High‐quality joints between titanium alloys and stainless steels have found applications for nuclear, petrochemical, cryogenic, and aerospace industries due to their relatively low cost, lightweight, high corrosion resistance, and appreciable mechanical properties. This article reviews diffusion bonding between titanium alloys and stainless steels with or without interlayers. For diffusion bonding of a titanium alloy and a stainless steel without an interlayer, the optimized temperature is in the range of 800–950°C for a period of 60–120 min. Sound joint can be obtained, but brittle FeTi and Fe‐Cr‐Ti phases are formed at the interface. The development process of a joint mainly includes three steps: matching surface closure, growth of brittle intermetallic compounds, and formation of the Kirkendall voids. Growth kinetics of interfacial phases needs further clarification in terms of growth velocity of the reacting layer, moving speed of the phase interface, and the order for a new phase appears. The influence of Cu, Ni (or nickel alloy), and Ag interlayers on the microstructures and mechanical properties of the joints is systematically summarized. The content of FeTi and Fe‐Cr‐Ti phases at the interface can be declined significantly by the addition of an interlayer. Application of multi‐interlayer well prevents the formation of intermetallic phases by forming solid solution at the interface, and parameters can be predicted by using a parabolic diffusion law. The selection of multi‐interlayer was done based on two principles: no formation of brittle intermetallic phases and transitional physical properties between titanium alloy and stainless steel.

Ferroelectric HfO2 films are usually polycrystalline and contain a mixture of polar and nonpolar phases. This challenges the understanding and control of polar phase stabilization and ferroelectric properties. Several factors, such as dopants, oxygen vacancies, or stress, among others, have been investigated and shown to have a crucial role on optimizing the ferroelectric response. Stress generated during deposition or annealing of thin films is a main factor determining the formed crystal phases and influences the lattice strain of the polar orthorhombic phase. It is difficult to discriminate between stress and strain effects on polycrystalline ferroelectric HfO2 films, and the direct impact of orthorhombic lattice strain on ferroelectric polarization has yet to be determined experimentally. Here, we analyze the crystalline phases and lattice strain of several series of doped HfO2 epitaxial films. We conclude that stress has a critical influence on metastable orthorhombic phase stabilization and ferroelectric polarization. On the contrary, the lattice deformation effects are much smaller than those caused by variations in the orthorhombic phase content. The experimental results are confirmed by density functional theory calculations on HfO2 and Hf0.5Zr0.5O2 ferroelectric phases.

Multi-walled carbon nanotubes (MWCNTs) and graphenes have been taken for novel reinforcements due to their unique structure and performance. However, MWCNTs or graphenes reinforced copper matrix composites could not catch up with ideal value due to reinforcement dispersion in metal matrix, wettability to metal matrix, and composite material interface. Taking advantage of the superior properties of one-dimensional MWCNTs and two-dimensional graphenes, complementary performance and structure are constructed to create a high contact area between MWCNTs and graphenes to the Cu matrix. Mechanical alloying, hot pressing, and hot isostatic pressing techniques are used to fabricate Cu matrix self-lubricating nanocomposites. Effects of MWCNTs and graphenes on mechanical properties and microstructures of Cu/Ti3SiC2/C nanocomposites are studied. The fracture and strengthening mechanisms of Cu/Ti3SiC2/C nanocomposites are explored on the basis of structure and composition of Cu/Ti3SiC2/C nanocomposites with formation and function of interface.

316L stainless steel (Fe–18Cr–11Ni) and a Kovar (Fe–29Ni–17Co or 4J29) alloy were diffusion-bonded via vacuum hot-pressing in a temperature range of 850–950 °C with an interval of 50 °C for 120 min and at 900 °C for 180 and 240 min, under a pressure of 34.66 MPa. Interfacial microstructures of diffusion-bonded joints were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). The inter-diffusion of the elements across the diffusion interface was revealed via electron probe microanalysis (EPMA). The mechanical properties of the joints were investigated via micro Vickers hardness and tensile strength. The results show that an Ni interlayer can serve as an effective diffusion barrier for the bonding of 316L stainless steel and the 4J29 Kovar alloy. The composition of the joints was 316L/Ni s.s (Fe–Cr–Ni)/remnant Ni/Ni s.s (Fe–Co–Ni)/4J29. The highest tensile strength of 504.91 MPa with an elongation of 38.75% was obtained at 900 °C for 240 min. After the width of nickel solid solution (Fe–Co–Ni) sufficiently increased, failure located at the 4J29 side and the fracture surface indicated a ductile nature.