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The hot deformation behavior and hot rolling based on the hot processing map of a nano-Y2O3 addition near-α titanium alloy were investigated. The isothermal compression tests were conducted at various deformation temperatures (950–1070 °C) and strain rates (0.001–1 s−1), up to a true strain of 1.2. The flow stress was strongly dependent on deformation temperature and strain rate, decreasing with increased temperature and decreased strain rate. The average activation energy was 657.8 kJ/mol and 405.9 kJ/mol in (α + β) and β region, respectively. The high activation energy and peak stress were contributed to the Y2O3 particles and refractory elements comparing with other alloys and composites. The deformation mechanisms in the (α + β) region were dynamic recovery and spheroidization of α phase, while the β phase field was mainly controlled by the dynamic recrystallization and dynamic recovery of β grains. Moreover, the constitutive equation based on Norton–Hoff equation and hot processing map were also obtained. Through the optimal processing window determined by the hot processing map at true strains of 0.2, 0.4 and 0.6, the alloy sheet with multi-pass hot rolling (1050 °C/0.03–1 s−1) was received directly from the as-cast alloy. The ultimate tensile strength and yield strength of the alloy sheet were 1168 MPa and 1091 MPa at room temperature, and 642 MPa and 535 MPa at 650 °C, respectively, which performs some advantages in current research.

Due to the excellent structural and functional properties, such as low density, high fracture toughness and fatigue strength, Al-Cu-Mg (2024 aluminum) alloy has become an attractive light weight material for inertial instruments and aerospace applications. However, it has relatively low dimensional stability. The aim of this investigation is to enhance the dimensional stability of 2024 aluminum alloy via two-stage aging method, and identify the precipitation behavior and the underlying stabilizing mechanisms of 2024 aluminum alloy. When the second aging time was 24 h, the uniformly distributed precipitates could effectively pin the dislocations and impede their movement. This leaded to a significant improvement of the micro-yield strength and the thermal strain in the 2024 aluminum alloy, and thus the dimensional stability of the alloy increased.

The effect of nano-Y2O3 addition on microstructure and tensile properties of high-Al TiAl alloys prepared by induction skull melting is investigated. The result shows that the addition of nano-Y2O3 affords an obvious refinement in lamellar colony due to the heterogeneous nucleation. A crystallographic model is used to predict the α and γ nucleation potencies of Y2O3 particles during solidification. Besides, Y2O3 induces the solidification pathway of TiAl alloys into high-Al side, resulting in the increase of γ phase. Owing to fine grain strengthening and second phase strengthening, the tensile strength and elongation of TiAl–Y2O3 alloys are enhanced significantly at room temperature.

In this work, the β and (α+β) forging deformation were conducted on (TiB + TiC + Y2O3)/α-Ti composite to investigate the effect of reinforcement on dynamic recrystallization and globularization behavior. During β deformation, the reinforcements not only accelerated discontinuous dynamic recrystallization by particle stimulated nucleation mechanism, but also promoted the heterogeneous nucleation of α phase thus conducted the {0001}α pole figure of composite more widely distributed. However, during (α+β) deformation, the microstructure was characteristic of kinked α colonies morphology. Moreover, compared to matrix, the (TiB + TiC + Y2O3)/α-Ti composite depicted a more homogeneous microstructure and larger crystallography rotation both along or transverse to the α lamellar. The distribution of Schmid factor value indicated that the deformation behavior of matrix showed varies with the α colony while it was more homogeneous in composite. Reinforced with (TiB + TiC + Y2O3) reinforcements, on the one hand, the random SF value of composite conducted the incompatibility slip between adjacent α lamellar thus at last leaded the formation of HABs in inter-lamellar; on the other hand, the reinforcement itself could obstruct dislocation that accelerated the dynamic globularization behavior. Therefore, the (TiB + TiC + Y2O3)/α-Ti composite had a great advantage in optimizing microstructure especially globularization that made the composite of great application prospect.

The as-extruded TiB whisker reinforced Ti6Al4V (TiBw/Ti6Al4V) composites with tailored architecture were fabricated by powder metallurgy followed by hot extrusion. High temperature tensile tests were conducted to study the superplastic deformation behavior at 900 °C, 925 °C, 950 °C and 975 °C with strain rates of 0.000316/s, 0.001/s and 0.00316/s, respectively. Microstructural observation showed that the fraction of β transformed microstructure increased with increasing strain, which indicated that the phase transformation was drastically affected by hot deformation. Voids next to the TiBw reinforcements were observed due to the incoordination deformation at small strain, but this kind of voids was refilled at large strain, which is attributed to the combined processes of recrystallization and coordination deformation. Furthermore, new voids were formed at the α/β interface at large strain, considered to be caused by the incoordination of phase boundary sliding. EBSD results implied that the texture intensity decreased during the superplastic tensile process due to recrystallization and grain rotation. TEM analysis revealed that the grains next to the TiBw reinforcements presented a higher dislocation density forming new boundaries by recrystallization. This effect led to grain refinement which was beneficial to grain boundary sliding, which resulted in the composites' high elongation.

