A comprehensive study on Sn macrosegregation behavior in ternary Al-Sn-Cu alloys was carried out by comparative analysis between gravity casting and squeeze casting samples.The microstructure and Sn distribution of th...A comprehensive study on Sn macrosegregation behavior in ternary Al-Sn-Cu alloys was carried out by comparative analysis between gravity casting and squeeze casting samples.The microstructure and Sn distribution of the castings were characterized by metallography,scanning electron microscopy(SEM),energy-dispersive X-ray(EDX)spectroscopy,and a direct reading spectrometer.Results show that there are obvious differences in Sn morphology between gravity casting and squeeze casting alloys.Under squeeze casting condition,the grain size of the casting is smaller and the distribution ofβ(Sn)is uniform.This effectively reduces the segregation of triangular grain boundary as well as the segregation of Sn.The segregation types of Sn in gravity casting and squeeze casting samples are obviously different.The upper surfaces of gravity casting samples show severe negative segregation,while all the lower surfaces have positive segregation.Compared with gravity casting,squeeze casting solidifies under isostatic pressure.Due to the direct contact between the upper surface of the casting and the mold,the casting solidifies faster under higher undercooling degree and pressure.Consequently,the uniform distribution of Sn reduces the segregation phenomenon on the surface of the casting.展开更多
The macrosegregation behaviors of Al-Sn-Cu ternary immiscible alloy castings and their effects on mechanical and tribological properties were investigated.The results demonstrate that Sn and Cu segregate in the castin...The macrosegregation behaviors of Al-Sn-Cu ternary immiscible alloy castings and their effects on mechanical and tribological properties were investigated.The results demonstrate that Sn and Cu segregate in the casting simultaneously,and the mass fraction of the two elements has a"U"shaped distribution.Significantly,positive and negative segregation occur in the casting,with positive segregation appearing on the top and lower surfaces and negative segregation on the remaining surfaces,with the 1/2 surface(hot node location)having the highest degree of negative segregation.Furthermore,the results of Vickers hardness,tensile strength,and elongation show that Sn and Cu cooperatively affect the mechanical properties of castings.The higher the mass fraction of Sn and Cu elements,the higher the hardness,the greater the tensile strength,and the better the elongation.The findings of the step-by-step loading tests demonstrate that the segregation of Sn and Cu significantly impacts the tribological characteristics of the castings.The higher the mass fraction of Sn and Cu on the sample surface,the better the tribological characteristics.展开更多
通过机械合金化制备了 Al-15%Pb-4%Si-1%Sn-1.5%Cu(质量分数)纳米晶粉末。采用 X 射线衍射(XRD),扫描电镜(SEM)和透射电镜(TEM)对不同球磨时间的混合粉末的组织结构、晶粒大小、微观形貌以及颗粒中化学成分分布情况进行了研究。结果表...通过机械合金化制备了 Al-15%Pb-4%Si-1%Sn-1.5%Cu(质量分数)纳米晶粉末。采用 X 射线衍射(XRD),扫描电镜(SEM)和透射电镜(TEM)对不同球磨时间的混合粉末的组织结构、晶粒大小、微观形貌以及颗粒中化学成分分布情况进行了研究。结果表明混合粉末经过球磨后形成了纳米晶,其组织非常均匀。球磨对 Pb 的作用效果明显大于对 Al 的作用效果,经过 40 h 球磨后 Pb 粒子达到 40 nm,而 Al 在球磨 60 h 后晶粒为 65 nm;经球磨后,Cu 和 Si 固溶于 Al 的晶格中,而 Sn 则固溶于 Pb 晶格中,并且 Al 和 Pb 发生了互溶,形成了 Pb(Al)超饱和固溶体;在球磨过程中硬度高的脆性粒子 Si 难于完全实现合金化。展开更多
选择Al Sn Si Cu Mg合金作为研究对象,采用Leica光学显微镜、EPM810Q电子显微镜等手段观察分析Cu、Mg、Sn、Si形态分布规律,进而研究了加工工艺对合金组织性能的影响,同时提出高温短时退火制度,最终确定预处理工艺和退火制度,发现通过...选择Al Sn Si Cu Mg合金作为研究对象,采用Leica光学显微镜、EPM810Q电子显微镜等手段观察分析Cu、Mg、Sn、Si形态分布规律,进而研究了加工工艺对合金组织性能的影响,同时提出高温短时退火制度,最终确定预处理工艺和退火制度,发现通过加工和热处理,可消除合金中Sn、Si晶间网状分布,从而改善合金的加工性能。展开更多
Al-20Sn-1Cu powders were prepared by gas atomization in an argon atmosphere with atomizing pressures of 1.1 and 1.6 MPa. The charac-teristics of the powders are determined by means of dry sieving, scanning electron mi...Al-20Sn-1Cu powders were prepared by gas atomization in an argon atmosphere with atomizing pressures of 1.1 and 1.6 MPa. The charac-teristics of the powders are determined by means of dry sieving, scanning electron microscopy (SEM), optical microscopy (OM), and X-ray diffractometry (XRD). The results show that the powders exhibit a bimodal size distribution and a higher gas pressure results in a broad size distribution. All particles in both cases are spherical or nearly spherical and satellites form on the surface of coarse particles. Dendritic and cellular structures coexist in the particle. With decreasing particle diameter, the secondary dendrite arm spacing (SDAS) decreases and the cooling rate increases. The particles processed under high gas atomization pressure (1.6 MPa) exhibit a lower SDAS value and a higher cooling rate than those of the same size under low gas atomization pressure (1.1 MPa). The XRD results show that the Sn content increases with decreasing particle size.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51575151)the Science and Technology Project of Anhui Province,China(No.1501021006)。
文摘A comprehensive study on Sn macrosegregation behavior in ternary Al-Sn-Cu alloys was carried out by comparative analysis between gravity casting and squeeze casting samples.The microstructure and Sn distribution of the castings were characterized by metallography,scanning electron microscopy(SEM),energy-dispersive X-ray(EDX)spectroscopy,and a direct reading spectrometer.Results show that there are obvious differences in Sn morphology between gravity casting and squeeze casting alloys.Under squeeze casting condition,the grain size of the casting is smaller and the distribution ofβ(Sn)is uniform.This effectively reduces the segregation of triangular grain boundary as well as the segregation of Sn.The segregation types of Sn in gravity casting and squeeze casting samples are obviously different.The upper surfaces of gravity casting samples show severe negative segregation,while all the lower surfaces have positive segregation.Compared with gravity casting,squeeze casting solidifies under isostatic pressure.Due to the direct contact between the upper surface of the casting and the mold,the casting solidifies faster under higher undercooling degree and pressure.Consequently,the uniform distribution of Sn reduces the segregation phenomenon on the surface of the casting.
