.% of Gd3+ /PO4 3- , the crystallization of GdPO4 as a secondary phase is noticed. Structural analysis revealed the expansion of zircon lattice due to the simultaneous occupancy of Gd3+ /PO4 3- for the corresponding Zr4+ /SiO4 4- sites. The mechanical strength of single-phase zircon solid solution was higher in comparison to that of multiphase materials, namely in the presence of GdPO4 formed as a secondary phase in samples with added equimolar Gd3+ /PO4 3- contents beyond 10 mol.%. Nevertheless, the paramagnetic behavior of the samples demonstrated a steady surge as a function of enhanced Gd3+ content.

Experimental Investigations of Ni-Ti-Ru System: Liquidus Surface Projection and 1150 °C Isothermal Section.

Ruthenium addition inhibits the formation of the topologically close-packed phases in Ni-based superalloys and improves the solid solution strength of Ni-Ti shape memory alloys. Therefore, the Ni-Ti-Ru phase stability is a very valuable indicator of the effects of Ru in Ni-based superalloys and Ni-Ti shape memory alloys. In this study, the isothermal section at 1150 °C and liquidus surface projection of the Ni-Ti-Ru ternary system were determined experimentally using the equilibrated alloy method and diffusion couple method, respectively. Alloys were prepared through the arc-melting of Ni, Ti, and Ru (all 99.99% purity), and then vacuum encapsulation in quartz tubes, followed by annealing at 1150 °C for 36 to 1080 h depending on the alloy composition. Diffusion couples were fabricated by joining one single-phase block (τ1) with one two-phase block (Ni3Ti + γ(Ni)), and the couples were annealed under vacuum at 1150 °C for 168 h. Reaction temperatures of as-cast alloys were determined by differential scanning calorimetry performed with heating and cooling rates of 10 °C/min. Scanning electron microscopy and X-ray diffraction were used to analyze the microstructure. Seven three-phase regions were found at the 1150 °C isothermal section. Seven primary solidification regions and five ternary invariant reactions were deduced in the liquidus surface projection. A new ternary compound τ1 was discovered in both the isothermal section at 1150 °C and liquidus surface projection. The results aid in thermodynamic modeling of the system and provide guidance for designing Ni-based superalloys and Ni-Ti shape memory alloys.

Modulating the microstructure and mechanical properties of β-Ti-reinforced bulk metallic glass composites by carbon addition

The effects of carbon addition on the microstructure modifications and mechanical response of Ti48Zr20Nb12Cu5Be15 BMGCs are investigated. With increasing carbon content from 0.1 at.% to 0.3 at.%, the evolution of morphology and solid solution strength is not obvious, and the ductile-brittle transition is presented due to the large changes of the sub-Tg relaxation enthalpies, ΔHrel, in the glass matrix when the interstitial C content increasing to 0.5 at. %. Once the C content excess this threshold value, a large melting area and open cracks are mainly related with the size and number of carbide particles and the magnitudes of free volume in the glass matrix, which indicates the appearance of large-sized vermicular-like structure is the cause of instability of composite material. In addition, when C exceeds its limit solute concentration, harder β-Ti-reinforced dendrites and precipitate phases can suppress the initiation of shear bands, and the transfer ability of the concentrated stress to the surrounding glass becomes weaker, which promotes the formation of cracks, resulting in brittle failure.

