The phase transformation of high-strength Ti-alloy is complex and closely related to the element partitioning during heat-treatment. The microstructure evolution and element partitioning behavior of metastable Ti-alloy Ti-5Al-5Mo-5V-3Cr-0.6Fe, being subjected to different solution and aging treatments were studied. The results showed that after β solution-treatment followed by furnace cooling to (α+β) solution-treatment, α grain boundary (α_GB) and a small amount of intracrystalline primary α(α_p) could form in the alloy. Next, after a two-stage aging-treatment at low-temperature and high-temperature, the ω-phase precipitated during low-temperature aging could affect the size of secondary α(α_s)-lamellar formed during high-temperature aging. The electron probe microanalysis was used to characterize the typical element partitioning effect occurred between α- and β-phase, during solution-treatment, and of which the influence on the microstructure evolution is discussed. The element partitioning behavior led to higher content of β stabilizing elements near α_GB and α_p, which improved the stability of β matrix in the above region. The precipitation free zone formed near α_GB and α_p during low-temperature. After high-temperature aging, the refined α_s precipitated away from α_GB induced by the ω-phase assisted nucleation. While the size of α_s was larger within 2 μm nearby α_GB owning to the absence of ω-assisted nucleation.

The effect of electropulsing treatment (EPT) in liquid nitrogen (LN) on the microstructure and mechanical properties of cold-rolled 316L austenitic stainless steel was assessed, aiming at tensile properties of the EPT-LN treated cold-rolled 316L steel at room and cryogenic temperature, and the relevant deformation mechanisms. It is found that the LN-EPT could induce recrystallization of the cold-rolled 316L stainless steel. The recrystallization ratio is dependent upon the EPT energy input, and after being treated by EPT-7.5LN with discharge voltage of 7.5 kV, the 316 steel presents a fully recrystallized microstructure. The EPT-LN treated steels exhibit significantly higher strength-ductility synergy when they were deformed at 77 K rather than at 293 K. The TEM observation result of the deformed steel revealed that the main mechanisms related with the tensile deformation of 316 steel at 293 K were mainly of dislocation slip and deformation twinning, however, there exist a large amount of deformation-induced martensite transition for that at 77 K. The martensite transitions and their subsequent deformation result in a significant increase in the strain hardening capability, thereby enhancing the strength-ductility synergy. Further analysis shows that the deformation mechanism transition is mainly caused by the significant reduction of stacking fault energy of the steel at low temperatures.

Foam materials of ZL104 alloy and 304 stainless steel fiber/ZL104 alloy composite were prepared by the infiltration casting method, and their pore structure, mechanical performance, sound absorption properties and the relevant mechanisms were investigated. The results show that within the prepared foam materials, there exist interconnected larger pores, and on the wall of which, there are many smaller sub-pores. The formation of such sub-porous structure may be ascribed to the effect of the second moderating salt adopted for the infiltration casting. Moreover, the fibers present in three states in the composite foam: pore wall fiber, perforated fiber, and inter-porous fiber. The typical composite foam with fiber diameter of 0.1 mm and porosity of 77-86%, while the mean diameter of 0.35mm for the main pores. The composite foam has better compression yield strength and sound absorption performance rather that those of the alloy foam with the same porosity. The compression and sound absorption properties of composite foams increased first and then decreased with the increasing porosity and fiber content. It is wealthy noted that among others the compression yield strength reaching the peak value of 2.6 MPa for the foam with porosity of 82% and fiber content of 5%, accordingly, the average sound absorption coefficient reaching the peak value 0.893 for the composite foam with porosity of 82% and fiber content of 8%, respectively. Finite element analysis shows that when being pressed, the pore wall fibers and perforated fibers can transfer and disperse stress, and the energy can be consumed by displacement and deflection of the fibers, thus enhancing the strength of the composite foam. J-A model analysis shows that the fibers protruded into the pores increase the surface roughness and specific surface area of the foam, resulting in an increasing acoustic wave loss of the composite foam, which is the reason for the higher sound absorption property of the composite foam.

