Influence Of Thermomechanical Processing Research Articles

Tailoring functional properties of a FeMnSi shape memory alloy through thermo-mechanical processing

The influence of thermo-mechanical processing on the microstructure and functional properties of a Fe–17Mn–5Si–10Cr–4Ni-1(V–C) (wt%) shape memory alloy was systematically investigated. The as-received material was subjected to 25 % cold rolling followed by a recrystallization at 925 °C and single or double aging treatments. Transmission electron microscopy revealed the formation of the ε-martensite and annealing twin boundaries and Shoji-Nishiyama orientation relationships of ε-martensite and γ-austenite in double aged specimen. Cyclic tensile testing demonstrated that the recrystallized and double aged alloy exhibited excellent pseudoelasticity. In the incremental strain test, the alloy achieved the highest peak stress and pseudoelasticity at each cycle. In the constant stresses test, the alloy accumulated a minimal residual strain of only 0.12 % over 50 cycles. This stability was attributed to a strong precipitation strengthening and the interactions between the martensite and the refined microstructural features. In addition, the recrystallized and double aged sample resulted in the greatest recovery stress of 450 MPa upon heating after pre-straining, because of its high yield strength suppressing new martensite formation during cooling process. The results of high-resolution transmission electron microscopy identified a non-Shoji-Nishiyama orientation relationship between the stress-induced ε-martensite after the stress recovery test and γ-austenite matrix, inducing additional irrecoverable strain and raising the recovery stress. Overall, the study can demonstrate that the tailored thermo-mechanical processing enables optimizing the functional performance of FeMnSi alloys.

Influence of thermo-mechanical processing on microstructure and properties of bulk metallic glassy alloys-reinforced Al matrix composites prepared by powder metallurgy

Al-matrix composites, reinforced with two different types of glassy particles and prepared by mechanical alloying, were consolidated via Spark Plasma Sintering (SPS) and hot extrusion to produce high-strength Al–5%Al65Cu20Ti15 and Al–5%Al84Ni7Co3Nb6 composites, along with pure Al sample for comparison. TEM observation and XRD analysis were used to investigate the crystal structure of the prepared powders. Metallurgical analysis tools, including SEM, TEM, XRD and EBSD, were used to investigate the effect of consolidation temperature and processing on the amorphous phase and the distribution of reinforcing particles in the composite. Also, the effect of the consolidation process on the grain morphology and size of the prepared composite was studied. Al-5% Al65Cu20Ti15 was fully densified, compared to nearly 98 % relative density for Al-5% Al84Ni7Co3Nb6 and pure Al sample prepared by hot extrusion. Moreover, Al-5% Al65Cu20Ti15 composite showed the highest hardness and ultimate tensile strength values, which are 63Hv and 226 MPa, respectively. An acceptable elongation of 15 % was also achieved. After SPS, hot extrusion process improved the strength of the composite compared with previously reported Al composites containing higher percents of Al-based glassy articles manufactured using various processing techniques. Homogenous reinforcement distribution, grain refinement and improved wettability between matrix and reinforcement are the key factors on improving the strength of Al–5%Al65Cu20Ti15 composite. The coefficient of thermal expansion (CTE) decreased by adding glassy particles to the Al-matrix, while Al-5% Al65Cu20Ti15 had the lowest values.

Influence of thermomechanical processing and tempering temperature on tensile flow and work hardening behaviour of India specific reduced activation ferritic martensitic steel

In the present work, an indetailed investigation has been carried out on the effect of thermomechanical treatment (TMT) and tempering temperature on microstructural features, tensile flow characteristics and work hardening behaviour of the India specific reduced activation ferritic martensitic (INRAFM) steel. The flow and work hardening characteristics of the studied steel are described by using the Voce constitutive equation and Kocks- Mecking (K-M) approach respectively in the temperature range of 300–873 K. The steel subjected to TMT and tempering for 90 min at 1033 K shows a refined martensitic lath width, finer size (Cr/W/Fe)23C6 and (V/Ta) (C/N) precipitates with an increment in number density. Furthermore, increase in tempering temperature coarsened the refined structural features. Voce equation closely fits the flow curves at 823 K and 873 K, but shows a slight deviation at temperatures below 773 K. The parameters derived from Voce equation are fairly in good correaltion with the experimental values. The strain hardening rate (θ) vs. true stress (σ) plots portrayed stage-I and stage-III work hardening stages and their corresponding phenomena were discussed. In addition, the effect of TMT and tempering treatment on the work hardening parameters obtained from K-M approach and inter-barrier spacing of the steel were also presented in this study. The work hardening characteristics of the steel signifcantly improved upon TMT due to refinement in microstructural features. The flow stress and work hardening parameters decreases with raise in test temperature due to the dominant effect of dynamic recovery.

