Alloy Heat Research Articles

Influence of Hot Rolling on Microstructure, Corrosion and Mechanical Properties of Mg–Zn–Mn–Ca Alloy

The effect of hot rolling on the microstructure, mechanical, and corrosion properties of the magnesium alloy 96 wt% Mg–2.3 wt% Zn–0.7 wt% Ca–1 wt% Mn was studied. After heat treatment, the original plates of an as-cast alloy were rolled from a 7 mm thickness to a 0.2 mm thickness at two temperatures—300 or 400 °C. It has been established that increasing the rolling temperature from 300 to 400 °C increases the fraction of recrystallized grains in the microstructure and after rolling at 400 °C, the microstructure is fully recrystallized. The best strength–ductility balance of the alloy was obtained after rolling at 300 °C, with a high total percentage reduction of 93–97%: the yield stress, the ultimate tensile strength, and the elongation averaged at 285 MPa, 310 MPa, and 5%, respectively. The alloy after rolling, annealed at 400 °C, shows improved ductility but lower strength: the yield stress, the ultimate tensile strength, and the elongation were 200 MPa, 260 MPa, and 17%, respectively. The strong dependence of corrosion resistance on respect to rolling direction is observed, which can be reduced after heat treatment. The as-rolled alloy and the heat-treated alloy had low corrosion rates in Hanks’ solution of 0.54 and 0.19 mm/year, respectively.

Assessment on heat treatment and machinability of DMLS-processed Ti64 alloy

Assessment on heat treatment and machinability of DMLS-processed Ti64 alloy

Enhanced heavy oil fouling resistance of cobalt-based spray-deposited coatings by alloy design and heat treatment

Enhanced heavy oil fouling resistance of cobalt-based spray-deposited coatings by alloy design and heat treatment

Feasibility Study of Solid-State Recycling through Direct Hot Rolling of AA5754 Aluminum Chips for Automotive Applications

Recently, researchers have done a lot of efforts to develop new solid-state recycling processes, both experimentally and developing numerical models. This kind of process is energy-saving and environmentally friendly compared to the conventional aluminum recycling process because avoided the melting step. The purpose of this work is to evaluate the feasibility of an innovative solid-state recycling process through direct hot rolling in a non heat-treatable aluminum alloy for automotive applications. AA5754 chips have been produced by turning a bar without the usage of lubricants and compacted with a 150 kN load; the compacted billets were treated at 400 °C and directly hot rolled in several successive passes. Rolled samples are then analyzed in terms of Vickers microhardness and microstructure in both as-rolled and heat treatment conditions, this last was performed at 185°C simulating the process of paint-bake. The produced samples show an excellent bonding between chips.

Optimizing dry milling of stir-cast and heat-treated AZ80 magnesium alloy using multiple criteria optimization technique: an experimental study.

The primary aspects of this research are to evaluate surface roughness, cutting force, and material removal rate and optimize it with dry milling process parameters for heat-treated and stir-cast AZ80 magnesium alloy. Multiple methodologies are utilized in the research, which includes the Integration of design of experiments-response surface methodology for experimental design with the technique for order of preference by similarity to ideal solution for multi-criteria optimization. In order to evaluate the effect of process parameters on the response, the experimental design manipulates the depth of cut, feed rate, and cutting speed in a systematic manner. An evaluation of the machined surface's quality is conducted via surface roughness measurements. Likewise, insights into the forces exerted during milling can be obtained through continuous monitoring of cutting forces. The calculation of material removal rate is predicated on weight reduction. The interaction between the depth of cut and feed rate has a significant impact on the critical-to-quality characteristics of the alloy, which has contribution percentage greater than 25%. This finding validates that despite the heat-treated alloy having a similar composition to the as-cast alloy (where the closeness coefficient is 0.9843), the optimal process parameters of the former are not applicable to the latter. Nevertheless, the technique used to prepare the specimen has no bearing on the material removal rate, which is a process parameter-specific effect.

