The effect of Ti addition on microstructure and mechanical properties of Zn-22Al eutectoid alloy with 0.15 wt%Ti was investigated.It was observed that the presence of Ti changes the morphology of n phase in the alloy....The effect of Ti addition on microstructure and mechanical properties of Zn-22Al eutectoid alloy with 0.15 wt%Ti was investigated.It was observed that the presence of Ti changes the morphology of n phase in the alloy.Addition of Ti to Zn-Al alloy caused the formation of Ti(Zn,Al)_(3);phase.Before applying equal channel angular pressing(ECAP),two times of homogenization treatment were conducted on the alloy.After secondary homogenization,the microstructure consisted of a homogeneous and fine mixture ofαand n phases and the as-cast lamellar structure removed.After homogenization,ECAP was carried out on Ti-containing Zn-22Al alloy.The fraction of high angle grain boundaries increased with increasing the number of ECAP passes.The average grain size reduced from 930 nm after secondary homogenization to 380 nm after 8 passes of ECAP.The texture of the alloy also changed by applying ECAP.Maximum elongation to failure of the homogenized alloy was 135%at a strain rate of 10^(-5)s^(-1)which enhanced to a maximum of 405%at a strain rate of 10^(-3)s^(-1)after 8 passes of ECAP.It was also observed that by conducting ECAP and increasing the number of passes the hardness decreases,which indicates work-softening behavior due to dynamic recovery/recrystallization.展开更多
To manufacture plate by the combination of equal channel angular processing （ECAP） and porthole die extrusion techniques, a novel technique, namely portholes-equal channel angular processing （P-ECAP）, was studied....To manufacture plate by the combination of equal channel angular processing （ECAP） and porthole die extrusion techniques, a novel technique, namely portholes-equal channel angular processing （P-ECAP）, was studied. Extrusion of AL6005A plate used for the bullet train plate was investigated by finite element method. The relevant porthole dies involving ECAP technique in channels were designed. Dimensional changes in the scrap part of the extrudate obtained after extrusion from the P-ECAP die, with different channel angles, were predicted. Effects of the channel angle and extrusion speed on the maximum temperature of the workpiece and other field variables were evaluated. At the channel angle of 160° of P-ECAP dies, the extrudate exhibited the optimal performance and the least amount of extrudate scrap was obtained. The optimal extrusion speed was 3-5 mm/s. Moreover, with the increase in ram speed from 1 to 9 mm/s, the peak extrusion load increased by about 49% and the maximum temperature was increased by about 70 ℃. The effective strain exhibited ascending trend in the comer of the ECAP deformation zone. In the solder seam and the side of die bearing of extrudate, the maximum principal stresses were tensile stress.展开更多
Mg-RE(rear earth) alloys with long period stacking(LPSO) structures have great potential in biomedical applications. The present work focused on the microstructure and corrosion behaviors of Mg 98.5 Y1 Zn0.5 alloys wi...Mg-RE(rear earth) alloys with long period stacking(LPSO) structures have great potential in biomedical applications. The present work focused on the microstructure and corrosion behaviors of Mg 98.5 Y1 Zn0.5 alloys with 18 R LPSO structure after equal channel angular pressing(ECAP). The results showed that the ECAP process changed the grain size and the distribution of LPSO particles thus controlled the total corrosion rates of Mg 98.5 Y1 Zn0.5 alloys. During the ECAP process from 0 p to 12 p, the grain size reduced from 160–180 μm(as-cast) to 6–8 μm(12 p). The LPSO structures became kinked(4 p), then started to be broken into smaller pieces(8 p), and at last comminuted to fine particles and redistributed uniformly inside the matrix(12 p). The improvement in the corrosion resistance for ECAP samples was obtained from 0 p to 8 p, with the corrosion rate reduced from 3.24 mm/year(0 p) to 2.35 mm/year(8 p) in simulated body fluid, and the 12 p ECAP alloy exhibited the highest corrosion rate of 4.54 mm/year.展开更多