Influence of thermomechanical processing on coarse particles, grain structure, and mechanical properties of Al–Cu alloy rings

Rings made of 2219 Al alloy are typically manufactured by multi-directional forging (MDF) and ring rolling at 460 °C, followed by heat treatment. However, this process often results in coarse elongated grains and a large number of coarse Al2Cu particles, resulting in rings with poor mechanical properties. As a strategy to refine the microstructure and improve the mechanical properties, a novel thermomechanical process was tested for ring manufacturing, with MDF at 510 °C and ring rolling at 240 °C. The results showed that use of MDF at higher temperatures resulted in increased spherical shapes and decreased numbers of coarse Al2Cu particles due to more complete dissolution. Decreasing the rolling temperature from 460 °C to 240 °C resulted in finer grain structure due to the increased nucleation ratio of static recrystallization during subsequent solution heat treatment. Samples prepared using this novel process exhibited fine equiaxed grains with sufficient dissolving of coarse Al2Cu particles, thus this method significantly improved the mechanical properties of the prepared material and decreased the anisotropy in three orthogonal directions.

A study of laves phase in high Nb non-oriented silicon steel for electric automobiles

In the study of precipitates in high-Nb non-oriented silicon steel for the rotor of electric automobiles, it was found that mass dispersed Nb-rich precipitates were formed during the rolling process of the steel, these precipitates are presumed to be Laves phases in published literatures. In this regard, two types of Laves phases of high-Nb non-oriented silicon steel for electric automobiles and their crystallographic relationship with the Fe matrix were determined using SAED, FFT and IFFT, and calculation of steel strength enhancement by precipitation strengthening. The results showed the elliptical Laves phase is Fe16Nb6Si7 and the rectangular strip Laves phase is Nb7P4, and the orientation relationship between Fe16Nb6Si7 phase and Fe matrix is : [001]Fe16Nb6Si7∥[001]Fe, [101]Fe16Nb6Si7∥[110]Fe, [113]Fe16Nb6Si7∥[112]Fe, the orientation relationship between Nb7P4 phase and Fe matrix is : [130]Nb7P4∥[001]Fe, [102]Nb7P4∥[110]Fe, [110]Nb7P4∥[112]Fe; Both Fe16Nb6Si7 and Nb7P4 precipitates have a good coherent relationship with the Fe matrix; The calculation results show that Fe16Nb6Si7, Nb7P4 and other precipitates can improve the yield strength of non-oriented silicon steel, but at the same time, the magnetic properties of the steel are expected to be negatively impacted. The research results can provide important theoretical guidance on the influence of thermo-mechanical processing on balancing the mechanical and magnetic properties of high niobium non-oriented silicon steel for electric vehicle rotor.

Influence of Thermomechanical Processing on Microstructure and Mechanical Properties of MoNbTaW Refractory High-Entropy Alloy

Influence of Thermomechanical Processing on Microstructure and Mechanical Properties of MoNbTaW Refractory High-Entropy Alloy

Influence of thermomechanical processing on the microstructural and mechanical properties of steel 22MnB5

In order to reduce CO2 emissions in the transport sector, the approach of load-adapted components is increasingly being pursued. For the design of such components, it is crucial to determine their resulting microstructure and mechanical properties. For this purpose, continuous cooling transformation diagrams and deformation continuous cooling transformation diagrams are utilized, however, their curves are strongly influenced by the chemical composition, the initial state and especially the process parameters.In this study, the influence of the process parameters on the transformation kinetics is systematically investigated using an innovative characterization method. The experimental setup allowed a near-process analysis of the transformation kinetics, resulting microstructure and mechanical properties for a specific process route with a reduced number of specimens. A systematic investigation of the effects of different process parameters on the microstructural and mechanical properties made it possible to reveal interactions and independencies between the process parameters in order to design a partial heating or differential cooling process. Furthermore, the implementation of two different cooling conditions, representative of differential cooling in the die relief method with tool-contact and non-contact areas, showed that the soaking duration has a significant influence on the microstructure in the non-contact tool area.