Powder metallurgy Inconel 718 alloy plates were prepared through hot isostatic pressing route using pre-alloyed Inconel 718 powder (produced by vacuum induction melting inert gas atomization, VIGA) in this paper, and then tungstun inert gas arc welding (TIG) is completed. Characterization of welded joints were performed using SEM, EBSD methods. Influence of post-welding heat treatment on joint microstructure and mechanical properties are analyzed. The results show that the base metal is fine equiaxed crystal, the grain size is about 28 μm, and the tensile strength is close to the requirement of wrought alloys. Powder metallurgy Inconel 718 alloy shows good weldability, no macroscopic porosities and inclusion defects are observed at the joints, and the joint strength is equivalent to the property of the base metal after heat treatment. After homogenization, the Laves phase is basically dissolved, the structure is uniform, ductility is obviously improved. Micropores and Laves can be eliminated by hot isostatic pressing treatment after welding that make mechanical properties more stable. Micro-porosities are easily formed at the interface between the Laves phase and the matrix, micro-porosities accumulate to form micro-cracks and eventually break.

Dual-layered composites of TiZr-based bulk metallic glass /TC21 Ti-alloy were successfully prepared by infiltration method, and their microstructure and mechanical property were investigated in detail. The results show that there is a good wettability of ZT3 (Ti_32.8Zr_30.2Ni_5.3Cu₉Be_22.7) melt with TC21 Ti-alloy, and the as-prepared dual-layered composites show an excellent interfacial bonding between BMGs and TC21 Ti-alloys. The temperature of preparation plays a critical role for the microstructure and mechanical property of the dual-layered composites. With the increasing temperature for preparation, the interfacial layers become thicker moreover, the TC21 Ti-alloy may dissolve increasingly into the BMGs matrix so that the dendrites precipitate significantly increase and they become coarser with the increasing temperature. The dual-layered composites exhibit a satisfied flexural mechanical property, namely a flexural strength of 2177 MPa with outstanding flexural plasticity. Additionally, the prepared dual-layered composites show the dynamic compressive strength up to 1326 MPa at ambient temperature, but decreases as the temperature increasing.

Carbon fiber was surface modified with dopamine via self-polymerizing deposition process, then the polyamide 6-based composites (CF/PA6) were prepared with the modified carbon fiber as reinforcement. The morphology, roughness, wettability and chemical construction of carbon fiber were characterized by scanning electron microscope (SEM), atomic force microscope (AFM), contact angle measuring device, Fourier transform infrared spectrometer (FTIR) and X-ray photoelectron spectroscopy (XPS). The effect of deposition time of polydopamine (PDA) on the interface mechanical properties of the composites was also investigated. The results show that the surface of the modified carbon fiber was covered by a uniform PDA film, which significantly increased the surface activity, surface roughness and chemical bond energy of the carbon fiber, and greatly improved the interfacial compatibility between the carbon fiber and polyamide 6 matrix. The optimal PDA deposition time for the modification of carbon fiber was 16h, correspondingly, with the optimally modified carbon fiber as reinforcement, the interlaminar shear strength and bending strength of composites reached 31.7 MPa and 308.2 MPa, which was 72.3% and 56.9% higher respectively than those of the ones reinforced with the blank carbon fiber.

The dynamic recrystallization mechanism and microstructure evolution of superalloy GH4169 during isothermal compression by strain rate of 0.01~1 s^-1 at temperature within the range of 1000~1150°C were systematically investigated via Gleeble thermal simulation technology, EBSD, SEM and OM. The results show that the maximum deformation resistance of the alloy can reach 400 MPa by the desired deformation parameters. The power dissipation diagram and rheological instability diagram of GH4169 were plotted based on the dynamic material model, and the deformation parameters of 1020°C~1070°C and 0.03~0.63 s^-1, which were taken as the optimal processing interval for the GH4169 alloy. The evolution regularity of dynamic recrystallization during the deformation process of GH4169 was analysed. It is clear that the dynamic recrystallization is mainly initiated by the discontinuous dynamic recrystallization at grain boundaries of the original austenite, while the continuous dynamic recrystallization may be due to the nucleation induced through the continuous rotation of sub-grains. The evolution regularity of Σ3ⁿ non-coherent twin boundary was determined. The larger the volume fraction of dynamic recrystallization grains, the much smaller the size of grains and the higher the density of Σ3 non-coherent twin boundaries. The growth of dynamic recrystallization grains takes the precedence over the formation of Σ3ⁿ non-coherent twin boundary.

