High Temperature Tensile Strength Research Articles

Influence of mechanical alloying and extrusion conditions on the microstructure and tensile properties of Low-Cr ODS FeCrAl alloys

Low-chromium (<10%Cr) high strength oxide dispersion strengthened (ODS) FeCrAl alloys are considered promising candidates for accident tolerant fuel cladding in light water fission reactors. These alloys are designed to combine the beneficial high temperature mechanical properties of ODS materials with the exceptionally high temperature oxidation resistance of FeCrAl in comparison to conventional Zr-containing cladding materials, while also providing good mechanical and aqueous corrosion behavior under normal light water reactor operating conditions. The initial (1st generation) ODS FeCrAl alloys combined gas atomized FeCrAl powders with yttria and other oxides for alloying element additions using the mechanical alloying approach. These alloys exhibited low ductility but excellent high temperature tensile strength while maintaining good oxidation resistance at temperatures up to 1400 °C. In an attempt to improve alloy ductility for accident tolerant fuel cladding applications, new low-Cr ODS FeCrAl alloys with decreased oxygen content were developed with the Zr alloying solute already gas atomized into the powder prior to mechanical alloying. The resultant Fe-10Cr-6.1Al-0.3Zr+0.3Y2O3 (106ZY) powders were ball milled for 10, 20, and 40hr followed by consolidation via hot extrusion at temperatures ranging from 900 to 1050 °C. Increasing the mechanical alloying time decreased the resultant grain size and improved high temperature tensile properties. Decreasing the extrusion temperature refined the grain size and subsequently strengthened the ODS FeCrAl 106ZY alloys while lowering the ductility. Scanning transmission electron microscopy (STEM) and energy dispersive spectroscopy (EDS) demonstrated the Zr solute addition effectively sequestered impurity C and N within the matrix. The root mean square (RMS) hardening superposition model for yield strength shows good agreement with experimental results. Errors between predicted and experimental values are discussed within the scope of processing parameters. These 2nd generation 106ZY alloys show a distinct increase in alloy ductility without sacrificing the high temperature tensile properties characteristic of legacy or 1st generation ODS FeCrAl alloys.

Effects of nanosized TiCp dispersion on the high-temperature tensile strength and ductility of in situ TiCp/Al-Cu-Mg-Si nanocomposites

In situ TiCp/Al-Cu-Mg-Si nanocomposites were prepared in Al-Ti-C systems with different carbon sources (pure carbon black, mixed carbon source (50 wt% CNTs + 50 wt% carbon black) and pure CNTs) via a combination of the combustion synthesis, hot press and hot extrusion methods. The in situ TiCp/Al-Cu-Mg-Si nanocomposites synthesized by the mixed carbon source obtained the most uniform distribution of nanosized TiCp, highest yield strength (σ0.2) and tensile strength (σUTS) and best fracture strain (εf). The 30 vol% TiCp/Al-Cu-Mg-Si nanocomposite synthesized by the mixed carbon source showed superior σ0.2 (217 MPa), σUTS (251 MPa), and εf (17.7%) at 533 K, which were respectively 4.3%, 4.1% and 136% higher than those of the nanocomposite synthesized by pure C black (208 MPa, 241 MPa and 7.5%) and respectively 3.8%, 1.6% and 88.3% higher than those of the nanocomposite synthesized by pure CNTs (209 MPa, 247 MPa and 9.4%). The superior high-temperature tensile strength and ductility of the nanocomposites prepared by the mixed carbon source were attributed to the homogeneous distribution of nanosized TiCp. The strengthening of the nanosized TiCp and θ′ precipitates was the main strengthening mechanism of the in situ TiCp/Al-Cu-Mg-Si nanocomposites at high temperatures.

