ZHAO Xinbing Zhejiang University
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Hangzhou
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China LCKEK Institut fur Metallkunde und Metallphysik der RWTH Aachen
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Germany Department of Materials Scicnce and Engineering
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Zhejiang Univer sity
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Hangzhou 310027
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China
金属学报(英文版)
Most of the available methods for the calculation of the three dimensional(3D)grain size dis- tribution functions(SDF)are based on the S model and lead a grave systematical error.The origin is the basic supposition of spherical grains in the S model,which does not correspond with the feature of real grains.A new model called A model is developed based on the hypothe- sis of polvhedral grains.The probability functions of the A model and the method to calculate the 3D SDFs using the A model are given in the present paper.The theoretical analyses and experimental tests have demonstrated that the A model reduces the systematical error radical- ly.It is nearly as simple as the so far used S model,but gives much better results in repro- ducing of 3D SDFs from the measured ID or 2D SDFs.
关键词:
grain size
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null
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null
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null
WU Min XU Yuehuang SHEN Gongtian Wuhan University
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Wuhan
,
China
金属学报(英文版)
The serratedflow of alloy LC9 with different regimes of heat treatment has been investigated at constant rate of stretching.The critieal strain ε_c at the starting of serrated flow increases with the extension of aging.The activation energy of the process is 0.63 e V which is consistent with the diffusion activation energy of vacancies in A1.The ε_c decreases while the strain rate ε increases,i.e.,with negative strain rate relation.This relation is contrary to that of the an- nealed samples.It shows that the serrated 17ow of annealed sample is controlled by deformation vaeancies,and that of aged sample is controlled by quenching vacancies.The den- sity and shape of the serration are changed by aging.The mechanism of the above mentioned results is discussed.
关键词:
serratedflow
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null
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null
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null
J. Huang
金属学报(英文版)
The Hot deformation and martensitic transformation behaviors of Fe-32%Ni alloy was investi?鄄gated by measurements of electrical resistance and X-ray diffraction. With the increase in strain, the austenite goes through from the work-hardened to the partial dynamically re-crystallized and then to the completed dynamically re-crystallized. The martensitic transformation characteristics depend on the austenite states. The work-hardening in small strain is helpful to martensitic transfor?鄄mation due to the low dislocation density and little lattice distortion, while the high dislocation den?鄄sity and severe lattice distortion by the increase in strain will hinder the martensitic nucleation. Once dynamic re-crystallization (DRX) takes place, the martensitic transformation will be enhanced again, which is related to the heterogeneous dynamic substructures. The growing DRX grain can enhance the martensitic nucleation due to the low dislocation density near its grain boundary.
关键词:
Fe-32%Ni alloy
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热变形
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加工硬化
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动态再结晶
Yuantao NING+
,
Fei WEN
,
Huaizhi ZHOU
,
Deguo DENG
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Institute of Precious Metals Kunming
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650221
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China
材料科学技术（英文）
The influence of 0.1-0.6 at.-%RE additions (RE= La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Yb) on the mechanical properties of Pd was studied. All above RE additions increased not only the strength properties at ambient temperature but also the tensile strength, creep rupture time and activation en- ergy at high temperatures, simultaneously increased the elongation of Pd. In the range of dilute con- centration, the strength properties of Pd-RE alloy enhanced linearly with RE concentration. When the strength properties of Pd-RE alloys were normalized at 0.1 at.-%RE, it was found that light RE elements had stronger effect on the properties of Pd than heavy RE, whereas Eu, Yb, Ce had anoma- lous effect. In all Pd-RF alloys, Pd-Eu alloy had the highest strength properties, successively Pd-Yb and Pd-Ce alloy. The effect mechanisms of RE in alloy, such as purifying impurities, increasing recrystallization temperature, refining grain size. expanding crystal lattice, increasing dislocation den- sity and decreasing stacking fault energy, forming stable RE oxidation by internal oxidation, and so on, were observed. They were strengthening sensitive factors. The influence of the factors on strength properties and elongation of Pd was discussed.
关键词:
RE
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null
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null
