Martensite Phase Fraction Research Articles

The BCC → FCC hierarchical martensite transformation under dynamic impact in FeMnAlNiTi alloy

The quasi-static superelastic responses and hierarchical martensite transformation from body-centered cubic (BCC) to face-centered cubic (FCC) under dynamic impact in Fe42Mn34Al15Ni7.5Ti1.5 alloys were investigated. Polycrystalline and oligocrystalline alloys were produced through solution heat treatment and cyclic heat treatment processes, respectively. The results show the volume fraction of residual martensite for oligocrystalline alloys is lower, which exhibits better superelastic responses compared with polycrystalline alloys. Dynamic impact tests indicate that, despite the weakening of the grain boundary strengthening effect, the ultimate strength of the oligocrystalline alloys closely matches that of the polycrystalline alloys under dynamic impact. The martensite transformation of the FeMnAlNiTi alloy is characterized as hierarchical under dynamic impact, and increasing strain rates and grain sizes can enhance the BCC→FCC martensite transformation, resulting in higher martensite phase fractions for oligocrystalline alloys. The increase in ultimate strength is attributed to the dynamic Hall-Petch effect introduced by more martensite phase interfaces under dynamic impact.

Effect of thermomechanical training on recovery stress of Fe-based shape memory alloy

This research explores the impact of thermomechanical treatment on the recovery stress induced by the shape memory effect in an Fe-based shape memory alloy with the composition of Fe-17Mn-5Si-10Cr-4Ni-1(V,C) wt.%. Fe-based shape memory alloys have gained considerable attention for their potential applications in vibration control, energy dissipation, and structural strengthening or re-centering within the construction industry. To evaluate the recovery stress behaviour of this Fe-based shape memory alloy, specimens underwent a two-step aging heat treatment process, involving initial aging at 600 °C for 20 hours, followed by subsequent aging at 680 °C for 8 hours. Then heat-treated samples subjected to a cyclic thermomechanical treatment, involving a combination of deformation up to 2% and heating at 200 °C for 30 min in each cycle. The microstructure and mechanical properties were assessed using techniques such as scanning electron microscopy, as well as tensile tests. The results revealed that the thermomechanical treatment had a notable impact on the microstructure and mechanical properties of the Fe-based shape memory alloy. It resulted in an enhancement of the shape memory effect and recovery stress. These improvements were associated with an increase in the martensitic phase fraction. Additionally, the presence of VC precipitates in the treated samples contributed to the enhancement of the shape memory effect.

Phase Fraction Estimation Using Measured Dilation, a Lattice Parameter Model, and a Curve-Fitting Method

Dilatometry is a measurement frequently used to analyze phase transformations in steels during austenite decomposition. Such analyses are essential for the design of heat treatments and for determining the final phase fractions. This paper presents a simple and systematic method to estimate the evolution of the non-measurable phase fraction of ferrite, pearlite, bainite, and martensite during Continuous Cooling Transformation (CCT) experiments. The optimization-based method uses the measured dilation curve, a lattice parameter model, and a semi-empirical curve-fitting method. The latter assumes specific shapes of the transformation rates. The proposed approach can reconstruct the dilation curve and estimate the phase fractions with high accuracy.

Structural metamaterial lattices by laser powder-bed fusion of 17-4PH steel

Additive manufacturing build parameters are used to engineer structural metamaterials lattices with controllable mechanical performance, achieved through microstructural grading of 17-4PH steel without compositional or geometric modification. The high solidification rates of laser powder-bed fusion suppress the thermal martensitic transformation and lead to elevated levels of retained austenite. Diamond cubic lattices built at low energy density (low thermal strain) retain a low martensite phase fraction (3 wt%) and exhibit a bend-dominated compression response. Lattices built at high energy density experience increased thermal strain during the build, causing in-situ deformation-driven transformation, yielding 44 wt% martensite; these exhibit a stretch-dominated compression response. Metamaterial lattices, with high and low energy density parameters in different configurations, exhibit mixed compression responses. Controllable mechanical response was achieved through control of microstructure, using build parameters to adjust thermal strain and selectively suppress or trigger the martensitic phase transformation in-situ.