Effect of nano-sized ZrO2 on high temperature performance of Mo-ZrO2 alloy

Mo-ZrO2 alloys were prepared through hydrothermal synthesis and powder metallurgy process. Room temperature microstructures of these alloy plates were observed, while high temperature tensile strength and plasticity of them were tested above 1000 °C using a Gleeble-1500D thermal simulated test machine. Results have shown that ZrO2 particles were fine in the alloy and distributed at grain boundaries and within the grains. The second phase of ZrO2 particles demonstrated a pinning effect to retard recrystallization progress and thus enhance high temperature tensile stress and plasticity of the alloys effectively. Besides, the strengthening effect of the second phase in the alloy could also effectively improve its high temperature tensile stress. Under 1400 °C, maximum tensile stress of Mo-1.5%ZrO2 alloy was 1.5 times that of pure molybdenum, while the alloy plasticity also increased dramatically. The area shrinkage of Mo-1.5% ZrO2 alloy at 1400 °C was 5 times that of pure molybdenum.

Creep Properties of Squeeze-Infiltrated Carbon Nanotube and Aluminum Borate Whisker Reinforced AS52 Mg Metal Matrix Composites

The effects of carbon nanotubes (CNTs) and aluminum borate whisker (ABw) on the creep and tensile properties of an AS52 alloy matrix composites were investigated. A hybrid 5 vol% CNT + 20 vol% ABw/AS52 Mg MMC and a single 25 vol% ABw/AS52 Mg MMC were fabricated by preform fabrication and squeeze infiltration. Creep tests were carried out at temperatures of 150–250 °C under stresses of 50 and 70 MPa. The tensile property was evaluated at room temperature and 150 °C. The minimum creep rate decreased in the order AS52 > single MMC > hybrid MMC. The creep activation energy of the hybrid MMC was 182.9 kJ/mol which was 28% and 83% higher than those of the single MMC and the AS52, respectively. The room-temperature and high-temperature tensile strengths of the hybrid MMC showed the highest values. Creep properties of the hybrid MMC improved on addition of CNTs, which prevented creep void initiation and crack propagation along the ABw interface.

Collapse of lamellar structure and stability with the addition of Misch metal (Mm) to the cast Ti–Al–Mo–Nb–(Mm) alloys

Misch metal (Mm), consisting of Ce and La, was added to Ti–45Al–3Mo–2Nb alloys in order to investigate phase transformation and microstructural changes. The pseudo-binary phase diagram was estimated via PANDAT software™. The addition of Mm caused a decrease in both the fractions of α2/γ lamella and the β0 phase, and served as an important factor for a collapse of lamellar structures. In addition, Mm significantly decreased the colony size of the alloy, resulting in an increase in high-temperature tensile yield strength of ~ 40% for the alloys with 0.3 at% Mm at 800 °C. It appears that the addition of Mm affects the phase stability and increase the proportion of the γ phase. The microstructural changes, with respect to Mm additions, were discussed in terms of structural observations during isothermal heat treatments.

Novel HIPIMS deposited nanostructured CrN/NbN coatings for environmental protection of steam turbine components

To increase efficiency, modern steam plants are pushing their operational regime from super-critical (600 °C/300 bar) to ultra-super-critical (740/760 °C/350 bar) stretching existing turbine materials to their limits. The focus is on new generation functional materials and technologies which complement the inherent properties of existing materials.Current work proposes a novel High Power Impulse Magnetron Sputtering (HIPIMS) deposition technology, for the first time, for deposition of a ceramic based CrN/NbN coating with a nanoscale multilayer structure (bi-layer thickness Δ = 1.9 nm) with superior adhesion (LC2 = 80 N) to protect low Chromium P92 steel widely used in steam power plants. Thermodynamic calculations predict the equilibrium phases and aggressive gaseous compounds generated by the interaction of steam with the coating. CrN/NbN coated P92 steel samples oxidised at 600 °C in a high pressure (50 bar) 100% steam atmosphere for up to 1000 h reveal the coating's superior oxidation resistance and protective mechanisms, especially against the detrimental effect of Hydrogen. High temperature (650 °C) Tensile Strength, Low Cycle Fatigue and Creep tests confirm that, unlike other state-of-the-art PVD technologies, HIPIMS is not detrimental to the mechanical properties of the substrate material. Water droplet erosion tests confirm no measurable weight loss after 2.4 × 106 impacts.

