A synthesis method for the production of porous bulk metallic glass (BMG) was introduced. This method utilizes the su- perplastic forming ability of amorphous powder in the supercooled liquid (SCL) state and intenerat...A synthesis method for the production of porous bulk metallic glass (BMG) was introduced. This method utilizes the su- perplastic forming ability of amorphous powder in the supercooled liquid (SCL) state and intenerating salt mixture as a placeholder to produce BMG foam by using a hot die pressing method. Scanning electron microscope (SEM), X-ray diffraction (XRD) and dif- ferential scanning calorimetry (DSC) were employed to characterize the morphologies of foaming structure, the crystallization and the percentage of crystallization of the as-produced porous BMG. The results suggested that the formation of porous structure by su- perplastic forming process is feasible. Good bonding effect was observed between amorphous powder particles. Less than 6.5% of crystalline phases were formed during hot pressing, and less than 5.5% of residual salt was enclosed in the foam. To remove any re- sidual salt particles, salt preforms with three-dimensional network and good connectivity is necessary.展开更多
The superplastic behavior of a commercial duplex stainless steel has beenstudied by means of isothermal hot tensile test at temperatures of 850-1050 deg C for the initialstrain rates ranging from 3X10^(-4) s^(-1) to 5...The superplastic behavior of a commercial duplex stainless steel has beenstudied by means of isothermal hot tensile test at temperatures of 850-1050 deg C for the initialstrain rates ranging from 3X10^(-4) s^(-1) to 5X10^(-2) s^(-1). At 960 deg C, the best superplasticdeformation that caused the maximum elongation greater than 840 percent was obtained for an initialstrain rate of 1.2X10^(-3) s^(-1). At 850 deg C, the best elongation 500 percent was achieved for aninitial strain rate of 2.5X10^(-3) s^(-1) During the deformation in higher temperature region,coarse gamma grains formed during the prior treatments were broken into spherical particles,resulting in a homogeneous dispersion of gamma particles within the delta-ferrite matrix. However,at lower temperatures between 800 and 950 deg C, the sigma phase was formed through the eutectoiddecomposition of delta->gamma+sigma, resulting finally in the stable equiaxed micro-duplexstructures with delta/gamma and gamma/sigma respectively. The precipitation of the sigma phaseplayed an important role in improving the superplasticity at 850 deg C. The strain-rate sensitivitycoefficient, m-values, were also determined by the strain rate change tests. The microstructurestudies show that the superplastic process occurs mainly by the local work hardening and thesubsequent dynamic recrystallization and a grain boundary sliding and grain switching mechanism.展开更多
The investigation on the superplastic bugling capability of 1.5?mm mill annealed Ti 6Al 4V buttcover plate by means of manual gas tungsten arc welding (M GTAW) and fusion type plasma arc welding (F PAW) have been eval...The investigation on the superplastic bugling capability of 1.5?mm mill annealed Ti 6Al 4V buttcover plate by means of manual gas tungsten arc welding (M GTAW) and fusion type plasma arc welding (F PAW) have been evaluated respectively. The result shows that untreated Ti 6Al 4V buttcover plate by M GTAW exhibits no superplasticity, while the same untreated plate by F PAW, shows good superplastic ability because of extremely fine acicular martensite microstructure of weld metal. To the buttcover plate by M GTAW, the microstructure of weld metal changed into streaky α structure which exhibits good superplasticity from the original β structure under the condition of the constant temperature of 940?℃ with the deformation degree of 45%, and changed into the fine equiaxed grain which possesses excellent superplastic ability under the condition of the constant temperature of 800?℃ with the deformation degree of 40%.展开更多
基金This work was financially supported by the Fundamental Research Project of Shenyang Science and Technology Bureau, China (No. 061508).
文摘A synthesis method for the production of porous bulk metallic glass (BMG) was introduced. This method utilizes the su- perplastic forming ability of amorphous powder in the supercooled liquid (SCL) state and intenerating salt mixture as a placeholder to produce BMG foam by using a hot die pressing method. Scanning electron microscope (SEM), X-ray diffraction (XRD) and dif- ferential scanning calorimetry (DSC) were employed to characterize the morphologies of foaming structure, the crystallization and the percentage of crystallization of the as-produced porous BMG. The results suggested that the formation of porous structure by su- perplastic forming process is feasible. Good bonding effect was observed between amorphous powder particles. Less than 6.5% of crystalline phases were formed during hot pressing, and less than 5.5% of residual salt was enclosed in the foam. To remove any re- sidual salt particles, salt preforms with three-dimensional network and good connectivity is necessary.
文摘The superplastic behavior of a commercial duplex stainless steel has beenstudied by means of isothermal hot tensile test at temperatures of 850-1050 deg C for the initialstrain rates ranging from 3X10^(-4) s^(-1) to 5X10^(-2) s^(-1). At 960 deg C, the best superplasticdeformation that caused the maximum elongation greater than 840 percent was obtained for an initialstrain rate of 1.2X10^(-3) s^(-1). At 850 deg C, the best elongation 500 percent was achieved for aninitial strain rate of 2.5X10^(-3) s^(-1) During the deformation in higher temperature region,coarse gamma grains formed during the prior treatments were broken into spherical particles,resulting in a homogeneous dispersion of gamma particles within the delta-ferrite matrix. However,at lower temperatures between 800 and 950 deg C, the sigma phase was formed through the eutectoiddecomposition of delta->gamma+sigma, resulting finally in the stable equiaxed micro-duplexstructures with delta/gamma and gamma/sigma respectively. The precipitation of the sigma phaseplayed an important role in improving the superplasticity at 850 deg C. The strain-rate sensitivitycoefficient, m-values, were also determined by the strain rate change tests. The microstructurestudies show that the superplastic process occurs mainly by the local work hardening and thesubsequent dynamic recrystallization and a grain boundary sliding and grain switching mechanism.
文摘The investigation on the superplastic bugling capability of 1.5?mm mill annealed Ti 6Al 4V buttcover plate by means of manual gas tungsten arc welding (M GTAW) and fusion type plasma arc welding (F PAW) have been evaluated respectively. The result shows that untreated Ti 6Al 4V buttcover plate by M GTAW exhibits no superplasticity, while the same untreated plate by F PAW, shows good superplastic ability because of extremely fine acicular martensite microstructure of weld metal. To the buttcover plate by M GTAW, the microstructure of weld metal changed into streaky α structure which exhibits good superplasticity from the original β structure under the condition of the constant temperature of 940?℃ with the deformation degree of 45%, and changed into the fine equiaxed grain which possesses excellent superplastic ability under the condition of the constant temperature of 800?℃ with the deformation degree of 40%.
