Content Of Alloying Elements Research Articles

Oxide Barrier Thinning in 1050, 2024 and 6062 Aluminum Alloys Using Linear Ramp at the End of Sulfuric Anodizing

A simple method for thinning barrier layers in various aluminum alloys was proposed, involving a linear voltage decrease at the end of sulfuric anodizing. Two techniques were used for barrier layer thickness assessment: direct measurement with field-emission gun scanning electron microscopy and indirect determination using electrochemical impedance spectroscopy. The linear thinning process was successfully tested on 1050 aluminum and on higher alloy element contents used for structural parts in aeronautics: 6062 and 2024 alloys. In our operating conditions, the linear thinning process reduces the barrier oxide at pore bottoms without modification of anodic layer porosity. The relationship for controlling barrier layer thickness (DBL) was established as DBL = U - a x Δt, with U (applied voltage) at 20 V, and Δt (ramp time) at 0 s, 30 s, 45 s, 60 s, and 90 s, with a constant rate (a) of 0.11 nm s−1 for all alloys. However, longer ramp times led to degradation at the pore bottoms, indicating that barrier layer morphology depends on the rate of voltage decrease. Shorter ramp times are preferable. The linear thinning process has potential applications in improving metal electrodeposition into the anodic layer by enhancing electrical accessibility to pore bottoms. Thinning the barrier layer effectively facilitates the electro-coloring process.

An approach to tunable advanced high-strength steel fabrication through multi-wire arc additive manufacturing (M-WAAM)

Advanced high-strength steel (AHSS) fabrication through conventional casting followed by thermomechanical processing always sets challenges for the research community in terms of weldability (microstructural degradation during welding) and formability (high wear of forming dies). Considering such limitations, multi-wire arc additive manufacturing (M-WAAM) has been developed that houses two feedstock (ER70S-6 and 316 L stainless steel (SS)) on a single gas metal arc welding (GMAW) power source. Here, both filler wire feed speeds (WFS) are monitored and controlled through an autonomous wire feed system (AWFS), leading to simultaneous melting for fabricating the near-net-shaped alloy structure. In the developed alloy, the proportion of 316 L SS is varied by regulating its WFS between 0 and 1.5 m/min, whereas WFS for ER70S-6 is fixed at 2 m/min. With the increase in WFS of 316 L SS, the deposition volume and alloying element concentration increases, whereas the penetration depth decreases with smooth side wall and negligible molten metal overflow, indicating adequate utilisation of developed heat for wire melting. Moreover, the ferrite-pearlite microstructure is transformed into ferrite, bainite, and martensitic structures by increasing the secondary WFS, as evident from microstructural and X-ray diffraction analysis. The development of multiple phases further boosts the mechanical performances (hardness and tensile strength) of deposits. Also, the mechanical strength offered by these fabricated alloys is in the range of AHSS steels.

Enhancing corrosion resistance of Al alloy sheets with potential gradient by arc-sprayed Zn coatings

To improve the corrosion resistance and wide the application of Al alloy sheet in the engineering production, a corrosion potential gradient along the thickness of the Al alloy sheet was fabricated using the sprayed Zn layer. The process of arc spraying was employed to obtain the Zn coating with optimizing the parameters. Electrochemical testing was conducted on the surface of Al alloy sprayed with Zn layers at different depths. As the depth in the thickness direction increases, the content of Zn alloy elements gradually decreases and the potential gradually increases. This exhibits a gradual decrease in corrosion tendency. The results of electrochemical impedance spectra (EIS) revealed the existence of pitting corrosion on the surface of the Al alloy. This even extended to the underlying substrate material. In contrast, the Zn coating, when exposed to a corrosive environment, demonstrated the beneficial cathodic effect as a sacrificial anode and the protective function of a passivating film, thus mitigating corrosion. The gradual increase in charge transfer resistance in the impedance spectrum suggested that the corrosion resistance of the sample is increasingly improved. Therefore, it exhibited remarkable resistance to corrosion. Additionally, the SEM surface morphology and XRD pattern were utilized to further explain the corrosion mechanism of the arc-sprayed Zn coating. The Zn coating can provide sacrificial protection to the Al layer due to its higher negative potential and localized corrosion reactivity. This is attributed to the micro-galvanic couples formed between the Zn and Al layer, thus increasing the corrosion resistance of the sheets.

