Combination Of Tensile Properties Research Articles

A biodegradable Fe–0.6Se alloy with superior strength and effective antibacterial and antitumor capabilities for orthopedic applications

Iron–selenium (Fe–Se) alloys have potential as attractive biodegradable bone–implant materials, given the antitumor properties of Se in cancer prevention and therapy. However, the fabrication of Fe–Se alloys is challenging due to the volatility of elemental Se and the significantly different melting points of Se and Fe. In this study, we successfully fabricated Fe–xSe (x = 0.2, 0.4, 0.6, 0.8, and 1 wt.%) alloys using suction casting, with FeSe compounds as the Se source. The microstructures, tensile properties, corrosion behavior, biocompatibility, antibacterial ability, and antitumor properties of the Fe–Se alloys were evaluated. The microstructures of the Fe–Se alloys were composed of α–Fe and FeSe phases. Among the Fe–Se alloys, Fe–0.6Se showed the best combination of tensile properties, with a yield strength of 1096.5 ± 7.2 MPa, an ultimate tensile strength of 1271.6 ± 6.3 MPa, and a fracture strain of 15.6 ± 3.3 %, and a degradation rate of 56.9 ± 0.4 μm/year. Moreover, the Fe–0.6Se alloy showed superb antibacterial ability against S. aureus, antitumor activity against 143B osteosarcoma cells, and osteogenicity and biocompatibility toward pre–osteoblast MC3T3–E1 cells. In summary, adding 0.2–1.0 wt.% Se to Fe does not affect the growth of healthy cells but effectively inhibits the growth and reproduction of tumor cells, and the Fe–0.6Se alloy is promising for orthopedic applications owing to its unique combination of mechanical and biofunctional properties. Statement of significanceThis work reports on Fe-xSe (x = 0.2, 0.4, 0.6, 0.8, and 1 wt.%) alloys fabricated using suction casting. The microstructures of the Fe–Se alloys were composed of α-Fe and FeSe phases. Among the Fe–Se alloys, the Fe-0.6Se showed the best combination of tensile properties, with a yield strength of 1058.6 ± 3.9 MPa, an ultimate tensile strength of 1134.1 ± 2.9 MPa, and a fracture strain of 16.8 ± 1.5 %, and a degradation rate of 56.9 ± 0.4 μm/year. Moreover, the Fe-0.6Se alloy showed superb antibacterial ability against S. aureus, antitumor activity against 143B osteosarcoma cells, and significant osteogenic ability and biocompatibility toward pre-osteoblast MC3T3-E1 cells. In summary, the Fe-0.6Se alloy is promising for orthopedic applications owing to its unique combination of mechanical and biofunctional properties.

Establishment of a facile technique to fabricate bulk AA6061/CNT composite with improved mechanical properties using combined stir-casting and squeeze-casting

Three dispersion techniques were investigated for fabricating AA6061–0.5 wt% CNT composites by combined stir-casting and squeeze-casting - direct drop of CNT (DD), mixed Al and CNT pellet drop (PD), and direct drop of ultrasonicated CNT (USDD). Al-20Mg alloy was added to enhance CNT wettability. The PD samples resulted in the highest retention of CNTs in the matrix along with a uniform distribution, confirmed by detailed transmission electron microscope analysis. The selected area electron diffraction pattern and X-ray diffraction confirmed the formation of Mg2Si. The hardness of all composite samples increased significantly over AA6061, predominantly due to a reduction in crystallite size and an increase in dislocation density. The best combination of tensile properties was achieved in the PD composite, yielding an improvement of ultimate tensile strength and yield strength by 40% and 33%, respectively, compared to as-cast AA6061 without sacrificing the ductility. Well-developed serrations were observed in the stress-strain plots of the samples, which have been attributed to the pinning-unpinning action of mobile dislocations by the Mg solute atoms. The fracture surface of the PD composite displays features of ductile fracture along with CNT bridging and rupture, confirming the presence of a strong interface and effective load transfer strengthening.

