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| 1 | INFLUENCE OF PULSED MAGNETIC FIELD ON MICROSTRUC-TURES AND MACRO-SEGREGATION IN 2124 Al-ALLOY显示文摘The structures and macro-segregation of 2124 Al-alloy were studied when a pulsedmagnetic field (PMF) was applied during solidification. It is found through experi-ments that a remarkable change occurs in the solidification structures of 2124 Al-alloyunder pulsed magnetic field. The eutectic phase at grain boundaries change from thickcontinuous eutectic network to thin discontinuous one, and the distribution of soluteelements was also homogenized. The typical negative segregation phenomenon of Cu incommon solidification condition was restrained, and the segregation of Mg decreased. | C.Y.Ban,J.Z.Cui,Q.X.Ba,G.M.Lu and B.J.ZhangP.O. Box 317, The Key Laboratory of Electromagnetic Processing of Materials, Ministry of Education, Northeastern University, Shenyang 110004, China Manuscript received 10 October 2001 | 2002 | Acta Metallurgica Sinica(English Letters)2002，15，4： | 19 |
| 2 | EVOLUTION OF AS-CAST MICROSTRUCTURES OF 356 ALUMINIUM ALLOY CAST BY LIQUIDUS CASTING显示文摘A new method (liquidus casting) was used for 356 Al alloy semi-solid slurry mak-ing. The structures of 356 Al alloy cast by a Fe mould and semi-continuous castingmachine at different temperatures were investigated. How the globular grains formwas also discussed. The results show that either being cast by single Fe mould orsemi-continuous machine, the microstructures are not conventional dendrites but fineand net-globular grains. The average grain size is smaller than 30μm and suitableenough for thixoforming, meanwhile it can improve the mechanical properties of fol-lowing products. Under the suitable casting velocity and cooling intensity, most ofglobal grains prolong their global growth and collide with each other before dendriticgrowth because of the large amount of the nucleation sites. | J.Dong G.M.Lu J.Z.Cui Z.H.Zhao | 2003 | Acta Metallurgica Sinica(English Letters)2003，16，1： | 5 |
| 3 | SEMI-SOLID MICROSTRUCTURE AND ITS EVOLUTION OF WROUGHT ALUMINUM ALLOY BY DIRECTLYHEATING-ISOTHERMAL TREATMENT显示文摘Microstructure evolution of wrought aluminum alloy extruded rods and the mechanism of liquid phase formation during reheating were investigated. And the relation between the volume fraction of liquid phase and the recrystallization microstructure was proposed. The results show that increase in reheating temperature and time can augment the volume fraction of liquid phase and accelerate the grain spheroidization, as a result of which the requirement of semi-solid forming can be satisfied. Due to the higher aberration energy of grain boundary, the melting point is lowered as a result of the easy diffusion of atoms. At higher reheating temperature the grain boundary melts, the growth of the recrystallized grain is inhibited and the grain is refined. The composition of the low melt-point phase along the recrystallized grains was determined using EDS. It can be seen from the experimental results that when the extrusion rod of the wrought aluminum alloy is reheated at 610℃ for 20min, perfect fine equiaxial grains can be obtained, the average grain size is about 66.34μm and the volume fraction of solid phase is about 68%. | X.T.Liu J.Z.Cui | 2004 | Acta Metallurgica Sinica(English Letters)2004，17，6： | 2 |
| 4 | A STUDY OF EXPERT SYSTEM FOR SECTION EXTRUSION PROCESS BASED ON FINITE ELEMENT METHOD SIMULATION显示文摘The samples obtained by Finite Element Method (FEM) simulation for section extrusion process have been trained on BP Neural Networks. The mapping relationsbetween die’s geometrical parameters and energetic parameters, such as stress and strain generated in the die are established. The extrusion process model and its expert system are also determined. The excellent expansibility this system possesses provides a new prospect for the future development of expert system for section extrusion dies. | H.W.Liu 1) , H.Ding 2) and J.Z.Cui 2) 1) School of Mechanical Engineering, Shenyang University, Shenyang 110044, China 2) School of Materials & Metallurgy, Northeastern University, Shenyang 110006, China | 1999 | Acta Metallurgica Sinica(English Letters)1999，12，5： | 1 |
| 5 | A APPLICATION OF ANSYS ON A SECTION EXTRUSION DIE显示文摘Porthole dies are important tools in extrusion process to produce hollow sections and the life of the dies counts for the cost of products. In this work, the finite element method was adopted to analyze a particular porthole die to produce hollow rectangle sections which are widely used in construction. The upper die was mainly studied. Because it is symmetrical, a quarter of the die was analyzed. The upper die was divided into 2199 elements with 3018 nodes. Elements were produced by four steps and the geometric shape of the die could be well simulated. The boundary condition was given according to the shape of the welding chamber and an empirical average extrusion stress was adopted, which was 210N/mm 2. Three-dimensional equivalent stresses were received. The original porthole die studied had obvious stress concentration and the stress distribution was very inhomogeneous, which would heavily affect the die life. A new design was proposed in which the portholes were rearranged and their shape and dimension were changed. According to the finite element analysis, the stress distribution of the improved die was quite homogeneous and the stress concentration was lessened. | H.W.Liu 1) ,H.Ding 2) and J.Z.Cui 2) 1) School of Mechanical Engineering, Shenyang University, Shenyang 110044, China 2) School of Materials & Metallurgy, Northeastern University, Shenyang 110006, China | 1999 | Acta Metallurgica Sinica(English Letters)1999，12，5： | 1 |
| 6 | EFFECT OF ELECTRIC FIELD ON THE AUSTENIZATION OF A LOW CARBON STEEL显示文摘With an electric field during austenitizing, the martensite transformation of the low carbon steel was promoted, and more martensite were obtained. The electric field promotes the homogeneity of carbon, and reduces the free energy of austenite. The critical neuclus r* and the critical driving force G* responsible for the nucleation of proeutectoid ferrite were increased. As a result of which the diffusion controlled proeuctoid ferrite transformation was retarded and the hardenability was improved. | X.T.Liu J.Z.Cui | 2004 | Acta Metallurgica Sinica(English Letters)2004，17，5： | 0 |
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