Residual stress refers to self-equilibrating stress present within materials, with the potential to significantly affect manufacturing processes and performance. Therefore, accurately and quantitatively measuring residual stress is always of great importance. This study provides a comprehensive review of various characterization techniques for residual stress, including their principles, development history, applications, and limitations. Initially, several destructive techniques such as the hole-drilling method, ring-core method, deep hole drilling method, slitting method, and contour method are summarized. Subsequently, three nondestructive techniques based on X-ray/electron diffraction, magnetic signals, and ultrasonic signals are evaluated. In the final part of this overview, special attention is given to a newly-developed technique for measuring residual stress, which combines incremental focused ion beam (FIB) milling and digital image correlation (DIC). Our review aims to guide further investigations on residual stress and identify the future development of techniques for measuring residual stress.

Titanium alloy has the advantages of low thermal conductivity, a small expansion coefficient and being non-magnetic, making it an ideal low-temperature structural material. In this paper, the typical TC4 titanium alloy in industrial titanium alloy is selected as the research object. The microstructure deformation law and mechanical behavior of TC4 titanium alloy at liquid nitrogen temperature are mainly investigated, and compared with the microstructure and properties at room temperature. The macroscopic and microscopic deformation mechanism of the simultaneous increase in elongation and hardening index of titanium alloy at low temperature is revealed, which provides a basic basis for the low-temperature deformation mechanism and strengthening and toughening design of titanium alloy. Based on the uniaxial tensile tests at room temperature (298 K) and low temperature (77 K), the effects of low temperature on the yield strength, elongation, tensile strength and work hardening curve of titanium alloy were compared and analyzed. The strength/plasticity synergistic improvement of TC4 titanium alloy under low-temperature deformation was found. At low temperature, the yield strength, tensile strength and elongation of TC4 titanium alloy are improved compared with room temperature. The tensile strength increases from 847.93 MPa at 298 K to 1318.70 MPa at 77 K, and the elongation increases from 21.8% at 298 K to 24.9% at 77 K. The grain morphology, grain orientation, dislocation density and fracture morphology of titanium alloy under room temperature and low-temperature tensile conditions were studied by SEM and EBSD. The results of fracture morphology characterization at room temperature and low temperature show that TC4 titanium alloy exhibits ductile fracture characteristics and a large number of dimples are formed on the fracture surface. The dimple depth at low temperature is shallower than that at room temperature and the overall surface is more flat. Compared with room temperature deformation, the deformation process of TC4 titanium alloy in a low-temperature environment produces stronger dislocation pile-up and forms a large number of twins, but the grain rotation is more significant, which effectively alleviates the stress concentration and delays the initiation and propagation of cracks at grain boundaries.

In this study, the microstructural evolution, distribution, morphology, and change mechanism of an as-rolled Ti₂AlNb alloy were quantitatively analyzed by X-ray diffraction and electron backscatter diffraction (EBSD). The results show that after solution treatment at 900 °C, the content of the O phase alloy decreased by 2%, which provided space for the nucleation of the α₂ phase, the content of which increased by 2%. After aging treatment at 760 °C, large quantities of acicular O phase and α₂ phase were precipitated in the B2 matrix, and the content of the α₂ phase increased. As the aging temperature increased to 840 °C, the elongated α₂ phases were connected to each other at a specific angle along the grain boundary, extending to the interior of the grain. The hardness reached its maximum value of 402 HV at 760 °C. This study deepened our understanding of the formation of the α₂ phase in the microstructure of rolled Ti₂AlNb alloy, and investigates the effect of α₂ phase content on the hardness of the alloy in more depth.

The microstructures and properties of powder metallurgy Ti-45Al-10Nb (at.%) alloys fabricated by vacuum hot pressing consolidation of milled powder have been investigated. Under the sintering conditions, the alloy exhibits much fine-grained microstructure, which consists of a double phase γ + α₂ microstructure containing Ti₂AlC precipitates. Tensile properties are measured at 900 °C–1000 °C under a strain rate of 1 × 10⁻⁴ s⁻¹. This alloy displayed outstanding high-temperature tensile strength, with tensile strength (UTS) 410.2 MPa and elongation (ε) 12.5% at 900 °C, and UTS 189 MPa and ε 16.7% at 1000 °C, respectively.