A new instrumented spherical indentation test methodology to determine fracture toughness of high strength steels

A new instrumented spherical indentation test (ISIT) methodology is proposed to determine fracture toughness of metallic materials that their strain hardening can be adequately described by a power-law function. Firstly, tensile properties, including Young’s modulus (E), yield stress (σy) and strain hardening exponent (n) are determined by an improved representative stress–strain method with the Meyer power-law correction. Secondly, by performing dimensional analysis and finite element computation, a new dimensionless function of critical indentation contact pressure (Pmcr) versus tensile properties is developed. To generalize the above dimensionless function to a broad scale of metallic materials, 100 different combinations of tensile properties have been implemented in the finite element computation of spherical indentation tests. Consequently, Pmcr of various tested metallic materials can be calculated conveniently by substituting the corresponding tensile properties into the dimensionless function. The critical indentation depth (hccr) of metallic materials can then be determined by identifying Pmcr on the curve of mean contact pressure versus indentation depth. Finally, fracture toughness is calculated by the concept of indentation energy to fracture at hccr. To demonstrate the repeatability of the above methodology, it has been applied to predict fracture toughness of three different high strength steels by two research groups, independently. The best measurement capacity of the present approach could be optimized in a relative small error, as ±6 % in tensile properties and ±10 % in fracture toughness, that is close to the conventional standard testing results upon multiple samples of the same group.

Enhancing the tensile properties of PA6/CNT nanocomposite in selective laser sintering process

AbstractThe aim of present study is to enhance the tensile strength, elongation at break and tensile modulus of polyamide 6/carbon nanotube (PA6/CNT) nanocomposite prepared by selective laser sintering. For this purpose, the optimal values of laser power, scanning speed and CNT content were estimated to enhance the tensile properties of PA6/CNT nanocomposite by using the response surface methodology and desirability function. The microstructure of specimens was observed using the scanning and transmission electron microscopy. It was observed that an increase in laser power from 5 to 10 W improved the tensile strength (21%) and elongation at break (11.4%) of the nanocomposite due to uniform dispersion of CNTs, while the further increase of laser power reduced the tensile strength (5.2%), elongation at break (5.8%) and tensile modulus (5.3%) due to thermal degradation of PA6 polymer. A rise of the scanning speed from 1000 to 2000 mm/s was associated with a reduction in the tensile strength, elongation at break and tensile modulus by about 8.3%, 13% and 3.3% respectively, which was due to lower heat input and consequently incomplete densification of the nanocomposite. The addition of CNTs up to 5 wt% can enhance the tensile properties of PA6/CNT nanocomposite, but needs increasing the laser power. The best combination of tensile properties was achieved at laser power of 7.3 W, scanning speed of 1000 mm/s and CNT content of 1.8 wt%. Moreover, the addition of CNTs up to 5 wt% showed a slight influence on thermal stability and crystallinity of the sintered nanocomposite.

Spinodal decomposition and martensitic transformation of the high manganese Mn‒xCu alloys fabricated by additive manufacturing

Mn‒Cu-based shape memory alloys have great potential owing to their excellent shape memory properties, high damping capacity, low production cost, and ease of fabrication. In this study, a selective laser melting (SLM) technique was used to design and manufacture a series of high-manganese Mn‒xCu (x=10–40 wt.%) alloys by blending the elemental powders. Spinodal decomposition and martensitic transformation of the alloys during SLM and heat treatment (HT) processes were investigated and correlated with the tensile, damping, and shape memory properties of the alloys. The results showed that γ‒(Mn, Cu) was the main constituent phase in all of samples subjected to SLM only (hereafter as-SLMed) and the SLMed + HTed Mn‒Cu alloys. The effect of the chemical composition and manufacturing process on the phase structural evolution of the Mn‒Cu alloys were monitored. The spinodal decomposition, martensitic transformation and α-Mn precipitation reactions occurred in the as-SLMed Mn‒xCu samples with x = 15–20 wt.%, x < 30 wt.%, and x < 15 wt.%, respectively. The tensile properties of the as-SLMed Mn‒xCu alloys followed a general downward trend with increasing Mn content, while the corresponding damping capacity and shape memory recovery strain showed the opposite trend. HT can promote spinodal decomposition and martensitic transformation to form an equiaxed γ‒(Mn, Cu) grain, parallel twin plate structure, tweed microstructure, and α-Mn precipitate in the alloys. The SLMed + HTed Mn‒30% Cu alloy displayed a better combination of tensile properties (764, 540 MPa, and 12.5%), damping capacity (tan δ = 0.072 at a strain amplitude of 900 × 10−6), and one-way and two-way (εsme = 1.6% and εtw = 0.7% under the pre-bending strain of 10%) shape memory properties. In addition, the performance of the as-SLMed Mn‒xCu (x = 15–20 wt.%) and SLMed + HTed Mn‒xCu (x = 30 wt.%) alloys is comparable with and even superior to those of multi-component and commercial Mn‒Cu-based alloys, respectively.

