Alloy Billets Research Articles

Simulation of the Process of Temperature Field Changing of a Zr–1%Nb Zirconium Alloy Billet During Equal-Channel Angular Pressing

Using mathematical modeling in the QFORM software package, the data on the temperature distribution of a billet made of a zirconium alloy E110 (Zr–1%Nb) in its longitudinal and transverse sections during an equal-channel angular pressing (ECAP) were obtained. The initial data on the geometric parameters of the billet and the die of the ECAP unit are presented, and the conditions for carrying out the process of severe plastic deformation, as well as the chemical composition and physical characteristics of the Zr–1%Nb alloy necessary for carrying out the computational modeling are described. The values of the billet temperature were determined for the calculated moments of the passage of the billet through the junction of the die channels, which corresponded to 25%, 50%, and 75% of its length. It is shown that during the ECAP process at a given pressing speed, in the section corresponding to the junction of the matrix channels, an increase in the billet temperature relative to its initial heating occurred by an amount of about 10 ºC.

A Modelling Framework for Rapid Evaluation of Speed Limitations during Extrusion of Aluminium Profiles

Hot tearing is a well-known limitation when trying to maximize the throughput rate in aluminium extrusion. In the present work an analytical modelling framework is presented which can be used to predict the maximum extrusion speed that can be applied in production without formation of this type of surface defect. The modelling framework allows almost instantaneous estimates on the resulting productivity in terms of maximum extrusion speed. This is obtained by developing an analytical model for the maximum temperature at the die exit which incorporate the effect of alloy composition and billet processing. The results are consolidated into extrusion limit diagrams, mapping the maximum allowable extrusion speed as a function of billet pre-heat temperature, alloy composition, and homogenisation heat treatment. The calculated temperatures and extrusion limit diagrams obtained from the analytical model are compared with measured temperatures and critical extrusion speeds from extrusion tests of various 6xxx series alloys for a simple rod-shaped geometry. The comparisons indicate that the presented modelling approach gives sufficiently accurate predictions for future application in optimisation of alloy composition and process parameters in extrusion of profiles.

Effect of hot isostatic pressing on microstructure and mechanical properties of TZM alloy formed by powder metallurgy

Abstract TZM alloy billets were fabricated using powder metallurgy (PM) and powder metallurgy + hot isostatic pressing (PM+HIP) techniques, and the influence of these two processes on the microstructure and mechanical properties of TZM alloy billets was compared. The experimental findings indicate that an enhanced hot isostatic pressing process effectively reduces the internal porosity of TZM alloy, leading to increased tensile strength and elongation at room temperature. However, there is no significant improvement in hardness and tensile strength at 600℃.

Mechanism of texture evolution propelled by recrystallization behavior of interactively alternating forward extruded AZ31 magnesium alloy under pre-upsetting deformation

Pre-upsetting deformation is an effective way to optimize the microstructure of plastic forming components and achieve deep modification. In this paper, the pre-upsetting deformation of AZ31 Mg alloy billet was carried out before alternating forward extrusion, and the effect of pre-upsetting deformation temperature on the recrystallization behavior and texture evolution of AZ31 Mg alloy formed by alternating forward extrusion was analyzed. The results showed that the strains generated by the pre-upsetting deformation at different temperatures all leaded to a high dynamic recrystallization (DRX) driving force. This results in a high percentage of recrystallized grains in all pre-upsetting alternating forward extrusion (UAFE) formations. The highest percentage of recrystallized grains 94.5% was observed in U2AFE (pre-upsetting deformation at 623 K). The behavior of DRX has a significant impact on both the distribution and strength of texture. In the case of U2AFE, the maximum basal texture strength is 8.65. This is due to the maximum pole density of the deformed texture, which is composed of non-recrystallized grains and is as high as 9.25. In contrast, the maximum pole density of the recrystallized texture, which is composed of recrystallized grains, is only 8.09. Therefore, non-recrystallized grains play a crucial role in the formation of texture in UAFE. This study provides scientific guidance and technical support for the research of high-performance Mg alloy alternating forward extrusion molding technology.

Microstructural Heterogeneity and Property Variations in Cast and Vacuum Hot-Pressed CoCrPtB Alloy.