Thermal conductivity of binary Al alloys with different alloying elements

This work investigates the physical properties of several binary Al-Si/Ni/Fe/Cu/Mg alloys with varying alloying element contents and microstructures. The findings indicate that as the content of alloying elements increases, the number of secondary phases in binary Al alloys rises, and these phases become coarser. In hypereutectic compositions, primary phases in Al-Ni and Al-Fe alloys take on a needle-like morphology with high aspect ratios, forming a dendritic network. Regarding properties, in the hypoeutectic region, both thermal conductivity and electrical conductivity of binary alloys initially decrease sharply, followed by a more gradual decline with the addition of alloying elements. This trend occurs because thermal conductivity is mainly influenced by supersaturated solid solutions. In hypereutectic Al-Ni and Al-Fe alloys, the presence of large, needle-like primary phases significantly hinder the heat transfer, resulting in a more apparent reduction in both thermal conductivity and electrical conductivity. Among the five binary alloys, Al-Ni and Al-Fe alloys, which have lower solute concentrations of alloying elements in the Al matrix, exhibit the highest thermal and electrical conductivity. Furthermore, with increasing alloying element contents, the phonon thermal conductivity of Al-Si alloy increases more markedly compared to other alloys. The study will offer a fundamental understanding for the development of advanced alloys.

Stepwise warm rolling for synergistic strength and ductility enhancement in heterolamellar medium-Mn steel

Medium manganese steel represents a promising third-generation advanced high-strength steel. However, achieving excellent plasticity in high-yield-strength medium manganese steel remains challenging, particularly with lower alloying element contents. In this study, we employed an innovative stepwise warm rolling process on 5Mn medium manganese steel, developing a heterolamellar microstructure along the rolling direction. The resulting steel exhibited a yield strength exceeding 1.5 GPa while maintaining a uniform elongation of approximately 29%. The high yield strength is attributed to fine lamellar grains with high dislocation density, while the excellent uniform elongation is due to the synergistic effect of multiple plastic deformation mechanisms, which promoted prolonged strain hardening and delayed the onset of necking. These mechanisms include hetero-deformation induced (HDI) hardening generated during the early deformation of the heterolamellar structure, transformation induced plasticity (TRIP) effect-induced work hardening, and delamination cracking that alleviates interface strain concentration and delays material failure. Collectively, these mechanisms enabled the material to achieve an exceptionally high product of yield strength and uniform elongation of 45 GPa·%. This work provides new insights into the design of high-strength, ductile medium manganese steels, advancing the application of high-performance medium manganese steels.

Discovering novel γ-γ′ Pt-Al superalloys via lattice stability in Pt3Al induced by local atomic environment distortion

The strength of Pt-Al superalloys can be effectively improved using a coherent structure composed of a disordered γ phase and an ordered γ′ phase. However, γ′-Pt3Al has a cubic phase only at high temperatures and a tetragonal phase at low temperatures, thus breaking the coherent interface and deteriorating its mechanical properties. Here, high throughput first-principles calculations and rational experiments were conducted to discover novel γ-γ′ Pt-Al superalloys. The alloying strategy stabilizes the γ′ phase through the local charge distortion (LCD) or the local lattice distortion (LLD). Alloying elements, such as, Ti, Hf, and Ta, occupy the Al site in combination with Pt, making the spherical shape of change density in Pt3Al showing obvious directionality, i.e., LCD. Therefore, the stability of the γ′ phase is proposed at a lower alloying element concentration (3.125 at.%). However, alloying elements near Pt, e.g., Ni, Co, and Ru, tend to occupy the Pt site and induce LLD to stabilize the γ′ phase at higher alloying element concentration (12.5 at.%). The shape of the change density is similar to that of Pt3Al, and no obvious LCD is found when alloying elements occupy the Pt site. LCD-induced phase stability is observed exclusively at the Al site, whereas LLD-induced phase stability is solely present at the Pt site. The Pt-12Al-6X (X = Hf, Ti, Ta, Cr, and Ni in at.%) alloys were prepared, among which Pt-12Al-6Hf possessed a stable γ′ phase, a lower lattice misfit between γ and γ′, and a higher precipitation strengthening, resulting in its hardness (442.1 HV) surpassing that of Ni-based superalloys IN718 (413.6 HV). The γ′ phase in Pt-12Al-6Hf was characterized by high-resolution transmission electron microscopy, suggesting that the Pt site of the γ′ phase was occupied by Pt, while the Al site was shared by Pt, Al, and Hf. This is consistent with the calculated results.