The role of thermomechanical processing routes on the grain boundary network of martensite in Ti–6Al–4V

The influence of thermomechanical processing (TMP) of a Ti–6Al–4V alloy on the transformation texture and intervariant boundary network were investigated by conventional EBSD mapping along with the five-parameter boundary analysis approach. The texture characteristics of Ti–6Al–4V subjected to deformation in the β regime followed by the β→α martensitic transformation were examined using visco-plastic self-consistent simulation and forward calculation of the transformation texture. Comparison of the simulated and experimental texture characterisitcs revealed that the transformed α′ texture was dominated by the variant selection associated with substructure development in the β parent phase and the occurrence of specific self-accommodating α′ variants in the microstructure, promoting the quadrilateral and/or V shape variant arrangement. This resulted in a progressive increase in the 63.26°/[10‾553‾] intervariant boundaries with the strain increment, at the expense of 60°/[112‾0]. Moreover, the grain boundary network for all conditions was dominated by the triple junctions (grain boundary network) terminating on 63.26°/[10‾553‾] and 60°/[112‾0] intervariants. It is shown that the elastic interactions among the variants during the martensitic transformation is the dominant parameter affecting the grain boundary network, despite the presence of dislocation based variant selection.

Influence of thermomechanical processing on microstructure, mechanical and strain hardening properties of single-phase Mg-4Li-0.5Ca alloy for structural application

The single-phase Mg- 4Li- 0.5Ca alloy was rolled at three different temperatures (250, 300 and 350 °C) and followed by annealing at 200 °C for 10 min. To evaluate the mechanical properties, the tensile test was conducted at a constant strain rate of 10−3 s−1. Factors influencing the tensile strength and strain hardening properties were assessed by microscopy, XRD and EBSD analysis. Besides, Kocks–Mecking plots (K-M) were used to determine the different stages of strain hardening exhibited by the variously processed Mg- 4Li- 0.5Ca alloy test specimens. The ultimate tensile strength has decreased as hot-rolling temperature increases with increased ductility. The strain hardening properties such as hardening capacity (Hc), strain hardening exponent (n) are increased significantly with an increase in hot rolling temperature and subsequent annealing.

Influence of thermo-mechanical processing on structure and mechanical properties of a new metastable β Ti–29Nb–2Mo–6Zr alloy with low Young’s modulus

A low Young’s modulus is required for titanium alloys used in orthopedic implants, such as hip prosthetic stems, in order to avoid stress shielding due to a large difference in Young’s modulus between the prosthetic stem and the cortical bone. The low Young’s modulus has been observed to occur in metastable β-Ti alloys by precipitation of a stress-induced α″ martensite during cold deformation. Under this context, the Influence of thermo-mechanical processing on the microstructure and mechanical properties of the metastable β Ti–29Nb–2Mo–6Zr alloy was studied as well as the influence of the degree of deformation by cold rolling with subsequent annealing after homogenization heat treatment. The alloy presents a β microstructure after solution heat treatment at 1000 °C for 24h, followed by water quenching, while posterior cold rolling induces the precipitation of α” martensite. Young’s modulus decreases and hardness increases with the degree of deformation. The annealed samples showed higher hardness and Young’s modulus than the cold rolled samples. A thickness reduction of 90% maximizes the hardness/Young’s modulus ratio and optimizes the required mechanical properties for orthopedic implants. The results indicate that the alloy is a promising alternative for the widely used Ti–6Al–4V.

The influence of thermomechanical processing on the structure and mechanical properties of rods made of high-strength titanium alloys of different classes

Abstract The paper investigated the influence of the parameters of thermomechanical processing on the structure formation in rods of 16 mm in diameter from (α + β) and near-β-titanium alloys. It is shown that changing the temperature and speed modes of deformation and heat treatment of alloys makes it possible to create structural and phase states which provide both enhanced ductility and increased strength at certain stages of production. A treatment mode has been developed for rods of VT16 and VT35 high-strength titanium alloys, which ensures high manufacturability of semi-finished products at room temperature and high operational durability for finished products.

