Y Alloy Research Articles

Microstructure, mechanical properties and bio-corrosion behavior of Mg–2Zn-0.3Ca-x (x= 0, 0.5, 1.0) Y alloys

Microstructure, mechanical properties, and bio-corrosion behavior of Mg–2Zn-0.3Ca-x (x = 0, 0.5, 1.0) wt.% Y series alloy have been investigated using microstructure observation, microhardness testing, tensile testing, immersion tests, and electrochemical measurements in simulated body fluid (SBF). The results show that the second phase's type, volume fraction, and distribution change with Y microalloying in the Mg–Ca–Zn alloys. The Mg–2Zn-0.3Ca (alloy 1) mainly comprises α-Mg and Ca2Mg6Zn3 phases. However, the amount of the Ca2Mg6Zn3 phase gradually decreases, and phases I (Mg3YZn6) and W (Mg3Y2Zn3) are also formed in Mg–2Zn-0.3Ca-0.5Y (alloy 2) and Mg–2Zn-0.3Ca–1Y (alloy 3), respectively. Furthermore, an increase in Y content to 1% refines the grains of alloy 1 leading to the improvement of microhardness (66.7 ± 4.2 HV), yield strength (141 ± 7 MPa), and ultimate tensile strength (385.7 ± 18 MPa) in alloy 3. The coarse and discontinuous eutectic phases (α-Mg + Ca2Mg6Zn3) in alloy 1 leads to accelerating the galvanic corrosion near the grain boundary. Moreover, polarization tests show that the addition of the rare earth element Y up to 0.5% in the alloy 2 leads to decreased corrosion current density (4.04 × 10−3 A cm−2) and the best anti-corrosion property as the result of formation of a protective corrosion product film.

Insights into the design of oxidation-resistant Mg alloy by alloying with rare-earth elements

The strategy of rare-earth elements addition into Mg alloys has been successfully developed and applied to enhance the mechanical performance and corrosion resistance of Mg alloys. Although this strategy has also been applied to enhance their high-temperature oxidation resistance, the mechanistic understanding of the beneficial effects remains elusive. Here, the oxidation of Mg–4Nd and Mg-4Nd–1Y alloys in Ar–20%O2 at 500 °C was studied and compared. It was found that even though a continuous layer of Nd2O3 did not form, the Nd addition could still enhance the oxidation tolerance of Mg–4Nd alloy by facilitating the generation of a more continuous and intact oxide scale and working as oxygen sinks to delay the violent oxidation of Mg. The formation of a continuous Y2O3 layer on Mg-4Nd–1Y alloy suggests that Y was more capable of facilitating the external oxidation due to its much faster diffusion rate in Mg matrix than that of Nd. However, the Nd addition could decrease the critical content of Y necessary for the oxidation transition from internal to external because of the synergistic effect of the Nd and Y addition. The dissolution of the thermal unstable Mg12Nd precipitates resulted in a localized increase of Nd content, accelerating the oxidation by increasing the preferential oxidation of Nd. Hence, in the design of oxidation-resistant Mg alloys, the addition of RE elements with faster diffusion rate and the addition of multiple alloy elements are preferred. In addition, the number of thermal unstable precipitates needs to be strictly controlled.

Microstructure and mechanical properties of cast Mg-6Gd–Zr alloy with different Y addition

Microstructures and mechanical properties of Mg-6Gd-xY-0.5Zr (wt.%, x = 0, 0.5, 1 and 3) alloys with different conditions (solution-treated and 200 °C peak-aged) are investigated. Species of precipitates in Mg-6Gd-0.5Zr alloys are modified by Y addition. In 0Y, 0.5Y and 1Y alloys, β′ precipitates and tentacle-like structures with specific crystallographic directions around β′ body are the main phases. The crystallographic directions of tentacle-like structures are {112‾0}Mg. When 3Y is added, β′ and β1 precipitates become the main phases. Except that, the size and area number density of β′ precipitate are also influenced by adding Y. With Y addition, the size of β′ precipitate is refined, and its area number density increases. This phenomenon has been explained by theoretical method in this paper. According to the study, Mg-6Gd-1Y-0.5Zr alloy with good combination properties is developed. The yield strength, ultimate tensile strength and elongation of Mg-6Gd-1Y-0.5Zr alloy are 164.4 MPa, 280.6 MPa and 16.1 %, respectively. The strengthening precipitates in the peak-aged Mg-6Gd-Y-0.5Zr alloys are β′ precipitates, and the strengthening effect of the β′ precipitates on the yield strength of the Mg-Gd-(Y)–Zr alloys with low Gd/Y content is more obvious than the Mg-Gd-(Y)–Zr alloys with high Gd/Y content.