Implications of annealing treatments on microstructure, texture, and tensile properties of hard plate hot forged Mg-Zn-Ca-Mn alloy

In the present investigation, annealing treatment at a temperature of 623 K for 5 min has been carried out on Mg-4Zn-0.5Ca-0.16Mn (wt%) alloy specimens forged at various temperatures viz., 523 K, 573 K, and 623 K. Furthermore, the specimen forged at 573 K was isothermally annealed at 623 K for different durations up to 120 min. Significant basal texture weakening along with typical heterogeneous distribution of grain size, is observed due to static recrystallization in the specimens forged at 523 and 573 K and each annealed at 623 K for 5 min, as compared to their forged counterparts. A better combination of tensile properties is achieved in the specimen forged at 573 K and subsequently annealed at 623 K for 5 min, than the other two identically annealed specimens, owing to the synergistic contributions of the typical grain size heterogeneity, smaller average grain size, higher basal texture intensity, and simultaneous existence of finer and coarser second phase particles. During the isothermal annealing treatment, the grain growth exponent is observed to be high (n ~ 9) due to the presence of the higher percentage of particles and PSN-assisted DRX grains in the forged specimen. The yield strength value decreases with the annealing duration predominantly due to grain size coarsening, whereas the ductility and work hardening behavior improve gradually under the combined influence of increasing grain size as well as its heterogeneity.

Mechanical Behavior of As-Cast and Extruded Mg-Si-Ni-Ca Magnesium Alloys

The mechanical performance of as-cast and hot extruded Mg-4Si-4Ni-xCa alloys was studied. In the as-cast microstructures, the dendritic primary Mg2Si particles, eutectic α-Mg + Mg2Si constituent, blocky χ-phase (Mg8Ni7Si5 intermetallic), and α-Mg phase were observed. Moreover, the needle-shaped CaMgSi intermetallic at high Ca additions was detected. The modification effect of Ca was discussed based on the size refinement and morphological enhancement of Mg2Si phase. Accordingly, the tensile properties of the as-cast alloys were enhanced by Ca addition no more than 1 wt.%. However, large additions (3 wt.%) resulted in the deterioration of strength and ductility due to the appearance of the needle-shaped CaMgSi intermetallic. Compared to the cast ingots, the wrought alloys (obtained by hot extrusion) showed superior mechanical performance with much larger work-hardening exponents and tensile toughness values. For instance, the tensile toughness of the extruded alloy with 1 wt.% Ca was determined as 78.65 MJ/m3, which is much higher than the value of 9.32 MJ/m3 for the as-cast 0 wt.% Ca alloy. As the best combination of tensile properties, the ultimate tensile strength and the total elongation of the extruded alloy with 1 wt.% Ca were 348.4 MPa and 16.6%, respectively.

Tailoring the mechanical properties of Mg–Zn magnesium alloy by calcium addition and hot extrusion process

Grain refinement and enhanced mechanical properties of Mg–2Zn-xCa alloys (with a wide range of calcium contents from 0 to 5 wt%) were studied in both as-cast and extruded conditions. It was revealed that Ca addition can effectively refine the grain size of the ingots based on the growth restriction factor (GRF) mechanism, where at high Ca additions, the dendritic microstructure was obtained. By increasing the amount of Ca, the binary Mg–Zn phase was replaced by the Ca2Mg6Zn3 phase and at high Ca contents, the Mg2Ca phase appeared in the microstructure. The tensile properties were enhanced at low Ca additions (up to 0.3 wt%) due to the grain refinement but they were deteriorated at higher Ca additions due to the formation of grain boundary second phases. Accordingly, the ultimate tensile strength (UTS) of 228 MPa and total elongation of 20% was obtained for the as-cast Mg–2Zn-0.3Ca (ZX20) alloy. During hot extrusion, significant grain refinement and the fracturing and dispersion of second phase particles were observed. The grain size refinement beyond ~1 wt% Ca was negligible and extrusion defects were observed at higher Ca contents, and hence, the best combination of mechanical properties was obtained for the Mg–2Zn–1Ca (ZX21) alloy with UTS of 283 MPa and elongation to failure of 29%. This alloy showed a desirable work-hardening behavior and the best combination of tensile properties, where the product of tensile strength and total elongation reached as high as ~8000 MPa%. Finally, the yield stress of the alloys was correlated to the average grain size via the classical Hall-Petch plot with a slope of 228.5 MPa μm0.5.

