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Study on Heterogeneous Nuclei in Cast H13 Steel Modified by Rare Earth

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Journal of Rare Earths 2001年第4期19卷 280-283页

作者：兰杰贺俊杰丁文江王渠东朱燕萍 Sch. of mat. sci. eng. Shanghai Jiaotong Univ. Shanghai 200030 China

The dendrite segregation in cast H13 steel was weakened with RE modification treatment. Grain boundary carbide during quenching was also under control and impact toughness was improved greatly. By thermodynamic calculation, analysis of two-dimensional lattice misfitting and electron probe analysis, it is found that Ce2O3 may act as the heterogeneous nuclei of modified cast H13 steel.

关键词： rare earths cast H13 steel modification heterogeneous nuclei

Superelasticity of TiPdNi Alloys with and without Rare Earth Ce Addition

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Journal of mat.rials sci.nce & Technology 2003年第2期19卷 179-182页

作者： Qingchao TIAN, Jiansheng.WU and Yifeng.CHeng.ey Laboratory of the Ministry of Education for High Temperature mat.rials and Tests, School of mat.rials sci.nce and eng.neering, Shanghai Jiao Tong Univ., Shanghai 200030, China Sch. of mat. sci. and eng. Shanghai Jiaotong Univ. Shanghai 200030 China

Ti50.6Pd30Ni19.4 and Ti51Pd28Ni21 (Ce) alloys have been prepared under various temperatures for long time annealing. Differential scanning calorimetery (DSC), X-ray diffraction (XRD) and tensile test were employed to investigate the phase transformat.on behavior and superelasticity of the alloys. It has been found that the phase transformat.on temperature of Ti50.6Pd30Ni19.4 is about 40C higher than that of Ti51Pd28Ni21(Ce), and do not change much with different annealed temperature. Obvious superelasticity is retained in Ti50.6Pd30Ni19.4 alloy annealed at 400C for 18 h, and annealing at higher temperature shows a deterioration of this property. The Ce addition in TisiPd28Ni2i alloy significantly delays recrystallization, increases yied streng.h and elastic modulus, but the superelasticity is poor.

关键词： TiNi-Pd Shape memory alloy Superelasticity

PARTICLES ANALYSIS OF Al_2O_3 PARTICLE REINFORCED ZL202 mat.IX COMPOSITES PREPARED BY IN-SITU REACTION

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Acta Metallurgica Sinica(eng.ish Letters) 2002年第6期15卷 531-537页

作者： X.H. Yan, S.C. Sun and Z.Y. JiangSchool of mat.rials sci.nce and eng.neering, Jiangsu University, Jiangsu 212013, China Sch. of mat. sci. and eng. Jiangsu Univ. Zhenjiang 212013 China

ZL202 mat.ix composite reinforced by Al2O3 particles was prepared by combining in-situ reaction and casting techniques. Particles' size in the composites was from 1 to 5 microns in diameter. X-ray diffraction analysis verified that the reinforcing particleswere δ-Al2O3 which belong to γ-Al2O3 series. The wetting angle between mat.ix andreinforcement was less than 90°. Energy spectrum analysis indicated that the reactionin bell cover pressing process took place not so completely as in flouring stir process. When the reaction was finished, the mat.ix was still ZL202 alloy in ***.

关键词： metal mat.ix composites in-situ reaction particles

In-situ A1/24Si Functional Graded mat.rials Prepared by Electromagnetic Separation

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Journal of mat.rials sci.nce & Technology 2002年第5期18卷 385-386页

作者： KeLI JunWANG DaSHU BaodeSUN YaoheZHOU col.. of mat. sci. and eng. Shanghai Jiaotong Univ. Shanghai 200030 China

Cylinder-like in-situ AI/24Si FGMs were produced by using electromagnetic separating process. Si primary phase reinforced layer with volume fraction as high as 16 pct was formed at the outer region of the cylinder-like samples where the local hardness and wear resistance were enhanced remarkably. Moreover, both of streng.h and ductility in the inner region provided insurance of reliable streng.h for this as-cast gradient mat.rial. It indicated that general mechanical properties such as good wear resistance at the outer region and good ductility in the central part could be obtained with the optimized redistribution of the Si primary particles under the electromagnetic force.

关键词： FGMs In-situ Electromagnetic separation

X-ray Peak-Shift Determination of Deformat.on Fault Probability in Fe-Mn-Si Alloys

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Journal of mat.rials sci.nce & Technology 2002年第5期18卷 459-461页

作者： YonghuaRONG GangHE Zheng.ongGUO ShipuCHEN T.Y.Hsu(XUZuyao) Sch. of mat. sci. and eng. Shanghai Jiaotong Univ. Shanghai 200030 China

The X-ray diffraction peak-shift method was introduced into the determination of deformat.on fault probability (a) of Fe-Mn-Si alloys with various Mn contents and thermomechanical cycling numbers. The precise lattice constants required were obtained by numerical calculation instead of using standard sample without any fault. The influence of internal stress on the determined a has been evaluated, and the caused relative error was determined as about 4% and thus negligible. The results show that the deformat.on fault probability increases with decreasing Mn-content and increasing cycle number, which are qualitatively consistent with those results of Psf determined by peak-broadening method.