Magnetization and phase transformation in Fe-Ga and Fe-Ge alloys

The magnetic properties and structural states of Fe-Ga and Fe-Ge alloys, known for their large magnetostriction, have been investigated. Experimental characterizations are supported by ab initio calculations and Monte Carlo simulations to reveal the complex interplay between magnetic properties and structural changes. Our findings are in agreement with previous investigations and show that the Curie temperature (TC) of these alloys changes gradually with increasing alloying element concentration while the A2 solid solution is being realized. Further alloying of Fe-Ga leads to the transition from a single-phase to a two-phase A2 + D03 state and results in two distinct TC values. At the same time Fe-Ge shows a more complex behavior with several phase transitions influencing the magnetic ordering temperatures. Theoretical calculations suggest a significant correlation between the magnetic moments, exchange interactions, and observed TC trends. It is shown that the D03 phase is characterized by the lowest TC among other phases. Using Monte Carlo simulations, we found that in ferromagnetic state of Fe-Ge alloy the D03 ordering develops homogeneously, while in Fe-Ga it follows a nucleation and growth scenario.

A study integrating in-process thermal signatures, microstructure, and corrosion behaviour of AISI 316L coatings on low carbon steel substrate deposited by laser-directed energy deposition (L-DED)

Surface coating through Laser Directed Energy Deposition (L-DED) of AISI 316L on low-carbon steel was carried out by varying laser fluence. The resulting melt pool characteristics, obtained through IR pyrometer, played a significant role in evolution of the microstructure. A higher heat input resulted in an equiaxed grain structure with finer grain sizes and improved deposition quality. The quantitative phase analysis revealed the presence of a dominant austenite phase and a secondary ferrite phase, along with traces of molybdenum carbide. Corrosion analysis reveals improved resistance at a higher laser fluence, attributed to increased content of corrosion-resistant alloying elements (Mo, Cr) and predominance of the austenite phase. Electrochemical Impedance Spectroscopy (EIS) confirms a higher corrosion resistance at a higher laser fluence, supported by a significantly higher polarization resistance and presence of a duplex-structured passive film. Results indicate that moderate laser fluence levels, ranging from 5 to 7.5 kJ/cm2, accompanied by medium to high thermal signatures and moderate cooling rates, yield coatings with refined microstructures, enhanced mechanical strength, and corrosion resistance. For superior corrosion resistance, a laser fluence of 10 kJ/cm2 is recommended, although careful consideration of its potential impact on mechanical properties is advised.

Influence of forging pretreatments on microstructure evolution and surface roughness of Al 6061 alloy