Limited research has been undertaken regarding the homogeneity of CoCrPtB alloy billets. A CoCrPtB alloy was processed through casting and vacuum hot pressing. This investigation delved into the interconnection between the secondary dendrite arm spacing (SDAS) in the as-hot-pressed samples and their corresponding attributes, specifically Vickers hardness and magnetic properties. Systematic sampling was conducted on the cross-sectional layer and longitudinal surface. Upon examination of the cross-sectional layer proximate to the uppermost region of the hot casting, a discernible parabolic trend was observed for the SDAS that exhibited a gradual increment from the peripheral regions toward the central area along the width. Simultaneously, the fraction of the dendrite phase displayed a consistent linear decline, attaining its peak value at the central portion of the billet. Conversely, on the longitudinal surface, SDAS and the fraction of the dendrite phase remained fairly uniform within the same column sampling regions. However, a notable divergence was identified in the central section, characterized by an augmented SDAS and diminished dendrite phase content. This inherent microstructural inhomogeneity within the CoCrPtB alloy engendered discernible disparities in material properties.

EFFECT OF PRELIMINARY DEFORMATION ON THE FORMATION OF ULTRAFINE-GRAINED STRUCTURE DURING EQUAL CHANNEL ANGULAR PRESSING OF MAGNESIUM ALLOYS

The formation of ultrafine-grained structure is very desirable in the microstructural design of magnesium alloys, in particular Mg-Zn-Ca medical alloy, for a substantial increase in their strength and corrosion resistance. However, conventional processing of these alloys by equal channel angular pressing is not easily applicable due to their low deformability, which often leads to rapid fracture of billets. In this paper, computer simulation data and principles of physical mesomechanics are used to demonstrate that preliminary deformation of Mg alloy billets by reduction at high temperatures and low strain rates significantly increases their deformation capacity and enables equal channel angular pressing at lower temperatures, resulting in billets with ultrafine-grained structure. Consideration is given to the physical nature of the established effect.

Improving the quality of cold-rolled deformable aluminum alloy billets

A mode of high-speed recrystallization annealing has been developed to increase technological plasticity while maintaining the strength of sheet cold-rolled blanks made of deformable aluminum alloys that are not strengthened by heat treatment. Problem. Cold deformation of cold-rolled plates is achieved by recrystallization annealing in hooded furnaces. However, such annealing often does not provide the technological plasticity for defect-free stamping of products and, as a result, has significant rejects. Hooded furnaces are not suitable for improving the deformation of individual billets. In addition, for products with complex configurations that operate in harsh environments, the requirements for rolled aluminum are increased, which is also not possible to realize in open hearth furnaces. These problems can be solved by high-speed continuous parting heat treatment. Goal. The aim is development of a high-speed recrystallization annealing regime for increasing technological plasticity while maintaining the strength of cold-rolled sheet billets from deformable aluminum alloys. Methodology. The object of the study was thin-sheet (1 mm) billets from cold-rolled aluminum alloys AD1, AMts, AMg3. Strip blanks were subjected to high-speed continuous recrystallization annealing using contact heating. The metal was heated at a rate of 5 ºC/c to temperatures from 250 to 400 ºC with an interval of 50 ºC with a holding time of 5 - 15 min at the heating temperature and cooling in air. The quality of the annealing was judged by the nature of the obtained structure and indicators of mechanical properties. The ability to extract metal in different states was evaluated by the Eriksen method. Result. The least energy-consuming modes of continuous high-speed annealing of workpieces from the studied alloys were developed to obtain increased plasticity indicators (while maintaining strength) and improve cold pressure processing in the manufacture of products of complex configuration. Practical value. High-speed recrystallization annealing provides reduction of defects, saving of metal, improvement of productivity in the production of thin-sheet items by the method of cold deformation with deep and complex drawing.