Enhanced strength-ductility relationship in a medium Mn high Al-alloyed multicomponent steel through thermomechanical processing

A medium Mn, high Al, multicomponent steel with duplex ferrite-austenite as the starting microstructure has been designed and the influence of thermo-mechanical processing on the microstructure-texture-tensile property relationship has been investigated. The hot forging-annealing followed by hot rolling-annealing treatment showed poor combination of strength and ductility in the studied alloy. However, a subsequent cold rolling-annealing or warm rolling-annealing treatment has resulted in significant improvement in strength-ductility relationship. An excellent combination of strength (1141–1184MPa) and ductility (18.1–22.2% elongation) has been achieved in both the cold rolled-1073K annealed and warm rolled-1073K annealed specimens due to the presence of fine ferrite grains. Higher fraction of fine M5(Al,Si)C precipitates have restricted the grain boundary migration thus leading to smaller ferrite grains in this annealing temperature. However, dissolution of the M5(Al,Si)C precipitates and the simultaneous increase in the grain size of ferrite at higher annealing temperature (i.e. 1173K and 1273K) deteriorates the strength-ductility relationship in both the cold rolled and warm rolled specimens. The cold rolled-annealed specimens have exhibited better ductility as compared to the warm rolled-annealed specimens due to combined effect of smaller grain size as well as larger volume fraction of gamma (γ) fiber of ferrite.

The influence of thermomechanical processing on the surface quality of an AISI 436 ferritic stainless steel

The authors gratefully acknowledge the financial contribution provided by the Advanced Metal Initiative (AMI) of the Department of Science and Technology (DST) through the Ferrous Metals Development Network (FMDN), and Columbus Stainless (Middelburg, South Africa).

Influence of thermomechanical processing on biomechanical compatibility and electrochemical behavior of new near beta alloy, Ti-20.6Nb-13.6Zr-0.5V.

This paper presents the results for the effect of different methods of thermomechanical processing on the mechanical properties and electrochemical behavior of metastable β alloy Ti-20.6Nb-13.6Zr-0.5V (TNZV). The thermomechanical processing included hot working, solution heat treatments at different temperatures, and cooling rates in addition to aging. The thermomechanical processing conditions used in the study resulted in attainment of a wide range of microstructures with varying spatial distributions and morphologies of elongated/equiaxed α, β phases, or martensite, as a result of which several tensile properties were achieved. Aging treatment led to an increase in hardness, elastic modulus, and tensile strength and a decrease in ductility (elongation). Electrochemical tests indicated that the TNZV alloy undergoes spontaneous passivation due to spontaneous formation of an oxide film in the environment of the human body. Because the air-cooled samples possessed high hardness and also a fine grain size, they showed a lower corrosion rate than the samples treated under other conditions.

Influence of thermomechanical processing on microstructure, texture evolution and mechanical properties of Al–Mg–Si–Cu alloy sheets

Influence of thermomechanical processing on the microstructure, texture evolution and mechanical properties of Al–Mg–Si–Cu alloy sheets was studied systematically. The quite weak mechanical properties anisotropy was obtained in the alloy sheet through thermomechanical processing optimizing. The highly elongated microstructure is the main structure for the hot or cold-rolled alloy sheets. H {001}〈110〉 and E {111}〈110〉 are the main texture components in the surface layer of hot-rolled sheet, while β-fibre is dominant in quarter and center layers. Compared with the hot-rolled sheet, the intensities of β-fibre components are higher after the first cold rolling, but H {001}〈110〉 component in the surface layer decreases greatly. Almost no deformation texture can be observed after intermediate annealing. And β-fibre becomes the main texture again after the final cold rolling. With the reduction of the thickness, the through-thickness texture gradients become much weaker. The through-thickness recrystallization texture in the solution treated sample only has cubeND {001}〈310〉 component. The relationship among thermomechanical processing, microstructure, texture and mechanical properties was analyzed.

Effect of thermo-mechanical processing on microstructure and electrochemical behavior of Ti–Nb–Zr–V new metastable β titanium biomedical alloy

The influence of thermo-mechanical processing (TMP) on the microstructure and the electrochemical behavior of new metastable β alloy Ti–20.6Nb–13.6Zr–0.5V (TNZV) was investigated. The TMP included hot working in below β transus, solution heat treatments at the same temperature and different cooling rates in addition to aging. Depending upon the TMP conditions, a wide range of microstructures with varying spatial distributions and morphologies of equiaxed/elongated β and β phases were attained, allowing for a wide range of electrochemical properties to be achieved. The corrosion behavior of the studied alloy was evaluated in a Ringer's solution at 37 °C via open circuit potential–time and potentiodynamic polarization measurements.