Influence of V and Al in enhancing the strength and ductility of Co-rich high-entropy alloys

Since the proposal of face-centered cubic (fcc)-structured high entropy alloys (HEAs) almost two decades ago, multiple compositional combinations have been significantly developed, exhibiting exceptional mechanical properties. In this study, we propose a strategy for developing an fcc-structured Co-rich Co40Fe25V20Ni15 HEA by incorporating V instead of Cr to take advantage of its efficient strengthening effect. The newly developed HEA possesses solid-solution strength (σo) and Hall-Petch coefficient (ky) of 204 ± 13 MPa and 955 ± 60 MPa·µm1/2. The estimated ky is the highest amongst all fcc-structured HEAs and indicates a high grain boundary strengthening effect. Additional minor alloying with Al further enhances the mechanical performance of the alloy via precipitation-strengthening effects which exhibit comparable mechanical properties as Ni-based superalloys. Microstructural analyses of the deformation microstructures for the Al-free and Al-containing Co-rich samples reveal that deformation twinning is prevalent at 298 K and 77 K. The present study further demonstrates the importance of utilizing V and Al in developing high-performance alloys.

PySSpredict: A python-based solid-solution strength prediction toolkit for complex concentrated alloys

The emergence of solid solution high entropy alloys (HEAs) and complex concentrated alloys (CCAs) offers opportunities to design novel alloys with tailored strength and ductility. The growing community of integrated-computational materials engineering (ICME) can benefit from implementing state-of-the-art solid-solution strengthening models to alloy design practices. This paper introduces pySSpredict, an open-source python-based toolkit that automates high-throughput calculations of solid-solution strengths of CCAs and thermodynamic properties. We present the functions of the pySSpredict code: (1) automating high-throughput calculations of strength for CCAs, (2) managing the data of thermodynamic calculations from databases or other software, and (3) visualizing and filtering the data to identify candidate alloys. The toolkit implements the latest theoretical edge dislocation model for face-centered cubic (FCC), and edge/screw dislocation models for body-centered cubic (BCC) alloys. The pySSpredict code is hosted on GitHub and deployed on nanoHUB for demonstrations.

Corrosion Resistance of Amorphous-Nanocrystalline Composite Structure Materials.

The purpose of this paper is to investigate the corrosion resistance of different nanoscale microstructures in the same material system and propose a novel method to obtain high-performance materials. During the last 2 decades, microstructure refinement and microalloying have become the main methods to prepare high-performance materials. The tensile strength of nanocrystalline solid solutions can reach 2.3 gigapascal, which is more than 1 fold the strength of traditional steel. However, there are few studies about the corrosion resistance of different nanoscale microstructures. In this paper, coatings with different microstructures (nanocrystalline, amorphous, and amorphous-nanocrystalline composite) have been successfully prepared by electrodeposition in the same material system (nickel-phosphorus alloy). Electrochemical test and high-pressure corrosion immersion test were carried out. The results show that the material loss of amorphous-nanocrystalline coating (P = 9.2 wt %) is about 1/4 that of crystalline coating at 8 MPa. In the range of 0.1 and 8 MPa, the average acceleration effect of hydrostatic pressure on the corrosion rate was calculated to be 1.611 × 10-6 g·cm-2·d-1·MPa-1.

Quantitative evaluation of the short-range order strengthening effect on solid solution and GB strength of Mg–Y alloys by ab initio calculations

Quantitative evaluation of the short-range order strengthening effect on solid solution and GB strength of Mg–Y alloys by ab initio calculations

Effects of aging time on the microstructural evolution and strengthening behavior of a VCoNiMo medium-entropy alloy

Medium-entropy alloys exhibit remarkable strengthening effects owing to their large solid-solution strength, providing high potential for further improvement of the mechanical properties by distributing secondary strengthening phases. In this respect, an equiatomic VCoNi alloy is an appropriate model alloy owing to its yield strength of approximately 1 GPa, with contributions from lattice and grain boundaries. However, the adoption of precipitation hardening is challenging because the solid-solution phase region is limited, which is obtainable only at high temperatures. In this study, Mo is used to generate strengthening phases and expand the region of a face-centered cubic (FCC) solid-solution phase at lower temperatures. The 10 at% Mo, determined through thermodynamic calculations, has little effect on solid-solution states. In low-temperature aging treatments, an ordered FCC (L12) phase forms first followed by the formation of intermetallic μ and κ phases, which are developed under prolonged heat treatment of up to 48 h. L12, which cannot be expected by thermodynamic calculations as an intermediate phase, results in remarkable strengthening effects with a slight reduction in tensile ductility. However, the (Co,Ni)3V-κ phase grows into the grain interiors and along the FCC grain boundaries forming lamellar structures with μ phase, which reduces ductility and increases strength. Thus, this work suggests that the Mo substitution to V overcomes the limitations of the VCoNi alloy and provides second-phase strengthening by forming homogeneous L12 within a large fraction of the FCC matrix; however, an appropriate heat treatment is required to prevent brittleness by suppressing grain-boundary μ and κ phases.

