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The effect of the addition of 0.1 wt% Sc and 0.1 wt% Er on the deformation microstructure, Vickers microhardness, and electrical conductivity of Al-0.2 wt% Zr-based alloy cables annealed at 400 °C for different times was investigated. The comprehensive properties of Al-0.2Zr-0.1Sc were better than those of Al-0.2Zr-0.1Er. The optimal conditions for the Al-0.2Zr-01Sc alloy cable were a microhardness of 575 MPa, an electrical conductivity of 34.5 MS/m for an annealing time of 36 h, and those for the Al-0.2Zr-0.1Er alloy cable were a microhardness of 550 MPa, an electrical conductivity of 33.6 MS/m for an annealing time of 8 h. During the annealing process, dispersed Al3(Zr,Sc/Er) precipitates were generated, which substantially impeded recrystallization by Zener pining of grain boundaries. Based on the ratio of volume fraction (FV) to average diameter ( d ¯ ) of the precipitates, their capability to inhibit recrystallization was as follows: Al3(Zr, Sc) > Al3(Zr, Er) > Al3Zr. Moreover, the electrical conductivity of Al-0.2Zr-0.1Sc was better than that of Al-0.2Zr-0.1Er, probably because Sc could better inhibit recrystallization than Er, leading to fewer grain boundaries and hence lesser electron scattering.

The effects of Sc additions and isothermal aging on the microstructure and mechanical properties of 2055 aluminum alloy have been investigated. The isothermal aging temperatures investigated were 175 °C and 200 °C. Results show that the aging temperature does not affect the type of precipitates in both Sc-free and Sc-added 2055 Al alloys. While remarkable changes in the size and number density of T1 (Al2CuLi) precipitates have been observed. For samples aged at 175 °C for 8 h, the average length of T1 precipitates was increased from 39.9 nm to 45.6 nm, the number density decreased from 5.77 × 1022 m−3 to 3.68 × 1022 m−3 after Sc addition. On the contrary, when samples were aged at 200 °C for 8 h, the length decreased from 59.89 nm to 43.32 nm and number density increased from 2.13 × 1022 m−3 to 3.00 × 1022 m−3 by adding trace Sc. Slight deterioration of tensile strength and yield strength with higher ductility was founded at the aging temperature of 175 °C for 8 h due to the larger size and lower number density of T1 precipitates along with the formation of a W (AlCuSc) phase during the casting or homogenization processes. When aging temperature increased to 200 °C, tensile strength and yield strength were significantly improved by Sc addition without losing ductility. Highly dense fine T1 precipitates take responsible for the strength improvement, and to some extent it compensated the strength loss caused by the formation of W phase. A “vacancy-prison” mechanism was adopted to explain the effect of Sc additions on the precipitation of T1 phase as a function of aging temperature.

The morphological evolution of the stress-induced α″ martensite with increases in the stretching and rolling deformation degrees as well as the related orientation relationship were investigated in a β titanium alloy (Ti–19Nb–1.5Mo–4Zr–8Sn)·For a stretching deformation of 1%, the α″ martensite exhibited a packet morphology consisting of parallel lamellar structures. On the other hand, in the 2%-rolled sample, the α″ martensite exhibited a long lath-like distribution, which was accompanied by a few small pieces. With an increase in the deformation degree, the α″ martensite gradually exhibited a ladder-like structure consisting of long and short α″ laths or ellipsoids. The existence of these self-accommodating martensitic variants decreased the elastic energy. The parallel α″ laths present within a single packet were found to have the same orientation. The interface between the α″ and β phases was coherent, and their lattice constant relationships were identified as 2 a β ≈ b α ″ ≈ c α ″ and aβ ≈ aα″. Further, with the increase in the deformation degree, the hardness of the alloy first decreased and then increased; this was the case both the stretched as well as the rolled samples.

