The restoration mechanism (RM) and subgrain characteristics of 0.05C-1.52Cu-1.51Mn steel in single-hit plane strain compression (PSC) were investigated using a thermomechanical simulator (Gleeble). It was observed that at diminished deformation temperature (DT) and larger strain rate, the austenitic phase (during deformation) showed some thermal/dynamic softening (TH/DRS), but it did not reach the condition where the "work hardening rate" (WH rate)became constant with the stress, i.e., dynamic recovery (DRV) softening balances work hardening (WH). However, it was observed that at higher DT and lower strain rate, the "WH rate" for samples deformed at 850 ℃ (at a strain rate of 0.01 s⁻¹), 950 ℃ (at strain rates of 0.1 and 0.01 s⁻¹) and 1000 ℃ (at strain rates of 0.1 and 0.01 s⁻¹) increased to negative peak, and then decreased to almost zero (for samples deformed at 950 and 1000 ℃ at a strain rate of 0.01 s⁻¹), which is the onset of steady-state flow. When the sample deformed at 750 ℃ followed by quenching, the microstructure was indicative of a deformed microstructure rather than a transformed microstructure. It was observed that there was an increase in the extent of substructure formation and a decrease in mean subgrain size with increasing strain rate. When samples deformed at 850,950 and 1000 ℃, these temperature ranges were above Ar₃ temperature. Hence quenching would lead to a phase transformation and hence the deformed microstructure would be eliminated. The room temperature microstructures when the sample deformed at a strain rate of 1 s⁻¹, were nicely equiaxed and clean with no dislocations present. However, at lower strain rates of 0.1 and 0.01 s⁻¹, microstructure showed substructures.

Aluminium is considered a green metal due to its environmental responsive characteristics. The 7475-T7351 aluminum alloy is extensively used in automotive and aerospace applications due to its light weight and high strength. In the present work, the effects of the corrosive environment on the high cycle fatigue (HCF) behaviors of the 7475-T7351 aluminum alloy was investigated. The aqueous solution of sodium chloride was used for solution treatment. The HCF test was performed on pre-cracked specimens using a servo-hydraulic universal testing machine, Instron 8800. The fractured specimens were characterized using a scanning electron microscope. It was observed that the crack propagation occurred through anodic dissolution at high stress and a significant crack tip blunting and crack extension occurred. However, no appreciable change in crack growth was noticed over the lower frequency range of 0.1 to 0.9 Hz. The slower growth rate envisages oxide debris formation between the cracked faces. When the alloy was treated under corrosive environments, the HCF tests depicted that the fatigue life reduces up to two orders of magnitude. The corrosion pits induced the crack initiation in stage-I at lower alternating stress; however, the fatigue crack growth rate (FCGR) was increased in the corrosive environment. The transition from stage-I to stage-II occurred at a lower stress intensity range (∆K) level; it was due to the combined effects of corrosion, hydrogen embrittlement, active path dissolution, and stress concentration. The corrosion fatigue test at low frequency also depicted a slower FCGR as compared to its moderate frequency counterpart and showed an irregular crack growth behavior.