The use of a constrained groove pressing(CGP) method to plastically deform AA6063 aluminum alloy led to the improved surface properties. It was found that hardness magnitude is dramatically improved and its uniformity...The use of a constrained groove pressing(CGP) method to plastically deform AA6063 aluminum alloy led to the improved surface properties. It was found that hardness magnitude is dramatically improved and its uniformity is considerably decreased after the first pass, while subsequent passes result in better hardness behavior for the processed material. Also, the elongated grains formed in the first pass of the CGP are gradually converted to the equiaxed counterparts by adding pass numbers. Eventually, higher corrosion resistance of the sample by imposing the CGP process is related to the quick formation of passivation film and the change in the morphology of the second phase and precipitates which hinder their electrochemical reactions and decrease the potential localized attack sites.展开更多
在半连续铸造过程中施加超声制备了ф1250 mm 2219铝合金大规格铸锭。利用光学显微镜、扫描电镜、电子万能试验机等仪器对常规铸锭和超声铸锭的微观组织与力学性能进行了检测与分析,探究超声作用的内在机制。结果表明：超声振动明显细...在半连续铸造过程中施加超声制备了ф1250 mm 2219铝合金大规格铸锭。利用光学显微镜、扫描电镜、电子万能试验机等仪器对常规铸锭和超声铸锭的微观组织与力学性能进行了检测与分析,探究超声作用的内在机制。结果表明：超声振动明显细化晶粒,减小截面上的晶粒尺寸不均匀性;改善组织形态,心部粗大的柱状晶转变为细小的球状等轴晶;有效抑制了晶内第二相的聚集和长大,使其呈均匀密集点状析出。超声不仅能有效提高铸锭各位置的综合力学性能,还能改善铸锭截面的力学均匀性。展开更多
Recently it is a hot topic to make full use of high abundant Y element in Nd_(2)Fe_(14)B-type permanent magnets.In contrast to Pr and Nd elements,Y shows different metallurgical behaviors during preparation process.In...Recently it is a hot topic to make full use of high abundant Y element in Nd_(2)Fe_(14)B-type permanent magnets.In contrast to Pr and Nd elements,Y shows different metallurgical behaviors during preparation process.In this paper,we have explored the magnetic properties,microstructures and corrosion performance of Pr-Nd-Y-Fe-B magnets fabricated by spark plasma sintering(SPS)technique from the ribbons of nanocrystalline and amorphous precursors,respectively.The coercivity and maximum energy product were improved for the magnets prepared from amorphous precursor materials(denoted as SPS-A hereafter)compared with the magnets prepared from crystalline precursor materials(denoted as SPS-C hereafter).Magnetic properties of Jr=0.79 T,Hci=864 k A/m,and(BH)_(max)=102 k J/m^(3)were obtained for SPS-A magnets.In contrast with SPS-C magnets,the magnetic properties of SPS-A magnets are not so sensitive to the preparation conditions,which is quite beneficial to the homogeneity of microstructure and enhancement of coercivity for large-scale production of the designated magnets.Aggregated(Pr,Nd,Y)-rich phase was found out in SPS-C magnets.Pr and Nd elements are rich at grain boundary while Y is distributed uniformly at main phase and grain boundary phase.The strip grains and equiaxed grains exist in SPS-C and SPS-A magnets,respectively.The enhanced magnetic properties for SPS-A magnets are accredited to the uniform distribution of rare-earth-rich phase and low demagnetization factor.It is revealed by electrochemical test and dipping test that the corrosion potential is more positive and the corrosion rate is slower for the SPS-A magnets in 3.5 wt.%Na Cl solution.The work is also expected to shed light on developing the nanocrystalline Pr-Nd-Y-Fe-B SPSed high-performance magnets in industry.展开更多
基金funded by“Quality Engineering Project of Anhui Province of China in 2016”entitled mold design and manufacturing experimental training center(2016sxzx050)。
文摘The use of a constrained groove pressing(CGP) method to plastically deform AA6063 aluminum alloy led to the improved surface properties. It was found that hardness magnitude is dramatically improved and its uniformity is considerably decreased after the first pass, while subsequent passes result in better hardness behavior for the processed material. Also, the elongated grains formed in the first pass of the CGP are gradually converted to the equiaxed counterparts by adding pass numbers. Eventually, higher corrosion resistance of the sample by imposing the CGP process is related to the quick formation of passivation film and the change in the morphology of the second phase and precipitates which hinder their electrochemical reactions and decrease the potential localized attack sites.
基金National Natural Science Foundation of China (51764043, 11762014)Scientific and Technological Program of Innovation and Guidance of Inner Mongolia (KCBJ2018017)+1 种基金Inner Mongolia Youth Talent Program of Science and Technology (NJYT-20-A16)Science Program for Returned Chinese Scholars of Inner Mongolia。
文摘在半连续铸造过程中施加超声制备了ф1250 mm 2219铝合金大规格铸锭。利用光学显微镜、扫描电镜、电子万能试验机等仪器对常规铸锭和超声铸锭的微观组织与力学性能进行了检测与分析,探究超声作用的内在机制。结果表明：超声振动明显细化晶粒,减小截面上的晶粒尺寸不均匀性;改善组织形态,心部粗大的柱状晶转变为细小的球状等轴晶;有效抑制了晶内第二相的聚集和长大,使其呈均匀密集点状析出。超声不仅能有效提高铸锭各位置的综合力学性能,还能改善铸锭截面的力学均匀性。
基金supported by the National Natural Science Foundation of China(Nos.51901089 and 51671097)the Foundation of Jiangxi Educational Committee(No.GJJ180472)+2 种基金the Science and Technology Program of Fujian Province(No.2017T3001)the Key Research and Development Program of Jinagxi Province(No.20201BBE51010)the Ph D.Start-up Foundation of Jiangxi University of Science and Technology(No.JXXJBS18052)。
文摘Recently it is a hot topic to make full use of high abundant Y element in Nd_(2)Fe_(14)B-type permanent magnets.In contrast to Pr and Nd elements,Y shows different metallurgical behaviors during preparation process.In this paper,we have explored the magnetic properties,microstructures and corrosion performance of Pr-Nd-Y-Fe-B magnets fabricated by spark plasma sintering(SPS)technique from the ribbons of nanocrystalline and amorphous precursors,respectively.The coercivity and maximum energy product were improved for the magnets prepared from amorphous precursor materials(denoted as SPS-A hereafter)compared with the magnets prepared from crystalline precursor materials(denoted as SPS-C hereafter).Magnetic properties of Jr=0.79 T,Hci=864 k A/m,and(BH)_(max)=102 k J/m^(3)were obtained for SPS-A magnets.In contrast with SPS-C magnets,the magnetic properties of SPS-A magnets are not so sensitive to the preparation conditions,which is quite beneficial to the homogeneity of microstructure and enhancement of coercivity for large-scale production of the designated magnets.Aggregated(Pr,Nd,Y)-rich phase was found out in SPS-C magnets.Pr and Nd elements are rich at grain boundary while Y is distributed uniformly at main phase and grain boundary phase.The strip grains and equiaxed grains exist in SPS-C and SPS-A magnets,respectively.The enhanced magnetic properties for SPS-A magnets are accredited to the uniform distribution of rare-earth-rich phase and low demagnetization factor.It is revealed by electrochemical test and dipping test that the corrosion potential is more positive and the corrosion rate is slower for the SPS-A magnets in 3.5 wt.%Na Cl solution.The work is also expected to shed light on developing the nanocrystalline Pr-Nd-Y-Fe-B SPSed high-performance magnets in industry.
