This paper reviews the current state of knowledge and advances on the stress-corrosion cracking(SCC)of Ti alloys subject to harsh corrosive environments in the deep sea,and presents the knowledge gaps and future direc...This paper reviews the current state of knowledge and advances on the stress-corrosion cracking(SCC)of Ti alloys subject to harsh corrosive environments in the deep sea,and presents the knowledge gaps and future directions.A comprehensive review of classifications and applications of Ti alloys for deep-sea engineering indicates that the near-αandα+βTi alloys with high strength and great weldability are the primary selection for deep-sea equipment.The role of residual stress,microstructure types,alloying elements and corrosive environmental factors on SCC performance of Ti alloys are also summarised.It is revealed that the Ti alloys with Widmanstatten structure show the lowest SCC susceptibility,and alloying of Nb,Mo and Al elements plays a positive role in the boost corrosion resistance of passive film.Syn-ergistic effects of environmental deep-sea factors include high hydrostatic pressure,low dissolved oxy-gen content,low temperature and decreasing pH levels intensify the SCC of Ti alloys by inducing local dissolution of the passive film and facilitating hydrogen-induced cracking at crack tip.The study also highlights future research requirements in SCC of Ti alloys in deep sea:including the set-up of unified and suitable methods of in-situ and simulated experiments,modeling and predicting of SCC behaviour in real situations,and exploring practical protective strategies specifically.These findings provide a refer-ence for further SCC mechanisms research and promote the microstructure optimisation and performance improvement of the advanced Ti alloy-based material systems for deep-sea engineering.展开更多
This study investigates the stress corrosion cracking(SCC)behavior of a Mg-8Gd-3Y-0.5Zr alloy in a 3.5 wt.%NaCl solution using slow strain rate tensile(SSRT)testing.The results reveal that SCC suscepti-bility increase...This study investigates the stress corrosion cracking(SCC)behavior of a Mg-8Gd-3Y-0.5Zr alloy in a 3.5 wt.%NaCl solution using slow strain rate tensile(SSRT)testing.The results reveal that SCC suscepti-bility increases as the strain rate decreases,with hydrogen embrittlement(HE)becoming more dominant at lower strain rates,leading to brittle fracture.Anodic dissolution(AD)plays a more significant role at higher strain rates,resulting in mixed fracture modes.Additionally,the mechanical properties and SCC resistance are strongly influenced by the sample orientation.TD-oriented samples show higher SCC susceptibility than RD-oriented ones due to the alignment of Gd-and Y-rich precipitates and grain boundaries,which act as initiation sites for SCC.These precipitates form micro-galvanic couples with the Mg matrix,accelerating localized corrosion and HE.The findings provide insights into the SCC mechanisms of VW83 alloy and highlight the importance of optimizing microstructure and processing conditions to improve its corrosion resistance.展开更多
Al-Mg-Mn-Sc-Zr alloys with excellent weldability have emerged as ideal candidates for aerospace applications.Currently,the investigations on the corrosion behavior of alloys under tungsten inert gas(TIG)welding condit...Al-Mg-Mn-Sc-Zr alloys with excellent weldability have emerged as ideal candidates for aerospace applications.Currently,the investigations on the corrosion behavior of alloys under tungsten inert gas(TIG)welding conditions are insufficient.Here,the stress corrosion cracking(SCC)behavior of base metal(BM)and weld zone(WZ)of TIG welded Al-Mg-Mn-Sc-Zr alloys was investigated by using pre-cracked compact tensile samples immersed in 3.5%NaCl solution.The direct current potential drop(DCPD)method was used to record the crack propagation.The microstructure and fracture morphology of different regions of TIG welded joints were studied by SEM,EBSD and TEM,and the SCC crack propagation mechanism of BM and WZ was analyzed.The results demonstrated that the critical stress intensity factor for stress corrosion cracking(K_(ⅠSCC))of BM and WZ was 7.05 MPa·m_(1/2) and 11.79 MPa·m_(1/2),respectively.Then,the crack propagation rate of BM was faster than that of WZ,and BM was more susceptible to SCC than WZ.Additionally,the fracture mode of the BM mainly exhibited transgranular fracture,while the fracture mode of the WZ mainly exhibited intergranular and transgranular mixed fracture.Moreover,SCC crack propagation was attributed to the combined effect of anodic dissolution and hydrogen embrittlement.This study will provide experimental and theoretical basis for the wide application of TIG welded Al-Mg-Mn-Sc-Zr alloys in aerospace.展开更多
基金supported by the National Natural Science Foundation of China(Nos.51931008 and 52201090).
