In this paper,the microstructure and hardness of HG980D heat-affected zone (HAZ) at different cooling rate t8/3 were studied,the implant critical fracture stress under three diffusible hydrogen conditions were measure...In this paper,the microstructure and hardness of HG980D heat-affected zone (HAZ) at different cooling rate t8/3 were studied,the implant critical fracture stress under three diffusible hydrogen conditions were measured,and the hydrogen-induced cracking (HIC) fractograph of steel HG980D were analyzed. The experimental results show that martensite exists in HAZ of HG980D till t8/3≥150 s,the harden quenching tendency of HG980D is greater; The implant critical fracture stress is related to diffusible hydrogen content significantly,at low hydrogen level,high restraint stress is needed to nucleate HIC,the fractograph is mainly microvoid coalescence,but at high hydrogen level,only small restraint stress can cause HIC occurrence,the fractograph is mainly quasicleavage. It is very important to choose ultra-low hydrogen welding consumable to weld steel HG980D to prevent hydrogen-induced cracking.展开更多
Double change channel angular extrusion(DCCAE) was performed in dual-phase Mg-9.5Li-3Al-1.6Y(wt.%) alloy to develop fine-grained microstructures. The microstructure evolution during DCCAE and conventional extrusion(CE...Double change channel angular extrusion(DCCAE) was performed in dual-phase Mg-9.5Li-3Al-1.6Y(wt.%) alloy to develop fine-grained microstructures. The microstructure evolution during DCCAE and conventional extrusion(CE) was investigated. The microstructure of the extruded dual-phase Mg-Li alloy consisted of recrystallized β-Li grains, banded α-Mg phases, and Al_2Y phases distributed in β-Li phases and phase-interface uniformly. Compared with CE, the specimens after DCCAE had smaller β-Li grain size(3–5 μm by the DCCAE and 6–10 μm by the CE) and the α-Mg phases were refined during the DCCAE. The distribution of the Al2 Y phases was improved a lot by DCCAE. Furthermore, the specimens after DCCAE had better tensile strength than conventional extrusion ones.展开更多
文摘In this paper,the microstructure and hardness of HG980D heat-affected zone (HAZ) at different cooling rate t8/3 were studied,the implant critical fracture stress under three diffusible hydrogen conditions were measured,and the hydrogen-induced cracking (HIC) fractograph of steel HG980D were analyzed. The experimental results show that martensite exists in HAZ of HG980D till t8/3≥150 s,the harden quenching tendency of HG980D is greater; The implant critical fracture stress is related to diffusible hydrogen content significantly,at low hydrogen level,high restraint stress is needed to nucleate HIC,the fractograph is mainly microvoid coalescence,but at high hydrogen level,only small restraint stress can cause HIC occurrence,the fractograph is mainly quasicleavage. It is very important to choose ultra-low hydrogen welding consumable to weld steel HG980D to prevent hydrogen-induced cracking.
基金Project supported by the Fundamental Research Funds for the Central Universities(106112015CDJXY130011)
文摘Double change channel angular extrusion(DCCAE) was performed in dual-phase Mg-9.5Li-3Al-1.6Y(wt.%) alloy to develop fine-grained microstructures. The microstructure evolution during DCCAE and conventional extrusion(CE) was investigated. The microstructure of the extruded dual-phase Mg-Li alloy consisted of recrystallized β-Li grains, banded α-Mg phases, and Al_2Y phases distributed in β-Li phases and phase-interface uniformly. Compared with CE, the specimens after DCCAE had smaller β-Li grain size(3–5 μm by the DCCAE and 6–10 μm by the CE) and the α-Mg phases were refined during the DCCAE. The distribution of the Al2 Y phases was improved a lot by DCCAE. Furthermore, the specimens after DCCAE had better tensile strength than conventional extrusion ones.