Greatly enhanced discharged energy density and efficiency of BiFeO3-Based ceramics by regulating insulation performance

BiFeO3 (BFO) with excellent intrinsic polarization (Ps > 100 μC/cm2) receives a great deal of attention for advanced lead-free ferroelectric materials. However, the low resistance and high leakage current density in its naturally seriously hinder the improvement of energy storage performances. Herein, we demonstrate that superb comprehensive performances of large discharged energy density (Wrec ∼ 6 J/cm3) along with superior discharged efficiency (η ∼ 90%), impressive frequency stability (1–500 Hz), fatigue resistance testing (1-105 cycles) and ultrafast discharged time (t0.9–0.08 μs) could be attained in 0.3BiFeO3-0.7(0.88BaTiO3-0.12Bi(Li1/3Hf2/3)O3 [BFO-(BT-BLH)] relaxor ferroelectric ceramics. Remarkably improved breakdown strength (Eb) of BFO-based solid solutions could be primarily contributed to the substitution of BT-BLH, which provides refined grain sizes, as well as increased bandgap, resistivity, and activation energy. The phase-field simulations further indicate that the refined grain sizes are beneficial to improving local electric field distribution and breakdown path, resulting in enhanced Eb. The uncovered BFO-based ceramics design method provides a platform for high-performance capacitors development for extreme conditions.

Effect of solid-solution strengthening on deformation mechanisms and strain hardening in medium-entropy V1-Cr CoNi alloys

• The solid-solution strength linearly increases with v in V 1- x Cr x CoNi alloys. • Addition of v highly increases SFE and induces planar slip behavior. • The V -abundant VCrCoNi alloys exhibit higher strain-hardening than TWIP CrCoNi alloy. • High friction stress is predominant than SFE in determining deformation mechanism. • High friction stress lowers cross-slip activation and dislocation annhiliation rate. High- and medium-entropy alloys (HEAs and MEAs) possess high solid-solution strength. Numerous investigations have been conducted on its impact on yield strength, however, there are limited reports regarding the relation between solid-solution strengthening and strain-hardening rate. In addition, no attempt has been made to account for the dislocation-mediated plasticity; most works focused on twinning- or transformation-induced plasticity (TWIP or TRIP). In this work we reveal the role of solid-solution strengthening on the strain-hardening rate via systematically investigating evolutions of deformation structures by controlling the Cr/V ratio in prototypical V 1- x Cr x CoNi alloys. Comparing the TWIP of CrCoNi with the dislocation slip of V 0.4 Cr 0.6 CoNi, the hardening rate of CrCoNi was superior to slip-band refinements of V 0.4 Cr 0.6 CoNi due to the dynamic Hall-Petch effect. However, as V content increased further to V 0.7 Cr 0.3 CoNi and VCoNi, their rate of slip-band refinement in V 0.7 Cr 0.3 CoNi and VCoNi with high solid-solution strength surpassed that of CrCoNi. Although it is generally accepted in conventional alloys that deformation twinning results in a higher strain-hardening rate than dislocation-mediated plasticity, we observed that the latter can be predominant in the former under an activated huge solid-solution strengthening effect. The high solid-solution strength lowered the cross-slip activation and consequently retarded the dislocation rearrangement rate, i.e., the dynamic recovery. This delay in the hardening rate decrease, therefore, increased the strain-hardening rate, results in an overall higher strain-hardening rate of V -rich alloys.