The creep behavior and microstructural evolution of 8030 alloy at 90–150 °C and 50–90 MPa of applied tensile stress were investigated by creep testing and transmission electron microscopy. The 8030 alloy possesses excellent creep resistance at low temperatures. The sizes of a small number of subgrains increase during the creep process due to subgrain merging. An Al 3 Fe phase non-uniformly pinned on the subgrain boundary made the pinned subgrains difficult to merge with the surrounding subgrains. At 90–120 °C/50–90 MPa, the stress exponent n was 5.1–5.7 and the activation energy Q c was 49.7–66.5 kJ/mol, suggesting that dislocation climb controlled by the grain boundary diffusion is the primary creep mechanism. At 150 °C, the ability of Al 3 Fe secondary phase to hinder the dislocations significantly decrease. When the tensile stress is 50–70 MPa, n = 6.8 and Q c = 49.7–66.5 kJ/mol, but n = 10.0 at a stress of 90 MPa. A creep activation energy of 123.2 kJ/mol is close to that of the lattice self-diffusion in aluminum, implying that a lattice self-diffusion mechanism is dominant at 150 °C/90 MPa.

The stress corrosion cracking (SCC) behavior of Ti-6Al-4 V alloy with different lamellar α microstructures in simulated oilfield brine was investigated in this study. The SCC susceptibility of the Widmanstatten sample was 11.0%, lower than that of the bimodal and trimodal samples (19.9%, and 18.0%, respectively). In the Widmanstatten sample, the crack growth path transitioned from a zigzag to a linear path when the crack moved from one colony to another because of the sliding variations in the slip bands with different orientations. The decrease in a SCC resistance of bimodal and trimodal samples resulted from the decrease in α/β colony size. Owing to the larger thickness and different orientation of lamellar α, the trimodal sample exhibited a slightly higher SCC resistance and more circuitous crack propagation than that in the bimodal sample. The deflection angle of the crack increased with an increase in the angle between the slip system, and the favorable slip system was prismatic in three samples. It can be concluded that one of the strategies to improve the SCC and crack growth resistance of Ti-6Al-4 V alloy in oil field applications is to tailor the lamellar α microstructure with different orientations and larger α colonies.

Effect of Ag addition on the age hardening and precipitation behavior of an Al-Cu-Li-Mg-Zn-Mn-Zr alloy has been investigated by transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) with an energy dispersive X ray spectroscope (EDS), convergent beam electron diffraction (CBED) and hardness. The results showed that the precipitation behavior of the Ag free Al-Cu-Li-Mg-Zn-Mn-Zr alloy was SSS → δ′/GP zone/δ′ + T1 → cubic σ phase + θ′ + T1 + S′/S phase, while in the Ag added Al-Cu-Li-Mg-Zn-Mn-Zr alloy, it was SSS → θ′ + δ′ + T1 → θ′ + δ′ + T1 + S′/S phase. The Ag added alloy exhibited higher strength than the Ag free alloy due to a promoted T1 precipitation, while the hardness loss of the Ag free alloy was smaller than that of the Ag added alloy due to the precipitation of cubic σ phase. Ag was mainly concentrated in T1 precipitates and stimulated the precipitation of T1 rather than providing nucleation sites for cubic σ phase. Hence, the precipitation of cubic σ phase was suppressed by competing with T1 for solutes in the Ag added Al-Cu-Li-Mg-Zn-Mn-Zr alloy.

The effects of deformation ageing treatment (DAT) on the microstructure and properties of aluminum alloy 2618 were investigated. The alloy was subjected to deformation ageing treatment which included solution treating at 535 °C quenching into water at room-temperature, cold rolling (10%) and further ageing to peak hardness level at 200 °C. The electron microscopic studies revealed that the treatment affects the ageing characteristics and the coarsening of ageing phase (S′) at elevated-temperature. The dislocation-precipitate tangles substructure couldn't be found in alloy 2618. The tensile and hardness tests showed that deformation-ageing treatment causes a significant improvement in tensile strength and hardness to alloy 2618 at room- and elevated-temperature.