Microstructure Characteristics of Ni-Nb Near Eutectic Alloy during EBFZM Directional Solidification

Microstructure Characteristic of Ni-Nb near eutectic alloy is systematically investigated during directional solidification with electron beam floating zone melting (EBFZM). The effect of the Zone melting rate on the microstructure has also been studied.

Hot compressive deformation of eutectic Al-17at%Cu alloy on the interface of the Cu-Al composite plate produced by horizontal continuous casting

On the interface of the Cu-Al composite plate from horizontal continuous casting,the eutectic microstructure layer thickness ac-counts for more than 90%of the total interface thickness,and the deformation in rolling forming plays an important role in the quality of the composite plate.The eutectic microstructure material on the interface of the Cu-Al composite plate was prepared by changing the cooling rate of ingot solidification and the deformation in hot compression was investigated.The results show that when the deformation temperature is over 300℃,the softening effect of dynamic recrystallization ofα-Al is greater than the hardening effect,and uniform plastic deformation of eutectic microstructure is caused.The constitutive equation of flow stress in the eutectic microstructure layer was established by Arrhenius hy-perbolic-sine mathematics model,providing a reliable theoretical basis for the deformation of the Cu-Al composite plate.

STUDY ON THE MICROSTRUCTURE OF LaB_6-ZrB_2 IN-SITU COMPOSITE

ＳＴＵＤＹＯＮＴＨＥＭＩＣＲＯＳＴＲＵＣＴＵＲＥＯＦＬａＢ６┐ＺｒＢ２ＩＮ┐ＳＩＴＵＣＯＭＰＯＳＩＴＥＣｈｅｎＣｈａｎｇｍｉｎｇ（陈昌明），ＺｈａｎｇＬｉｔｏｎｇ（张立同），ＺｈｏｕＷａｎｃｈｅｎｇ（周万城），ＣｈｅｎｇＬａｉｆｅｉ（成来飞）（Ｓｔａ...

Morphology evolution of Al_9(Mn, Ni)_2 eutectic phase in Al-4Ni-2Mn alloy during heat treatment at 350℃

The morphology evolution of AI9（Mn,Ni）2 eutectic phase in AI-4Ni-2Mn alloy at 350 .C was examined. Two kinds of morphology evolution trends of AIg（Mn, Ni）2 eutectic phase were observed by using scanning electron microscopy and transmission electron microscopy. The ribbon-like AIg（Mn, Ni）2 eutectic phase taking up a small portion of the eutectic structures gradually changes from ribbon-like morphology to rod-like during the heat treatment. The rod-like AIg（Mn, Ni）2 eutectics, primary eutectic structure in the alloy, become unstable at the transverse sub- boundaries of the eutectic rod when the samples are heat treated at 350 .C, and then split up into short rods with the extension of heat treatment time. Also, the Vickers microhardness test was used to characterize the change of local mechanical properties. The hardness test results indicate that local morphology evolution of eutectic phase has no obvious effect on the local mechanical properties of the alloy. The microhardness of the eutectic area increases slightly when the heat treatment time is extended to 192 h or 360 h.

Phase-field simulation of lamellar growth for a binary eutectic alloy

Using general multi-phase-field model,detailed microstructures corresponding to different initial lamellar sets were simulated in a binary eutectic alloy with an asymmetric phase diagram.The simulation results show that regular or unstable oscillating lamellar structures depend on the initial lamellar widths of two solid phases.A lamellar morphology map associating with the initial widths has been derived,which is capable of showing the condition of forming various lamella structures.For instance,a regular lamella was formed with fast solidification while large lamella resulted from disorder growth with low interfacial velocity. The investigated interface velocities indicate that with fast solidification to form regular lamella,a disorder growth manner or a large lamellar spacing causes a low interface velocity.These results are in good agreement with those proposed by Jackson-Hunt model.

Effect of Mischmetal on As-cast Microstructure and Mechanical Properties of M2 High Speed Steel

High speed steel has been widely used in various fields due to their excellent red hardness and good wear resistance. However, the influence of mischmetal （Ce-La） on the as-cast microstructures and mechanical properties of high speed steel has rarely been reported. Thus, the microstructure and mechanical properties of M2 high speed steel with addition of mischmetal （Ce-La） were investigated. The morphology and distribution of the eutectic carbides of the steel were observed by using optical microscopy and scanning electron microscopy, and the impact toughness and bending strength were tested. The results show that adding mischmetal has an obvious effect on the microstructure and mechanical properties of M2 high speed steel. The coarse eutectic structure is refined, the weak connection of the carbide networks is broken and the flake carbides become short and fine. More networks of eutectic carbides dissolve into the matrix. When a suitable adding content of mischmetal is selected, for example, 0.3 mass%, the impact strength and bending strength can increase by 27% and 10.76% compared with that without misehmetal, respectively.

Microstructure and Mechanical Properties of Fiber Laser Welded GH3535 Superalloy

As a primary material of the thorium molten salt reactor（TMSR） that is a suitable candidate reactor of the Generation IV nuclear reactors, GH3535 superalloy was successfully welded. The effect of laser beam welding（LBW） on microstructure evolution of fusion zone（FZ） and heat affected zone（HAZ）, such as element segregation, precipitate behavior and grain evolution, was investigated. The microhardness and tensile properties were tested and discussed. The results of microstructure evolution showed that a number of fine M6C-y eutectic phases precipitated at solidification grain boundaries and interdendritic region in FZ. Compared to base metal zone（BMZ）, the grain size of HAZ has no obvious change. While a few of M6C-y eutectic phases were observed in partially melted zone（PMZ） of HAZ. The results of microhardness indicated that the hardness of FZ was higher than that of HAZ and BMZ. The results of tensile test showed that the ultimate tensile strength of joints at room temperature, 650 and 700？C were98%, 97% and 99% of that of BM, respectively. All the tensile specimens of joints failed in BMZ rather than in PMZ where M6 C carbides had been transformed into M6C-y eutectic phases.