The energy absorption capacity of the Al5083 thin-walled tube produced by parallel tubular angular pressing(PTCAP) process was evaluated. Also, microstructure, mechanical properties, and anisotropy coefficients were s...The energy absorption capacity of the Al5083 thin-walled tube produced by parallel tubular angular pressing(PTCAP) process was evaluated. Also, microstructure, mechanical properties, and anisotropy coefficients were studied in the peripheral and axial directions. Results showed that values of energy absorption decreased with processing pass increasing and the values for the unprocessed, first and second passes were obtained to be 167, 161.4 and 160.7 J, respectively. The differences between the simulation results for the energy absorption values and their experimental values for the unprocessed, the first and the second PTCAP passes samples are about 5%, 10%, and 13%, respectively. The energy absorption capacity was related to the anisotropy coefficient and microstructure. The results demonstrated that grain refinement occurred and ultimate tensile strength(UTS) and microhardness after the first and second PTCAP passes were enhanced, while the increase rate in the first pass was much severer. Also, by applying PTCAP, the deformation modes were altered, such that the deformation mode of the annealed tube was quite symmetrical and circular while for the first and second passes there have been triple and double lobes diamond. The results of the numerical simulation for the deformation mode of the annealed and PTCAPed tubes were consistent with the experimental results. The deformation mode of tubes is dependent on their mechanical properties and variation of the mechanical properties during PTCAP process.展开更多
The non-isothermal crystallization kinetics of Ni55Nb35Si10 amorphous alloy,prepared by mechanical alloying,was studied using differential scanning calorimetry.The amorphous alloy showed one-stage crystallization on h...The non-isothermal crystallization kinetics of Ni55Nb35Si10 amorphous alloy,prepared by mechanical alloying,was studied using differential scanning calorimetry.The amorphous alloy showed one-stage crystallization on heating,which led to the formation of nano-intermetallic crystals in amorphous matrix.The apparent activation energy for the crystallization of the alloy,determined by the Kissinger equation,was relatively high(468 kJ/mol),indicating that this amorphous alloy has high thermal stability.Changes in the activation energy during the crystallization process,were also evaluated by iso-conversional methods.The results showed that it decreases slowly from the beginning to crystallized fractionα=0.35 and it remains almost constant to the end of the process.The nano-crystallization mechanism for the non-isothermal crystallization of the amorphous alloy was explained by determining Avrami exponents.Transmission electron microscopy studies revealed the microstructural modification of amorphous alloy via nanocrystallization during annealing.The results suggest that the nucleation rate decreases with increasing time and the crystallization mechanism is governed dominantly by a three-dimensional diffusion-controlled growth.A predictive equation was obtained based on the Sestak-Berggren autocatalytic model to describe quantitatively the non-isothermal crystallization kinetics.展开更多
文摘The energy absorption capacity of the Al5083 thin-walled tube produced by parallel tubular angular pressing(PTCAP) process was evaluated. Also, microstructure, mechanical properties, and anisotropy coefficients were studied in the peripheral and axial directions. Results showed that values of energy absorption decreased with processing pass increasing and the values for the unprocessed, first and second passes were obtained to be 167, 161.4 and 160.7 J, respectively. The differences between the simulation results for the energy absorption values and their experimental values for the unprocessed, the first and the second PTCAP passes samples are about 5%, 10%, and 13%, respectively. The energy absorption capacity was related to the anisotropy coefficient and microstructure. The results demonstrated that grain refinement occurred and ultimate tensile strength(UTS) and microhardness after the first and second PTCAP passes were enhanced, while the increase rate in the first pass was much severer. Also, by applying PTCAP, the deformation modes were altered, such that the deformation mode of the annealed tube was quite symmetrical and circular while for the first and second passes there have been triple and double lobes diamond. The results of the numerical simulation for the deformation mode of the annealed and PTCAPed tubes were consistent with the experimental results. The deformation mode of tubes is dependent on their mechanical properties and variation of the mechanical properties during PTCAP process.
基金supported by the Future Material Discovery Program of the National Research Foundation of Korea(NRF) funded by the Ministry of Science,ICT and Future Planning(MSIP)of Korea(2016M3D1A1023532)
文摘The non-isothermal crystallization kinetics of Ni55Nb35Si10 amorphous alloy,prepared by mechanical alloying,was studied using differential scanning calorimetry.The amorphous alloy showed one-stage crystallization on heating,which led to the formation of nano-intermetallic crystals in amorphous matrix.The apparent activation energy for the crystallization of the alloy,determined by the Kissinger equation,was relatively high(468 kJ/mol),indicating that this amorphous alloy has high thermal stability.Changes in the activation energy during the crystallization process,were also evaluated by iso-conversional methods.The results showed that it decreases slowly from the beginning to crystallized fractionα=0.35 and it remains almost constant to the end of the process.The nano-crystallization mechanism for the non-isothermal crystallization of the amorphous alloy was explained by determining Avrami exponents.Transmission electron microscopy studies revealed the microstructural modification of amorphous alloy via nanocrystallization during annealing.The results suggest that the nucleation rate decreases with increasing time and the crystallization mechanism is governed dominantly by a three-dimensional diffusion-controlled growth.A predictive equation was obtained based on the Sestak-Berggren autocatalytic model to describe quantitatively the non-isothermal crystallization kinetics.
