BACKGROUND Hydroxyurea,an antimetabolite,is frequently prescribed for various hemato-logical disorders,and its common side effects include gastrointestinal problems,cutaneous or mucosal lesions and pyrexia/fever.CASE ...BACKGROUND Hydroxyurea,an antimetabolite,is frequently prescribed for various hemato-logical disorders,and its common side effects include gastrointestinal problems,cutaneous or mucosal lesions and pyrexia/fever.CASE SUMMARY This study reports the case of a 67-year-old woman who developed recurrent abdominal pain after 10 years of continuous hydroxyurea therapy for primary thrombocythemia.Colonoscopy revealed an ileocecal ulcer.After discontinuing hydroxyurea therapy for 6 months,follow-up colonoscopy showed a significant reduction in the ulceration.CONCLUSION We consider cecal ulcers as a rare complication of hydroxyurea therapy which typically resolves upon stopping the drug.展开更多
This study focuses on finding a solution to the sharp decline in mechanical properties of Al-Si-Cu-Mg alloys due to rapid coarsening of traditional intermediate phases at high temperature.A new type of modified al oy,...This study focuses on finding a solution to the sharp decline in mechanical properties of Al-Si-Cu-Mg alloys due to rapid coarsening of traditional intermediate phases at high temperature.A new type of modified al oy,to be used in automobile engines at high temperatures,was prepared by adding Zr and Mo into Al-Si-Cu-Mg alloy.The synergistic effects of Zr and Mo on the microstructure evolution and high-temperature mechanical properties were studied.Results show that the addition of Zr and Mo generates a series of intermetallic phases dispersed in the alloy.They can improve the strength of the alloy by hindering dislocation movement and crack propagation.In addition,some nano-strengthened phases show coherent interfaces with the matrix and improve grain refinement.The addition of Mo greatly improves the heat resistance of the alloy.The extremely low diffusivity of Mo enables it to improve the thermal stability of the intermetallic phases,inhibit precipitation during aging,reduce the size of the precipitates,and improve the heat resistance of the alloy.展开更多
To investigate the effect of yttrium(Y) on microstructure refinement and mechanical properties of aluminum alloy A356.2,the different trace contents of Y(0 wt%,0.025 wt%,0.050 wt%,0.075 wt%,or 0.100 wt%)were introduce...To investigate the effect of yttrium(Y) on microstructure refinement and mechanical properties of aluminum alloy A356.2,the different trace contents of Y(0 wt%,0.025 wt%,0.050 wt%,0.075 wt%,or 0.100 wt%)were introduced into the liquid alloy.The alloys were fabricated in a preheated permanent mold,and subsequently treated by a T6 heat treatment.The results of tensile testing indicate that the yield strength(YS),the ultimate tensile strength(UTS) and the elongation(El) of the A356.2 alloy are improved by the Y additions.The YS dependence on grain size for the test alloys follows the Hall-Petch equation,which gives YS=-354.1+2875.2 d^(-1/2) with a correlation of R^(2)=0.83.As 0.050 wt%Y is added,the optimum values of the YS,UTS and El are achieved after T6 heat treatment.The secondary phases were identified by X-ray diffraction(XRD) which mainly consisted as Si,Mg2 Si and Al3 Y.The scanning electron microscope(SEM) and energy-dispersive spectrometer(EDS) analyses reveal the presence of the nano-sized Al3 Y particles on the surface of the Si phase.The A356.2 alloy with the Y addition is strengthened by the dendritic refinement,and the presence of the micron-and nano-sized Al3 Y precipitates.展开更多
The A356 castings were fabricated using a well-developed temperature controlled permanent mold.To improve the strength and hardness of cast A356,the microstructures and mechanical properties of as-cast and T6 heat tre...The A356 castings were fabricated using a well-developed temperature controlled permanent mold.To improve the strength and hardness of cast A356,the microstructures and mechanical properties of as-cast and T6 heat treated A356 alloy with various mold and pouring temperatures were studied.The results reveal that the undercooling is closely related to the mold and pouring temperatures.As the mold/pouring temperature changed from 258°C/680°C and 270°C/680°C to 288°C/650°C,the in-situ undercooling is 12°C,17°C and 11°C,respectively.It is observed that the Si phase changes from long continuous flake to discontinuous globular-fibrous morphology after T6 heat treatment as the mold and pouring temperature is 270°C/680°C,and the T6 heat treated specimens exhibit better mechanical properties in comparison to those as-cast ones with an increase of 162%and 102%in yield strength and elongation,which are 34.6%and 190%higher than the ASTM B108-03 a standard,respectively.As a result,the tensile fracture morphology of the as-cast A356 alloy shows quasi-cleavage fracture and the T6 heat treated A356 alloy shows ductile fracture.展开更多