基金This research was financially supported by the National Natural Science Foundation of China(No.51575151 and No.52005005)the Science and Technology Project of Anhui Province,China(No.1501021006).
文摘The macrosegregation behaviors of Al-Sn-Cu ternary immiscible alloy castings and their effects on mechanical and tribological properties were investigated.The results demonstrate that Sn and Cu segregate in the casting simultaneously,and the mass fraction of the two elements has a"U"shaped distribution.Significantly,positive and negative segregation occur in the casting,with positive segregation appearing on the top and lower surfaces and negative segregation on the remaining surfaces,with the 1/2 surface(hot node location)having the highest degree of negative segregation.Furthermore,the results of Vickers hardness,tensile strength,and elongation show that Sn and Cu cooperatively affect the mechanical properties of castings.The higher the mass fraction of Sn and Cu elements,the higher the hardness,the greater the tensile strength,and the better the elongation.The findings of the step-by-step loading tests demonstrate that the segregation of Sn and Cu significantly impacts the tribological characteristics of the castings.The higher the mass fraction of Sn and Cu on the sample surface,the better the tribological characteristics.
基金This work is supported by Jiangsu Key Laboratory for Advanced Metallic Materials,China(No.BM2007204)the Fundamental Research Funds for the Central Universities,China(No.2242016k40011).
文摘通过机械合金化制备了 Al-15%Pb-4%Si-1%Sn-1.5%Cu(质量分数)纳米晶粉末。采用 X 射线衍射(XRD),扫描电镜(SEM)和透射电镜(TEM)对不同球磨时间的混合粉末的组织结构、晶粒大小、微观形貌以及颗粒中化学成分分布情况进行了研究。结果表明混合粉末经过球磨后形成了纳米晶,其组织非常均匀。球磨对 Pb 的作用效果明显大于对 Al 的作用效果,经过 40 h 球磨后 Pb 粒子达到 40 nm,而 Al 在球磨 60 h 后晶粒为 65 nm;经球磨后,Cu 和 Si 固溶于 Al 的晶格中,而 Sn 则固溶于 Pb 晶格中,并且 Al 和 Pb 发生了互溶,形成了 Pb(Al)超饱和固溶体;在球磨过程中硬度高的脆性粒子 Si 难于完全实现合金化。
文摘选择Al Sn Si Cu Mg合金作为研究对象,采用Leica光学显微镜、EPM810Q电子显微镜等手段观察分析Cu、Mg、Sn、Si形态分布规律,进而研究了加工工艺对合金组织性能的影响,同时提出高温短时退火制度,最终确定预处理工艺和退火制度,发现通过加工和热处理,可消除合金中Sn、Si晶间网状分布,从而改善合金的加工性能。
基金the Major State Ba-sic Research Development Program of China (Nos. 2006CB605203 and 2006CB605204)
文摘Al-20Sn-1Cu powders were prepared by gas atomization in an argon atmosphere with atomizing pressures of 1.1 and 1.6 MPa. The charac-teristics of the powders are determined by means of dry sieving, scanning electron microscopy (SEM), optical microscopy (OM), and X-ray diffractometry (XRD). The results show that the powders exhibit a bimodal size distribution and a higher gas pressure results in a broad size distribution. All particles in both cases are spherical or nearly spherical and satellites form on the surface of coarse particles. Dendritic and cellular structures coexist in the particle. With decreasing particle diameter, the secondary dendrite arm spacing (SDAS) decreases and the cooling rate increases. The particles processed under high gas atomization pressure (1.6 MPa) exhibit a lower SDAS value and a higher cooling rate than those of the same size under low gas atomization pressure (1.1 MPa). The XRD results show that the Sn content increases with decreasing particle size.