A Review on Friction Stir Welding of High-Strength Al-Zn-Mg Alloy: Insights on Second-Phase Particles

The friction stir welding (FSW) process is a unique combination of deformation and high temperature, which provides opportunities to modify microstructures through the adjustment of the processing parameters and is an ideal way to join non-weldable aluminum alloys by avoiding the formation of a molten pool. The 7xxx series heat-treatable aluminum alloys are widely used in the aerospace field as high-performance structural materials. The microstructure evolution and mechanical performance of these alloys are affected by the effects of thermomechanical processing, which provides opportunities to optimize the material properties by controlling microstructural features such as intermetallic constituent particles, dispersoids and nanoscale precipitates. This paper focuses on the basic principles of the thermal and mechanical effects generated during FSW on the evolution of second-phase particles in different zones of the weld.

The evolution and dissolution mechanism of θ-Al2Cu phase and the analysis of precipitation of a novel AlCu phase during elevated aging

The evolution and dissolution mechanism of the θ-Al2Cu precipitates were investigated in this study by transmission electron microscopy (TEM) during the re-aging at high temperatures for a long time. The results advance the current knowledge of dissolution and its associated mechanisms of the θ-Al2Cu phase in AlCu alloys. In this study, the coarsening and dissolution of θ-Al2Cu phase in T6 heat-treated Al4Cu alloy during various times (0−1000h) of re-aging temperature 420 °C were studied experimentally and theoretically. The morphological characterization revealed that the θ-Al2Cu phases gradually increase in size and decrease in volume density during the aging process, which can be attributed to coarsening and dissolution phenomena occurring during re-aging. Additionally, a body-centered tetragonal AlCu phase is precipitated within the θ-Al2Cu phase during the high temperature re-aging process, which is a characteristic of this phase prior to dissolution. Moreover, the primary mechanisms responsible for the high temperature melting of the θ-Al2Cu phase are the formation of the AlCu phase and the initial melting of the Cu-poor region in the θ-Al2Cu phase. The Cu atoms in θ-Al2Cu phase dissolve and diffuse into the Al matrix, forming L12 ordered AlCu solute clusters through long-range diffusion.

Evaluation of Physical and Thermo-Mechanical Behavior of Heat-Treated Novel Nimonic Alloy

Evaluation of Physical and Thermo-Mechanical Behavior of Heat-Treated Novel Nimonic Alloy

Machine learning-augmented modeling on the formation of Si-dominated Non-β″ early-stage precipitates in Al-Si-Mg alloys with Si supersaturation induced by non-equilibrium solidification

Recent experiments have shown that Al-Si-Mg alloys solidified under high cooling rates may lead to the nucleation of Si-enriched clusters that are remarkably different from the conventional Mg-Si co-clusters (e.g. β″ particles), and yet the responsible mechanism remains to be elucidated. Here we tackle the problem using a multiscale modeling framework that integrates atomistic modeling, energy landscape sampling, and lattice-based kinetic Monte Carlo (kMC) simulation. The migration energy barriers for vacancy-mediated diffusion amid complex local chemical environments are predicted on-the-fly using a surrogate machine learning model. We discover that the actual vacancy-Si migration barriers are much lower than those assumed in the classic linear interpolation approximation. Such a strong deviation from conventional wisdom, in conjunction with differing Si solute composition, can lead to a great variety in the nucleated early-stage precipitates. More specifically, a high-level supersaturation of Si solute (i.e.xSi/(xSi+xMg)>0.75) would lead to an unexpectedly high enrichment of Si in the nucleated clusters with the Si:Mg ratio up to 5∼6; while at a lower-level supply of Si solute the Mg-Si co-clusters (i.e. Si:Mg ratio around 1∼2) are nucleated instead. These findings provide a viable explanation for the diverse types of early-stage precipitates observed in various experiments, from Si-enriched precipitates in high-pressure die cast Al alloys to β″ particles in conventional casting and/or heat-treated alloys. The implications of our findings are also discussed.