In order to establish the quantitative relationship between equivalent strain and the performance index of the deformed material within the range of certain passes for equal channel angular processing （ECAP）, a new ...In order to establish the quantitative relationship between equivalent strain and the performance index of the deformed material within the range of certain passes for equal channel angular processing （ECAP）, a new approach to characterize the equivalent strain was proposed. The results show that there exists better accordance between mechanical property （such as hardness or strength） and equivalent strain after rolling and ECAP in a certain range of deformation amount, and Gauss equation can be satisfied among the equivalent strain and the mechanical properties for ECAP. Through regression analysis on the data of hardness and strength after the deformation, a more generalized expression of equivalent strain for ECAP is proposed as：ε=k0exp[-（k1M-k2）^2], where M is the strength or hardness of the material, k1 is the modified coefficient （k1∈ （0, 1））, ko and k2 are two parameters dependent on the critical strain and mechanical property that reaches saturation state for the material, respectively. In this expression the equivalent strain for ECAP is characterized novelly through the mechanical parameter relating to material property rather than the classical geometry equation.展开更多
Ultrafine-grained(UFG) high purity aluminum exhibits a variety of attractive mechanical properties and special deformation behavior. Equal channel angular pressing(ECAP) process can be used to easily and effectively r...Ultrafine-grained(UFG) high purity aluminum exhibits a variety of attractive mechanical properties and special deformation behavior. Equal channel angular pressing(ECAP) process can be used to easily and effectively refine metals. The microstructure and microtexture evolutions and grain boundary characteristics of the high purity aluminum(99.998%) processed by ECAP at room temperature are investigated by means of TEM and EBSD. The results indicate that the shear deformation resistance increases with repeated EACP passes, and equiaxed grains with an average size of 0.9 μm in diameter are formed after five passes. Although the orientations distribution of grains tends to evolve toward random orientations, and microtextures(80°, 35°, 0°),(40°, 75°, 45°) and(0°, 85°, 45°) peak in the sample after five passes. The grain boundaries in UFG aluminum are high-angle geometrically necessary boundaries. It is suggested that the continuous dynamic recrystallization is responsible for the formation of ultrafine grains in high purity aluminum. Microstructure evolution in the high purity aluminum during ECAP is proposed.展开更多
文摘The effect of Ti addition on microstructure and mechanical properties of Zn-22Al eutectoid alloy with 0.15 wt%Ti was investigated.It was observed that the presence of Ti changes the morphology of n phase in the alloy.Addition of Ti to Zn-Al alloy caused the formation of Ti(Zn,Al)_(3);phase.Before applying equal channel angular pressing(ECAP),two times of homogenization treatment were conducted on the alloy.After secondary homogenization,the microstructure consisted of a homogeneous and fine mixture ofαand n phases and the as-cast lamellar structure removed.After homogenization,ECAP was carried out on Ti-containing Zn-22Al alloy.The fraction of high angle grain boundaries increased with increasing the number of ECAP passes.The average grain size reduced from 930 nm after secondary homogenization to 380 nm after 8 passes of ECAP.The texture of the alloy also changed by applying ECAP.Maximum elongation to failure of the homogenized alloy was 135%at a strain rate of 10^(-5)s^(-1)which enhanced to a maximum of 405%at a strain rate of 10^(-3)s^(-1)after 8 passes of ECAP.It was also observed that by conducting ECAP and increasing the number of passes the hardness decreases,which indicates work-softening behavior due to dynamic recovery/recrystallization.
基金Project(B08040)supported by the Program of Introducing Talents of Discipline to Universities(111 Project),ChinaProject(2009ZX04005-031-11)supported by the National Science and Technology Special Program,China
文摘To manufacture plate by the combination of equal channel angular processing （ECAP） and porthole die extrusion techniques, a novel technique, namely portholes-equal channel angular processing （P-ECAP）, was studied. Extrusion of AL6005A plate used for the bullet train plate was investigated by finite element method. The relevant porthole dies involving ECAP technique in channels were designed. Dimensional changes in the scrap part of the extrudate obtained after extrusion from the P-ECAP die, with different channel angles, were predicted. Effects of the channel angle and extrusion speed on the maximum temperature of the workpiece and other field variables were evaluated. At the channel angle of 160° of P-ECAP dies, the extrudate exhibited the optimal performance and the least amount of extrudate scrap was obtained. The optimal extrusion speed was 3-5 mm/s. Moreover, with the increase in ram speed from 1 to 9 mm/s, the peak extrusion load increased by about 49% and the maximum temperature was increased by about 70 ℃. The effective strain exhibited ascending trend in the comer of the ECAP deformation zone. In the solder seam and the side of die bearing of extrudate, the maximum principal stresses were tensile stress.