Fatigue crack growth rate and propagation mechanisms of SiC particle reinforced Al alloy matrix composites

PurposeThis study aims to investigate the fatigue crack propagation behavior of SiC particle-reinforced 2124 Al alloy composites under constant amplitude axial loading at a stress ratio of R = 0.1. For this purpose, it is performed experiments and comparatively analyze the results by producing 5, 10, 15 Vol.% SiCp-reinforced composites and unreinforced 2124 Al alloy billets with powder metallurgy (PM) production technique.Design/methodology/approachWith the PM production technique, SiCp-reinforced composite and unreinforced 2124 Al alloy billets were produced at 5%, 10%, 15% volume ratios. After the produced billets were extruded and 5 mm thick plates were formed, tensile and fatigue crack propagation compact tensile (CT) samples were prepared. Optical microscope examinations were carried out to determine the microstructural properties of billet and samples. To determine the SiC particle–matrix interactions due to the composite microstructure, unlike the Al alloy, which affects the crack initiation life and crack propagation rate, detailed scanning electron microscopy (SEM) studies have been carried out.FindingsOptical microscope examinations for the determination of the microstructural properties of billet and samples showed that although SiC particles were rarely clustered in the Al alloy matrix, they were generally homogeneously dispersed. Fatigue crack propagation rates were determined experimentally. While the highest crack initiation resistance was achieved at 5% SiC volume ratio, the slowest crack propagation rate in the stable crack propagation region was found in the unreinforced 2124 Al alloy. At volume ratios greater than 5%, the number of crack initiation cycles decreases and the propagation rate increases.Originality/valueAs a requirement of damage tolerance design, the fatigue crack propagation rate and fatigue behavior of materials to be used in high-tech vehicles such as aircraft structural parts should be well characterized. Therefore, safer use of these materials in critical structural parts becomes widespread. In this study, besides measuring fatigue crack propagation rates, the mechanisms causing crack acceleration or deceleration were determined by applying detailed SEM examinations.

Microstructure and properties of HEA fabricated through metal powder wire arc additive manufacturing

This study underscores the successful attainment of a homogeneous chemical composition within the billet, demonstrating its aptness for uniform material properties. Nevertheless, microstructural variations, encompassing texture, grain size, dislocation density, and microhardness, were discernible along the height of the billet. These variations are attributed to the presence of intricate oxides, which originate from the purity of the initial metal powder. Importantly, despite these microstructural disparities, the mechanical properties of the high-entropy alloy (HEA) billet exhibited consistent distribution. These observations emphasize the pivotal role of microstructural control in customizing HEA properties for specific applications.

Impact of ECAP processing on dislocation density and subgrain size in a ti6al4V alloy prepared by direct energy deposition

Ti6Al4V alloy billets were additively manufactured by direct energy deposition and then equal channel angularly pressed (ECAPed) at 700 °C. The originally prepared α′ martensite microstructure was completely converted to an equiaxed fine grain structure during ECAP processing. The α′ martensite decomposed into α + β dual phase structure. The dislocation density in the deposited and ECAPed samples was measured by X-ray profile analysis in samples of two orientations. The dislocation density estimated in the deposition plane was found to be higher than that estimated perpendicularly. This difference is probably a consequence of the internal stresses generated in the samples during the deposition process. A similar anisotropy in dislocation density and crystallite size was found in the ECAPed samples. Lattice constants were measured for the α′ martensite and α phase of the ECAPed alloy. The crystallite size distribution was found to be moderately different for samples cut parallel and perpendicular to the extrusion direction.

Technology and equipment for electron beam sintering of hard alloy billets

Technology and equipment for electron beam sintering of hard alloy billets

Effects of rolled fibrous microstructure on fatigue properties of extruded Cu-5Al planar micro springs

Planar micro spring is an important elastic component in microelectromechanical system devices, and one of its main failures is fatigue. In this work, a new method to improve the cycles of a planar micro spring by introducing pre-rolled fibrous microstructure was proposed. Cu-5Al alloy billets with a fibrous microstructure rolled at room temperature with a reduction ratio of 70% were obtained. Three types of planar micro springs with fibrous microstructure were prepared through extrusion by varying the angle between the fibrous microstructure direction and the extrusion direction. Fatigue tests were conducted using a customized micro-fatigue test system. The best fatigue performance was obtained by preparing the micro springs with the fibrous microstructure direction perpendicular to the extrusion direction, while the worst fatigue performance was obtained by preparing the planar micro springs with the fibrous microstructure direction parallel to the extrusion direction. The fibrous microstructure direction affected the local strain in the micro springs. The fibrous microstructure slightly affected the location of the crack initiation region but significantly affected the area of crack initiation and steady-state expansion region of the micro spring. The fatigue life cycle of extruded Cu-5Al alloy planar micro spring with the pre-rolled fibrous microstructure improved by 58% more than that of extruded Cu-7Al alloy planar micro spring without the pre-rolled fibrous microstructure. Micro spring fatigue life cycle decreased with increasing strain amplitude. This work provides a new approach for preparing planar micro springs with high fatigue performance.