Enhanced anisotropy of Pr-Nd-Fe-B HDDR magnetic powders by regulating the hydrogen decrepitated process

The evolution of microstructures for different hydrogen decrepitated routes was investigated in hydrogenation-disproportionation-desorption-recombination (HDDR) magnetic powders, with particular focus on the fracture of the SC heat-treated alloy during two-step hydrogen decrepitation (HD) and the influence of the first step temperature on magnetic properties. As the temperature increases, the properties of the magnetic powders increase and then decrease, the optimized performance of HDDR magnetic powders was obtained with Br=1.45 T, (BH)max=393 kJ·m−3, DOA=0.79 when the first HD temperature is 65°C. The microscopic analysis shows that there are two problems in the one-step HD route: one is that the particle size is larger ∼150 μm and there are incomplete fractured cracks, the particle surface is more PrNd-rich phase, which leads to different reaction rates between the surface and center in HDDR particles, and the texture orientation of the fine grains at the edge of surface and crack is disordered. The second issue is that HD grains have significant angular difference with the c-axis orientation in incomplete fractured grain clusters, which is directly inherited by the HDDR magnetic powder, resulting in a misalignment texture. In comparison, the two-step HD process effectively addresses the issues derived from one-step HD process. Not only is the grain size of HDDR magnetic powders uniform and the width of the thin grain boundary phases (GBs) is less than the exchange coupling length, but also (Fe+Co) content exceeding 30 at% in GBs with weak magnetism. This is beneficial for enhancing exchange coupling effect between adjacent grains. Moreover, magnetic powder particle exhibits single-domain characteristics, which improves the grain texture orientation. This research provides a new insight for the development of high-orientation and high-performance HDDR magnetic powders.

Effect of microstructural anisotropy and heat treatment on the corrosion behaviour of additively manufactured Ti-6Al-2Sn-4Zr-6Mo alloy

The electrochemical behaviour of Ti-6Al-2Sn-4Zr-6Mo alloy produced by Powder Bed Fusion – Laser Based/Metals has been investigated to identify the corrosion mechanism characteristic of the material processed by additive manufacturing technology. A microstructural characterisation of the material in as-built and heat-treated conditions was carried out to identify the different phases and assess the degree of anisotropy of the additive manufactured material. After that, the corrosion behaviour was studied by potentiodynamic polarisation and electrochemical impedance spectroscopy. Results showed that a homogeneous and compact oxide layer characterises the as-built material due to the presence of a finely dispersed α’’ phase in the β grains. Conversely, in the heat-treated alloy, the corrosion attack proceeds preferentially on the large α phase domains, where the oxide layer is less protective. Despite the anisotropy in the microstructure of the as-built material, the electrochemical behaviour was revealed to be the same for the section parallel and perpendicular to the building direction, noting the less influential factor of grain orientation on corrosion mechanisms.

Microstructural Features, Corrosion and Wear Behavior of the AlCrFeCoNiCu High-Entropy Alloy, Electrodeposited Coatings, and Subsequent Heat Treatment

Microstructural Features, Corrosion and Wear Behavior of the AlCrFeCoNiCu High-Entropy Alloy, Electrodeposited Coatings, and Subsequent Heat Treatment

Comparative Analysis of NiTi Instruments with Different Alloy Treatments.

This study aims to compare the cyclic fatigue resistance of nickel-titanium (NiTi) endodontic instruments, focusing on the impact of various alloy treatments and manufacturing processes across different generations of these instruments; Twenty instrumentation systems from different generations, comprising both continuous and reciprocating motion designs, were tested. Four hundred instruments underwent cyclic fatigue testing using an INSTRON machine, with the time and number of cycles to fracture (NCF) recorded for each instrument. Statistical analyses were performed to compare the fatigue resistance between systems, generations, and motion types; Instruments treated with advanced thermal processing, such as Excalibur, Reciproc Blue, and TruNatomy, demonstrated superior resistance to fracture, whereas systems like Protaper Universal, K3XF, and 2Shape showed the lowest resistance. Reciprocating instruments generally exhibited higher cyclic fatigue resistance than continuously rotating instruments; Technological advancements in NiTi instrument design, especially the implementation of heat-treated alloys, have improved cyclic fatigue resistance, enhancing the safety and efficiency of endodontic treatments. Reciprocating systems, in particular, exhibit superior fracture resistance, suggesting their greater utility in challenging clinical conditions.

