The effects of under-aging treatment on the microstructure and mechanical properties of Al-Zn-Mg-Cu alloy produced by squeeze casting were investigated using optical microscopy(OM),X-ray diffractometry(XRD),scanning e...The effects of under-aging treatment on the microstructure and mechanical properties of Al-Zn-Mg-Cu alloy produced by squeeze casting were investigated using optical microscopy(OM),X-ray diffractometry(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM)and hardness and tensile testing.The results showed that most of secondary phases were dissolved intoα(Al)matrix while no significant grain growth happened under the condition of solution treatment at 470°C for 4 h.Due to the strengthening effect of GP zones,for alloys treated by under-aging process,the increase of aging time and aging temperature improved the ultimate tensile strength(UTS)and yield strength(YS),but decreased the elongation(δ)to some extent.By utilizing appropriate aging time and temperature,the best combination of strength and ductility could be obtained to fulfill the design requirements of automobile components.展开更多
As an advanced near-net shape technology, squeeze casting is an excellent method for producing high integrity castings. Numerical simulation is a very effective method to optimize squeeze casting process, and the inte...As an advanced near-net shape technology, squeeze casting is an excellent method for producing high integrity castings. Numerical simulation is a very effective method to optimize squeeze casting process, and the interfacial heat transfer coefficient(IHTC) is an important boundary condition in numerical simulation. Therefore, the study of the IHTC is of great significance. In the present study, experiments were conducted and a "plate shape" aluminum alloy casting was cast in H13 steel die. In order to obtain accurate temperature readings inside the die, a special temperature sensor units(TSU) was designed. Six 1 mm wide and 1 mm deep grooves were machined in the sensor unit for the placement of the thermocouples whose tips were welded to the end wall. Each groove was machined to terminate at a particular distance(1, 3, and 6 mm) from the front end of the sensor unit. Based on the temperature measurements inside the die, the interfacial heat transfer coefficient(IHTC) at the metal-die interface was determined by applying an inverse approach. The acquired data were processed by a low pass filtering method based on Fast Fourier Transform(FFT). The feature of the IHTC at the metal-die interface was discussed.展开更多
Dear Editor, The incidence of cryptorchidism is approximately 0.8% at 1 year of age and remains at this level throughout adulthood. One-third of these patients have bilaterally cryptorchid testes.1 Most patients with...Dear Editor, The incidence of cryptorchidism is approximately 0.8% at 1 year of age and remains at this level throughout adulthood. One-third of these patients have bilaterally cryptorchid testes.1 Most patients with cryptorchidism have this condition corrected by surgery before puberty. Therefore, adult bilateral cryptorchidism （BC） is not observed frequently in clinical practice. Bilateral undescended testes are commonly associated with azoospermia and male infertility. Orchiopexy is usually considered a cosmetic operation and to reduce cancer risk when performed in adult men, and is generally thought to have no effect on spermatogenic recovery. We conducted a single-center retrospective study to evaluate the efficacy of orchidopexy and its effect on fertility in adult men with BC.展开更多
The solidification microstructure of Mg-Gd-YZr alloy was investigated via an experimental study and cellular automaton(CA)simulation.In this study,stepshaped castings were produced,and the temperature variation inside...The solidification microstructure of Mg-Gd-YZr alloy was investigated via an experimental study and cellular automaton(CA)simulation.In this study,stepshaped castings were produced,and the temperature variation inside the casting was recorded using thermocouples during the solidification process.The effects of the cooling rate and Zr content on the grain size of the Mg-Gd-Y-Zr alloy were studied.The results showed that the grain size decreased with an increase in the cooling rate and Zr content.Based on the experimental data,a quantitative model for calculating the heterogeneous nucleation rate was developed,and the model parameters were determined.The evolution of the solidification microstructure was simulated using the CA method,where the quantitative nucleation model was used and a solute partition ceoefficient was introduced to deal with the solute trapping in front of the solid-liquid(S/L)interface.The simulation results of the grain size were in good agreement with the experimental data.The simulation also showed that the fraction of the eutectics decreased with an increasing cooling rate in the range of 2.6-11.0℃·s^(-1),which was verified indirectly by the experimental data.展开更多
基金Project(2017ZX04006001)supported by the National Science and Technology Major Project of China
文摘The effects of under-aging treatment on the microstructure and mechanical properties of Al-Zn-Mg-Cu alloy produced by squeeze casting were investigated using optical microscopy(OM),X-ray diffractometry(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM)and hardness and tensile testing.The results showed that most of secondary phases were dissolved intoα(Al)matrix while no significant grain growth happened under the condition of solution treatment at 470°C for 4 h.Due to the strengthening effect of GP zones,for alloys treated by under-aging process,the increase of aging time and aging temperature improved the ultimate tensile strength(UTS)and yield strength(YS),but decreased the elongation(δ)to some extent.By utilizing appropriate aging time and temperature,the best combination of strength and ductility could be obtained to fulfill the design requirements of automobile components.