Effect of minor Ca addition on microstructure and corrosion behavior of Mg–Y–Ca alloys

The poor corrosion resistance of magnesium and magnesium alloys limited their industry applications, especially attributed to the loose and porous corrosion product film. Moreover, it is of great importance to improve the corrosion resistance of magnesium alloy by economic and environmental protection methods. In this study, the Mg–Y–Ca alloys prepared by the addition of trace Ca and Y elements showed good corrosion resistance. In addition, the effects of minor Ca on the microstructure and corrosion behavior of Mg–1Y alloy were systematically studied. With the increase of Ca content, the corrosion resistance of Mg–1Y-xCa alloys (x = 0, 0.05, 0.1 and 0.2 wt%) was found to improve and then decrease. Among prepared Mg–1Y-xCa alloys, Mg–1Y-0.05Ca exhibited the lowest corrosion rate of 0.757 mm y−1. The high corrosion resistance of Mg–1Y-0.05Ca can be attributed to the fine grain size, and the formation of a protective corrosion passivation film rich in Y2O3, CaCO3 and (MgCa)CO3. However, the excessive addition of Ca element led to the decline of corrosion resistance, resulting from the mass generated Mg2Ca phase causing serious micro-galvanic corrosion, which destroyed the stability of the corrosion product film and damaged the corrosion protection.

Optimizing LPSO phase to achieve superior heat resistance of Mg–Gd–Y–Zn–Zr alloys by regulating the Gd/Y ratios

The microstructural features of long period stacking ordered (LPSO) phase in Mg–(11-x)Gd–xY–1Zn–0.3Zr (wt.%) alloys were optimized by adjusting Gd/Y ratios to10:1, 8:3, 6:5, 4:7 and 2:9, respectively. Superior high-temperature strength was successfully obtained in the extruded 6Gd–5Y alloy with ultimate tensile strength (UTS) values of 338 MPa and 286 MPa at 250 °C and 300 °C, respectively. In the as-cast alloys, with the decrease of Gd/Y ratio, the type of intermetallic compound gradually changed from (Mg, Zn)3(Gd, Y) (W) to LPSO phase. After homogenization, the W phase was completely converted to LPSO phase except for the 10Gd–1Y alloy. Importantly, the block-shaped LPSO phases with the smallest size and the abundant lamellar LPSO phases were formed in the 6Gd–5Y alloy, which significantly influenced the microstructures of the extruded alloy. Firstly, the small sized block-shaped LPSO phase before extrusion provided favorable conditions for the formation of thin plate-shaped LPSO phase at DRXed regions, which effectively hindered the grain boundary migration at high temperature due to superior thermal stability. Secondly, the profuse lamellar LPSO phases prior to extrusion contributed to the highest density of low angle grain boundaries (LAGBs) and residual dislocations in the extruded 6Gd–5Y alloy, which obstructed dislocation slip at elevated temperatures. In addition, the abundant lamellar LPSO phase also caused the fine DRXed grain size and strong basal texture to enhance the high-temperature strength of the extruded 6Gd–5Y alloy.

Improved oxidation resistance of ODS-CrFeNi medium entropy alloys by different Y2O3/Ti/Zr additions