Enhanced comprehensive mechanical properties of laser additive manufactured TC17 by design of new heat treatment based on continuous cooling transition

Heat treatment is critical for enhancing the mechanical properties of high strength titanium alloys, especially for exploiting the potential of laser additive manufactured titanium alloys. In this work, the influence of the cooling rate of continuous cooling transition on microstructure evolution and mechanical behavior was investigated in TC17 titanium alloy fabricated by laser directed energy deposition (LDED) technology. It was found that the number density and orientation characteristics of grain boundary α phases (αGB) are jointly influenced by the cooling rate and the structure of β/β grain boundaries (GBs). The average number density (λavg) of αGB has a consistent trend with the degree of variant selection (DVS) for precipitated α clusters subsequently, which is attributed to the autocatalytic effect of the pre-existing α on the post-precipitated α phases. The largest λavg of αGB and the highest DVS of α clusters could be simultaneously obtained at a suitable cooling rate (4 °C/min). In that case, plenty of α/β phase interfaces and dominant variant type ensure high strength, meanwhile, the combinations of activated multi-slip systems and varied crack propagation paths extend work-hardening to maintain greater plastic deformation. This paper provides a novel thought for designing customized heat treatments of LDEDed high strength titanium alloys, and more importantly, promotes the engineering applications of large and complex components prepared by additive manufacturing technology.

Microstructure and Properties of Complex Concentrated C14–MCr2 Laves, A15–M3X and D8m M5Si3 Intermetallics in a Refractory Complex Concentrated Alloy

Abstract: The refractory complex concentrated alloy (RCCA) 5Al–5Cr–5Ge–1Hf–6Mo–33Nb–19Si–20Ti–5Sn–1W (at.%) was studied in the as-cast and heat-treated conditions. The partitioning of solutes in the as-cast and heat-treated microstructures and relationships between solutes, between solutes and the parameters VEC and Δχ, and between these parameters, most of which are reported for the first time for metallic UHTMs, were shown to be important for the properties of the stable phases A15–Nb3X and the D8m βNb5Si3. The nano-hardness and Young’s modulus of the A15–Nb3X and the D8m βNb5Si3 of the heat-treated alloy were measured using nanoindentation and changes in these properties per solute addition were discussed. The aforementioned relationships, the VEC versus Δχ maps and the VEC, Δχ, time, or VEC, Δχ, Young’s modulus or VEC, Δχ, nano-hardness diagrams of the phases in the as-cast and heat-treated alloy, and the properties of the two phases demonstrated the importance of synergy and entanglement of solutes, parameters and phases in the microstructure and properties of the RCCA. The significance of the new data and the synergy and entanglement of solutes and phases for the design of metallic ultra-high temperature materials were discussed.

The effect of forming conditions and treatment process applied to the material on springback

Abstract Heat treatment is often used to optimize the balance between the strength and formability of a material. However, aging during treatment affects the ability to return to its original shape after deformation. In this study, the effects of surface treatments during the painting of mild steel and aging time in the W-temper heat treatment on springback were investigated. Consequently, because of artificial aging during surface treatment, the material precipitates certain phases and enhances the mechanical properties of the material, which leads to the pre-painted mild steel being more sensitive to springback. On the other hand, it is also noted that springback is highly dependent on the transfer time between the W-temper heat treatment of high strength aluminum alloy and forming operations, and the change in shape increases with time. In summary, the springback phenomenon is a result of the interaction between the material properties, treatment procedures, and forming circumstances.