The application of ultrasonic vibration to the casting process can be realized through mould(die)vibration.However,the resonant vibration of the mould is always accompanied by a non-uniform vibration distribution at d...The application of ultrasonic vibration to the casting process can be realized through mould(die)vibration.However,the resonant vibration of the mould is always accompanied by a non-uniform vibration distribution at different parts,which may induce a complex liquid flow and affect the casting fluidity during the mould filling process.The influence of non-uniform ultrasonic vibration on the fluidity of liquid AlSi9Cu3 alloy was studied by mould vibration with different vibration gradients.It is found that ultrasonic mould vibration can generate two opposite effects on the casting fluidity:the first,ultrasonic cavitation in melt induced by mould vibration promotes the casting fluidity;the second,the non-uniform mould vibration can induce a melt flow toward the weak vibration areas and turbulence there,consequently decreasing the casting fluidity.When the melt flow and turbulence are violent enough to offset the promoting effect of cavitation on fluidity,the ultrasonic vibration will finally induce a resultant decrease of casting fluidity.The decreasing effect is proportional to the vibration gradient.展开更多
The application of ultrasonic vibration during the casting process has been proven to refine the microstructure and enhance the properties of the casting.By using the direct inserting method,wherein the ultrasonic hor...The application of ultrasonic vibration during the casting process has been proven to refine the microstructure and enhance the properties of the casting.By using the direct inserting method,wherein the ultrasonic horn is inserted directly into the melt,ultrasonic treatment can be utilized in the semi-continuous casting process to produce aluminum ingots with simple shapes.However,due to the attenuation of ultrasound,it is challenging to apply the direct inserting method in the die casting process to produce complex castings.Thus,in this study,the impact of ultrasonic vibration on the microstructure of a gravity die-cast AlSi9Cu3end cap was investigated by applying ultrasonic vibration on the core(indirect method).It is found that the effect of ultrasonic vibration relies greatly on the resonance mode of the core.Selection of ultrasonic vibration schemes mainly depends on the core structure,and only a strong vibration can significantly refine the microstructure of the casting.For castings with complex structures,an elaborated ultrasonic vibration design is necessary to refine the microstructure of the specified casting.In addition,strong vibration applied on the feeding channel can promote the feeding ability of casting by breaking the dendrites during solidification,and consequently reduce the shrinkage porosity.展开更多
Diesel engines, characterized by higher breakout pressure and compression ratio in comparison with gasoline engines, require particularly elevated tensile properties for their engine parts. In order to maintain both h...Diesel engines, characterized by higher breakout pressure and compression ratio in comparison with gasoline engines, require particularly elevated tensile properties for their engine parts. In order to maintain both high strength and high ductility in the cylinder head, i.e., to obtain higher percent elongation without further reducing the tensile strength, Al Si9Cu1 alloy was used to prepare the cylinder head in an aluminum diesel engine. At the same time, the effect of different modification elements, Na or Sr, and Fe content on the reduction of secondary dendrite arm spacing(SDAS) was discussed, and the design of T7 heat treatment parameters were analyzed in order to improve the tensile ductility. The result shows:(1) The SDAS is as small as 18±3 μm for the Sr modified alloy.(2) The percent elongation of the alloy with Sr modification increases by 66.7% and 42.9%, respectively, compared with the unmodified alloy and the alloy with Na modification.(3) Lower Fe content alloy(0.10%) gives good results in percent elongation compared to the alloy with higher Fe content(0.27%); in particular, after Sr modification and T7 heat treatment, the elongation of over 5% is obtained.展开更多
基金Supported by National Natural Science Foundation of China,No.82370604Major Science and Technology innovation Project of Fujian Province,No.2023Y9269Natural Science Foundation of Fujian Province,China,No.2023J01239.