文摘This paper reviews the current state of knowledge and advances on the stress-corrosion cracking(SCC)of Ti alloys subject to harsh corrosive environments in the deep sea,and presents the knowledge gaps and future directions.A comprehensive review of classifications and applications of Ti alloys for deep-sea engineering indicates that the near-αandα+βTi alloys with high strength and great weldability are the primary selection for deep-sea equipment.The role of residual stress,microstructure types,alloying elements and corrosive environmental factors on SCC performance of Ti alloys are also summarised.It is revealed that the Ti alloys with Widmanstatten structure show the lowest SCC susceptibility,and alloying of Nb,Mo and Al elements plays a positive role in the boost corrosion resistance of passive film.Syn-ergistic effects of environmental deep-sea factors include high hydrostatic pressure,low dissolved oxy-gen content,low temperature and decreasing pH levels intensify the SCC of Ti alloys by inducing local dissolution of the passive film and facilitating hydrogen-induced cracking at crack tip.The study also highlights future research requirements in SCC of Ti alloys in deep sea:including the set-up of unified and suitable methods of in-situ and simulated experiments,modeling and predicting of SCC behaviour in real situations,and exploring practical protective strategies specifically.These findings provide a refer-ence for further SCC mechanisms research and promote the microstructure optimisation and performance improvement of the advanced Ti alloy-based material systems for deep-sea engineering.
基金the National Natural Science Foundation of China(Nos.52471012,52471043).
文摘This study investigates the stress corrosion cracking(SCC)behavior of a Mg-8Gd-3Y-0.5Zr alloy in a 3.5 wt.%NaCl solution using slow strain rate tensile(SSRT)testing.The results reveal that SCC suscepti-bility increases as the strain rate decreases,with hydrogen embrittlement(HE)becoming more dominant at lower strain rates,leading to brittle fracture.Anodic dissolution(AD)plays a more significant role at higher strain rates,resulting in mixed fracture modes.Additionally,the mechanical properties and SCC resistance are strongly influenced by the sample orientation.TD-oriented samples show higher SCC susceptibility than RD-oriented ones due to the alignment of Gd-and Y-rich precipitates and grain boundaries,which act as initiation sites for SCC.These precipitates form micro-galvanic couples with the Mg matrix,accelerating localized corrosion and HE.The findings provide insights into the SCC mechanisms of VW83 alloy and highlight the importance of optimizing microstructure and processing conditions to improve its corrosion resistance.
基金Project (2023GK1080) supported by the Major Special Projects of Hunan Province of China。
文摘Al-Mg-Mn-Sc-Zr alloys with excellent weldability have emerged as ideal candidates for aerospace applications.Currently,the investigations on the corrosion behavior of alloys under tungsten inert gas(TIG)welding conditions are insufficient.Here,the stress corrosion cracking(SCC)behavior of base metal(BM)and weld zone(WZ)of TIG welded Al-Mg-Mn-Sc-Zr alloys was investigated by using pre-cracked compact tensile samples immersed in 3.5%NaCl solution.The direct current potential drop(DCPD)method was used to record the crack propagation.The microstructure and fracture morphology of different regions of TIG welded joints were studied by SEM,EBSD and TEM,and the SCC crack propagation mechanism of BM and WZ was analyzed.The results demonstrated that the critical stress intensity factor for stress corrosion cracking(K_(ⅠSCC))of BM and WZ was 7.05 MPa·m_(1/2) and 11.79 MPa·m_(1/2),respectively.Then,the crack propagation rate of BM was faster than that of WZ,and BM was more susceptible to SCC than WZ.Additionally,the fracture mode of the BM mainly exhibited transgranular fracture,while the fracture mode of the WZ mainly exhibited intergranular and transgranular mixed fracture.Moreover,SCC crack propagation was attributed to the combined effect of anodic dissolution and hydrogen embrittlement.This study will provide experimental and theoretical basis for the wide application of TIG welded Al-Mg-Mn-Sc-Zr alloys in aerospace.