Effects of mechanical alloying methods on structural phase stability, chemical state, optical, electrical and ferroelectric properties in Sc-doped α-Fe2O3 system

The development of metal doped α-Fe2O3 (hematite) based wide band gap semiconductors with high electrical conductivity, high electrical polarization and wide optical band gap is a challenging problem and also useful for application point of view. In this work, a substantial enhancement of electrical conductivity, optical band gap and ferroelectric polarization have been recorded at room temperature for Sc doped α-Fe2O3 system. Two different methods of the mechanical alloying and subsequent heat treatment have been used to synthesize the samples of α-Fe2-xScxO3 oxide (x = 0.2–1.0). The X-ray diffraction patterns have confirmed formation of single-phased Rhombohedral structure for low Sc doping content (x = 0.2), whereas a mixture of Rhombohedral-structured α-Fe2O3 type phase and cubic-structured Sc2O3 type phase has been formed for the higher Sc contents (x = 0.5 and 1.0). The phase fractions varied depending on the amount of Sc content, chemical reaction during mechanical alloying of the elementary oxides and solid-state reaction during the heat treatment. Response of the Sc2O3 type phase in Raman spectra is sensitive depending on the methods of inter-mixing the α-Fe2O3 and Sc2O3 by mechanical alloying. X-ray photoelectron spectroscopy (XPS) confirmed the metal (Fe, Sc) ions in +3 charge state, although the samples for low Sc content x = 0.2 showed a signature of Fe+2 and Sc+4 states. A detailed analysis of the Fe 3s XPS band confirmed a strong 3s-3d spins exchange coupling of strengths 1.18 eV–1.34 eV.

On electrochemical corrosion of mechano-activated and thermally processed AlxCryNiz 2D decagonal quasicrystalline structures and crystalline approximants

This article represents a pioneering study centered on the corrosion kinetics of untreated and thermally processed mechano-synthesized AlxCryNiz two-dimensional decagonal quasicrystalline structure and crystalline approximants. It sheds light on the distinguished corrosion behavior of untreated and heat-treated mechano-synthesized Al72Cr15Ni13 and Al86Cr12Ni2 alloys, including a wide diversity of miscellaneous intermetallic phases. A comprehensive characterization was performed to analyze crystallographic structure and thermal characteristics of AlxCryNiz powder particles. Electrochemical evaluations of the mechano-synthesized Al72Cr15Ni13 and Al86Cr12Ni2 specimens and their heat-treated counterparts were conducted under cyclic potentiodynamic polarization tests with 0.1 mol/L Na2SO4 (pH=2) and 3.5% NaCl (pH=8.5) electrolytes at room temperature, respectively. Al72Cr15Ni13 two-dimensional decagonal quasicrystalline phase was attained following 6 h mechano-synthesis and subsequent annealing treatment at 1035°C. There is no evidence of quasicrystal formation in the Al86Cr12Ni2 alloy system after 6 h mechano-synthesis and successive thermal processing at 445 and 570°C. In this study, we conducted the first investigation into electrochemical performance of both Al72Cr15Ni13 and Al86Cr12Ni2 intermetallics. Both Al72Cr15Ni13 and Al86Cr12Ni2 alloys develop a protective passive film in 0.1 mol/L Na2SO4 electrolyte. It was determined that 6 h mechano-synthesized Al72Cr15Ni13 sample, subjected to annealing at 1035°C, stands out in the Al-Cr-Ni alloy systems for applications necessitating exceptional corrosion resistance, passivation behavior, and minimal susceptibility to pitting corrosion when compared to other tested counterparts. This alloy is characterized by a corrosion current density of 3.73 µA/cm2 and a corrosion potential of -0.16 V(vs. Ag/AgCl), revealing a remarkably stable passive film up to a current density of 0.02 A/cm2 and a potential of 2.41 V(vs. Ag/AgCl) within 0.1 mol/L Na2SO4 medium. Likewise, it exhibited a drastically diminished corrosion current density of 11.65 µA/cm2 and a reduced corrosion potential of -0.27 V(vs. Ag/AgCl) within 3.5% NaCl electrolyte, attributed to the formation of two-dimensional decagonal quasicrystalline phase and hexagonal δ-Al3Ni2 crystalline approximant at 1035°C. It also encompassed a re-passivation current density and potential of 50.35 µA/cm2 and -0.04 V(vs. Ag/AgCl), respectively, within the latter solution. Its corrosion mechanism may be ascribed to a two-step surface precipitation process: initially, Al dissolves into a hydroxide, succeeded by the formation and precipitation of Al oxides, such as NaAlO2 and Al2O3∙xH2O.