Isothermal oxidation tests of four types of oxide dispersion strengthened (ODS)-CrFeNi medium entropy alloys (MEAs) with different Y2O3/Ti/Zr additions, i.e., 1Y alloy (Y2O3), 1YT (Y2O3/Ti), 1YZ (Y2O3/Zr), and 1YTZ (Y2O3/Ti/Zr), were conducted at 1000 ℃ and 1100 ℃ for 12 h to explore the effects of oxide-forming elements on the high-temperature short-term oxidation resistance. XRD, SEM and EDS analyses were performed to characterize the microstructure and phase composition of the oxide layers of the four alloys at different oxidation temperatures. The results showed that the surface oxide layers formed on all ODS-MEAs are mainly composed of hexagonal Cr2O3. The thickness and defects (e.g. pores and microcracks) of the oxide layer strongly depend on the Y2O3/Ti/Zr additions and the oxidation temperature. In general, the thickness of the oxide layer increases with increasing temperature. The oxide layer on 1YZ alloy is very dense and the thickness hardly changes with increasing temperature (0.8 µm at 1000 °C and 0.9 µm at 1100 °C), which exhibits the best oxidation resistance and is comparable to that of ODS-FeCrAl. However, 1YTZ alloy shows the worst oxidation resistance at both 1000 ℃ and 1100 ℃. The oxide layer is loose together with many pores and microcracks, and the thickness is the thickest among the four alloys. In addition, severe internal oxidation occurs in 1YTZ, which is not obviously observed in the other three alloys. The excellent oxidation tolerance of 1YZ is due to the addition of Zr, which results in the formation of thermodynamically stable oxides Y4Zr3O12, which has the highest number density and smallest oxide size among the four alloys. High-density interfaces between the oxides and the matrix effectively slow down the inward diffusion rate of O and the outward diffusion rate of Cr, and inhibit/moderate the coarsening of the oxides and the formation of volatile CrO3. Therefore, pores and microcracks are effectively suppressed in Zr-containing 1YZ.

Influence of Heat Treatments on the Microstructure and Mechanical Properties of Two Fine Mg–Li–Y Alloy Wires for Bioresorbable Applications

Two Mg–4Li–xY (x = 0.5 and 2.0 wt%) alloy wires are investigated for application in bioresorbable medical devices that experience high levels of plastic deformation. The two wires are supplied cold drawn to a diameter of 125 μm, and a series of thermal treatments are applied to maximize ductility. The ductility of the alloys is maximized soon after complete recrystallization. Prolonged annealing causes grain coarsening in the Mg–4Li–0.5Y alloy and precipitation of a Mg24Y5 phase in both alloys. Both wires are shown to achieve ≈20% elongation to failure in tension and survive high idealized bending strains (>40%). When heat treated for optimum mechanical properties for the intended application, the Mg–4Li–0.5Y alloy develops an intense transverse basal texture; however, this is shown to weaken with increased Y content in the Mg–4Li–2Y alloy wire. The increased Y content also prevents grain coarsening, indicating that the increased Y content restricts grain boundary mobility during annealing. Both alloys have relatively high ductility, meaning both are identified as promising new materials for application in bioresorbable medical devices that require to achieve and support high levels of plastic deformation during their life cycle.

Improving mechanical, degradation and biological behavior of biodegradable Mg–2Ag alloy: effects of Y addition and heat treatment

Biodegradable Mg–Ag alloys are promising implants for bone regeneration owing to their ability to decrease inflammation and infection after implantation by the presence of Ag. However, their bioperformance requires further enhancement. In this regard, the effects of 1 wt % Y addition and solid solution heat treatment (T4) on microstructure, biocorrosion behavior, mechanical properties and biological features of a cast Mg–2Ag alloy were studied. Corrosion tests indicated the remarkable role of T4 treatment in promoting corrosion resistance by increasing microstructure homogeneity, reduction of defects and volume fraction of secondary phases as well as eliminating the dendritic microstructure of as-cast Mg–2Ag alloy. The presence of a stable Y-rich corrosion film on the surface of heat-treated Mg–2Ag–1Y alloy could effectively improve the corrosion resistance by inhibiting corrosion propagation. The results of cell culture experiments proved the good cell attachment and proliferation of osteoblast-like cell line MG63 on Mg–2Ag and Mg–2Ag–1Y alloys. Furthermore, the cell attachment and viability were significantly enhanced by the incorporation of Y in the solution state of Mg–2Ag alloy due to the low volume of evolved hydrogen bubbles and superb corrosion resistance.