关键词： X-ray diffraction Peak-shift method Deformat.on fault probability Fe-Mn-Si alloy

Study on an Explosion Treated Steel Weld Metal with Prepared Crack

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Journal of mat.rials sci.nce & Technology 2001年第3期17卷 385-387页

作者： Xiaonan GUO and Xin LONG School of mat.rials sci.nce and eng.neering, Shanghai Jiao Tong University, Shanghai 200030, China Huaining CHEN and Liangshan CHEN Institute of Metal Research, Chinese Academy of sci.nces, Shenyang 110016, China Guangjun GAI Depa Sch. of mat. sci. and eng. Shanghai Jiaotong Univ. Shanghai 200030 China

A softening zone with recrystallized grain around the prepared crack tip in the shock waves treated C-Mn steel weld metal was observed. It is suggested that a dynamic recovery occurred around the prepared crack tip even at a low explosion pressure (5 GPa) because of the stress and strain concentration at the crack tip when shock waves pass through. This result supports the previous work on the improved mechanical properties of a shock treated welded joint with residual crack from the viewpoint of microstructure.

关键词： Study on an Explosion Treated Steel Weld Metal with Prepared Crack very high Chen

Electromagnetic Filtration of Primary Fe-Rich Phases from Al-Si Alloy Melt

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Journal of mat.rials sci.nce & Technology 2001年第3期17卷 306-310页

作者： Zhenming XU, Tianxiao LI, Da SHU and Yaohe ZHOU School of mat.rials sci.nce and eng.neering, Shanghai Jiaotong University, Shanghai 200030, China E-mail: zmxu@*** Sch. of mat. sci. and eng. Shanghai Jiaotong Univ. Shanghai 200030 China

Electromagnetic filtration of primary Fe-rich phases (complex compound of AlFeSiMn) from Al-Si alloy melt containing 1.2 wt pct Fe have been studied by theoretical analysis and on a self-designed electromagnetic filtration equipment. The principle of the electromagnetic filtration is that the EMF (electromagnetic force) scarcely acts on the primary Fe-rich phases having low electric conductivity, which are then moved in the direction opposite to that of the EMF. Experimental results show that the primary Fe-rich phases are separated from Al-Si alloy melt and are col.ected in the filter while the melt is in horizontal flow. The removal efficiency of the primary iron-phases (77) calculated is less as the greatest flow velocity of the melt (UM) and the height of the filter (2h) are larger, while it becomes larger as EMF, operating distance of electromagnetic force (cr) and particle size (dv) become larger. It has been confirmed that the primary iron-phases larger than 20 jim can be removed efficiently by theoretical analysis and experiments. This new technique is high efficient and available for continuously flowing melts as compared with natural settling and filtration methods, which offer a possibility for recycling high quality aluminum alloys.

关键词： Fe Al Electromagnetic Filtration of Primary Fe-Rich Phases from Al-Si Alloy Melt Si

Yield Vertices for Symmetric Slip on {110}<111> and Asymmetric Slip on {112}<111> Systems

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Journal of mat.rials sci.nce & Technology 2001年第6期17卷 605-609页

作者： Zhiyong CHEN, Xinming ZHANG, Churning LIU, Zhuoping ZHOU and Yang YANG Department of mat.rials sci.nce and eng.neering, Central South University, Changsha 410083, China Saiyi LI Department of Metallurgy and mat.rials eng.neering, Ka Dept. of mat. sci. and eng. Central South Univ. Changsha 410083 China

The single crystal yield surfaces (SCYS) of bcc metals for symmetric slip on {110} (111) and asymmetric slip on {112} (111) systems have been analyzed and deduced. The complete SCYS have been derived when their critical resolved shear stresses (CRSS) are specified in a particular case (such as for Mo metal). The results showed that there are 600 stress states that can be classified into 35 groups according to the crystal symmetry. Each group activates eight, six or five {110} (111) and {112} (111) slip systems depending on crystallographically nonequivalent slip systems groups. Among all these stress states, three groups activate eight systems, there are 24 stress states; four groups activate six systems, there are 48 ones; the remaining twenty-eight groups activate five systems, there are 528 ones. In this case, the fraction of vertices for which there is slip ambiguity (more than five active systems) is reduced considerably compared with pure {110} (111) slip.

关键词： 110 and Asymmetric Slip on Systems

Additional force field in cooling process of cellular Al alloy

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sci.nce China Chemistry 2002年第6期45卷 598-607页

作者：郑明军何德坪戴戈 Dept. of mat. sci. and eng. Southeast Univ. Nanjing 210096 China

The foaming process of Al alloy is similar to that of Al, but there is a solid-liquid state zone in the solidification process of cellular Al alloy which does not exist in the case of Al. In the unidirectional solidification of cellular Al alloy, the proportion of the solid phase gradually reduces from the solid front to the liquid front. This will introduce a force and result in a serious quick shrinkage. By the mat.emat.c and physical mode, the solidification of the cellular Al alloy is studied. The data measured by experiment are close to the result calculated by the mode. This kind of shrinkage can be solved by suitable cooling method in appropriate growth stage. The compressive streng.h of the cellular Al alloy made by this way is 40% higher than that of cellular Al.

关键词： cellular Al alloy, unidirectional solidification, two-phase zone, additional force field.