Influence of thermo-mechanical processing on microstructure, mechanical properties and corrosion behavior of a new metastable β-titanium biomedical alloy

This paper presents the results on the influence of different thermo-mechanical processing (TMP) on the mechanical properties and electrochemical behavior of new metastable β-alloy Ti–20.6Nb–13.6Zr–0.5V (TNZV). TMP included hot working in below β-transus, solution heat treatments at same temperature in different cooling rates in addition to aging. Depending upon the TMP conditions, a wide range of microstructures with varying spatial distributions and morphologies of equiaxed/elongated α, β phases were attained, allowing for a wide range of mechanical and electrochemical properties to be achieved. The corrosion behavior of studied alloy was evaluated in Ringer’s solution at 37∘C using open-circuit potential-time and potentiodynamic polarization measurements.

Influence of thermomechanical processing and heat treatment on microstructure, tensile properties and fracture toughness of Ti-1100-0.1B alloy

The effects of thermomechanical processing and heat treatment on the microstructure, tensile properties and fracture toughness of 0.1wt.% boron modified Ti-1100 alloy (Ti-1100-0.1B) processed by vacuum arc melting was investigated at room temperature and compared with that of the base alloy. The tensile properties of the base alloy (Ti-1100) were significantly lower in the β-processed as compared to α−β-processed conditions whereas the tensile properties of boron modified alloy (Ti-1100-0.1B) were similar irrespective of whether it was α−β or β-processed. The B addition resulted in a higher strengthening in β-processed alloy as compared to α−β-processed alloy. The fracture toughness of Ti-1100-0.1B alloy was also found to be lower than that of the base Ti-1100 alloy irrespective of the processing conditions and solution treatment temperatures. Neither the solution treatment temperature nor the processing condition had a significant effect on the fracture toughness of the B modified Ti-1100-alloy whereas in the case of the base alloy, the fracture toughness was distinctly higher in the β processed condition for all the solution treatment temperatures. The results were explained on the basis of the effect of processing and heat treatment on the microstructure as well as the role of TiB whiskers in influencing the strengthening as well as fracture mechanisms in Ti-1100 alloy.

The influence of thermomechanical processing on the microstructure and mechanical properties of 13.5Cr ODS steels

Reduced activation oxide dispersion strengthened (ODS) ferritic steels are the most promising structural materials for future fusion power plants and innovative fission nuclear reactors. The structure and mechanical properties of fine-grained 13.5% Cr ODS ferritic steels, processed by hot cross rolling to large strains of 70% and subsequent annealing have been investigated. The microstructure after hot cross rolling is partially recrystallized. The texture of the ODS ferritic steel after rolling and annealing has a sharp rotated cube ({100} 〈110〉) texture component. The γ-fiber component (〈111〉||normal direction) typical of recrystallized rolled ferritic steels is absent. Similar values of tensile strength are obtained for rolled samples regardless of the sample orientation in comparison with hot isostatically pressed samples whereas a substantial enhancement in total elongation (22%) is present at 500°C. Cross-rolled ODS steels represent an increase in upper shelf energy to 2J compared with hot isostatically pressed samples. The relatively poor toughness properties, compared to 9Cr ODS RAFM steel EUROFER ODS, can be attributed mainly to the absence of the γ-fiber texture component, bimodal grain size distribution and high amounts of interstitial impurities (O, N).

Influence of Omega-Phase Precipitation Hardening on the Static and Dynamic Properties of Metastable Beta Ti-Nb-Zr and Ti-Nb-Ta Alloys

The influence of thermomechanical processing on the Ti-21.8Nb-6Zr (TNZ) and Ti-19.7Nb-5.8Ta (TNT) (at%) alloys’ structure, phase composition, mechanical and functional properties is studied. Both alloys possess polygonized dislocation substructure (average subgrain size  100 nm), and manifest superelastic behavior at room temperature and recovery stress generation during constant-strain temperature scanning experiments. After aging treatment, both alloys were -phase precipitation hardened, but their mechanical behavior was impacted differently -- it was detrimental for TNZ and beneficial for TNT. The different impact of aging heat treatment on the mechanical behavior of these alloys is explained by the differences in the -phase nucleation rate, precipitates’ size, shape, volume fraction and distribution, and by their effect on the alloys’ critical stresses and transformation temperatures.