Precipitation behaviour during the \u03b2\u2009\u2192\u2009\u03b1/\u03c9 phase transformation and its effect on the mechanical performance of a Ti-15Mo-2.7Nb-3Al-0.2Si alloy

The activation energy of the β → α/ω phase transformation increased monotonously with the application of a continuous heating process to a Ti-15Mo-2.7Nb-3Al-0.2Si alloy. Precipitation behaviour of the alloy aged at different temperatures were analysed with scanning electron microscopy, electron backscattered diffraction and transmission electron microscopy. Selected-area diffraction patterns of the ω, ω/α and α phases in the alloy aged at different temperatures indicated that the type of phase transformation was influenced by the precipitation process. Precipitate-free zones in the alloy aged at 450 °C for 8 h were harmful to the mechanical performance. Fine α precipitates with an obvious texture were obtained in the alloy aged at 500 °C. A good combination of tensile properties with an ultimate tensile strength of 1310 MPa and an elongation of 13.5% were obtained due to the expected microstructure and texture of the precipitates that transformed in the specimen when it was aged at 500 °C for 8 h. The size of the precipitates increased with increasing aging temperature. Furthermore, the amount of precipitates and their degree of texture decreased substantially in the alloy aged at 600 °C. The investigation of the tensile properties and fractures also revealed a correlation between the mechanical properties and precipitation behaviour in the Ti-15Mo-2.7Nb-3Al-0.2Si alloy aged at different temperatures.

The Effect of Rapid Heating and Fast Cooling on the Transformation Behavior and Mechanical Properties of an Advanced High Strength Steel (AHSS)

The major goal of this work was to study the effect of rapid heating and fast cooling on the transformation behavior of 22MnB5 steel. The effect of the initial microstructure (ferrite + pearlite or fully spheroidized) on the transformation behavior of austenite (during intercritical and supercritical annealing) in terms of heating rates (2.5, 30 &amp; 200 °C/s) and fast cooling, i.e., 300 °C/s rate, were studied. As expected, the kinetics of austenite nucleation and growth were strongly related to the heating rates. Similarly, the carbon content of the austenite was higher at lower intercritical annealing temperatures, particularly when slower heating rates were used. The supercritical temperatures used in this study were similar to those used during commercial hot stamping operations, i.e., 845 and 895 °C, respectively, followed by a fast cooling rate. The prior austenite grain size (PAGS) was not strongly influenced by the nature of the initial microstructure, heating rate, reheating temperatures (845 or 895 °C), at 30 s holding time. The decomposition of austenite using fast cooling rates was examined. The results showed that 100% martensite was not obtained. The observed low temperature transformation products consisted of mixtures of martensite-bainite plus undissolved Fe3C carbides and small amounts of martensite-austenite (M-A). At higher supercritical temperatures, i.e., 1000 °C and 1050 °C, the final microstructure showed an increase in the volume fraction of martensite and a decrease in the volume fraction of bainite. The Fe3C and the M-A microconstituent were not observed. The best combination of tensile properties was obtained on samples reheated in the lower temperature range (845 to 895 °C). Interestingly, when the samples where reheated at the higher temperature range (1000 to 1050 °C) and fast cooled, the results of the mechanical properties did not exhibit significantly higher strength levels independent of heating rate or initial microstructural condition. This can be attributed to the change in the microstructural balance %martensite+%bainite as the reheating temperature increases. The results of this study are presented and discussed.

Microstructure evolution and mechanical properties of near-α Ti-8Al-1Mo-1V alloy at different solution temperatures and cooling rates

Nine solution-ageing treatments with different solution temperatures (915 °C, 960 °C, 1010 °C) and cooling media (water quenching, oil cooling, air cooling) were firstly conducted on the rolled near-α Ti-8Al-1Mo-1V alloy. The microstructure evolution behavior and various mechanical properties of this alloy were studied. The results show that solution temperature can greatly influence microstructure features. By increasing solution temperature, the volume fraction of primary α phase continuously decreased, the original shapeless primary α phase was sectioned and gradually showed equiaxed shape, and the β grain kept growing until its grain boundary reached the biggest sectional area of primary α particles (pinning effect). Due to the proper mixture of primary α and lamellar α phase, Ti-8Al-1Mo-1V alloy can achieve the best combination of tensile properties, thermal exposure properties and creep properties after being solution-treated at 1010 °C followed by oil cooling. Based on above results, high solution temperature is necessary to the application of Ti-8Al-1Mo-1V alloy. Thus a comprehensive study on the microstructure evolution behavior of Ti-8Al-1Mo-1V alloy at various precisely controlled cooling rates on cooling down from 1010 °C is of great significance. The results show that: with decreasing cooling rate on cooling down from 1010 °C, the volume fraction and the diameter of equiaxed α as well as the thicknesses of the grain boundary α and the lamellar α continuously increased. Equiaxed α shows an evolution process of precipitation, growth, mergence of adjacent equiaxed α and mergence between equiaxed α and lamellar α. Obvious changes of equiaxed α only happened at the cooling rates below 15 °C/s. However, for grain boundary α and lamellar α, the mutant range is “below 40 °C/s”. The exponential decay formula perform well in quantitatively characterizing the microstructure features-cooling rate relations.