Effects of mechanical deformation on dislocation density and phase partitioning in 4130 steel

Interrupted tensile tests were performed on an AISI 4130 pressure vessel steel and investigated by neutron diffraction and scanning microscopy techniques. Analysis of the neutron diffraction patterns reveal a partitioning of ferrite and martensite phases resulting from deformation. A modified Williamson-Hall approach was used to model the broadening of Bragg peaks associated with the two phases as a function of applied strain, revealing an order of magnitude increase in their dislocation densities when the material was strained beyond the ultimate tensile strength (UTS). Lattice strains measured in the ferrite phase were consistently larger than those measured in the martensite phase for all the applied strain levels investigated. Moreover, a strain-induced phase transformation from a predominately martensitic steel to a ferritic steel was observed, with the average martensite phase fraction of an as-received specimen going from 78% to 22% when pulled to failure. Electron Backscatter Diffraction (EBSD) and Scanning Kelvin Probe Force Microscopy (SKPFM) were used to characterize the microstructure and phase fractions of ferrite and martensite associated with the various strain levels. These results agree well with those obtained from neutron diffraction and demonstrate the utility of SKPFM to distinguish between metallic phases with similar crystal structures that may be difficult to detect using conventional methods such as EBSD.

A data driven computational microstructure analysis on the influence of martensite banding on damage in DP-steels

Material design and optimisation for specific applications are key factors to reduce material usage. Thus, they are an important component towards more sustainable materials and process engineering. Additionally to optimising the chemical composition and the processing chain, the microstructure is another important factor. Especially for the damage properties, which are especially influential for forming processes. To achieve the best possible component performance it is important to understand the influences of the material and its microstructure on the performance. While damage evolution during forming is not equivalent to failure, understanding the characteristics and implications is extremely important for optimal service behaviour. However, a comprehensive way to quantify the influence of the microstructure on the damage properties is still not fully available. Thus, it is unclear how individual parameters of the microstructure influence the damage properties and, in extension, the mechanical properties. For dual phase (DP) steels the martensite phase plays an important role for strength, ductility, formability and damage resistance. While the influence of martensite phase fraction and morphology was often investigated experimentally, it is not possible to draw comprehensive, quantitative conclusions from such tests, as there are many factors at play in the microstructure, that cannot be changed individually. This study applies a simulative approach utilising statistically representative volume elements (sRVE) to quantify the influence of martensite banding on damage properties. Bending tests are taken as a forming process application, and investigations on the testing material show that the martensite bands play a major role during the cracking of the sample. In front of the crack tip, damage forms inside the banded structures leading to the crack running along or through the bands when enough voids have formed. To quantify the influence the bands have on the damage initiation, two microstructure states are compared: banded and without bands. For both states 29 sRVE are simulated to ensure a statistical analysis of the influence. The simulative comparison shows that the banded structures lead to an earlier damage initiation by margins of 2 to 20% of PEEQ. The methods applied in this study enable the investigation of individual influences of microstructure parameters on different mechanical or damage properties.

Visualising Martensite Phase Fraction in Bulk Ferrite Steel by Superimposed Bragg-edge Profile Analysis of Wavelength-resolved Neutron Transmission Imaging

Visualising Martensite Phase Fraction in Bulk Ferrite Steel by Superimposed Bragg-edge Profile Analysis of Wavelength-resolved Neutron Transmission Imaging

Load partitioning behavior in a metastable austenitic stainless steel subjected to pre-deformation below and above Md temperature: Experimental and modeling studies

A physics-based model coupling the evolution of dislocation density in the austenite and strain-induced martensite phases with composite flow strength and kinetics of martensite transformation was developed to describe ambient temperature uniaxial tensile deformation behavior of mill annealed and pre-deformed 304 SS. The applicability of the model was evaluated by fitting the experimental stress-strain data and validated with the experimentally estimated dislocation density in the austenite phase of the steel. The modeling results revealed that the initial microstructure of the steel significantly influences the dislocation accumulation and annihilation rates as well as the load partitioning between austenite and martensite phases. Despite a lower initial dislocation density than the pre-deformed conditions, the mill annealed condition revealed a higher capacity (approximately two orders of magnitude) for dislocation accumulation in the austenite phase. The initial volume fraction of strain-induced martensite phase and the initial dislocation density of pre-deformed 304 SS are governed by the degree of pre-deformation and pre-deformation temperature, either below or above Md temperature (where Md is defined as the temperature above which plastic deformation does not result in austenite to martensite transformation). It is observed that storage, as well as annihilation rates in the austenite phase, are higher for the steel having a higher initial volume fraction of martensite and dislocation density. Though the pre-deformation altered the evolution of martensite volume fraction, the steel exhibited a minor variation in dislocation accumulation capability in the martensite phase for different conditions.

