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Mo-12Si-8.5B alloy with layered Mo 2 TiAlC 2 (a new MAX phase) additions, in order to improve its fracture toughness, were prepared by hot pressing. The composition analysis combined with microstructure features revealed that after hot pressing sintering, the Mo 2 TiAlC 2 does not decompose but still maintains the layered structure and exhibits a good interface bonding with the matrix. The grain size of Mo-12Si-8.5B alloys was apparently refined by Mo 2 TiAlC 2. The mechanical properties suggested that the Mo 2 TiAlC 2 phase affects the hardness of Mo-12Si-8.5B alloy mainly through grain refinement. As the amount of Mo 2 TiAlC 2 increased, the compressive strength and flexure strength of alloys improved nonlinearly which is caused by the relatively low strength of Mo 2 TiAlC 2 and stress release due to its basal plane sliding, the enhanced strength was attributed to the particle strengthening and fine grain strengthening. The Mo 2 TiAlC 2 phase exhibits a remarkably toughening effect on Mo-12Si-8.5B alloy. The fracture toughness of Mo-12Si-8.5B-2%Mo 2 TiAlC 2 alloy increased by about 52% compared with the Mo 2 TiAlC 2 free alloy. Except for the fine-grain toughening caused by Mo 2 TiAlC 2 particles, the improvement of fracture toughness of Mo-12Si-8.5B alloy by Mo 2 TiAlC 2 is mainly caused by the crack deflection, the steps formed by Mo 2 TiAlC 2 fracture and basal plane (0001) sliding of Mo 2 TiAlC 2. • The layered Mo 2 TiAlC 2 MAX phase was firstly added to Mo-12Si-8.5B alloy. • Mo 2 TiAlC 2 shows a good interface bonding with matrix and refine the grain size. • Compressive and flexure strength improved nonlinearly with Mo 2 TiAlC 2 increasing. • The Mo 2 TiAlC 2 exhibits a remarkably toughening effect on Mo-12Si-8.5B alloy. [ABSTRACT FROM AUTHOR]

The development of emerging high-temperature-resistant semiconductor materials is of great significance for the stability of signals and the reliability of sensors during extreme probing processes such as deep earth and space. However, current reports only focused on the properties of the semiconductor materials, neglecting the high-temperature-resistant properties of subsidiary components, such as substrate. In this study, for the first time, the feasibility of the Molybdenum-14Rhenium (Mo-14Re) alloy as a high-temperature semiconductor substrate material was verified at five temperature points (25 ℃ (room temperature, Rt.), 100 ℃, 200 ℃, 300 ℃, and 400 ℃, respectively). The results showed that the hardness (2.8 GPa to 2.4 GPa) of the Mo-14Re alloy changed slightly during the temperature up to 400 ℃; the Mo-14Re alloy generated protective Mo6+ and Re3+ oxides at different temperatures, which enhanced its oxidation resistance; the thermal expansion coefficient of the Mo-14Re alloy was 5.04 × 10−6/℃ at 400 ℃, which can be perfectly adapted to semiconductor components, such as silicon, silicon nitride, and gallium nitride. Simultaneously, the Mo-14Re alloy combined appropriate thermal conductivity, making it the most promising candidate for a new generation of high-temperature semiconductor substrate materials. This study can promote the application of semiconductor materials in extreme environments, such as high temperatures. Concurrently, this study can promote the development of deep earth exploration and aerospace fields and guide the selection of emerging high-temperature resistant substrate materials. • The high-temperature indentation tests of Mo-14Re alloy were conducted for the first time; • The feasibility of Mo-14Re as a semiconductor substrate material was verified for the first time; • The high-temperature resistance mechanism of Mo-14Re alloys was analyzed. [ABSTRACT FROM AUTHOR]