Improved microstructure and mechanical properties of ODS-CoCrFeNiMn high entropy alloys by different Ti, Zr and Y2O3 addition

Four ODS-CoCrFeNiMn high entropy alloys (HEAs) with different Ti/Zr/Y2O3 addition were produced by powder metallurgy. The role of Ti, Zr, Y2O3 on improving microstructure and mechanical properties of ODS-CoCrFeNiMn HEAs was studied. The type of nanoscale oxides is effectively changed from Y2O3 (1Y alloy), Y2TiO5, YTiO3 and Y2Ti2O7 (1YT), Y4Zr3O12 and Y2Zr2O7 (1YZ) to YTiO3, Y2TiO5, Y2Ti2O7, Ti2O3 (1YTZ) by introducing different addition. The joint addition of Ti, Zr and Y2O3 in 1YTZ has the most significant refinement on grain size and increases number density of nanoscale oxides, which reach 130 nm and 2.01 × 1021/m3, respectively. The well refined grains and high density of nanoscale oxides in 1YTZ alloy lead to the highest hardness and compressive yield strength, which are 449 HV and 1309 MPa, respectively. The different formation mechanisms of nanoscale oxides due to different addition and its influence on mechanical properties in ODS-CoCrFeNiMn HEAs are disclosed. Data availability statementAll data included in this study are available upon request by contact with the corresponding author.

Dynamic compression behaviour and constitutive description of fine-grain Mg–4Zn–1Y alloy

In this research, the dynamic compression behaviour of 5 and 1.5 µm grain size samples of Mg–4Zn–1Y alloy was investigated by the split Hopkinson pressure bar at the strain rate of 1000–1700 s−1. The microstructure, texture evolution, and the deformation mechanisms of samples were characterised by electron backscattering diffraction. The result showed that the grain refinement caused tension twining, which resulted in the distinct true stress–strain curves with specific grain sizes. It was found that the pyramidal < c + a > and pyramidal <a > slips were the main deformation mechanisms of 5 and 1.5 µm samples under dynamic compression, respectively. The constitutive modelling of Mg–4Zn–1Y with different grain sizes was also developed by introducing the grain size adjustment parameters.

Tailoring bimodal grain structure of Mg-9Al-1Zn alloy for strength-ductility synergy: Co-regulating effect from coarse Al2Y and submicron Mg17Al12 particles

Grain boundary strengthening is an effective strategy for increasing mechanical properties of Mg alloys. However, this method offers limited strengthening in bimodal grain-structured Mg alloys due to the difficultly in increasing the volume fraction of fine grains while keeping a small grain size. Herein, we show that the volume fraction of fine grains (FGs, ∼2.5 µm) in the bimodal grain structure can be tailored from ∼30 vol.% in Mg-9Al-1 Zn (AZ91) to ∼52 vol.% in AZ91–1Y (wt.%) processed by hard plate rolling (HPR). Moreover, a superior combination of a high ultimate tensile strength (∼405 MPa) and decent uniform elongation (∼9%) is achieved in present AZ91–1Y alloy. It reveals that a desired bimodal grain structure can be tailored by the co-regulating effect from coarse Al 2 Y particles resulting in inhomogeneous recrystallization, and dispersed submicron Mg 17 Al 12 particles depressing the growth of recrystallized grains. The findings offer a valuable insight in tailoring bimodal grain-structured Mg alloys for optimized strength and ductility.

High temperature mechanical behaviour of Mg–6Zn–1Y alloy with 1 wt.% calcium addition: Reinforcing effect due to I-(Mg3Zn6Y1) and Mg6Zn3Ca2 phases

The influence of small calcium additions on the high-temperature mechanical behaviour in an extruded Mg–6Zn–1Y (wt.%) alloy reinforced by the I-phase has been investigated. Calcium promotes the formation of the intermetallic Mg 6 Zn 3 Ca 2 phase instead of I-phase, which results in a noticeable improvement of the yield strength and ultimate tensile strength of the alloy above 100 °C. The strength of the alloys was analysed taking into account the contribution due to the grain size, the crystallographic texture and the volume fraction and nature of second phase particles. In situ synchrotron radiation diffraction experiments have been used to evaluate the load partitioning between the magnesium matrix and the second phase particles (I- and Mg 6 Zn 3 Ca 2 phases) in both alloys. The load transfer from the magnesium matrix towards the Mg 6 Zn 3 Ca 2 phase is markedly more effective than that for the I-phase over the entire temperature range, especially at 200 °C, temperature at which the reinforcement effect of the I-phase is null.

