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In the present work, low-current-density electropulsing was applied to study the recrystallization behavior of a hot-rolled TiBw/TA15 composite. To highlight the athermal effect of electropulsing, traditional heat treatment experiments on composite materials were conducted under the same conditions. Test results indicated that recrystallization behavior can be improved compared with that in traditional heat treatment. The potential mechanism by which electropulsing promotes recrystallization was investigated, and the influence of the reinforcement phase on recrystallization was discussed. This work will provide freedom for the composite's process design and microstructure control.

Electrically-assisted diffusion bonding (EADB) of a TiBw/TA15 composite with a novel network architecture was studied under a vacuum degree of 3 × 10−3 Pa in this work. Traditional diffusion bonding (TDB) was also investigated to verify the electroplasticity effect. Characterization of the bonding interface revealed that the interface bonding ratio and shear strength increased with bonding time, and the maximum shear strength of the EADB sample could reach 786 MPa when bonded at 4.23 A/mm2 and 2 MPa for 60 min. However, when bonded in the same condition, the EADB sample achieved higher bonding quality than the TDB sample did. Moreover, the potential mechanism through which electropulsing promoted diffusion bonding was studied in detail. The findings provide ideas for EADB of titanium matrix composites.

Understanding the micromechanical responses during hot forming between TiB whiskers (TiBw) and matrix titanium alloy as well as grains is essential to effectively control the properties of the final products. In this work, a method to study the deformation inhomogeneity of network-structured TiBw/TA15 composites during rolling in high temperature single-phase regions at macro and micro scales was proposed. A crystal plastic finite element model with dislocation slip and grain boundary (GB) sliding as the deformation mechanism was established. Results showed that the discontinuous distribution of TiBw reinforcements along the GB reduced the strain difference between the network boundary region and the matrix region during high temperature deformation. Therefore, the plasticity of the composites was improved. For the high temperature β-phase, the {110} with higher activity was the main deformation mode. The difference in stress distribution between the grains was caused by the different combinations of the “soft” and “hard” states of adjacent grains, which was determined by whether the value of Schmid factors was greater than 0.45. The local stress concentrations tended to spread at the interface of “soft-hard” grains. The TiBw reinforcements increased the GB strength and reduced the deformation difference between the GB and intragranular.

The process of diffusion bonding in air was successfully used to join 5A90 Al–Mg–Li alloy, which can greatly reduce the welding cycle and equipment requirements. Before diffusion bonding, the Cu nano-coating prepared on the surface of Al–Mg–Li alloy by ultrasonic electrodeposition was used as interlayer to hinder the formation of oxide film and increase the atomic diffusion. The effects of coating thickness, diffusion temperature and interlayer types on the microstructure and performance of joints were investigated. When the diffusion temperature was 530 °C and the coating thickness was 5.12 μm, the optimal shear strength of the joint with 1 μm-thick diffusing interface was 187.9 MPa, which was 90.6% of that in base metal. As the decomposition of unstable Li20Mg6Cu13Al42, Cu atoms diffused into the Al matrix to precipitate Al6CuMg4, and enhanced nano-MgO phase was formed in situ. In addition, the element diffusion behavior and formation mechanisms of the joints were discussed in detail.

The iso-thermal oxidation of the quaternary Co-20Re-25Cr-3Si alloy at 1,000–1,200 C under laboratory air for 24 h has been studied. The oxidation kinetics at 1,000–1,200 C follow parabolic law perfectly and the value of oxidation activation energy is 220.74 kJ/mol. Unlike the experimental condition of 0.1 MPa pure oxygen, under laboratory air Co-20Re-25Cr-3Si alloy presents a good oxidation resistance due to the formation of a dense and continuous layer of Cr2O3 in contact with the alloy. A 79% drop in oxygen pressure has changed the oxidation mode from catastrophic oxidation to mild oxidation. The thickness of the protective Cr2O3 layer decreases when temperature increases. Therefore, Co-20Re-25Cr-3Si alloy shows the best oxidation resistance at 1,000 C. Moreover, from another perspective, compared with Co-17Re-23Cr-3Si alloy, the addition of about 2% Cr can also improve the oxidation resistance of the alloy greatly by forming the protective Cr2O3 layer.