Research on the solidified microstructure and segregation behaviors of the UNS N10276 alloy produced by electroslag remelting

In this study,the solidified microstructure and segregation behaviors of the alloying elements and precipitate behaviors of the UNS N10276 alloy in a large-scale electroslag remelting(ESR)ingot were studied.Further,the formation of the solidified microstructure and segregation of ESR were systematically analyzed via thermodynamic calculations.The ESR ingot of the UNS N10276 alloy exhibits a typical dendritic structure.The secondary dendrite spacing at the head of the ingot is clearly larger than that at the bottom of the ingot.The alloying elements(e.g.,Mo,Mn,Si,and C),which are positive segregation elements,segregate to the interdendritic zones during the solidification process.However,Fe,W,and Cr segregate to the dendritic trunk zones,indicating that they are negative segregation elements.Among the alloying elements,Mo segregates the most,especially at the head of the ESR ingot.Majority of the precipitates that precipitate in the interdendritic zones and at grain boundaries belong to large-scale μ and M6C phases,respectively.Mo is the main element of the precipitates.The precipitates at the head of the ESR ingot are more abundant and larger than those at the bottom of the ingot.Hence,to improve the metallurgical quality and hot working properties of the UNS N10276 alloy,the segregation of the Mo element should be minimized,whereas the formation of the precipitates should be reduced as much as possible during the optimization of the composition and production processes.

Effects of Additional Elements on Microstructure and Precipitation Behaviour in Rapidly Solidified Al-Ti Base Alloys

Rapidly solidified Al-Ti base alloys were prepared by melt spinning at the cooling rate about 107 K/s. The melt-spun ribbons were used to observe the dricrostructures after heat treatment.In the supersaturated Al-Tl-Si alloy, age hardening occurred after 1 h anneal in the temperature range of 4000~500℃, which seems to be attributed to the precipitation of metastable Ll2- (Al,Si)3Ti phase. However. the microhardness was relatively low because of the low v/o and the insufflcient stability of precipitates. Thus. Cr was added to Al-Ti-Si alloys in order to stabilize the microstructures and to increase the v/o of precipitate5. As a result. the alIoys containing Cr were evaluated to possess the improved properties at the service temperature.

Microstructure of Rapidly Solidified Al-3.8Li-0.8Mg-0.4Cu-0.13Zr Alloy by Spray Deposition Processing

谷物是在尺寸的 5-20 亩 m，并且微观结构展出快速的团结优点。收缩孔被避免了，并且优先的粒子边界的形成被阻止了到大程度。但是仍然在那里存在有各种各样的形状的一些微毛孔。相对密度同样 -- 扔的材料平均是 94% 。主要在测试合金猛抛是三角洲(AlLi ) ， S (Al//2CuMg ) 和三角洲素数(Al//3Li ) 分阶段执行。(编辑作者摘要) 10 个裁判员。

Positron Annihilation Study on the Microstructural Stability in Rapidly Solidified Al_(92.3)Fe_(4.3)V_(0.7)Si_(1.7)Mm_(1.0) Alloy

Rapidly solidified Al92.3Fe4.3V0.7Si1.7Mm1.0 alloy has been studied by positron lifetime spectroscopy and the variations on the intedecial defects with the annealing temperature were revealed by an analysis of the lifetime results. The intedece characteristics derived from the positron-lifetime results could be used to give a satisfactory interpretation of the dependence of mechanical properties on the annealing temperature

Microstructure and compression deformation behavior in the quasicrystalreinforced Mg-8Zn-1Y alloy solidified under super-high pressure

The microstructure of Mg-8Zn-1Y alloy solidified under super-high pressure was analyzed through X-ray diffraction（XRD）, scanning electron microscopy（SEM） and energy dispersive spectroscopy（EDS）. And, compression deformation behavior at room-temperature was studied. The results showed that the microstructure of Mg-8Zn-1Y alloy solidified under ambient pressure and super-high pressure was both mainly composed of ■-Mg and quasicrystal I-Mg3Zn6 Y. Solidification under super-high pressure contributed to refining solidified microstructure and changing morphology of the intergranular second phase. The morphology of intergranular second phase（quasicrystal I-Mg3Zn6Y） was transformed from continuous network（ambient pressure） to long island（high pressure） and finally to granular（super-high pressure） with the increase in pressure. The compressive strength, yield strength and rupture strain of the samples solidified under ambient pressure were significantly improved from 262.6 MPa, 244.4 MPa and 13.3% to 437.3 MPa, 368.9 MPa and 24.7% under the pressure of 6 GPa, respectively. Under ambient pressure, cleavage plane on compressive fracture was large and smooth. When it was solidified under the pressure ranging from 4 to 6 GPa, cleavage plane on compressive fracture was small and coarse. In addition, dimple, tear ridge and lobate patterns existed.

Microstructure Refinement of Mg-Gd-Y-Zr Alloy Under Pulsed Magnetic Field

The effects of pulsed magnetic field on the solidified microstructure of Mg-Gd-Y-Zr alloy were investigated. Fine uniform equiaxed grains are acquired in the whole ingot by the pulsed magnetic field treatment,and the average grain size of the as-cast φ50 mm and φ100 mm ingots is refined to 37 μm and 47 μm with the pulsed magnetic field.The macrosegregation of solute elements of Mg-Gd-Y-Zr alloy is also reduced by the pulsed magnetic field treatment. Structure refinement is due to the electromagnetic undercooling zone in front of the solid/liquid interface by the magnetic pressure,and reduction of temperature gradient by the vibration of melt resulted from the pulsed magnetic field,which increases the nucleation rate and prohibits dendrite growth.In addition,primary α-Mg dendrites break into fine crystals, resulting in a refined solidification structure of the magnesium alloys.The Joule heat effect induced in the melt also strengthens the grain refinement effect and the spheroidization of dendrite arms.