Effect of Y addition on microstructure and mechanical properties of extruded Mg–Mn alloys

Two homogenized as-cast magnesium (Mg)–1 wt% manganese (Mn) alloys containing 1·0 and 4·0 wt% alloying yttrium (Y) were processed at an extrusion ratio of 17:1 at 400°C using a ram speed of 0·3 mm/s. The effect of yttrium additions on the microstructure and mechanical properties of the extruded alloy was analyzed and compared. The average grain size of the extruded Mg–1Mn–4Y (MW14) alloy was much smaller than that of the extruded Mg–1Mn–1Y (MW11) alloy. In addition, the tensile strength of the MW14 alloy was higher than that of the MW11 alloy at the investigated temperature ranging form RT to 200°C, although the former exhibited a lower elongation to failure. The fracture surface of the MW14 alloy exhibited the cleavage fracture mode. Conversely, a dimple was observed in the MW11 alloy which the significant differences in performance between the two alloys are attributed to their Y contents.

Influence of pre-straining on creep behaviors of Mg–2Y alloy sheets

A compressive pre-straining of 0.05 was applied to two Mg–2Y alloy sheets with different initial textures along their normal directions. Creep behaviors of these sheets before and after the pre-straining were investigated at 493 K under stresses ranging from 20 to 100 MPa. The influence of pre-straining on creep behaviors was then discussed. The results show that the effects of pre-straining on creep behaviors of the two sheets are quite different. A profound strengthening effect of this pre-straining is observed on the creep resistance of the extruded sheet with creep strain decreased by half and steady strain rate reduced by 75% at most. By contrast, for the rolled sheet, the improvement of creep resistance by the pre-straining is negligible. The difference lies in the number of anomalous twins introduced by the pre-straining. After the pre-straining, considerable {10–12} anomalous twins have been introduced in the extruded sheet with a random initial texture, compared to the rolled one. Dislocation movements during the creep can be impeded by the large amounts of twins in the pre-strained extruded sheets, resulting in the obvious improved creep resistance. Meanwhile, different predominant dislocation mechanisms are found along different creep directions. Since a more excellent impeding effect of the twins is obtained on cross-slip, better improvement of the creep resistance can be achieved along the TD than along the ED of the pre-strained extruded sheet.

Effect of Asymmetric Rolling on the Microstructure, Mechanical Properties and Texture Evolution of Mg–8Li–3Al–1Y Alloy

Asymmetric rolling was applied to dual phase Mg–8Li–3Al–1Y alloy with different speed ratio and rolling reduction. With increasing reduction at the same speed ratio the population of β-Li grains decreased with a feature of fibered grains along the rolling direction. As for different speed ratio under the same reduction, β-Li grains kept equiaxed, but α-Mg phase was first elongated and fibered and then transited to equiaxed small grains. The enhanced yield strength and tensile strength were achieved with the increase of rolling reduction and speed ratio. In particular, when speed ratio reached to 1:1.3 under the same rolling reduction (30%), the optimal mechanical properties were obtained. As for texture evolution, we found the basal texture was obviously weakened and some new weak texture was formed after asymmetric rolling. Interestingly, it was noted that the texture on the side of slow roll is distinct from that on the side of the fast roll due to the different rolling speed.

Evaluation of the mechanisms and effects of Mg-Ag-Y alloy on the tumor growth and metastasis of the MG63 osteosarcoma cell line.

Osteosarcoma is a malignant primary bone tumor, which often associates with pulmonary metastasis. The radical surgery of osteosarcoma often requires internal orthopedic implants. Therefore, implants with antitumor properties should be developed. Magnesium (Mg) and its alloys possess great potential as orthopedic materials, given their biodegradable properties, superior osteogenesis performance, and antitumor features. However, problems arise with their uncontrolled degradation rates and their unknown antitumor mechanisms. In our study, when compared with pure Mg, the rare element silver alloyed with yttrium (Ag-Y) could extremely enhance the corrosion resistance of these elements, giving the Ex-Mg-1Ag-1Y alloy better anticorrosion rates. Here, we implanted the Ex-Mg-1Ag-1Y alloy and pure Mg and Ti alloy in vivo around tumors in nude mice (BALB/c). Notably, the local tumor weight in Mg alloy and pure Mg groups were much smaller than that in Ti alloy group in 36 days after surgery (6.59 ± 0.70, 6.76 ± 0.62, and 8.54 ± 0.56 g), while the general scores of lung metastasis in Mg alloy and pure Mg groups were also lower than Ti alloy group (64.50 ± 7.64, 62.73 ± 7.84, and 87.60 ± 9.43). Therefore, the Mg and Ex-Mg-1Ag-1Y alloy, both demonstrated resisting effects against local tumor growth and pulmonary metastasis, which could be performed by changing the extracellular acidosis microenvironment, elevating the Mg concentration, suppressing C-X-C chemokine receptor type 4 (CXCR4) levels, and increasing prostacyclin (PGI2 ) synthesis. Our work revealed that the Ex-Mg-1Ag-1Y alloy may be a promising orthopedic implant for treating osteosarcoma due to its better corrosion resistance and antitumor attributes. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B:2537-2548, 2019.

