To characterize the grain morphology from multiple apsects such as size， shape and distribution， and then realize the quantitative ultrasonic evaluation of the uniformity of grain morphology， an ultrasonic multi-parameter evaluation method for grain morphology is proposed. GH738 grain morphology is used as the characterization object， and 10 quantitative parameters are extracted with the grain as the measurement unit. Eight quantitative parameters are measured for the field-of-view image. The correlation screening rule using pearson coefficient is established， then seven metallographic quantitative parameters are selected， the radial layout visualization star coordinate method is used to calculate two parameters， r and \theta， which are used to comprehensively characterize grain morphology. Six ultrasonic parameters， such as sound velocity and attenuation coefficient， are extracted， and a sample library of two-dimensional comprehensive characterization parameters of grain morphology and ultrasonic multi-characteristic parameters is established. Three ultrasonic evaluation model based on MLR， RFR or PSO-SVM algorithm are built to characterize the two comprehensive parameters of grain. The verification experimental results show that the multi-dimensional comprehensive characterization of grain morphology is feasible.The ultrasonic evaluation model based on MLR has a higher accuracy and more balanced evaluation for two parameters.

According to the maximum solid solubility of Zn， Mg， Cu in aluminum and their precipitation strengthening phases， Al-12Zn-2Mg-0.5Cu-0.3Sc high strength aluminum alloy is designed. The billet of this alloy is hot rolled followed by clod rolling and heat treatment to explore the optimal heat treatment process for aluminum alloy with high solid solubility to obtain good tensile properties. Optical microscopy （OM）， X-ray diffractometry （XRD） ， and scanning electron microscopy （SEM） are used to observe and analyze the microstructure of the alloy under different heat treatment conditions， and universal tensile testing machine is used to test the tensile properties of the alloy at room temperature. The results show that after solution treatment of 470 ℃/1 h， the microstructure of the cold-rolled alloy is incomplete recrystallized with elongated grains along the rolling direction. The ultimate tensile strength of the alloy is 599 MPa， and the elongation reaches 15.4%. After aging treatment of 120 ℃/30 h， fine η （MgZn₂） and T（AlZnMgCu） strengthened phases precipitate in the microstructure， which further improve the properties of the alloy. The corresponding tensile strength reaches 736 MPa， and the elongation is 10.6%.

To promote the further application of high-strength aluminum alloys in the aviation field，the 7050-T7451 aluminum alloy with 4 mm thickness is carried out by laser-melt inert-gas（MIG）hybrid welding. The results show that a well-formed weld seam can be obtained with reasonable matching of welding parameters，while welding at higher speeds is easy to produce cracks. When the welding speed is controlled at 0.9 m/min or below，and the weld back-width ratio is controlled above 0.4，the cracks and porosity defects can be effectively suppressed. The weld zone is mainly composed of equiaxed grain structures with significant differences in size. Near the fusion zone，there is a fine-grained layer approximately 20-50 μm wide，and only a minimal amount of columnar grains forms adjacent to this fine-grained layer. No phase transformation or recrystallization occurs in the heat-affected zone. The as-welded joint achieves an average tensile strength of approximately 377 MPa， equivalent to about 73% of the base metal strength， significantly outperforming the tensile properties of laser self-fusion welded joints.

To study the corrosion behavior and differences between 1070A and 6063 aluminum alloys in simulated marine atmospheric environments， the corrosion processes of 1070A and 6063 aluminum alloys in marine atmospheric environments are simulated by indoor cyclic salt spray experiments. The corrosion morphology， pitting parameters and the corrosion products of the 1070A and 6063 aluminum alloys are observed and detected by ultra-depth-of-field microscope and X-ray diffractometer respectively. The corrosion mass loss of 1070A and 6063 aluminum alloys is analyzed by corrosion kinetics methods. The differences of corrosion behaviors between the 1070A and 6063 aluminum alloys are analyzed by electrochemical impedance and polarization curves. The test results show that pitting corrosion is the main corrosion form on 1070A and 6063 aluminum alloys in the simulated marine atmospheric environment. With the extension of corrosion time， the average pitting depth， the maximum pitting depth and the pitting density gradually increase. The corrosion behaviors of 1070A and 6063 aluminum alloys are similar in the early stage of corrosion test. However， the pitting depth and pitting density of 6063 aluminum alloy doubled in the later corrosion stage， which is due to the re-cracking of the surface corrosion layer， resulting in a serious increase in the corrosion degree of 6063 aluminum alloy. What’s more， the corrosion mass loss and corrosion time of both 1070A and 6063 aluminum alloys show a power exponential relationship. Combined with the analysis of electrochemical impedance spectra and polarization curves， it is confirmed that the 6063 aluminum alloy is more susceptible to corrosion in simulated marine atmospheric environments， with a higher degree of corrosion compared to 1070A aluminum.