Simultaneously increasing the high-temperature tensile strength and ductility of nano-sized TiCp reinforced Al-Cu matrix composites

Adding various amounts of nano-sized TiCp (0.1–0.7 wt%) made a simultaneous improvement in high-temperature strength and ductility of the Al-Cu matrix alloy. The influences of temperature and strain rate on the high-temperature tensile properties and θ′ precipitate sizes in the Al-Cu matrix alloy and the nano-sized TiCp/Al-Cu composites were investigated. Theoretical calculations suggest that the yield strength increment of the composites at 453 K was primarily attributed to the strengthening effect of both the refined θ′ precipitates and TiCp, while at 493 K only the strengthening effect of TiCp was predominant due to the significant coarsening of θ′ precipitates at this temperature.

Improvement of High-Temperature Mechanical Properties of Low-Carbon RAFM Steel by MX Precipitates

To investigate the influence of tantalum content on high-temperature mechanical properties of low-carbon reduced activation ferritic/martensitic (RAFM) steels, RAFM steels containing different tantalum contents (0 and 0.073%) were fabricated, and the tensile tests at room temperature and high temperature were performed, as well as the creep tests were conducted at 550 °C with the applied stress of 180 and 220 MPa. It was found that 0.073% tantalum addition results in the increase in amount of stable carbonitrides (MX), and the creep rupture time of the steel under 180 MPa is obviously increased. In addition, the increase in MX caused by tantalum addition also leads to the improvement of high-temperature tensile strength. The improvement of high-temperature mechanical properties of RAFM steels is primarily related to the evolution of precipitates.

Syntheses of cellulose branched ester derivatives and their properties and structure analyses

Traditionally, cellulose linear acyl esters such as cellulose acetate or cellulose propionate have been used as thermo-plasticized materials from renewable resources for decades. The properties of these kinds of cellulose esters can be varied by changing carbon number (C) of acyl substituents. In this study, a series of cellulose ester derivatives with branched acyl substituents were synthesized by the heterogeneous reaction, and their thermal, mechanical, and structural properties were investigated in comparison with cellulose linear acyl esters. All cellulose branched esters have crystallinity, and tended to show higher melting temperature and glass transition temperature than those of cellulose linear esters with the same C number. Cellulose isobutyrate (branched ester, C = 4) had especially high melting temperature (248 °C) compared with those of cellulose linear esters such as cellulose butyrate (C = 4, 182 °C) and cellulose propionate (C = 3, 235 °C). Colorless and transparent films of cellulose branched esters were fabricated by solvent-casting method. These films showed harder and less flexible properties than those of cellulose linear esters. Structural analyses were conducted by 1D- and 2D-WAXD measurements. Crystal lattice parameters and molecular conformation with 3-fold screw symmetry of cellulose isobutyrate indicated that it has similar crystal structure with cellulose propionate, which could cause high melting temperature and high tensile strength of cellulose isobutyrate. Thus, material properties of cellulose acyl esters can be controlled not only by carbon number of acyl substituents but also by branching structure of acyl groups.