Influence of Quenching and Partitioning Parameters on Phase Transformations and Mechanical Properties of Medium Manganese Steel for Press-Hardening Application

It has been proven that through targeted quenching and partitioning (Q & P), medium manganese steels can exhibit excellent mechanical properties combining very high strength and ductility. In order to apply the potential of these steels in industrial press hardening and to avoid high scrap rates, it is of utmost importance to determine a robust process window for Q & P. Hence, an intensive study of dilatometry experiments was carried out to identify the influence of quenching temperature (TQ) and partitioning time (tp) on phase transformations, phase stabilities, and the mechanical properties of a lean medium manganese steel. For this purpose, additional scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and energy dispersive X-ray spectroscopy (EDX) examinations as well as tensile testing were performed. Based on the dilatometry data, an adjustment of the Koistinen–Marburger (K-M) equation for medium manganese steel was developed. The results show that a retained austenite content of 12–21% in combination with a low-phase fraction of untempered secondary martensite (max. 20%) leads to excellent mechanical properties with a tensile strength higher than 1500 MPa and a total elongation of 18%, whereas an exceeding secondary martensite phase fraction results in brittle failure. The optimum retained austenite content was adjusted for TQ between 130 °C and 150 °C by means of an adapted partitioning.

Tailoring microstructure of wire arc additively manufactured C–Mn–Si steel with post process heat treatment

Wire + arc additive manufacturing (WAAM), a promising technology to produce complex parts, was used to produce steel components with a custom-designed cored-metal wire. The chosen chemical composition of the cored wire is known to produced advance high-strength steel. The as-printed microstructure consists of martensite, retained austenite, and different morphological phases of ferrite, including quasi-polygonal, acicular, and Widmanstatten. Nanoindentation shows the highest hardness value for martensite, followed by acicular ferrite and then quasi-polygonal ferrite. However, a considerable spatial microstructural heterogeneity was observed in as-printed samples due to thermal cycling and chemical segregation. A higher fraction of harder martensite phase was observed at the bottom of the printed coupon, and the phase fraction of martensite decreased due to heat accumulation along the deposition height. Microstructural heterogeneity is reflected in the inhomogeneous distribution of nanohardness. Tempering of the printed sample results in carbide precipitation in martensite phases, leading to a decrease in the martensite hardness, but the heterogeneity is conserved. Both quench hardening and quenching and partitioning (Q&P) treatment were found to homogenize the microstructures. The quench-hardened samples' microstructure was comprised of lath martensite, while the Q&P treatment led to formation of tempered martensite and retained austenite.

Effect of Low Transformation Temperature Welding Consumable on Microstructure, Mechanical Properties and Residual Stress in Welded Joint of A516 Carbon Steel

The microstructure, mechanical properties and residual stress of flux-cored arc welded ASTM A516-70N carbon steel using a Mn-based low-temperature transformation (LTT) welding consumable were investigated. Microstructural analysis with X-ray diffraction, an electron backscattered diffractometer and a field-emission scanning electron microscope showed that the LTT weld metal was made up of ferrite, austenite, martensite, and bainite with phase fractions 50.5%, 0.2%, 40.2% and 9.1%, respectively. The increase in hardness and the decrease in absorbed impact energy of the LTT weld metal compared with conventional consumable welds were confirmed to be due to the relatively high fraction of martensite phase in the weld metal. The welding residual stress distributions in three coupons (LTT, conventional and postweld heat-treated conventional weld) were compared by the results using instrumented indentation testing. The LTT weld coupon showed compressive residual stress distributed in the weld metal and heat-affected zone (HAZ), confirming previous studies in which this residual stress was attributed to a martensitic phase transformation at relatively low temperature. PWHT in the conventionally welded coupon considerably reduced the tensile residual stress distributed in the weld metal and HAZ. The LTT consumable, however, showed a significant advantage in welding residual stress, even compared with the heat-treated conventional consumable.