Achieving ultra-smooth surfaces is the goal of aluminum optical manufacturing. Under certain processing conditions, improving the microstructure of aluminum and understanding its relationship with surface roughness requires systematic study. The grain structure and various types of second-phase particles are of paramount importance. This study analyzed the microstructure of 6061 alloy after undergoing severe plastic deformation under various processing conditions followed by T6 homogenization heat treatment. Utilizing a white light interferometer, a comparative analysis of the surface roughness was conducted on specimens that underwent single-point diamond turning to achieve a mirror finish. The assessment of surface roughness on machined surfaces is solely based on white light interferometry. The analysis and discussion focus on the effects of phases (causing scratches and voids), the grains and grain boundaries. Experimental findings signify: the grain size, grain boundary and residual second phase can both influence the surface quality, the increase in deformation temperature and accumulated strain both facilitate the dissolution and fragmentation of the secondary phases. However, they also contribute to some extent to grain growth, resulting in a minimum secondary phase area fraction of 0.87% and grain sizes reaching 147.8 μm. Subsequent heat treatments, while effective in reducing the negative impact of the phases, reveal noticeable step-like structures affecting the quality of surface roughness, with the lowest obtained Ra value being 0.8 nm. A proposed pretreatment method in cleaner ingot processing with lower alloy element content addresses the trade-off between reducing phases and controlling grain growth, aiming to achieve improved surface roughness, promoting the application of polycrystalline aluminum alloys in the field of optics manufacturing.

Effect of alloying element content, temperature, and strain rate on the mechanical behavior of NbTiZrMoV high entropy alloy: A molecular dynamics study

High entropy alloys (HEAs) have drawn attention among researchers due to their excellent mechanical properties at low and high temperatures, which pave the way for their numerous applications in various sectors. In this study, we have investigated the effect of temperature and strain rate on the mechanical properties of single crystal equimolar NbTiZrMoV alloy, a refractory HEA (RHEA), using molecular dynamics simulation with the help of a newly developed modified embedded atom method (MEAM) potential. Uniaxial tensile simulations were conducted along x-direction at temperatures between 77 K and 600 K, with temperature intervals of 100 K, and at strain rates of 0.001 ps−1, 0.005 ps−1, 0.025 ps−1, and 0.125 ps−1. Stress-strain curves were plotted from the simulation data, and different tensile properties of the alloy were calculated from the graph. This study suggests that the tensile strength and the elastic modulus of the HEA decrease with increasing temperature as the materials become soft at higher temperatures. Strain rate improves the tensile mechanical properties with increasing rate due to the lack of required time for atom rearrangement and dislocation entrapment requiring higher stresses to continue deformation. Ultimately, the tensile characteristics of the HEA are shown to be influenced by the content of alloying elements. Specifically, Mo content has a rising effect, and Nb content is having a reducing impact on the tensile properties of NbTiZrMoV HEA. The study provides insights into the mechanical properties of NbTiZrMoV HEA, which could inform its applications in various sectors due to its promising mechanical features at different temperatures and strain rates.

Additive manufacturing of high-strength low-alloy AISI 4340 steel with an optimal strength-ductility-toughness trade-off

Additive manufacturing (AM) has revolutionised steel part fabrication, yet not all steels are amenable to its unique solidification features, characterised by cyclic and rapid heating/cooling, and directional solidification. These conditions often result in challenges such as columnar grain formation, microstructural heterogeneity, and consequently, inferior mechanical performance, brittleness and severe anisotropy in particular. Recent studies have adopted inoculation or post-fabrication treatments to address this issue, but often entailing extra cost and processing time. This study aims to verify that some steels such as AISI 4340 steel are inherently compatible to AM, producing components that are innately robust and ready for use in the as-built state. The medium carbon content and low alloying element concentration enable AM processing to produce a uniform and refined bainite microstructure with minimal elemental segregation, avoiding the formation of unstable retained austenite. The high AM-processability of this steel is demonstrated by achieving high densification (>99.9 %) across a broad processing window, which allows precise microstructural control via proper tunning the processing parameter modifications, inducing a transition from upper bainite to lower bainite dominance, to tailor mechanical properties for specific applications. The as AM-fabricated AISI 4340 steel exhibits a good combination of strength, ductility, and toughness, manifested by a yield strength range from 1240 to 1370 MPa, an ultimate tensile strength from 1360 to 1740 MPa, an elongation from 7 % to 14 %, and an impact toughness range of 11–44 J. The mechanical properties of the AM-fabricated 4340 steel are comparable to those of the wrought counterpart and superior to the majority of other AM-fabricated steels. This research reveals the high potential of AM to process high-strength low-alloy steels.