文摘BACKGROUND Hydroxyurea,an antimetabolite,is frequently prescribed for various hemato-logical disorders,and its common side effects include gastrointestinal problems,cutaneous or mucosal lesions and pyrexia/fever.CASE SUMMARY This study reports the case of a 67-year-old woman who developed recurrent abdominal pain after 10 years of continuous hydroxyurea therapy for primary thrombocythemia.Colonoscopy revealed an ileocecal ulcer.After discontinuing hydroxyurea therapy for 6 months,follow-up colonoscopy showed a significant reduction in the ulceration.CONCLUSION We consider cecal ulcers as a rare complication of hydroxyurea therapy which typically resolves upon stopping the drug.
基金supported by the Key R&D Program of Shandong Province of China(Grant number 2019QYTPY057)the Natural Science Foundation of Shandong Province of China(Grant numbers ZR2020ME110,ZR2021ME023)。
文摘This study focuses on finding a solution to the sharp decline in mechanical properties of Al-Si-Cu-Mg alloys due to rapid coarsening of traditional intermediate phases at high temperature.A new type of modified al oy,to be used in automobile engines at high temperatures,was prepared by adding Zr and Mo into Al-Si-Cu-Mg alloy.The synergistic effects of Zr and Mo on the microstructure evolution and high-temperature mechanical properties were studied.Results show that the addition of Zr and Mo generates a series of intermetallic phases dispersed in the alloy.They can improve the strength of the alloy by hindering dislocation movement and crack propagation.In addition,some nano-strengthened phases show coherent interfaces with the matrix and improve grain refinement.The addition of Mo greatly improves the heat resistance of the alloy.The extremely low diffusivity of Mo enables it to improve the thermal stability of the intermetallic phases,inhibit precipitation during aging,reduce the size of the precipitates,and improve the heat resistance of the alloy.
基金financially supported by the National Natural Science Foundation of China (No.51601102)the Natural Science Foundation of Shandong Province (No.ZR2016EEM48)the Key Research and Development Program Plan of Shandong Province (No.2018GGX103012)。
文摘To investigate the effect of yttrium(Y) on microstructure refinement and mechanical properties of aluminum alloy A356.2,the different trace contents of Y(0 wt%,0.025 wt%,0.050 wt%,0.075 wt%,or 0.100 wt%)were introduced into the liquid alloy.The alloys were fabricated in a preheated permanent mold,and subsequently treated by a T6 heat treatment.The results of tensile testing indicate that the yield strength(YS),the ultimate tensile strength(UTS) and the elongation(El) of the A356.2 alloy are improved by the Y additions.The YS dependence on grain size for the test alloys follows the Hall-Petch equation,which gives YS=-354.1+2875.2 d^(-1/2) with a correlation of R^(2)=0.83.As 0.050 wt%Y is added,the optimum values of the YS,UTS and El are achieved after T6 heat treatment.The secondary phases were identified by X-ray diffraction(XRD) which mainly consisted as Si,Mg2 Si and Al3 Y.The scanning electron microscope(SEM) and energy-dispersive spectrometer(EDS) analyses reveal the presence of the nano-sized Al3 Y particles on the surface of the Si phase.The A356.2 alloy with the Y addition is strengthened by the dendritic refinement,and the presence of the micron-and nano-sized Al3 Y precipitates.
基金Natural Science Foundation of Shandong Province(ZR2016EEM48).