Characterization of Microstructure and Mechanical Properties of Mg–8Li–3Al–1Y Alloy Subjected to Different Rolling Processes

The mechanical properties and microstructure evolution of Mg–8Li–3Al–1Y alloy undergoing different rolling processes were systematically investigated. X-ray diffraction, optical microscope, scanning electron microscopy, transmission electron microscopy as well as electron backscattered diffraction were used for tracking the microstructure evolution. Tensile testing was employed to characterize the mechanical properties. After hot rolling, the MgLi2Al precipitated in β-Li matrix due to the transformation reaction: β-Li → β-Li + MgLi2Al + α-Mg. As for the alloy subjected to annealed hot rolling, β-Li phase was clearly recrystallized while recrystallization rarely occurred in α-Mg phase. With regard to the microstructure undergoing cold rolling, plenty of dislocations and dislocation walls were easily observed. In addition, the microstructure of alloys subjected to annealed cold rolling revealed the formation of new fresh α-Mg grains in β-Li phase due to the precipitation reaction. The mechanical properties and fracture modes of Mg–8Li–3Al–1Y alloys can be effectively tuned by different rolling processes.

Hot tearing susceptibility of Mg–xZn–2Y alloys

Effects of Zn content (0, 0.5%, 1.5% and 4.5%) on the hot tearing characteristics of Mg–2%Y alloy were studied in a constrained rod casting (CRC) apparatus attached with a load cell and data acquisition system. The experimental results indicate that the hot tearing susceptibility (HTS) is affected by the content of Zn. The Zn-free base alloy shows the lowest HTS. The HTS of Mg–xZn–2Y alloys increases with increasing Zn content, reaches the maximum at 1.5% Zn, and then decreases with further Zn addition. The high HTS observed in the alloy with 1.5% Zn is attributed to its high force release rate and large force drop during solidification. The hot cracks of casting are initiated and propagate along the dendritic or grain boundaries. The predictions of HTS of Mg–xZn–2Y alloys using ProCAST software are in good agreement with the results obtained by experimental measurements.

The nano-eutectic in the microstructure of semisolid Mg–6Zn–1Y alloy

The microstructures of Mg–6Zn–1Y (at%) alloys cooling in the 20°C water and 20°C air respectively from semisolid state at 540°C were investigated in this work. An (α-Mg+I-phase) nano-eutectic was discovered in the water-cooled samples. The details of the nano-eutectic were investigated under TEM. Compared with the face-centered icosahedral I-phase solidified at slow cooling rate, the icosahedral type of I-phase solidified at fast cooling rate is primitive. The orientation relationship of the two phase in the nano-eutectic was also studied, namely {011̅1̅}Mg∥{τ10}I−phase and {101̅0}Mg∥2fI−phase. The two phases with different lattice structure matched as semi-coherent, which indicated that the interface was in a low energy state.

Effect of Sr addition on microstructure and elevated temperature mechanical properties of Mg–3Zn–1Y alloy

The effects of Sr addition on the microstructure and elevated temperature mechanical behavior of Mg–3Zn–1Y alloys have been investigated in this research. The results show that α-Mg, W-phase and S-phase are found in the Sr-containing alloys. The S-phase has a higher thermal stability than W-phase, which significantly improves the elevated temperature mechanical properties of the alloy. To further confirm the crystal structure of the S-phase, high resolution transmission electron microscopy analysis was performed and the phase was confirmed to be Mg6Zn2Sr1. With increasing content of Sr, the elevated temperature mechanical properties of the Mg–3Zn–1Y are improved. When the Sr content reached to 0.9wt%, the alloy shows a much higher ultimate tensile strength of 204MPa and yield strength of 171MPa at 250°C.