基金supported by the National Science and Technology Major Project of China(2017ZX04080001)the National Key Research and Development Program of China(2016YFB0701204)
文摘As an advanced near-net shape technology, squeeze casting is an excellent method for producing high integrity castings. Numerical simulation is a very effective method to optimize squeeze casting process, and the interfacial heat transfer coefficient(IHTC) is an important boundary condition in numerical simulation. Therefore, the study of the IHTC is of great significance. In the present study, experiments were conducted and a "plate shape" aluminum alloy casting was cast in H13 steel die. In order to obtain accurate temperature readings inside the die, a special temperature sensor units(TSU) was designed. Six 1 mm wide and 1 mm deep grooves were machined in the sensor unit for the placement of the thermocouples whose tips were welded to the end wall. Each groove was machined to terminate at a particular distance(1, 3, and 6 mm) from the front end of the sensor unit. Based on the temperature measurements inside the die, the interfacial heat transfer coefficient(IHTC) at the metal-die interface was determined by applying an inverse approach. The acquired data were processed by a low pass filtering method based on Fast Fourier Transform(FFT). The feature of the IHTC at the metal-die interface was discussed.
文摘Dear Editor, The incidence of cryptorchidism is approximately 0.8% at 1 year of age and remains at this level throughout adulthood. One-third of these patients have bilaterally cryptorchid testes.1 Most patients with cryptorchidism have this condition corrected by surgery before puberty. Therefore, adult bilateral cryptorchidism （BC） is not observed frequently in clinical practice. Bilateral undescended testes are commonly associated with azoospermia and male infertility. Orchiopexy is usually considered a cosmetic operation and to reduce cancer risk when performed in adult men, and is generally thought to have no effect on spermatogenic recovery. We conducted a single-center retrospective study to evaluate the efficacy of orchidopexy and its effect on fertility in adult men with BC.
基金financially supported by the National Key Research and Development Program of China(No.2016YFB0701204)the National Science and Technology Major Project of China(No.2017ZX04006001)the National Natural Science Foundation of China(No.U1737208)。
文摘The solidification microstructure of Mg-Gd-YZr alloy was investigated via an experimental study and cellular automaton(CA)simulation.In this study,stepshaped castings were produced,and the temperature variation inside the casting was recorded using thermocouples during the solidification process.The effects of the cooling rate and Zr content on the grain size of the Mg-Gd-Y-Zr alloy were studied.The results showed that the grain size decreased with an increase in the cooling rate and Zr content.Based on the experimental data,a quantitative model for calculating the heterogeneous nucleation rate was developed,and the model parameters were determined.The evolution of the solidification microstructure was simulated using the CA method,where the quantitative nucleation model was used and a solute partition ceoefficient was introduced to deal with the solute trapping in front of the solid-liquid(S/L)interface.The simulation results of the grain size were in good agreement with the experimental data.The simulation also showed that the fraction of the eutectics decreased with an increasing cooling rate in the range of 2.6-11.0℃·s^(-1),which was verified indirectly by the experimental data.