Bi-Directional Origami-Inspired SMA Folding Microactuator

We present the design, fabrication, and characterization of single and antagonistic SMA microactuators allowing for uni- and bi-directional self-folding of origami-inspired devices, respectively. Test devices consist of two triangular tiles that are interconnected by double-beam-shaped SMA microactuators fabricated from thin SMA foils of 20 µm thickness with memory shapes set to a 180° folding angle. Bi-directional self-folding is achieved by combining two counteracting SMA microactuators. We present a macromodel to describe the engineering stress–strain characteristics of the SMA foil and to perform FEM simulations on the characteristics of self-folding and the corresponding local evolution of phase transformation. Experiments on single-SMA microactuators demonstrate the uni-directional self-folding and tunability of bending angles up to 180°. The finite element simulations qualitatively describe the main features of the observed torque-folding angle characteristics and provide further insights into the angular dependence of the local profiles of the stress and martensite phase fraction. The first antagonistic SMA microactuators reveal bi-directional self-folding in the range of −44° to +40°, which remains well below the predicted limit of ±100°.

Synchrotron x-ray diffraction and crystal plasticity modeling study of martensitic transformation, texture development, and stress partitioning in deep-drawn TRIP steels

The micromechanics of the formability of a lean duplex TRIP steel was investigated using Synchrotron X-Ray Diffraction (S-XRD) measurements and Crystal Plasticity Finite Element Modeling (CPFEM). Specifically, the effect of the ferrite phase on the reduction of stress concentrations in the martensite phase and the influence of the austenite texture on the distribution of the martensite phase in the deep-drawn duplex TRIP steel were studied in comparison to a TRIP steel case. A series of deep-drawing processes were carried out to examine the sheet formability at ambient temperature, followed by S-XRD evaluations of the phase fraction, texture, and the residual-stress distributions in the deep-drawn cups. The macroscopic residual stress and its partitioning among constituent phases were studied using both S-XRD and CPFEM. In the deep-drawn TRIP steel, large tensile hoop residual stresses concentrated in the strain-induced α’ martensite phase, correlating well with the cracking phenomenon observed. Furthermore, the initial austenite texture influenced the martensite transformation kinetics during the deep-drawing process, resulting in a heterogeneous distribution of the martensite phase fractions around the circumference of the deep-drawn cups, which, in turn, caused an orientation-dependent cracking behavior. In the deep-drawn duplex TRIP steel, the tensile hoop residual stresses in the α’ martensite phase were significantly reduced due to a favorable load partitioning to the ferrite phase, resulting in a better formability.

High-performance manufacturing enabling integrated design and processing of products: A case study of metal cutting

Greater integration of materials, product and processes is demanded ultimately toward a knowledge-based control of advanced manufacturing. We propose a framework of high-performance manufacturing theory and methodology to enable the integrated design and processing of a product, with a material–product–process linking developed on the pivot role of surface integrity determining the final performance. Metal cutting, as a representative process of conventional manufacturing, is demonstrated for the new development of manufacturing from a trial-and-error approach to a knowledge-based approach under the framework. A physical model of integrated design and processing is established on thermodynamics for cutting of a metastable AISI 304 austenitic stainless steel component during processing under the multi-source constraints of component geometry, material and structure, where surface integrity changes in surface residual stress and martensitic phase fraction are predicted by FEM modeling. The profound processing effect is described by process signature that derives a quantitative correlation of processing loads in effective force/power input and material loading in transferred/dissipated thermal and mechanical energies to the surface integrity changes. A material-oriented regularization (MOR) method is thus contrived as incorporating the process signature by utilizing identified characteristic correlations of high sensitivity to solve the involved inverse problems. The processing parameters of cutting speed/depth of cut and the design parameters of geometry are synergistically determined through the required surface integrity toward a desired final fatigue performance. The high-performance manufacturing overcomes the intrinsic trial-and-error limitations of conventional manufacturing, knowledgeably considering the coupling effect of processing in the design otherwise merely employed as an empirical design criterion in the past.