CoCrFeNiTi _x (x=0, 0.2, 0.5, 0.8) high-entropy alloy coating was prepared on 40Cr steel surface by laser cladding technology and its thermodynamic parameters were calculated. The phase composition, microstructure, element distribution, hardness and wear resistance of the alloy were detected by X-ray diffractometer (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), microhardness tester and friction and wear tester. The effects of Ti content on the microstructure and wear resistance of the alloy were investigated. The results show that with the increase of Ti content, the alloy phase forms a body-centered cubic (BCC) structure on the basis of the face-centered cubic (FCC) structure. The microstructure in the middle of the cladding layer is composed of equiaaxial crystals with obvious grain boundaries and uniform grain distribution, and finally the columnar dendrites are formed. With the increase of Ti content, the hardness of cross section of the alloy increases gradually, and the highest is 412.32 HV_0.2, which is 1.8 times higher than that of the matrix. The wear amount and friction coefficient of the coating decrease accordingly. When Ti content is 0.8, the coating has the best wear resistance, the minimum wear amount is 6.8mg, and the friction coefficient is 0.35. The wear mechanism of coating is mainly abrasive wear, adhesive wear and oxidation wear.

A new lead-free ceramic system (1-x)(Bi_0.5Na_0.5Ti_0.95Al_0.025Nb_0.025O₃)-x(SrSc_0.5Nb_0.5O₃) [(1-x)BNTA-xSSN, x=0.05、0.1、0.15、0.2] was prepared by solid-state method. The effects of the introduction of SrSc_0.5Nb_0.5O₃ on the structure, phase transformation, energy storage and dielectric properties were studied. The results showed that (1-x)BNTA-xSSN owns perovskite structure at room temperature. The T_mdecreases with the increase of SSN content, and the phase structure changes from tetragonal phase to pseudo-cubic phase. The ferroelectric properties of the ceramics were weakened and the relaxation ferroelectric properties were enhanced. When x=10%, the maximum effective energy storage density (W_rec) of BNTA-SSN ceramics is 2.7 J/cm³. The maximum energy storage efficiency (η) of BNTA-SSN ceramics is 85% at x=15%.

The anisotropy of microstructure and mechanical properties of 2060 Al-Li alloy thick plate was investigated by OM, TEM, EBSD and tensile properties at room temperature. The main results are as follows: 1) The strength in 0° direction is the highest, the elongation and the section shrinkage are lower; The strength in 45° direction is the lowest, but the elongation and the section shrinkage are the highest; The strength in 90° direction is slightly lower than 0° direction, and the elongation and section shrinkage are the lowest. 2) The main precipitated phase of the alloy in the directions of 0°, 45° and 90° is T₁ phase, and θ' phase and a small amount of spherical δ' phase are also found in 0° and 45° directions. In the direction of 0°, the number of precipitated phases is the largest and the distribution is uniform. In the direction of 45°, the size of precipitated phases is large, and most of THE T₁ phase is coarse and flake. In the direction of 90°, the number of precipitated phases is relatively small, but the size of T₁ phase is significantly smaller than that in the direction of 45°. 3) 2060 Al-Li alloy thick plate has the highest texture strength at 45° direction, and a strong recrystallization texture P{011}<122> appears.The texture strength is still high in the direction of 0°, mainly recrystallized P{011}<122>, there is also a weak deformation texture copper {112} <111>; The texture strength in the 90° direction is relatively weak, and the deformation texture Copper {112}<111> and deformation texture S{123}<634> are the main textures.