Enhancing mechanical properties of friction stir welded joints of Al-Si-Mg alloy through post weld heat treatments

In the present research, three different post weld heat treatments were carried out on friction stir welded joints of precipitation hardening Al-Si-Mg alloys to explore their effect on microstructure and mechanical properties. In general, applied post weld heat treatments significantly affected the microstructure and morphology of α aluminium grains and strengthening precipitates in all the zones of friction stir weld joints. Post weld heat treatments homogenized the morphology of strengthening precipitates. Artificial aging resulted in better combination of tensile properties than other post weld heat treated weld joints. Solution treatment with artificial aging can be used to improve tensile strength at the expense of% elongation while solution treatment is not viable option to improve joint performance. Post weld heat treatments also affected the mode of fracture during tensile test.

Improvement of low temperature toughness of ferritic Mn steels by alloy modification

A study has been made on the effects of Mn content and addition of Al on the microstructure and mechanical properties of (4-6)Mn steels, with the aim of developing ferritic Mn steels having good combination of tensile properties and impact toughness. It has been shown that the reduction of Mn content to 6 wt% and lower from 8-12 wt% of conventional steels can effectively prevent the occurrence of intergranular fracture, which has been a major problem of (8-12)Mn steels with poor toughness at cryogenic temperature. While increasing Mn content in the binary (4-6)Mn steels results in an increase in strength and a decrease in impact toughness, the addition of 1Al to (4-6)Mn steels results in improvements in both strength and impact toughness as compared to those of the binary (4-6)Mn steels and the best impact toughness has been obtained in the as-rolled 1Al added 4Mn steel, whose microstructure consists of fine acicular ferrite grains.

Effect of initial microstructure on the work hardening behavior of plain eutectoid steel

Work hardening capability and tensile properties of the plain eutectoid steel rods are the key factors in the wire drawing process to fabricate high strength wire rods with a minimum failure. In the present research, the work hardening behavior of eutectoid steel with different initial microstructures of bainite, duplex bainite+pearlite, pearlite, partially spheroidized and spheroidized pearlite was assessed in terms of instantaneous work hardening exponent (n value) and work hardening rate (θ) using room temperature tensile test. The results show an inverse parabolic behavior for variation of instantaneous n value versus true strain, i.e., work hardening exponent initially increases up to a maximum value and then decreases. The bainitic microstructure exhibits the lowest n value, whereas the spheroidized pearlitic one shows the highest. It is shown that the fine pearlitic microstructure containing partially spheroidized regions exhibited the best combination of tensile properties, n value and work hardening rate.

Tensile Properties and Fractographic Analysis of Low Density Polyethylene Composites Reinforced with Chemically Modified Keratin-Based Biofibres

This research has investigated the tensile properties and fractography of animal fibre-reinforced low density polyethylene composites. The composites were synthesized by hot compression moulding using chemically modified white and black cow hair biofibres as the reinforcing phase of composites. Alkaline solutions of varying molarities were used to prepare the chemical treatments in this present study. Tensile properties of the developed composites were evaluated based on molarities of chemical treatment and % fibre loading. Scanning electron microscopy was used to characterize the morphologies of the fractured surfaces of composites. Obtained tensile test results revealed significant enhancement in the tensile properties of composites, with the optimum combination of tensile properties presented by 2 wt% white cow hair biofibre reinforcement treated with 0.15 M sodium hydroxide. Observations from the fractographic analysis of the developed composites revealed shearing of the polymer matrix at the fibre-matrix interface and no fibre pullout behaviour.