Nozzle materials always withstand ultra-high temperatures (above 2000 °C) in space propulsion and other fields, which results in complex physical-chemical phenomena under actual operating conditions. The ablation mechanism and microstructural evolution of W-3Re-xHfC alloys were investigated to simulate the actual service conditions. Results show an outstanding ablation resistance. The linear ablation rate of the W 3Re matrix is 6.67 μm/s, the W-3Re-0.5HfC, W-3Re-5HfC and W-3Re-10HfC alloys are 2.93 μm/s, 2.23 μm/s and 2.26 μm/s, respectively. The linear ablation rates of W-3Re-0.5HfC, W-3Re-5HfC, and W-3Re-10HfC alloys decreased by 66%, 67%, and 67% compared with the W 3Re matrix, respectively. Thermochemical oxidation of the W 3Re matrix and HfC was the primary ablation mechanism of W-3Re-xHfC alloys. This work contributes to the design and improving the ablation resistance of W Re alloy applications in extreme environments. • Adding HfC particles significantly improves the ablation properties of W- 3Re alloy. • The ablation distance is shortened or the ablation time is prolonged, the worse ablation resistance • HfC and HfO 2 particles have high melting points, which nail the matrix grains and improve improving ablation resistance. • Thermochemical oxidation of the W- 3Re matrix and HfC particles is the primary ablation mechanism. [ABSTRACT FROM AUTHOR]

Act as a candidate for heat pipe reactor core, molybdenum‑rhenium (47.5 wt%) alloy possesses excellent mechanical properties at a wide temperature range (from room temperature to recrystallized temperature). Compressions at varied temperatures and strain rates were given to study the microstructural evolutions of Mo-47.5Re alloy. Yield strength is similar in sample compressed at 400 °C with high strain rate (1.67 × 10−1 /s) and the one at room temperature with low strain rate (1.67 × 10−3 /s). However, deformation twins are only observed under room temperature and are absent as temperature rises to 400 °C. Thus. Twinning in Mo Re alloy is much sensitive to temperature. The microstructure of Mo-47.5Re alloy is quite stable even compression at 1200 °C. Although sub-grains increasing after 1200 °C compressions, no recrystallization was detected. In addition, microstructural evolutions of Mo-47.5Re are outstandingly dependent on strain rates at 400 °C, while are much less obviously at 800 °C and 1200 °C. No phase changes are detected, which verifies good structural stability in Mo-47.5Re. • Deformation twins in Mo-47.5Re are carefully characterized under room temperature compression. • Deformation twins in Mo-47.5Re are absent as compressive temperature rises. • The rate-dependent microstructural evolutions are outstanding at 400 °C, while are much less obvious at 1200 °C. [ABSTRACT FROM AUTHOR]

• Helium ion-irradiation responses in Mo-Re alloys at room temperature were evaluated via micro-pillar compression. • Orientation-dependent irradiation-induced hardening is obvious in low Re Mo-Re alloys, while is weak on high Re alloys. • Irradiated pillars with [1 0 0] orientation all shows higher flow stresses than pillars with [1 1 0] orientation after yield. Helium ion-irradiation responses in molybdenum (Mo) and molybdenum-rhenium (Mo-Re) alloys at room temperature were evaluated via micro-pillar compression. Irradiation-induced hardening is closely dependent on orientation in Mo-Re alloys with low Re content, while is weak orientation-dependence on high Re alloys. Irradiated pillars with [1 0 0] orientation all shows higher flow stresses than pillars with [1 1 0] orientation after yield, which is distinguishing from pillars before irradiation that has been shown in our previous work. High density of dislocation loops and helium bubbles after irradiation at room temperature induces severe hardening in Mo. Voids / small loops induced by irradiation lead to less hardening in Mo-Re alloy than in Mo. No precipitation is observed in all samples, which may be attributed to low irradiated temperature and implantation energy. [ABSTRACT FROM AUTHOR]