Site-specific microstructure, porosity and mechanical properties of LENS™ processed Ti–6Al–4V alloy

In the present study, pre-alloyed Ti–6Al–4V powder is deposited on CP-Titanium substrate by laser engineered net shaping (LENS™) process using parameters optimized for best adhesion and densification. The optical montages from the three surfaces (front, side and top) show columnar β grains growing along the building direction due to conductive heat transfer through the substrate. The as-deposited microstructure contains thin lamellar (α+β)-colonies besides prior β grain boundaries and basket-weave (α+β)-structure inside prior β grains. Narrow band-like structure forms between consecutive layers due to re-melting of previously deposited layers, thereby creating additional interfaces in the microstructure. In addition, tiny isolated pores appears in negligible fraction throughout the LENSTM-processed specimen due to gas entrapment, shrinkage during cooling and un-melted or partially melted powder particles. Both the number and volume of the pores increase along the building direction. Hardness on different surfaces (front, side and top) differs considerably due to the presence of different heating/cooling zones, residual stresses and variations in the thermal cycles and consequent change in the α'-martensite phase fraction. Larger variation in the hardness between these surfaces is observed in nano-indentation technique signifying for inhomogeneity in nano-scale structure. These microstructural variations also resulted in measurable changes in the coefficient in friction (COF) during scratch testing from the substrate along the building direction due to presence of different heating/cooling zones (diffused vs. reheating/re-melting zones). The variation in hardness and COF along different directions can ultimately lessen the in-service performance of the as-deposited parts.

Вплив Q&P-обробки на мікроструктуру та механічні властивості низьковуглецевої TRIP-assisted сталі

. The article describes the effect of heat treatment according the «Quenching and Partitioning» (Q&P) technology on the phase-structural status and mechanical properties of low-alloy 20Si2Mn2Nb steel. It is found that the standard heat treatment which is an isothermal annealing at 300°C (holding for 20 min) after heating in intercritical temperature range (ITR) provides a moderate complex of mechanical properties at low impact toughness. The heat treatment according to the ITR/Q&P scheme (austenitization in intercritical temperature range with a quenching cooling to 200°C and subsequent holding at 350-400°C for 5-20 min) significantly increases the ductile behavior of low carbon TRIP-assisted steels compared to its standard heat treatment. The positive effect of ITR/Q&P heat treatment on steel ductility was caused by the presence of high content of ductile ferrite (54,4 vol. %) in the steel structure. Heat treatment according to the FA/Q&P scheme (FA-full austenitization) with quenching cooling to 235°C and subsequent holding at 350-400°C for 5-20 minutes provided a considerable increase in the strength properties and impact toughness of steel. High strength level was ensured by the formation of a multiphase structure with a high volume fraction of hard martensite phase. The maximum combination of strength and ductility (PSE » 20 GPa·%) was provided by ITR/Q&P treatment conducted according to modes A770Q200P400(5 min) and A770Q200P400(20 min). The improvement in mechanical properties was associated with the formation of multiphase micro-structure which contains an increased amount of retained austenite. It is shown that Q&P treatment with heating in the intercritical temperature range notably improved a steel ability to work-hardening under cold plastic deformation

Industrial Steel Heat Treating: Numerical Simulation of Induction Heating and Aquaquenching Cooling with Mechanical Effects

This paper summarizes a mathematical model for the industrial heating and cooling processes of a steel workpiece corresponding to the steering rack of an automobile. The general purpose of the heat treatment process is to create the necessary hardness on critical parts of the workpiece. Hardening consists of heating the workpiece up to a threshold temperature followed by a rapid cooling such as aquaquenching. The high hardness is due to the steel phase transformation accompanying the rapid cooling resulting in non-equilibrium phases, one of which is the hard microconstituent of steel, namely martensite. The mathematical model describes both processes, heating and cooling. During the first one, heat is produced by Joule’s effect from a very high alternating current passing through the rack. This situation is governed by a set of coupled PDEs/ODEs involving the electric potential, the magnetic vector potential, the temperature, the austenite transformation, the stresses and the displacement field. Once the workpiece has reached the desired temperature, the current is switched off an the cooling stage starts by aquaquenching. In this case, the governing equations involve the temperature, the austenite and martensite phase fractions, the stresses and the displacement field. This mathematical model has been solved by the FEM and 2D numerical simulations are discussed along the paper.