Effects of Nb and C additions on the microstructure and tensile properties of lightweight ferritic Fe–8Al–5Mn alloy

Additions of Nb and C result in the formation of NbC and κ-carbide in Fe–8Al–5Mn alloy. Both NbC and κ-carbide particles inhibit recrystallization during hot rolling with the resultant formation of pancake-shaped grain structure in Fe–8Al–5Mn–0.1Nb–0.1C alloy, but κ-carbide particles also promote recrystallization via particle-stimulated nucleation mechanism during subsequent warm/cold rolling and annealing. As a result, Fe–8Al–5Mn–0.1Nb–0.1C alloy has a much finer grain size and a better combination of tensile properties than Fe–8Al–5Mn alloy.

Fracture Toughness (K1C) evaluation for dual phase medium carbon low alloy steels using circumferential notched tensile (CNT) specimens

The fracture behavior of dual phase medium carbon low alloy steels produced using two different chemical compositions (A - 0.34C, 0.75Mn, 0.12Cr, 0.13Ni steel and B - 0.3C, 0.97Mn, 0.15Cr steel) was investigated using circumferential notched tensile (CNT) specimens. Intercritical treatments were performed on samples with composition A by 1) austenitizing at 860 °C for 1 hour cooling in air, then treating at 770 °C for 30 minutes before oil quenching; 2) austenitizing at 860 °C for 1 hour quenching in oil, then treating at 770 °C for 30 minutes before quenching in oil; and 3) austenitizing at 860 °C for 1 hour, super-cooling to 770 °C and then quenching in oil. Samples of composition B were subjected to intercritical treatment at temperatures of 740, 760, and 780 °C for 30 minutes, followed by quenching rapidly in oil. Tensile testing was then performed on specimens without notches and the CNT specimens. It was observed that the dual phase steel produced from procedure (2) yielded a fine distribution of ferrite and martensite which gave the best combination of tensile properties and fracture toughness for composition A while the dual phase structure produced by treating at 760 °C yielded the best combination of tensile properties and fracture toughness for composition B. The fracture toughness results evaluated from the test were found to be valid (in plain strain condition) and a high correlation between the fracture toughness and notch tensile strength was observed. The fracture toughness values were also found to be in close agreement with data available in literature.

Microstructure and tensile properties of twin-roll cast Mg–Zn–Mn–Al alloys

The microstructure and tensile properties of twin-roll cast (TRC) Mg–6% Zn–1% Mn (ZM61) alloys with varying Al contents were investigated. The microstructure of the alloys becomes finer with the addition of Al. The type of dispersoid particles also changes with the Al addition: from MgZn2 in ZM61 alloy to Al8Mn5 in the ZM61–1% Al (ZMA611) and ZM61–3% Al (ZMA613) alloys. ZMA611 alloy has a better combination of tensile properties than ZM61 alloy. However, ZMA613 alloy shows poor ductility due to the formation of coarse Mg21(Al, Zn)17 phase during TRC.

Development of creep resistant die cast Mg–Sn–Al–Si alloy

A study has been made on the tensile properties and high temperature properties of die cast Mg–Sn–Al–Si (TAS831) alloy. The microstructure of TAS831 alloy is characterized by the presence of thermally stable Mg 2Sn particles within matrix and along grain boundaries. It also contains a small volume fraction of thermally stable Mg 2Si particles. It has been shown that TAS831 alloy has better combinations of tensile properties at room and elevated temperatures than die cast AZ91 alloy. Creep properties of TAS831 alloy are also superior to those of AZ91 alloy. Analyses of creep behavior and load-relaxation behavior at elevated temperatures in the context of internal variable theory indicate that the presence of thermally stable dispersoids in TAS831 alloy increases the resistance to dislocation movement, thereby improving creep properties over those of AZ91 alloy.

Optimisation of hot die forging processes of Ti–10V–2Fe–3Al alloy

In order to optimise the hot die processes of Ti–10V–2Fe–3Al alloy, the effects of forging processes on the microstructures and mechanical properties were studied and processing maps were used to try to aid the process design. The results show that processing maps for Ti–10V–2Fe–3Al alloy exhibit three process ranges, but only the range near β transus is suitable for hot die forging of this alloy. The alloy forged at Tβ−30°C has a higher strength and ductility while the alloy forged at Tβ+30°C offers higher fracture resistance than the former. Process C, where the alloy was forged at Tβ+30°C to form the acicular αp and then at Tβ−30°C to get globular αp, was designed and the total amount of deformation equal to 50% was chosen. Through process C the alloy has a better combination of tensile properties and fracture resistance than any other processes because a proper mixture between globular αp and acicular αp is obtained.