The hot forging of the 2024Al/Al18B4O33w composite fabricated by the squeeze casting technique was carried out at 450 °C to improve the ductility. The microstructure and tensile properties of the as-cast and forged 2024Al/Al18B4O33w composites are studied. Non-homogeneous distribution of the reinforcement whiskers was revealed in the as-cast composite. The forging led to significant variations in the average length and distribution of the reinforcement whiskers in comparison with the as-cast composite. After forging, the tensile tests showed an increase in the ultimate tensile strength at room temperature and a decrease at elevated temperature. The forging highly increased the ductility both at room and elevated temperature.

The Ti–(SiC p /Al) laminated composite was prepared by roll bonding of pure Ti and SiC p /Al foils. The microstructure analysis shows that the work-hardening of Ti reduces the deformation compatibility of the Ti and SiC p /Al layers with increasing the rolling reduction. A nano-sized TiAl 3 interfacial layer was formed at the interface between the Ti and SiC p /Al layers, which resulted in a good interlaminar bonding strength and an improved ductility of the laminated composite due to the nano-sized effect. A good strength–ductility balance, 307 MPa yield strength and 21.4% elongation to failure, was achieved. Combining with the low density of 3.62 g/cm 3 , 20% lower than that of Ti, this Ti–(SiC p /Al) laminated composite presents the potential application in the aerospace field.

In the present work, TiAl 3 layers were synthesized by reaction annealing of a multi-laminated Ti-(SiC P /Al) composite at 650 °C. It was found that Si dissolved in the TiAl 3 layers during annealing. The effect of Si in the TiAl 3 layers on mechanical properties was investigated both by experiment and theory. The experimental results show that after annealing at 650 °C for 3 h, the solid solubility of Si in the TiAl 3 layer is about 6 at%, which leads to the lattice distortion of TiAl 3 . Due to the solid solution of Si in TiAl 3 , the elastic modulus and nanohardness increased up to 280 Gpa and 10.7 Gpa, respectively. Furthermore, the mechanism of increased modulus due to the solid solution of Si is verified by first-principles calculation of the theoretical elastic properties and can be explained from the electronic structure: (i) a new hybridization between Si3s and Al3s; (ii) primarily covalent interactions along Al3Si bonds.

The coarse insoluble intermetallic phase in 2024Al was refined to nanometer scale by an effective powder metallurgy approach, which involved atomization to form oversaturated solution powder, high energy ball milling to produce a high dislocation density and fine grains in the powder, and sintering to generate highly dispersed nanosized intermetallic particles. The structure of refined nanosized intermetallic particles have been determined to be an ordered body center cubic with a lattice parameter of a = 12.65 A for the first time. The nanosized intermetallic particles play a positive role in enhancing dispersion-strengthening effect and thermal stability of 2024Al alloy. This refined approach can be applied to many commercial alloy systems that contain insoluble coarse intermetallic phases.

Aluminum matrix hybrid composite reinforced with tungsten oxide particles (WO 3p ) and aluminum borate whiskers (ABOw), which have great specific gravity difference was fabricated by squeeze casting. The hybrid composite was observed by scanning electron microscope (SEM). The ultimate tensile strength, yield strength and elastic modulus of the hybrid composite are higher than those of matrix, but the elongation of the hybrid composite is relatively low. On the fractured surfaces of the composite the WO 3p fractured and ABOw debonded from the matrix. The bonding strength of interface between reinforcements and matrix was found to be very weak comparatively.

A novel in situ Al12W particles reinforced aluminum matrix composite was synthesized by reaction sintering of tungsten and aluminum powders and followed by hot extrusion. The microstructures were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The tensile tests of composite and pure aluminum materials were measured. The XRD analysis identifies that the in situ Al12W particles are formed by the reaction between tungsten and aluminum powders. Meanwhile, SEM observation shows that the Al12W particles are distributed uniformly in the Al matrix, and TEM observation shows that the interfacial condition of Al12W particles and Al is good. It is found from the tensile tests that the in situ synthesized Al12W particles can significantly enhance the strength of the composite in spite of decreasing elongation. The fracture morphology analysis reveals that the fracture mode of composite is ductile fracture.

Titanium matrix composite reinforced by in situ TiB whisker and TiC particle was prepared by reactive hot-pressing of the blended powder of Ti and B4C. The microstructure of the composite was studied by SEM and TEM. The symbiosis structure of TiC particle and TiB whisker was found apparently. The results showed that the position of TiC particle to TiB whisker was relatively fixed, and TiCp was more likely to grow up on the (101)TiB and (101(_))TiB planes but seldom on the (100)TiB plane. The fabrication method of the composite, reaction mechanism of Ti and B4C, and the surface microstructure of TiB whisker were taken into consideration to explain the phenomenon.