Microstructure and properties of 1300-MPa grade Nb microalloying DH steel

In this study, ultra-high-strength DH steels with different phase compositions were designed, their tensile strengths were greater than 1300 MPa, and the multiphase microstructures contained ferrite, martensite, retained austenite, and small amounts of carbides. The effects of different phase compositions on the mechanical properties and strain hardening behaviors of the ultra-high-strength DH steels were compared, and the mechanism of the retained austenite in the ultra-high-strength DH steels was comprehensively studied. The results show that with the increase in the volume fraction of martensite and retained austenite and decrease in the ferrite volume fraction, the yield strength and tensile strength increase, whereas, the elongation rate first increase and then decrease. The decrease in the soft-phase ferrite volume fraction and increase in the volume fraction of the hard martensite phase led to an increase in yield strength and tensile strength. Compared with tempered martensite, quenched martensite could improve the strength more significantly. The retained austenite transformed in the tensile process was the main cause of the change in elongation. The remarkable banded structure in the microstructure will cause a significant decrease in elongation after necking. The analysis of the strain hardening behavior show that the strain hardening rate decrease with the increase in the true strain. When the true strain was greater than 2%, the strain hardening rate of the steels followed the order: DH1 > DH2 > DH3; this trend was mainly influenced by the ferrite volume fraction. The strain hardening rate of DH2 was higher than those of DH1 and DH3 when the true strain was greater than 5.73%, which was mainly related to the more significant transformation-induced plasticity (TRIP) effect in the DH2. In addition to the retained austenite volume fraction, the carbon content in the retained austenite also had a significant effect on the TRIP effect. The high proportion of the hard-phase martensite, appropriate proportion of the soft-ductile-phase ferrite, and retained austenite contributed to the DH2 steel having the greatest tensile strength and elongation (13.17 GPa·%); moreover, the yield strength was 880 MPa, tensile strength was 1497 MPa, uniform elongation was 6.71%, total elongation was 8.8%, elongation after necking was 2.09%, and yield ratio was 0.59.

Microstructures and Mechanical Properties of Deposited Fe-8Cr-3V-2Mo-2W on SCM420 Substrate Using Directed Energy Deposition and Effect of Post-Heat Treatment.

In this study, the Fe-8Cr-3V-2Mo-2W tool steel powder was deposited on the SCM420 substrate through the directed energy deposition (DED) process. This study focuses on the mechanical properties of the deposited Fe-8Cr-3V-2Mo-2W and the effect of heat treatment on it. The changes in the microstructural characteristics of the deposited region due to heat treatment after deposition were observed. The influence of heat treatment on the mechanical properties was then analyzed accordingly and hence, the hardness, wear, impact and tensile tests were conducted on the deposited material. These properties were compared with those of the commercial tool steel powder M2-deposited material and the carburized specimen. In the deposited Fe-8Cr-3V-2Mo-2W layer, an increased martensite phase fraction was obtained through post-heat treatment and the amount of precipitated carbides was also increased. This increased the hardness from 48 to 62 HRc after heat treatment and the wear resistance was significantly improved as well. The amount of impact energy absorbed decreased from 11 J before heat treatment to 6 J after heat treatment, but the tensile strength significantly increased from 607 to 922 MPa. When compared with the M2-deposited surface, the Fe-8Cr-3V-2Mo-2W deposits had 3% lower surface hardness and 76% lower fracture toughness but exhibited 56% higher tensile strength. When compared with the carburized SCM420, the Fe-8Cr-3V-2Mo-2W deposits exhibited 3% higher surface hardness and wear resistance, 90% lower fracture toughness and 5% higher tensile strength. This study shows that surface hardening through DED can exhibit similar or superior mechanical properties when compared to carburizing.

Improvement in Mechanical Performance of Biomaterial Ti Alloy by Controlling Volume Fraction of Martensite Phase

Recently, biomaterial α + β type Ti alloys with relatively low Young’s modulus and high specific strength have been widely used all over the world. Martensite (M) phase in α + β type Ti alloy has been reported to improve the toughness and ductility, therefore, there is high possibility of improvement in the mechanical properties easily by controlling the volume fraction of M phase. In this study, the change in mechanical properties of α + β type Ti-6Al-7Nb (Ti67) with various volume fractions of M phase were systematically investigated through the various heat treatments and thermo-mechanical treatments. Microstructures of Ti67 subjected to ST at 1173 K to 1273 K below the temperature of β transus were composed of martensite and primary α phases. The volume fraction of M phase increased with an increase in ST temperature. Tensile strength increased simply with an increase in the volume fraction of M phase, while the elongation, reduction of area and Young’s modulus showed a reverse trend. Fatigue limit of Ti67 subjected to ST at 1243K showed the highest value of 880 MPa.