Influence of heat treatment on the structure and mechanical properties of pseudo α-titanium alloy in a welded joint

The object of this study was the weld material of a new Ti-6.1Al-6.0Zr-6.3Sn-3.2Mo-1.1Nb-1.2Si alloy, which was obtained by electron beam welding. Electron beam welding (EBW) provides rapid melting and cooling with crystallization under significant temperature gradients. For the pseudo α-titanium alloy, this leads to the appearance of significant residual stresses in the joint and determines the specificity of the dispersion decay of the β-phase. Residual stresses are reduced by preliminary heating, removed by heat treatment. Such processing exerts a critical influence on the formation of the structure and phase composition of the weld and the zone of thermal influence of the electron beam; it can form macro defects, undesirable phases, and structural states. The conditions of heat treatment have been determined to bring the welded joint from complex alloyed pseudo α-titanium alloy to the required level of mechanical characteristics. The structure, phase morphology, elemental composition, and mechanical characteristics of welded joints without additional heat treatment have been compared, with preliminary local heating of 400 °C, with additional post-weld local annealing at ТТ=750 °С, tT=4 minutes and sequential annealing in the furnace at ТТ=850 °C, tT=60 minutes. It has been established that a full cycle of heat treatment of a welded joint provides the highest characteristics of strength and plasticity, but local heat treatment also makes it possible to obtain a defect-free joint with satisfactory characteristics for less responsible products. It is shown how heat treatment of pseudo α-titanium alloy makes it possible to get rid of unwanted phase formations (Zr,Ti)5Si3Al and transform them into (Zr,Ti,Nb,Mo)3SiAl. The results are promising for use in the production of aircraft engine parts

Influence of Heat Treatment on Fretting Wear Behavior of Laser Powder Bed Fusion Inconel 718 Alloy

Abstract This research paper focuses on the fretting wear characteristics of self-mated laser powder bed fusion (L-PBF)-produced Inconel 718 alloy, with the primary aim of characterizing its distinct wear-rate in relation to fretting cycles. This study investigates both the as-built and heat-treated Inconel 718 Superalloy. Experiments were conducted under aggressive contact conditions, involving a flat-on-flat contact pressure of 100 MPa (1645 N) and a temperature of 650 °C sustained over a million cycles. From the preliminary observation, the microstructure reveals that the heat-treated L-PBF alloy has denser and harder precipitates than its as-built counterpart. This indicates that heat-treated alloy is much harder (470 HV0.3) than the as-built Inconel 718 (275 HV0.3). The heat treatment process resulted in the precipitation of beneficial strengthening phases like γ′ and γ″, along with maintaining stable carbides (NbC). Notably, the heat-treated material displays an approximately two-fold lower wear-rate (0.103 μm/cycle at the end of 1000 k cycles) compared to the as-built material (0.238 μm/cycle), attributed primarily to its high strength characteristics. Additionally, the heat-treated material demonstrates a reduced steady-state friction coefficient (0.34) in contrast to the as-built material (0.37), owing to its inherent capability to form a uniform and stable lubricious glaze oxide layer. Both as-built and heat-treated systems show dominant adhesive wear mechanisms along with localized abrasion resulting from the combination of oxidation and cyclic wear processes.