To investigate the impact of substrate roughness， crystal type， and coefficient of thermal expansion （CTE） on the stress of electroplated copper films， an experiment is conducted utilizing four distinct substrate types： smooth sapphire， rough sapphire， amorphous sintered alumina， and pure copper. The copper films are electroplated onto the substrate surfaces and subsequently annealed. Pre- and post-annealing measurements are taken to assess warp and a stress. Electron backscatter diffraction （EBSD） is employed to study the microstructural transformation of the copper films. The experimental results reveal that annealing transforms the copper film stress from compressive to tensile， with stress levels decreasing in the order of sintered alumina， smooth sapphire， rough sapphire， and pure copper substrates. Additionally， annealing leads to significant grain growth. Analysis indicates that post-annealing copper film stress arises from CTE mismatch and volume shrinkage. Stress reduction in copper films can be achieved by selecting rough single-crystal substrates and materials with CTEs close to that of copper. These experimental findings contribute valuable insights to the study of electroplating stress and the selection of appropriate electroplating.

To study the impact of V-notch radius on the mechanical properties of TA15 titanium alloy，tensile，stress-rupture，fatigue tests and fracture analysis are conducted on both smooth specimens and those with varing V-notch radii. By using the finite element method，the distribution of the stress-strain field at the notch is analyzed，the relationship between the stress-strain field and the notch strength，stress-rupture time，fatigue life and fracture behaviour of TA15 titanium alloy are further investigated. The results show that under static loading，as the notch radius decreases from 0.85 mm to 0.15 mm，both the tensile strength and stress-rupture time of TA15 titanium alloy increase，while the proportion of the shear-plastic zone in fracture decreases. Stress triaxiality around the notch initially increases and then decreases as it extends inward from the root of the notch，as determined by finite element analysis. The fracture originates from the peak position of stress triaxiality （near the notch root）. During the prolonged stress-rupture tests，stress redistribution around the notch occurrs，resulting in a strengthening effect at the notch. Under dynamic loading，the fracture surface of the notched specimen exhibits multi-source crack propagation. Different stress concentrations and gradients around the notch result in varying degrees of fatigue damage. As the notch radius decreases，the size of the critical fatigue damage area decreases，effective stress increases，leading to a decrease in fatigue life and the proportion of crack propagation zones.

Austenite reversion heat treatment is a proven strategy for enhancing the mechanical properties of 300M steel； however， the phase transformation mechanisms governing austenite evolution during this process remain inadequately understood. This study employs in-situ electron backscatter diffraction （EBSD） to systematically investigate the microstructural evolution and crystallographic characteristics of 300M steel during high-temperature austenite reversion. Results demonstrate that during isothermal holding above the austenitizing temperature， martensite transforms into two distinct austenite morphologies： needle-shaped austenite （γ_（A））， which retains the orientation of the original martensite， and spherical austenite （γ_（G）） with a random orientation. Notably， γ_（A） preferentially nucleates and grows within the grains， maintaining a Kurdjumov-Sachs （K-S） orientation relationship with the surrounding martensitic blocks. Consequently， most of the γ_（A） phase shares the same orientation and size as the initial austenite phase， hindering the refinement of the final microstructure. In contrast， γ_（G） has a small grain size and nucleates at the grain boundaries of the original austenite as well as within the newly formed γ_（A） crystals. γ_（G） lacks a K-S orientation relationship with the untransformed martensite and adopts a random orientation， playing a crucial role in refining the final microstructure. Furthermore， heating temperature and duration exhibit significant control over the completeness of martensite-to-austenite transformation， with γ_（G） propagating into the matrix via diffusion-driven growth kinetics. These findings elucidate the dual-phase transformation pathways and their distinct roles in microstructural evolution， offering a mechanistic foundation for optimizing heat treatment protocols to achieve tailored microstructures in 300M steel.