Mo 42Re alloy, as a high-temperature structural and functional material, has broad application prospects in the nuclear industry. In this study, the hot deformation behavior of Mo 42Re alloy was systematically investigated using hot compression tests and electron backscatter diffraction (EBSD) techniques in the temperature range of 1200–1500 °C and strain rate range of 0.001–1 s−1. The results showed that the flow stress of Mo 42Re alloy exhibited a strong dependence on temperature and strain rate. The strain rate sensitivity index (m -value) was high under the conditions of 1350–1450 °C and 0.001 s−1. With increasing deformation temperature and decreasing strain rate, dynamic recrystallization (DRX) was significantly promoted, and the recrystallized volume fraction increased from 2.79% at 1200 °C/1 s−1 to 20.3% at 1500 °C/0.001 s−1. Meanwhile, the occurrence of and DRX effectively reduced the grain reference orientation deviation (GROD) gradients and kernel average misorientation (KAM) levels within the grains. This study revealed the mechanisms of microstructural evolution during hot deformation of Mo 42Re alloy, providing important guidance for optimizing its thermomechanical processing parameters. • The Mo 42Re alloy exhibits pronounced strain-rate sensitivity at 1350 -1450 ℃ and 0.001 s -1 strain rate. • Elevating the deformation temperature and lowering the strain rate significantly enhance DRX fraction. • Raising temperature and lowering the strain rate promote DRV and DRX, reducing GROD gradients and KAM levels. [ABSTRACT FROM AUTHOR]

The hot compression behavior of sintered W-3Re-5HfC alloy was investigated using the Gleeble1500D thermo-mechanical simulator at deformation temperatures and strain rates from 1200 °C to 1500 °C and 0.001 s−1 to 1 s−1, respectively. The microstructural evolution and flow behavior were studied. The microstructural observations reveal that the original grains are initially squashed, and then refined, which can be attributed to the occurrence of dynamic recovery and continuous dynamic recrystallization. Moreover, the electron backscattered diffraction analysis demonstrates a typical fibrous texture at low temperatures and high strain rates, which gradually transforms into the plate-like texture with the increase of temperature and decrease of strain rate. Based on the experimental results, arrhenius constitutive equations and an artificial neural network (ANN) model were developed for the characterization and prediction of the high-temperature deformation behavior in the W-3Re-5HfC alloy. The results indicate that the ANN model is more efficient in predicting the hot compressive behavior of W-3Re-5HfC alloy than the constitutive equations. The correlation coefficient and average absolute relative error in constitutive equations are found to be 0.99299 and 4.09%, respectively, whereas the corresponding values in the ANN model are found to be 0.99892 and 0.99%. In order to meet the performance requirements of different high-temperature structure parts, thermal deformation of W-3Re-5HfC alloy is needed to obtain the required microstructure and mechanical properties. ANN model provide theoretical basis for reducing deformation defects, saving process design time and obtaining machining parts with excellent microstructure. • The hot deformation behavior be predicted by Arrhenius model and artificial neural network model. • Dynamic evolution of coarse grains can be controlled by DRV and DRX. • A typical fibrous texture at low temperature and high strain rate • Artificial neural network model has higher accuracy in predicting the hot deformation behavior. [ABSTRACT FROM AUTHOR]

W–3Re alloys reinforced with various HfC particles contents (0 wt%, 0.5 wt%, 1 wt%, 5 wt%, 10 wt%) were fabricated using spark plasma sintering (SPS) at 2050 °C for 10 min. Microstructure, Vickers hardness and high temperature compression properties of the sintered W-3Re- x HfC alloys were investigated. Spherical HfC nanoparticles and micron scale clusters are distributed at the grain boundaries of the W–Re matrix. These nanoscale HfC particles pin dislocations and grains boundary as well as refine grain, thus enhancing the strength of composites. Furthermore, the HfC-W interfaces are well bonded semi-coherently without apparent interfacial gaps. The high temperature strength and micro-hardness of sintered composites are significantly increased with an increase of HfC contents. The micro-hardness of W–3Re alloy was 659.4 HV when 10 wt % HfC was added, which is enhanced up to 92.5 % compared with matrix. Its compressive strength is 850 MPa, increased by ~286 % compared with that of W–Re matrix. Quantitative analysis indicates that the main strength mechanisms are grain refinement, Orowan strengthening and interfacial thermal mismatch strengthening, which are influenced significantly by the HfC contents. This study provides new insights into composites performance optimization, reinforcement designs and strengthening mechanisms of particles reinforced W matrix alloys. [ABSTRACT FROM AUTHOR]