Regulating the grain refinement and rolling properties of coarse-crystalline Mg-Zn-Gd-Ca-Mn alloy through multi-pass cold rolling and annealing

The newly developed Mg–Zn-RE (rare earth) alloy sheet shows significant prospects for 3C applications due to its superior room-temperature malleability compared to the commercial AZ31 alloy. However, the casting ingots of these alloys often exhibit coarse grains due to low alloying element content and the absence of the grain-refining element Zr, making them susceptible to significant cracking while hot-rolling. This study applies a multi-pass cold rolling technique with minimal reduction to a cast Mg–Zn-Gd-system alloy characterized by coarse grains, followed by a static annealing process to enhance its rolling capability. The impact of cold rolling and annealing temperatures on microstructure, plastic deformation mechanism, and static recrystallization (SRX) behavior were studied. It was found that multi-pass cold rolling with minimal decrease promoted the generation of more twins and slip lines, resulting in more uniform deformation and a substantial accumulated rolling strain of 10 %. Consequently, the significant accumulated strain, coupled with stress concentration at positions such as grain boundaries, twin boundaries, and dislocation tangles, acted as nucleation sites for complete static recrystallization at a specific annealing temperature of 375 °C. As a result, the coarse cast grains were successfully refined from 400 μm to 37 μm. Fortunately, this improvement has significantly enhanced the hot-rolling qualities, removing fractures throughout the process. This advancement not only enables industrial-scale rolling but also enhances production efficiency.

Improved mechanical properties of Al-xMg-yZn-Cu alloys via optimized Mg/Zn ratio and thermomechanical processing

Three Al-xMg-yZn-1Cu alloys with equal total alloying element contents but different Mg/Zn ratios have been prepared in this work, i.e., Al–6Mg–1Zn–1Cu, Al–5Mg–2Zn–1Cu and Al–4Mg–3Zn–1Cu alloys. The influences of Mg/Zn ratios on microstructure and mechanical properties of heat-treated Al-xMg-yZn-1Cu alloys have been systematically studied. The results show that Al-xMg-yZn-1Cu alloys with higher Zn contents exhibit the faster aging response as Zn atom features the largest diffusion coefficient. Additionally, rod shaped and ellipsoidal T′ precipitates are observed in the Al–6Mg–1Zn–1Cu alloy. While in Al–4Mg–3Zn–1Cu alloy under TMT-2 process, T′ precipitates mainly exist in an ellipsoidal shape, with a higher number density (∼1.79 × 1023 m-3) and smaller size (∼4.1 nm) compared to the Al–6Mg–1Zn–1Cu alloy. The optimized thermomechanical treatment (80 °C/5 h + rolling + 130 °C/x h) could effectively improve the yield strength of Al–5Mg–2Zn–1Cu and Al–4Mg–3Zn–1Cu alloys, with values increasing from ∼419 MPa to ∼441 MPa–∼454 MPa and ∼470 MPa, respectively. In contrast, the Al–6Mg–1Zn–1Cu alloy exhibit almost no increment in yield strength after the same thermomechanical treatment. This could mainly be attributed to the higher density of T′ precipitates in alloys with higher Zn contents, resulting from the higher nucleation rate of T′ precipitates caused by high contents of Zn atoms featuring fast diffusion rates, with the assistance of dislocations introduced by rolling. This work provides theoretical supports for the development and production of age-hardenable Al-xMg-yZn-1Cu alloys.

Influence of Solution Treatment Process on the Properties of Duplex Stainless Steels: A Comparative Study on Microstructure and Corrosion Properties of UNS S32205 and UNS S32760