The service performance and operation life of thermal barrier coatings are closely related to the phase composition and structure of the bond coat alloy， which is directly determined by its composition. In this work， the effects of the basic elements Co and Al and the modified element Zr on the precipitation behavior of equilibrium phases are analyzed by Thermo-Calc software. Then， the influence of Zr content on phase composition and Zr-rich phase distribution of NiCoCrAlY bond coat alloy is investigated using an X-ray diffractometer and a field emission scanning electron microscope. Thermodynamic calculation results show that the σ-CoCr phase begins to precipitate in the alloy with 10%（mass fraction， the same below）Co， and the maximum precipitation amount （mole fraction） of σ-CoCr phase increases from 0.055 to 0.229 when the Co content increases from 10% to 16%， and it exists in the high-temperature service range of coatings with Co content exceeding 14%. When the Al content is 8%-10%， the γ-Ni phase precipitates from the liquid before the β-NiAl phase， which is opposite in the alloys containing 12%-16%Al. Moreover， with the increase of Al content from 8% to 16%， the solidification interval significantly enlarges from 75 ℃ to 171 ℃， and the β-NiAl content continuously increases. When the Zr content increases from 0.15% to 1.0%， the liquidus temperature obviously decreases from 1264 ℃ to 1136 ℃， and the solidification temperature range enlarges from 151 ℃ to 275 ℃. In addition， the non-equilibrium phase composition at room temperature of the bond coat alloy designed based on thermodynamic calculation is composed of β-NiAl and γ'-Ni₃Al matrix phases， and a small amount of α-Cr precipitate on the matrix. Meanwhile， Ni₅Y is distributed surrounding γ'-Ni₃Al phase. For the alloy containing 0.5% and 1.0%Zr， the precipitation position of H_L21 phase is different. This Zr-rich phase mainly precipitates at the interface of β-NiAl/γ'-Ni₃Al for the former， while it also precipitates on the β-NiAl matrix phase for the latter.

To improve the service temperature of high-temperature components in engines and search for high-temperature resistant and high thermal insulation thermal barrier coating materials to replace YSZ， a high entropy rare earth zirconate ceramic material is designed based on a multi-element rare earth doping modification strategy， combined with the phase structure formation law， size disorder， and thermal conductivity theory of rare earth zirconate. The A-site high entropy of rare earth zirconate is synthesized using solid-phase synthesis method to prepare two high entropy ceramic materials （Sm_0.2Gd_0.2Eu_0.2Lu_0.2Dy_0.2）₂Zr₂O₇. The microstructure， phase stability， and thermal physical properties of high entropy ceramic materials are studied. The results indicate that （Sm_0.2Gd_0.2Eu_0.2Lu_0.2Dy_0.2）₂Zr₂O₇ ceramic material has a defect fluorite structure， a dense ceramic material structure， no obvious defects， and the synthesized ceramic material configuration entropy shows that it belongs to a high entropy system； after sintering at 1400 ℃， the （Sm_0.2Gd_0.2Eu_0.2Lu_0.2Dy_0.2）₂Zr₂O₇ ceramic material shows no significant grain growth， no precipitation of single oxides phases， and exhibits good high-temperature stability； at 1000 ℃ and 1200 ℃， the thermal conductivity of （Sm_0.2Gd_0.2Eu_0.2Lu_0.2Dy_0.2）₂Zr₂O₇ ceramic material is 1.781 W·m^-1·K^-1 and 2.056 W·m^-1·K^-1， respectively. Compared with conventional rare earth zirconate and YSZ materials， it has lower thermal conductivity and is a promising material for ultra-high temperature thermal barrier coatings.

Carbon fiber reinforced thermoplastic composites（CFRTP） have superior comprehensive mechanical property，as well as rapid prototyping，weldability and recyclability.The application of CFRTP are gradually increasing in aerospace，vehicle manufacturing and other fields.Ultrasonic welding is recognized as one of the most suitable methods for CFRTP.With the increase of the application of CFRTP in aerospace main load-bearing structures，the discrete solder joints in the form of traditional ultrasonic spot welding are difficult to meet the requirement of the strength of them.Accordingly，foreign scholars have proposed ultrasonic continuous welding technology to realize the seam welding connection of CFRTP structures，which has not been reported in domestic literature.In this paper，the research results of CFRTP ultrasonic continuous welding are reviewed from four aspects：CFRTP ultrasonic continuous welding equipment，joint design，process characteristics and quality inspection.The scientific problems and technical bottlenecks to be solved in CFRTP ultrasonic continuous welding are discussed，so as to provide a reference for the development of CFRTP ultrasonic continuous welding technology of our country.