基金the National Natural Science Foundation of China(Nos.51774109,51979099 and 51901068)the Fundamental Research Funds for the Central Universities(No.2018B690X14)+3 种基金the Natural Science Foundation of Jiangsu Province of China(No.BK20191303)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX18_0570)the Key Research and Development Project of Jiangsu Province of China(No.BE2017148)the Public Service Platform Program of Suqian City of China(No.M201614)。
文摘Mg-RE(rear earth) alloys with long period stacking(LPSO) structures have great potential in biomedical applications. The present work focused on the microstructure and corrosion behaviors of Mg 98.5 Y1 Zn0.5 alloys with 18 R LPSO structure after equal channel angular pressing(ECAP). The results showed that the ECAP process changed the grain size and the distribution of LPSO particles thus controlled the total corrosion rates of Mg 98.5 Y1 Zn0.5 alloys. During the ECAP process from 0 p to 12 p, the grain size reduced from 160–180 μm(as-cast) to 6–8 μm(12 p). The LPSO structures became kinked(4 p), then started to be broken into smaller pieces(8 p), and at last comminuted to fine particles and redistributed uniformly inside the matrix(12 p). The improvement in the corrosion resistance for ECAP samples was obtained from 0 p to 8 p, with the corrosion rate reduced from 3.24 mm/year(0 p) to 2.35 mm/year(8 p) in simulated body fluid, and the 12 p ECAP alloy exhibited the highest corrosion rate of 4.54 mm/year.
基金Projects(50471102,50671089) supported by the National Natural Science Foundation of China
文摘In order to establish the quantitative relationship between equivalent strain and the performance index of the deformed material within the range of certain passes for equal channel angular processing （ECAP）, a new approach to characterize the equivalent strain was proposed. The results show that there exists better accordance between mechanical property （such as hardness or strength） and equivalent strain after rolling and ECAP in a certain range of deformation amount, and Gauss equation can be satisfied among the equivalent strain and the mechanical properties for ECAP. Through regression analysis on the data of hardness and strength after the deformation, a more generalized expression of equivalent strain for ECAP is proposed as：ε=k0exp[-（k1M-k2）^2], where M is the strength or hardness of the material, k1 is the modified coefficient （k1∈ （0, 1））, ko and k2 are two parameters dependent on the critical strain and mechanical property that reaches saturation state for the material, respectively. In this expression the equivalent strain for ECAP is characterized novelly through the mechanical parameter relating to material property rather than the classical geometry equation.
基金Project(12JJ2028)supported by the Hunan Provincial Natural Science Foundation of ChinaProject(201308430093)supported by the China Scholarship CouncilProjects(201012200006,2013zzts185,2012zzts066)supported by the Freedom Explore Program of Central South University,China
文摘Ultrafine-grained(UFG) high purity aluminum exhibits a variety of attractive mechanical properties and special deformation behavior. Equal channel angular pressing(ECAP) process can be used to easily and effectively refine metals. The microstructure and microtexture evolutions and grain boundary characteristics of the high purity aluminum(99.998%) processed by ECAP at room temperature are investigated by means of TEM and EBSD. The results indicate that the shear deformation resistance increases with repeated EACP passes, and equiaxed grains with an average size of 0.9 μm in diameter are formed after five passes. Although the orientations distribution of grains tends to evolve toward random orientations, and microtextures(80°, 35°, 0°),(40°, 75°, 45°) and(0°, 85°, 45°) peak in the sample after five passes. The grain boundaries in UFG aluminum are high-angle geometrically necessary boundaries. It is suggested that the continuous dynamic recrystallization is responsible for the formation of ultrafine grains in high purity aluminum. Microstructure evolution in the high purity aluminum during ECAP is proposed.