Melt thermal-rate treatment for uniform solute distribution and improved mechanical properties of an Al-Zn-Mg-Cu alloy prepared by direct-chill casting

Melt thermal-rate treatment (MTRT), a promising technique for improving microstructure uniformity, has been rarely applied in direct-chill (DC) casting. In this study, we investigated the effects of MTRT on the microstructure and mechanical properties of an Al-Zn-Mg-Cu alloy billet prepared using DC casting. Results indicate that MTRT improved the uniformity of solute distribution in the Al matrix, thereby enhancing mechanical properties such as hardness, tensile strength, and ductility. In particular, yield strength, ultimate tensile strength, and elongation of the near-surface region of the billet increased from 250 to 274 MPa, from 319 to 393 MPa, and from 2% to 8%, respectively. It has been reported that twinned dendrite grains (TDGs) form on the surface of billets because of directional solidification or DC casting at high cooling rates. However, this study reveals that the formation of TDGs was induced in the central region of the billet by MTRT. Furthermore, the effects of TDGs on the mechanical properties are evaluated and compared with those of regular grains of MTRT billets. Overall, these findings suggest that MTRT is an efficient technique used to improve the mechanical properties of Al alloys fabricated using DC casting.

Friction extrusion of AZ91/bioactive glass gradient composite

The effect of the pre-friction extrusion microstructure of AZ91 billet on the microstructure, mechanical properties, and corrosion resistance of AZ91-bioactive glass surface composite rods was investigated. The results show that friction extrusion on AZ91 alloy billet with cast microstructure results in agglomerated bioactive glass particles in the composite rod microstructure. Compared to as-cast AZ91 alloy, friction extrusion on AZ91 alloy billet with cast microstructure results in 93% more corrosion resistance. Also, friction extrusion on AZ91 alloy billet with extruded microstructure leads to a gradient AZ91-bioactive glass composite rod with ultimate tensile strength, yield strength, and corrosion resistance of 9, 2, and 74% higher than AZ91 alloy rods, respectively.

Effects of PMMT on microstructure and macrosegregation of large-sized 6061 alloy billet

The pulsed magnetic field melt treatment (PMMT) was applied in the direct chill (DC) casting of 6061 alloy billets with a diameter of 430 mm. The results indicated that the billet solidification structure was refined and homogenised. The grain size was reduced by 20.4% in the billet centre. Meanwhile, the PMMT can reduce the addition of grain refiner. The negative macrosegregation in the billet centre was reduced significantly. This can be attributed to the melt structure being changed by the energy of the pulsed magnetic field, which leads to the temperature of the melt variation and increased nucleation rate. This study may offer a promising method for the high-quality large-sized 6061 alloy billets preparation with less grain refiner.

Improvement of Grain Structure of AA6063 Alloy Billet Casting

In this study; it was aimed to develop AA6063 alloy Aluminum alloy billet properties of 203 mm in diameter. For this purpose; metal temperature, casting and liquid metal height at the casting table. After the casting process, the homogenization process was carried out at different times, temperatures and different cooling rates. Microstructure, hardness and tensile tests were carried out on the samples taken from the test billets and parameters were determined for the production of AA6063 alloy billets with a diameter of 203 mm.

β Grain Size Inhomogeneity of Large Scale Ti-5Al-5V-5Mo-3Cr Alloy Bulk after Multi-Cycle and Multi-Axial Forging in α + β Field