Effect of flotation phosphorus tailings on the microstructure and compressive strength of white Portland cement

The phosphate mining industry produces large amounts of tailings. Rational utilisation of phosphorus tailings (PT) is of great significance for the full exploitation of waste resources and environmental protection. In this study, PT were used as one of the raw materials to prepare white Portland cement clinker (WPCC). Various techniques were used to study the effect of PT on the mineral composition, ionic solid solution and compressive strength of the WPCC. The results showed that using PT in WPCC significantly improved the burnability of the raw material, increased the liquid phase content and promoted the formation of minerals. The addition of PT was found to stabilise α′-C2S crystals and promoted the change of C3S crystals in the clinker from T-type to M-type. The addition of PT had no significant effect on the decomposition temperature of calcium carbonate, the appearance temperature of the liquid phase and the formation temperature of C3S. A PT content of 2.5% produced the highest strength of the WPCC: compared with the control group, the 3-day strength increased by 46.86% and the 28-day strength increased by 82.59%.

Influence of Composition and Structure on Wear Resistance of Deposited Metal

Comparison of the data on resistance of alloys against abrasive wear made it possible to establish that alloys with a predominantly austenitic or austenitic-martensite matrix and eutectic component based on alloyed chromium carbide Cr7C3 [5] or Cr23C6 have the highest wear resistance, while microhardness of austenite and martensite should be higher than 5000 N/mm2. In alloys with high wear resistance, there is also no significant difference in microhardness of eutectic and primary crystals of γ-iron, which is probably one of the indicators of adhesion strength of carbides and solid solution. In the case of formation of a pearlite component, wear resistance drops sharply.

Microstructure and mechanical properties of lightweight AlxCrNbTiV(x = 0.2, 0.5, 0.8) refractory high entropy alloys

A novel lightweight refractory high entropy alloys AlxCrNbTiV (x = 0.2, 0.5 and 0.8, in terms of molar ratios) are prepared by vacuum arc melting. In the as cast condition, the alloys have BCC phase with significant dendrite structure, with a low density of 5.82–6.38 g /cm3 and hardness increase from 462 HV0.2 to 549 HV0.2 with the solid solution strengthening effect by adding Al. Due to simultaneous dislocation motion and development of kink bands, Al0.2CrNbTiV exhibits good combination of strength and ductility at room temperature, enabling deformation in compression to ε > 50%, with yield strength of 1570 MPa, and attractive specific yield strength of 246 MPa·cm3/g. And Al0.5CrNbTiV and Al0.8CrNbTiV shows typical brittle feature. Cr2Nb-type C14 Laves phase precipitated with the compression temperature increase to 1000 °C. EBSD analysis shows discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) are activated together in the hot-compression process, and result in softening and a substantial increase in ductility of all the alloys. Furthermore, the theoretical yield stress of AlxCrNbTiV is calculated through estimating the solid solution strength effect attributed to atomic misfit and modulus misfit, and the results indicated the degree of solid solution could affect the estimation accuracy.

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.

Ductile Ti1.5ZrNbAl0.3 refractory high entropy alloy with high specific strength

The ambient temperature brittleness and high density of refractory high entropy alloys (RHEAs) are the obstacles for their applications as structural materials. A novel ductile body-centered cubic Ti1.5ZrNbAl0.3 RHEA with high specific strength was developed. The tensile specific yield strength and fracture elongation of this alloy are 145.5 MPa · g−1 · cm3 and 23.0%, respectively. The specific yield strength is the highest among all other reported RHEAs. The superior mechanical properties of the Ti1.5ZrNbAl0.3 RHEA arise from the solid solution strength and cross-slip of dislocations. The ultrahigh specific yield strength and superior strength-plasticity synergy may promote the applications of RHEAs.