Influence of microstructure on the mechanical

Effect of Homogenization and Aging Treatment on Mechanical Properties and Stress-Corrosion Cracking of 7050 Alloys

“…This implies that the SQA treatment can effectively improve SCC resistance in the 7050 alloy via controlling the expected GBP microstructure, as reported in earlier studies. [12,13,[22][23][24] For the 7075 alloy, although the SQA decreases the UTS seriously, as just mentioned, the GBP act upon it in a way similar to that in the 7050 alloy. Figures 17(a) through (d) show the coarse GBP together with the large interparticle spacing and wide PFZs of the SQA-1 tempered alloy in various homogenization conditions, as have been seen in the 7050 alloy.…”

“…[1,2] However, the larger size and spacing of the GBP is helpful in resisting the SCC. [10][11][12][13][22][23][24] Therefore, attainment of both optimum strength and SCC resistance may be possible by controlling the morphology of both the GBP and the precipitates in the matrix. The proposed SQA treatment applied to the 7050 alloy, as described previously, is designed to control the characteristics of microstructures mentioned here.…”

“…The major microstructural features are focused on the precipitate-free zone (PFZ), matrix precipitates, and grain-boundary precipitates (GBP). [10][11][12][13][14] Adler and Poulose [12,13] claimed that SCC BIN resistance could be improved by increasing the size and spacing of the GBP and by widening the PFZ. Green et al [15] indicated that Zn and Mg elements may accumulate at the PFZ, resulting in the increase in SCC susceptibility.…”

“…There is considerable evidence showing that SCC resistance could be improved by increasing the size and spacing of GBP. [6,[10][11][12][13][22][23][24] Since the larger precipitates of g in the grain boundary act as trapping sites for atomic hydrogen to nucleate hydrogen bubbles, the hydrogen concentration can be reduced below a critical value, therefore retarding the hydrogen embrittlement and improving the SCC resistance. For the alloy with large-spacing GBP, the coalescence of cracks is retarded due to the larger individual segment of crack; therefore, the propagation rate of crack can be effectively reduced and, thus, the SCC resistance is increased.…”

Microstructures and mechanical properties of ultrafine grained 7075 Al alloy processed by ECAP and their evolutions during annealing

“…In either case, higher density of precipitates leads to higher strength. For naturally aged 7075 Al alloy, the dislocation cutting of the G-P zones and g 0 fine plates is the main strengthening mechanism, because the strong atomic bonds in the zones can effectively hinder dislocation motion [38][39][40]. Both XRD and HREM revealed that the volume fraction of the G-P zones in the UFG sample is larger than that in the CG sample.…”