The study investigated the effect of the solution treatment process on the corrosion behavior and microstructure of the duplex stainless steel. It was also aimed to reveal this effect comparatively depending on the chemical composition and alloying element content. For this purpose, UNS S32205 and UNS S32760 alloys were treated at 1000 °C, 1020 °C and 1040 °C for an hour. A solution treatment temperature was determined according to Thermo-Calc analysis. The examined samples were characterized by an optical microscope, scanning electron microscope, and XRD analysis. Also, electrochemical impedance spectroscopy and potentiodynamic polarization analyses revealed the corrosion properties of solution-treated samples. Microstructural studies showed that enhanced solution treatment temperature increased ferrite content for both alloys. A lower solution treatment temperature caused the formation of sigma in the microstructure of S32760 alloy. On the other hand, the charge transfer resistance of the passive layer was reduced after solution treatment at 1000 °C and 1020 °C, indicating decreasing corrosion resistance. A higher austenite ratio in S32205 led to pitting, while corrosion resistance improved with higher treatment temperatures. The presence of the sigma phase in S32760 significantly impacted corrosion properties by increasing ion transfer on the surface, leading to reduced corrosion resistance. It was determined that solution treatment at 1040 °C was appropriate for both alloys to achieve the desired microstructure and corrosion properties.

Properties and prospects for biomedical application of new Ti-Nb-Sn alloys obtained by electrical resistance sintering

Active research of new β titanium alloy compositions is underway. At the same time, new ways of alloy preparation by powder metallurgy methods are being investigated. In this work Ti-35Nb-XSn alloy (X = 0, 4, 6 wt%) were obtained via electrical resistance sintering (ERS) at current intensities of 11 and 12 kA respectively. The influence of alloying element content and process conditions on the alloys structure and properties in the context of biomedical application were investigated.

The influence of rapid-diffusive β-stabilizers on the microstructure formation and superplasticity of titanium-based alloys

The superplasticity of Ti-based alloys is improved due to grain refinement, an increase in grain size stability, and an increase in the β-phase fraction up to ∼0.5. Alloying with β-stabilizers reduces the β-transus temperature and increases the β-phase fraction at low forming temperatures, thus improving the superplasticity and lowering its temperature. Both grain growth and superplastic deformation mechanisms are diffusion-controlled phenomena, and, therefore, the diffusivity of the alloying elements should have a significant effect on superplasticity. This work deals with the influence of the high-diffusive elements Fe, Co, and Ni on the grain structure and superplasticity of titanium alloys. For this purpose, the Ti-Al-Mo-V alloy, and alloys with proportional replacement of low-diffusive Mo by Fe, Co, or Ni, exhibiting an interstitial diffusion mechanism, were studied. The alloying elements content was selected to ensure the same β-phase fraction at a deformation temperature of ∼875 °C. The microstructure evolution after thermomechanical processing, annealing, and superplastic deformation, as well as post-deformation room-temperature mechanical properties of the studied alloys, were compared. The actual phase ratio was reconstructed by comparing scanning electron microscopy images in backscattered electrons and electron backscatter diffraction data for the same fragments. It was found that Mo replacement for highly diffusive elements accelerated dynamic grain growth during superplastic deformation at an elevated temperature of 875 °C but improved superplasticity at a lower temperature of 775 °C. The results confirmed that alloying with high-diffusive elements is a promising strategy for the design of low-temperature superplastic forming alloys.

Microstructure and mechanical properties of 7075/5356 aluminum alloy laminated composite fabricated by wire arc additive manufacturing

A 7075/5356 aluminum alloy laminated composite was fabricated by alternately depositing a 7075 wire and a 5356 wire layer by layer using wire arc additive manufacturing (WAAM). The microstructure and mechanical properties of the produced components under as-deposited and heat-treated conditions were investigated. The results revealed that the grain morphology of the specimen was mainly composed of equiaxed grains in each layer, while the grain size of the interlayer region was reduced due to the heterogeneous nucleation relying on the partially remelted previous layer. Moreover, a reduced amount of second phase was observed due to decreased Zn and Cu alloying elements content in this region, which resulted in a gradient change in microhardness distribution. The tensile strength and elongation of the heat-treated samples in vertical and horizontal directions were 321 MPa, 10.12 %, and 377 MPa, 9.72 %, respectively. The results indicated good comprehensive mechanical properties, which is promising for further application of WAAM fabricated laminated metal composite.