文摘The A356 castings were fabricated using a well-developed temperature controlled permanent mold.To improve the strength and hardness of cast A356,the microstructures and mechanical properties of as-cast and T6 heat treated A356 alloy with various mold and pouring temperatures were studied.The results reveal that the undercooling is closely related to the mold and pouring temperatures.As the mold/pouring temperature changed from 258°C/680°C and 270°C/680°C to 288°C/650°C,the in-situ undercooling is 12°C,17°C and 11°C,respectively.It is observed that the Si phase changes from long continuous flake to discontinuous globular-fibrous morphology after T6 heat treatment as the mold and pouring temperature is 270°C/680°C,and the T6 heat treated specimens exhibit better mechanical properties in comparison to those as-cast ones with an increase of 162%and 102%in yield strength and elongation,which are 34.6%and 190%higher than the ASTM B108-03 a standard,respectively.As a result,the tensile fracture morphology of the as-cast A356 alloy shows quasi-cleavage fracture and the T6 heat treated A356 alloy shows ductile fracture.
基金supported by the Natural Science Foundation of Shandong province (ZR2021ME023)the Innovation Team Project of Jinan,China (2019GXRC035)
文摘The application of ultrasonic vibration to the casting process can be realized through mould(die)vibration.However,the resonant vibration of the mould is always accompanied by a non-uniform vibration distribution at different parts,which may induce a complex liquid flow and affect the casting fluidity during the mould filling process.The influence of non-uniform ultrasonic vibration on the fluidity of liquid AlSi9Cu3 alloy was studied by mould vibration with different vibration gradients.It is found that ultrasonic mould vibration can generate two opposite effects on the casting fluidity:the first,ultrasonic cavitation in melt induced by mould vibration promotes the casting fluidity;the second,the non-uniform mould vibration can induce a melt flow toward the weak vibration areas and turbulence there,consequently decreasing the casting fluidity.When the melt flow and turbulence are violent enough to offset the promoting effect of cavitation on fluidity,the ultrasonic vibration will finally induce a resultant decrease of casting fluidity.The decreasing effect is proportional to the vibration gradient.
基金supported by the Natural Science Foundation of Shandong province(Grant No.ZR2021ME023)the Innovation Team Project of Jinan,China(Grant No.2019GXRC035)SQ project[2021370113124591]。
文摘The application of ultrasonic vibration during the casting process has been proven to refine the microstructure and enhance the properties of the casting.By using the direct inserting method,wherein the ultrasonic horn is inserted directly into the melt,ultrasonic treatment can be utilized in the semi-continuous casting process to produce aluminum ingots with simple shapes.However,due to the attenuation of ultrasound,it is challenging to apply the direct inserting method in the die casting process to produce complex castings.Thus,in this study,the impact of ultrasonic vibration on the microstructure of a gravity die-cast AlSi9Cu3end cap was investigated by applying ultrasonic vibration on the core(indirect method).It is found that the effect of ultrasonic vibration relies greatly on the resonance mode of the core.Selection of ultrasonic vibration schemes mainly depends on the core structure,and only a strong vibration can significantly refine the microstructure of the casting.For castings with complex structures,an elaborated ultrasonic vibration design is necessary to refine the microstructure of the specified casting.In addition,strong vibration applied on the feeding channel can promote the feeding ability of casting by breaking the dendrites during solidification,and consequently reduce the shrinkage porosity.
基金supported by the major project of Shandong Science and Technology(No.2015ZDZX03004)the project of Shandong Science and Technology Development Plan(No.2014GGX103035)the National“Thousand Talents Plan”of China
文摘Diesel engines, characterized by higher breakout pressure and compression ratio in comparison with gasoline engines, require particularly elevated tensile properties for their engine parts. In order to maintain both high strength and high ductility in the cylinder head, i.e., to obtain higher percent elongation without further reducing the tensile strength, Al Si9Cu1 alloy was used to prepare the cylinder head in an aluminum diesel engine. At the same time, the effect of different modification elements, Na or Sr, and Fe content on the reduction of secondary dendrite arm spacing(SDAS) was discussed, and the design of T7 heat treatment parameters were analyzed in order to improve the tensile ductility. The result shows:(1) The SDAS is as small as 18±3 μm for the Sr modified alloy.(2) The percent elongation of the alloy with Sr modification increases by 66.7% and 42.9%, respectively, compared with the unmodified alloy and the alloy with Na modification.(3) Lower Fe content alloy(0.10%) gives good results in percent elongation compared to the alloy with higher Fe content(0.27%); in particular, after Sr modification and T7 heat treatment, the elongation of over 5% is obtained.
