AZ80 magnesium alloy was prepared by hot extrusion of recycled machined chips and its microstructure and mechanical properties were investigated. Hot pressing was employed to prepare extrusion billets of AZ80 chips, t...AZ80 magnesium alloy was prepared by hot extrusion of recycled machined chips and its microstructure and mechanical properties were investigated. Hot pressing was employed to prepare extrusion billets of AZ80 chips, then the billets were hot extruded at 623 K with an extrusion ratio of 25∶1. The extruded rods show a high ultimate tensile strength of 285 MPa and a high elongation of 6%. Due to grain refinement by extrusion, mechanical properties of the extruded rods are much higher than those of as-cast AZ80 alloy. Process technique and chips densification mechanism were also studied. Results show that hot extrusion is an efficient method for AZ80 alloy chips recycling.展开更多
Recent studies have indicated that hypervelocity impacts by meteoroids and space debris can induce spacecraft anomalies. However, the basic physical process through which space debris impacts cause anomalies is not en...Recent studies have indicated that hypervelocity impacts by meteoroids and space debris can induce spacecraft anomalies. However, the basic physical process through which space debris impacts cause anomalies is not entirely clear. Currently, impact-generated plasma is thought to be the primary cause of electrical spacecraft anomalies, while the effects of impact-generated mechanical damage have rarely been researched. This paper presents new evidence showing that impact-generated mechanical damage strongly influences electrostatic discharge. Hypervelocity impact experiments were conducted in a plasma drag particle accelerator, using particles with diameters of 200–500 ?m and velocities of 2–7 km/s. The impact-generated mechanical damage on a specimen surface was measured by a stereoscopic microscope and 3D Profilometer and it indicated that microscopic irregularities around the impact crater could be responsible for local electric field enhancement. Furthermore, the influence of impact-generated mechanical damage on electrostatic discharge was simulated in an inverted potential gradient situation. The experimental results show that the electrostatic discharge voltage threshold was significantly reduced after the specimen was impacted by particles.展开更多
文摘AZ80 magnesium alloy was prepared by hot extrusion of recycled machined chips and its microstructure and mechanical properties were investigated. Hot pressing was employed to prepare extrusion billets of AZ80 chips, then the billets were hot extruded at 623 K with an extrusion ratio of 25∶1. The extruded rods show a high ultimate tensile strength of 285 MPa and a high elongation of 6%. Due to grain refinement by extrusion, mechanical properties of the extruded rods are much higher than those of as-cast AZ80 alloy. Process technique and chips densification mechanism were also studied. Results show that hot extrusion is an efficient method for AZ80 alloy chips recycling.
文摘Recent studies have indicated that hypervelocity impacts by meteoroids and space debris can induce spacecraft anomalies. However, the basic physical process through which space debris impacts cause anomalies is not entirely clear. Currently, impact-generated plasma is thought to be the primary cause of electrical spacecraft anomalies, while the effects of impact-generated mechanical damage have rarely been researched. This paper presents new evidence showing that impact-generated mechanical damage strongly influences electrostatic discharge. Hypervelocity impact experiments were conducted in a plasma drag particle accelerator, using particles with diameters of 200–500 ?m and velocities of 2–7 km/s. The impact-generated mechanical damage on a specimen surface was measured by a stereoscopic microscope and 3D Profilometer and it indicated that microscopic irregularities around the impact crater could be responsible for local electric field enhancement. Furthermore, the influence of impact-generated mechanical damage on electrostatic discharge was simulated in an inverted potential gradient situation. The experimental results show that the electrostatic discharge voltage threshold was significantly reduced after the specimen was impacted by particles.