In order to fabricate homogeneous large-scale Ti-5Al-5V-5Mo-3Cr (Ti-5553) alloy bulk with fine and equiaxial β grain, we performed a series of multi-axial α + β field forging with 62 forging cycles on the large-scale Ti-5553 billet by using 12.5 MN high-speed hydraulic press. The β-annealed microstructure was the starting microstructure of the billet. After the 6th forging cycle, β grain deformed dramatically, and the grain-boundary network developed within the irregular β grain. As the forging cycle increased to 44, the volume fraction of the fine and equiaxial β grain that is less than 20 μm, which is caused by dynamic recrystallization, increased gradually. However, the incomplete dynamic recrystallization region within the original β grain could not be eliminated. As the forging cycle further increased, the volume fraction of the fine and equiaxial β grain did not increase. In contrast, the abnormal grain growth of the β phase occurred during 50th~62nd forging cycle. Here, we attribute the formation of the incomplete dynamic recrystallization region and the abnormal grain growth of the β phase to the high deformation rate of the α + β forging. The refining behavior of β grain and the abnormal coursing β grain, which is found during the multi-cycle multi-axial forging of large-scale Ti-5553 alloy billet, are seldom reported in the isothermal compression of small-scale Ti-5553 alloy specimen. The findings of the paper are instructive for improving the sub-transus forging strategy that is used to fabricate the large-scale homogeneity Ti-5553 alloy billet with fine and equiaxial β grain.

Effect of initial microstructures on microstructures and properties of extruded AZ31 alloy

The raw materials for extruded preparing magnesium alloy tubes were electromagnetic stirring (EMS) AZ31 magnesium alloy billets and conventional casting (CC) AZ31 magnesium alloy billets. According to the findings, the mechanical properties of the EMS extrusion tubes were far superior to those of the CC extrusion tubes. The key explanation was that the samples of EMS billet had variable initial grain sizes and twin boundaries, which provide additional nucleation sites for DRX nucleation during the extrusion process. With the increase of extrusion temperature and extrusion ratio, the elongation of the tube is further improved. During the extrusion process, the recrystallization mechanism changed from continuous dynamic recrystallization (CDRX) to discontinuous dynamic recrystallization (DDRX).

Effect of Cu concentration on high-temperature mechanical properties and microstructures of Al-Si alloy for forging fabricated by continuous casting process with the heat-insulating-mold

Al-Si alloy billets with 0, 2, 4, and 6 mass%Cu have been fabricated by the Heat-Insulating-Mold method. The microstructures and high-temperature mechanical properties at 423 K, 523 K, and 623 K have been investigated. Increasing Cu concentration changed the types of constituent particles and increased their area fraction. 0.2% proof stress (σ0.2) and ultimate tensile strength (σUTS) increased with increasing Cu concentration at each temperature. SEM observation showed that precipitates increased with increasing Cu concentration and remained in the matrix below 523 K but dissolved into the Al matrix at 623 K. The former suggested that the precipitates contributed to the strength below 523 K. On the other hand, significant work-hardening was confirmed until 0.2% strain at 623 K, which suggested that the constituent particles contributed to the strength just like particle-reinforced composites. The work-hardening rate and the amount of work-hardening increased with increasing Cu concentration and correlated with the interparticle spacing of the constituent particles. It indicated that decreasing interparticle spacing enhanced constraining matrix deformation, and it led to an increase of σ0.2 and σUTS.

Achievement of high strength and good ductility in the large-size AZ80 Mg alloy using a designed multi-directional forging process and aging treatment

Most high-performance Mg alloy samples obtained by severe plastic deformation processes are difficult to implement in industrial utilization due to their small size. The strength of large samples developed using the multi-directional forging (MDF) process is significantly lower than that of small samples. This work developed a large commercial AZ80 alloy sample with dimensions of 100 × 100 × 140 mm3 using a two-step MDF process and artificial aging. The designed process is different from the reported MDF and aging processes. The T5 treated sample exhibits uniform mechanical properties with the ultimate tensile strength of 430 MPa (Engineering stress) and elongation to failure of 11.4%, reaching the level of wrought Mg-RE alloys. MDF at elevated temperatures improves the plasticity of the sample resulting in a good forgeability at 180 °C. The high density defects introduced by the MDF process include grain boundaries, dislocations and stacking faults (SFs) that accelerate the subsequent aging response. The good strength-ductility synergy is attributed to the simultaneous effect of an overall bimodal microstructure composed of fine grains and coarse grains, nanoscale β-Mg17Al12 precipitates, and a high density of dislocations and SFs. The designed process can benefit the general community of Mg alloys since the excellent mechanical properties do not rely on the strengthening mechanism due to the addition of specific elements. This work provides an effective way to develop large-size Mg alloy billets applied to load-bearing components.