Physical simulation of the underclad heat affected zone in a reactor pressure vessel to study intergranular cracking

Underclad cracking in nuclear pressure vessels was of significant concern in the 1970s and 1980s before mitigating adjustments were made both to steel compositions and manufacturing practice. Unfortunately, the cracking mechanisms are still not well understood, and this can undermine confidence when changes to cladding operations are under consideration. In this work, Charpy-sized test coupons of 18MND5 steel were subject to a range of thermal cycles that can be experienced by the substrate immediately adjacent to the interface with the overlay. The Charpy test results are considered in combination with analysis of the samples through field emission gun (FEG) scanning electron microscopy (SEM) and wavelength dispersive X-ray spectroscopy (WDXS). The findings suggest that the heat affected zone subject to the coarse grained plus intercritical thermal cycle, before post weld heat treatment, has a peculiar and potentially brittle microstructure. However, in a steel with no obvious macrosegregation, no clear evidence of intergranular cracking in the early stages of the post weld heat treatment could be found. The second part of the work focuses on the effects of segregation regions in large forgings, more specifically ghost lines, on the tendency for underclad cracking. Ghost line regions that subsequently form a coarse grained heat affected zone (CGHAZ), and are then heated to just under the A1 temperature, seem to be the most prone to intergranular cracking. Cracking susceptibility appears to be associated with elevated concentrations of alloying and impurity elements at grain boundaries.

In situ chemical analysis of duplex stainless steel weld by laser induced breakdown spectroscopy

The high corrosion resistance and good mechanical properties of duplex stainless steel (DSS) are due to its special chemical composition, which is a balanced phase ratio of ferrite (α) and austenite (γ). Many industrial applications require the integration of DSS components. For this, Gas tungsten arc welding (GTAW) is an excellent choice, as it allows an automated operation with high reproducibility. However, when the weld pool solidifies, critical ratios of α- and γ- phases can occur, which lead to solidification cracking, increased susceptibility to corrosion, and a decrease in ductility and critical strength. Previous studies have shown that these defects can be caused by the accumulation of manganese and chromium in the heat affected zone (HAZ), requiring ongoing monitoring of this accumulation. A suitable method for such monitoring is laser-induced breakdown spectroscopy (LIBS), which can be used in two operating modes: calibration using standard reference samples and calibration-free. Unlike conventional quantitative LIBS measurements, which require reference samples to generate a calibration curve, calibration-free LIBS (CF-LIBS) allows chemical compositions to be determined solely from the emission spectrum of the plasma. Numerous publications show that CF-LIBS is a fast and efficient analytical method for the quantitative analysis of metal samples. In this work, CF-LIBS is applied to spectra obtained during GTAW DSS welding and the result is compared with those obtained by PLS analysis. A good correlation was found between both types of analysis, demonstrating the suitability of the CF-LIBS method for this application. The CF-LIBS method has a significant advantage over conventional LIBS due to the rapid in situ measurement of concentrations of major alloying elements without calibration procedure. This, combined with fast feedback and appropriate adjustment of welding parameters, helps prevent welding defects.

Work hardening of quaternary powder metallurgy Ti alloys

The concurrent addition of Al as α stabiliser and Nb and Cu or Mn as β stabilisers was used to design new powder metallurgy quaternary Ti alloys and investigate their manufacturability and consequent performance. It is found that the powder blend's compressibility decreases with the total amount of alloying elements due to the characteristics of the powders used. Consequently, the sintered density of the quaternary Ti alloys decreases and slightly higher values are achieved if Mn instead of Cu is used, despite the higher diffusivity of Cu at the sintering temperature. The quaternary Ti alloys are characterised by a lamellar microstructure comprising α grain boundaries and α+β lamellae where the amount and type of alloying elements determine the coarseness of the microstructural features. This results in stronger and harder but less ductile quaternary Ti alloys for higher alloying elements contents and for stronger β stabilisers, although of their overall elastoplastic behaviour. Because of their lamellar microstructure, the quaternary Ti alloys show similar deformation behaviour but the actual work hardening rate is governed by the fineness of the microstructure.