The plastic work-heat conversion coefficient is one key parameter for studying the work-heat conversion under dynamic deformation of materials. To explore this coefficient of 7075-T651 aluminum alloy under dynamic com...The plastic work-heat conversion coefficient is one key parameter for studying the work-heat conversion under dynamic deformation of materials. To explore this coefficient of 7075-T651 aluminum alloy under dynamic compression, dynamic compression experiments using the Hopkinson bar under four groups of strain rates were conducted, and the temperature signals were measured by constructing a transient infrared temperature measurement system. According to stress versus strain data as well as the corresponding temperature data obtained through the experiments, the influences of the strain and the strain rate on the coefficient of plastic work converted to heat were analyzed.The experimental results show that the coefficient of plastic work converted to heat of 7075-T651 aluminum alloy is not a constant at the range of 0.85–1 and is closely related to the strain and the strain rate. The change of internal structure of material under high strain rate reduces its energy storage capacity, and makes almost all plastic work convert into heat.展开更多
Metal inert gas(MIG)welding was conducted with 12 mm thick 6082-T651 aluminum alloy plate to investigate the microstructure and mechanical properties of welded joint.The microstructure and element distribution of weld...Metal inert gas(MIG)welding was conducted with 12 mm thick 6082-T651 aluminum alloy plate to investigate the microstructure and mechanical properties of welded joint.The microstructure and element distribution of weld seam were characterized by electron backscattered diffraction(EBSD)and electron probe microanalysis(EPMA).The weld seam has typical cube texture({001}<100>)characteristics.The closer to the center of weld seam,the weaker the texture feature,the higher the proportion of high-angle grain boundaries.The average tensile strength of joint was 232 MPa which is up to 72%of 6082 aluminum alloy base metal,and the bending angle for the root bend test sample reached 90°without cracks.The lack of strengthening phase and the existence of welding pores and inclusions in the weld seam caused the degradation of mechanical properties of resultant joint.The microhardness increased from the weld center to the base metal,but the overaging zone caused by welding thermal cycle was softening part of the joint,which had lower hardness than the weld seam.展开更多
In this work, the morphologies of weld of 7075-T6 aluminum alloy via friction stir welding （FSW） were analyzed by optical microscopy, the temperature field was attained by numerical simulation, and the effect of tem...In this work, the morphologies of weld of 7075-T6 aluminum alloy via friction stir welding （FSW） were analyzed by optical microscopy, the temperature field was attained by numerical simulation, and the effect of temperature on material transfer behavior in the thermal-mechanical affected zone （TMAZ） at different stages was mainly investigated. The FSW process consists of three stages. It is very interesting to find that the maximum transfer displacement of material appears at the final stage of welding process, then at the stable stage and at the initial stage, which results from the difference of peak temperatures at different stages. At any stage, the material in TMAZ near the surface of weld transfers downwards, the material in the middle of weld moves upwards and the material near the bottom of weld hardly moves. In any cross section of weld, the largest transfer displacement of material appears in the middle of weld. The increase of rotational velocity and the decrease of welding speed are both beneficial to the transfer displacement of material in the middle of weld.展开更多
基金supported by the National Nature Science Foundation of China (Grants 11132011 and 11472288)
文摘The plastic work-heat conversion coefficient is one key parameter for studying the work-heat conversion under dynamic deformation of materials. To explore this coefficient of 7075-T651 aluminum alloy under dynamic compression, dynamic compression experiments using the Hopkinson bar under four groups of strain rates were conducted, and the temperature signals were measured by constructing a transient infrared temperature measurement system. According to stress versus strain data as well as the corresponding temperature data obtained through the experiments, the influences of the strain and the strain rate on the coefficient of plastic work converted to heat were analyzed.The experimental results show that the coefficient of plastic work converted to heat of 7075-T651 aluminum alloy is not a constant at the range of 0.85–1 and is closely related to the strain and the strain rate. The change of internal structure of material under high strain rate reduces its energy storage capacity, and makes almost all plastic work convert into heat.
基金Project was supported by the National Natural Science Foundation of China(51674060)the Collaborative Innovation Center of Major Machine Manufacturing in Liaoning。
文摘Metal inert gas(MIG)welding was conducted with 12 mm thick 6082-T651 aluminum alloy plate to investigate the microstructure and mechanical properties of welded joint.The microstructure and element distribution of weld seam were characterized by electron backscattered diffraction(EBSD)and electron probe microanalysis(EPMA).The weld seam has typical cube texture({001}<100>)characteristics.The closer to the center of weld seam,the weaker the texture feature,the higher the proportion of high-angle grain boundaries.The average tensile strength of joint was 232 MPa which is up to 72%of 6082 aluminum alloy base metal,and the bending angle for the root bend test sample reached 90°without cracks.The lack of strengthening phase and the existence of welding pores and inclusions in the weld seam caused the degradation of mechanical properties of resultant joint.The microhardness increased from the weld center to the base metal,but the overaging zone caused by welding thermal cycle was softening part of the joint,which had lower hardness than the weld seam.
基金the National Natural Science Foundation of China (No.51204111)the Education Department Foundation of Liaoning Province (No.L2012047)the State Key Lab of Advanced Welding and Joining in Harbin Institute of Technology (AWJ-M13-07)
文摘In this work, the morphologies of weld of 7075-T6 aluminum alloy via friction stir welding （FSW） were analyzed by optical microscopy, the temperature field was attained by numerical simulation, and the effect of temperature on material transfer behavior in the thermal-mechanical affected zone （TMAZ） at different stages was mainly investigated. The FSW process consists of three stages. It is very interesting to find that the maximum transfer displacement of material appears at the final stage of welding process, then at the stable stage and at the initial stage, which results from the difference of peak temperatures at different stages. At any stage, the material in TMAZ near the surface of weld transfers downwards, the material in the middle of weld moves upwards and the material near the bottom of weld hardly moves. In any cross section of weld, the largest transfer displacement of material appears in the middle of weld. The increase of rotational velocity and the decrease of welding speed are both beneficial to the transfer displacement of material in the middle of weld.