High temperature tensile fracture characteristics of the oriented TiB whisker reinforced TA15 matrix composites fabricated by pre-sintering and canned extrusion

In this paper, the high-temperature (range from 673 K to 973 K with an interval of 100 K) tensile mechanical properties, fracture mechanism and fracture process of the monolithic TA15 alloy and 5 vol% in situ synthesized oriented TiB whisker-reinforced TA15 titanium matrix composites (TiBw/TA15) fabricated by pre-sintering and canned extrusion were investigated. The results showed that the TiBw/TA15 composites fabricated by this method possessed an upper high temperature tensile strength, at the same time, had better high temperature plastic deformation capacity compared to TiCp (TiBw) reinforced TA15 composites fabricated by other methods. TiBw/TA15 showed an obvious improvement in high temperature tensile strength compared to monolithic TA15 alloy while the plasticity was the opposite. The fracture results suggested that TiBw could reinforce the TA15 matrix below 873 K, while the debonding between the matrix and TiBw occurred when the stretching temperature reached 973 K. The presence of micro-pores would not become the source of crack initiation during the tensile process and therefore did not adversely affect the high temperature properties of the composites. With the addition of TiBw, the fracture mechanism was changed to a mixture of brittle fracture and ductile failure (composites) from ductile failure (monolithic TA15 alloy). Additionally, analyzing the different parts of the fracture sample could qualitatively analyze the fracture process of the composites and maybe could replace the in-situ tensile observation at high temperature.

Ternary Copolymerization of Supercritical CO2, Propylene Oxide and Maleic Anhydride

With zinc glutarate loaded molecular sieve catalyst in supercritical CO2, the copolymerization of CO2, propylene oxide, and maleic anhydride was studied in detail. The optimum conditions of copolymerization are: T = 70℃, P = 8MPa, reaction time 15 hours, 0.7g catalyst per 20ml propylene oxide, and product yield is 26%. The functional polymer products have some special characteristics, such as high glass transition temperature and good tensile strength. It is biodegradable so that it can gradually replace the traditional plastic. The structure of the copolymer products was characterized by FTIR, 1H-NMR, 13C-NMR, and SEM analysis.DOI: http://dx.doi.org/10.5755/j01.ms.23.4.17323

Effects of tantalum on microstructure and mechanical properties of cast IN617 alloy

Effects of Ta on microstructure and mechanical properties of cast IN617 alloy were investigated. The results showed that the addition of Ta increased size and area fraction of MC carbides, which was in agreement with the prediction of thermodynamic calculation, rather than influencing as-cast microstructure features such as grain size, secondary dendrite arm spacing, and carbide distribution. Ta-doped cast microstructure showed that Ti (C, N) nitride-carbide was substituted by MC carbide and at the same time, M6C and MC tended to form a eutectic structure. The lattice constant of the matrix in a heat treatment condition increased from 3.593 to 3.601nm and the high temperature tensile strength also improved, when Ta content are from 0 to 2.0wt%. It was attributed to the solution of Ta with solid solution strengthening in the matrix. However, when the Ta level exceeded 1.0wt%, the ductility and fracture toughness significantly reduced. It was believed that remained Ta-rich MC carbides in the supersaturated matrix accelerated the initiation and propagation of cracks. Therefore, the optimized Ta content in cast IN617 alloy is suggested to below 1.0wt% for balanced properties.

High Temperature Flexural, Tensile Strength and Oxidation Behavior of Ti3SiC2 Ceramic at 900°C–1300°C in Ambient Air

Abstract High temperature flexural and tensile strength of hot-pressed Ti3SiC2 ceramic were measured and analyzed from 900 to 1300°C in ambient air atmosphere. The high temperature flexural and tensile strength are strong functionals of temperature. With the temperature increasing, the high temperature flexural and tensile strength decrease correspondingly. Moreover, the transition from brittle to plastic deformation was observed for both flexural and tensile testing. The oxidation behavior and oxidation mechanism were investigated.

