For Ti-6Al-4V,a titanium alloy increasingly used in aerospace structure,selective laser melting(SLM)is an attractive additive manufacturing technology,which is attributed to its complex construction capability with hi...For Ti-6Al-4V,a titanium alloy increasingly used in aerospace structure,selective laser melting(SLM)is an attractive additive manufacturing technology,which is attributed to its complex construction capability with high accuracy and good surface quality.In order to obtain qualified mechanical properties,SLM parameters and post processing should be tailored for diverse service conditions.Fracture toughness and fatigue crack growth(FCG)behavior are critical characteristics for damage tolerance evaluation of such metallic structures,and they are affected by post processing technologies significantly.The objective of this study is to obtain the fracture toughness and fatigue crack growth behavior of Ti-6Al-4V manufactured by SLM,and to evaluate the influence of post-SLM thermomechanical treatment and surface machining.Fracture toughness and FCG tests were performed for SLM Ti-6Al-4V in three types of post processing status:as-built,heat treated and hot isostatically pressed(HIPed),respectively.Specimens with as-built and machined surface were tested.The microstructure and fractography were analyzed as well in order to investigate the relevance among manufacture process,microstructure and mechanical properties.The results demonstrate that as-built SLM Ti-6Al-4V presents poor ductility and FCG behavior due to martensitic microstructure and residual stresses.Both heat treatment and hot isostatic pressing improve the plane-stress fracture toughness and FCG performance considerably,while surface machining shows slight effect.展开更多
Hydrogen adsorption experiments were carried out in special stainless steel vessels at room temperature (298K) and under 10 MPa using self-synthesized multi-walled carbon nanotubes. In the experiments, carbon nanotube...Hydrogen adsorption experiments were carried out in special stainless steel vessels at room temperature (298K) and under 10 MPa using self-synthesized multi-walled carbon nanotubes. In the experiments, carbon nanotubessynthesized by the seeded catalyst method were pretreatedby being soaked in chemical reagents or annealed at hightemperature before they were used to adsorb hydrogen, but their capacity for hydrogen storage was still poor. Carbonnanotubes synthesized by the floating catalyst method were found to be able to adsorb more hydrogen. They have ahydrogen storage capacity of over 4% after they wereannealed at high temperatures, which suggested that theycould be used as a promising material for hydrogen storage.展开更多
基金supported by the Innovation Fund of Aircraft Strength Research Institute of China(No.16-025-03)
文摘For Ti-6Al-4V,a titanium alloy increasingly used in aerospace structure,selective laser melting(SLM)is an attractive additive manufacturing technology,which is attributed to its complex construction capability with high accuracy and good surface quality.In order to obtain qualified mechanical properties,SLM parameters and post processing should be tailored for diverse service conditions.Fracture toughness and fatigue crack growth(FCG)behavior are critical characteristics for damage tolerance evaluation of such metallic structures,and they are affected by post processing technologies significantly.The objective of this study is to obtain the fracture toughness and fatigue crack growth behavior of Ti-6Al-4V manufactured by SLM,and to evaluate the influence of post-SLM thermomechanical treatment and surface machining.Fracture toughness and FCG tests were performed for SLM Ti-6Al-4V in three types of post processing status:as-built,heat treated and hot isostatically pressed(HIPed),respectively.Specimens with as-built and machined surface were tested.The microstructure and fractography were analyzed as well in order to investigate the relevance among manufacture process,microstructure and mechanical properties.The results demonstrate that as-built SLM Ti-6Al-4V presents poor ductility and FCG behavior due to martensitic microstructure and residual stresses.Both heat treatment and hot isostatic pressing improve the plane-stress fracture toughness and FCG performance considerably,while surface machining shows slight effect.
基金This work was supported by the State Key Project for Fundamental Research of MOST China (Grant No. G20000264-04).
文摘Hydrogen adsorption experiments were carried out in special stainless steel vessels at room temperature (298K) and under 10 MPa using self-synthesized multi-walled carbon nanotubes. In the experiments, carbon nanotubessynthesized by the seeded catalyst method were pretreatedby being soaked in chemical reagents or annealed at hightemperature before they were used to adsorb hydrogen, but their capacity for hydrogen storage was still poor. Carbonnanotubes synthesized by the floating catalyst method were found to be able to adsorb more hydrogen. They have ahydrogen storage capacity of over 4% after they wereannealed at high temperatures, which suggested that theycould be used as a promising material for hydrogen storage.