Nano-scaled Ti5Si3 evolution and Strength Enhancement of titanium matrix composites with two-scale architecture via heat treatment

To further improve the mechanical properties of Ti5Si3 and TiBw reinforced Ti6Al4V ((Ti5Si3 + TiBw)/Ti6Al4V) composites with a two-scale network structure, heat treatments were carried out to adjust nano-scaled Ti5Si3 (n-Ti5Si3) particles and matrix characteristics. The fraction of Ti5Si3 particles in the vicinity of first-scale TiBw reinforcements decreases with increasing quenching temperatures. When the quenching temperature is elevated to 1200°C, the Ti5Si3 particles dissolve and re-solute into the matrix. Both the size and fraction of n-Ti5Si3 particles increase with increasing aging temperatures. The size of n-Ti5Si3 particles in the β phase can be refined from 400–500nm (as-sintered) to 10–60nm after heat treatments. The strength of the heat-treated composites was significantly enhanced through heat treatments, when compared with the composites with one-scale architecture and Ti6Al4V alloy. The room temperature compressive strength and high temperature (600°C) tensile strength can reach 2245MPa and 880MPa, respectively. This can be attributed to the heat treatments adjustment of n-Ti5Si3 particles, supersaturated martensite α' phase and two-scale network structure.

Effect of transition elements on the microstructure and tensile properties of Al–12Si alloy cast under ultrasonic melt treatment

This paper shows that the addition of transition elements significantly influences the microstructure and tensile properties of Al–12Si alloy cast under ultrasonic melt treatment (UST). The alloys contained primary Si, eutectic Si and a variety of intermetallic compounds (IMCs); the addition of Mn and Ni changed the solidification sequence by forming primary α-Al15(Fe,Mn)4Si2 and ε-Al3Ni prior to primary Si formation. The primary Si and primary IMCs competitively consumed the nucleation sites introduced by UST, thereby influencing their refining efficiencies; the efficiency of primary Si refinement by UST increased with increasing the fraction of primary Si formed prior to IMC formation, whereas it deteriorated with increasing primary IMC fraction. The refining efficiency of eutectic Si and eutectic IMCs was not affected by the type and fraction of the primary phase. Using a Ti sonotrode for UST caused Ti contamination, resulting in grain refinement by forming Ti(Al,Si)3 particles and increasing the amount of Ti solutes. Regardless of transition elements content, the application of UST improved the tensile strength at 25 °C and 350 °C. The refinement of IMCs caused by UST allowed the alloy to contain more IMCs without deterioration of room-temperature tensile strength. This enhanced the increment of high-temperature tensile strength by IMCs. Ductility of heavily alloyed systems was also improved by UST.

Microstructure and mechanical properties of the laser-welded Mg-3Nd-0.2Zn-0.4Zr (NZ30K) magnesium alloy

This study aimed to investigate the microstructure and mechanical properties of the laser-welded Mg-3Nd-0.2Zn-0.4Zr (NZ30K) magnesium alloy. A fiber optic laser was used to weld 4-mm-thick Mg-3Nd-0.2Zn-0.4Zr (NZ30K) and AZ31 magnesium alloy plates. The microstructures of NZ30K and AZ31 joints were compared, and the distribution of Nd in NZ30K was emphatically investigated. Besides, microhardness distributions and tensile properties of NZ30K and AZ31 joints at room temperature and high temperature (200°C) were tested, and fracture features were observed and analyzed. The results indicated that the NZ30K rare-earth magnesium alloy showed better properties especially at a high temperature (200°C), benefiting from the strengthening phase, compared with the AZ31 joint, such as high-temperature tensile strength, creep resistance at high temperature, and corrosion resistance. The microhardness in the fusion zone of NZ30K changed a little compared with that in base metal, while the microhardness in the fusion zone of AZ31 decreased significantly. The grain of NZ30K in the fusion zone was significantly refined with strengthening-phase distribution on the grain boundary. The tensile strength of NZ30K laser beam–welded joints at a high temperature (200°C) decreased by 29% compared with that at room temperature, while the tensile strength of AZ31 joint at a high temperature (200°C) decreased by 53% compared with that at room temperature, which was mainly because of the stable existence of the strengthening-phase Mg12Nd in the NZ30K rare-earth magnesium alloy while the strengthening-phase Mg17Al12 in AZ31 would soften and coarsen with the rise in temperature.

Effects of first-scale TiBw on secondary-scale Ti5Si3 characteristics and mechanical properties of in-situ (Ti5Si3+TiBw)/Ti6Al4V composites

Abstract In order to further improve mechanical properties, Ti6Al4V matrix composites reinforced with secondary-scale Ti 5 Si 3 particles and first-scale TiB whiskers were designed and prepared by reaction hot pressing. The effects of first-scale TiBw fractions on secondary-scale Ti 5 Si 3 microstructure characteristics and mechanical properties of two-scale network structured composites were investigated. With increasing TiBw fractions, the size of Ti 5 Si 3 particles in β phase increased, the quantity of Ti 5 Si 3 particles near TiBw reinforcement increased and the morphology changed from isolated particles to interconnected particles. These changes resulted in that the room and high temperature tensile strength of the composites increased, moreover, the creep resistance of the composites improved. Compared with the Ti6Al4V alloy, the room and high temperature tensile yield strength of the composites with 3.4 vol%TiBw increased by 36.5% and 70%, and the elongation remained at 5.0% and 11.5%, respectively. The composites possess approximately one order of magnitude lower steady-state creep rate and about eight times higher time-to-rupture at 873 K/200 MPa. The superior tensile and creep properties can be attributed to adjustment of secondary-scale Ti 5 Si 3 characteristics and two-scale network structure.

Transient Thermal Tensile Behaviour of Novel Pitch-Based Ultra-High Modulus CFRP Tendons.

A novel ultra-high modulus carbon fibre reinforced polymer (CFRP) prestressing tendon made from coal tar pitch-based carbon fibres was characterized in terms of high temperature tensile strength (up to 570 °C) with a series of transient thermal and steady state temperature tensile tests. Digital image correlation was used to capture the high temperature strain development during thermal and mechanical loading. Complementary thermogravimetric (TGA) and dynamic mechanical thermal (DMTA) experiments were performed on the tendons to elucidate their high temperature thermal and mechanical behaviour. The novel CFRP tendons investigated in the present study showed an ambient temperature design tensile strength of 1400 MPa. Their failure temperature at a sustained prestress level of 50% of the design tensile strength was 409 °C, which is higher than the failure temperature of most fibre reinforced polymer rebars used in civil engineering applications at similar utilisation levels. This high-temperature tensile strength shows that there is potential to use the novel high modulus CFRP tendons in CFRP pretensioned concrete elements for building applications that fulfill the fire resistance criteria typically applied within the construction industry.

High Temperature Tensile Strength Evaluation with Non-contact Measuring Method for Small Diameter Solders Specimen

High Temperature Tensile Strength Evaluation with Non-contact Measuring Method for Small Diameter Solders Specimen

Combined effects of ultrasonic melt treatment, Si addition and solution treatment on the microstructure and tensile properties of multicomponent Al[sbnd]Si alloys

The effects of ultrasonic melt treatment (UST) on the microstructure and tensile properties of three multicomponent AlSi alloys with different Si contents (12, 15, and 18 wt%Si) and solution treatments were systematically investigated at room and elevated (350 °C) temperatures. The microstructures of these alloys consisted of primary Si, eutectic Si, Mg2Si, and various types of aluminides, but the average size and area fraction of the primary Si increased with Si content. The application of UST caused a transformation from dendritic to equiaxed cells and a reduction in grain size, with a significant reduction in the size of all secondary phases (i.e., Si, Mg2Si and aluminides). Both the strength and ductility at room and elevated temperatures were greatly improved by UST, mainly due to microstructure refinement. Improvements in the high-temperature tensile strength as a result of UST increased with increasing Si contents, due to the enhanced refinement of primary Si by UST with increasing Si contents. The spherodization of rigid phases induced by solution treatment can improve the strength and ductility at room temperature, but can also cause a loss of strength at elevated temperatures due to the relaxation of the interconnected network structure of rigid phases caused by their spherodization.