J. X. Zhang
,
Y. F. Zheng
,
W. Cai and L.C.Zhao(School of Materials Science and Engineering
,
Harbin Institute of Technology Harbin 150001
,
China)(Laboratory of Atomic Imaging of Solids
,
Institute of Metal Research
,
The Chinese Academy of Sciences
,
Shenyang 110015
,
China)
金属学报(英文版)
Type H defect in 18R martensite in a Cu-Zn-Al alloy has been studied by high resolution electron microscopy. It was found that Type H defect is not fault internal to martensite plate; rather,it is a stack of plates A and C. The rare observation of Type H defect is considered to be due to the fact that thc slice is too thin to exist for self-accommodation.
关键词:
shape memory alloy
,
null
,
null
Journal of Materials Research
The morphology of the dark and bright regions observed by transmission electron microscopy for the Zr(64.13)Cu(15.75)Ni(10.12)Al(10) bulk metallic glass strongly depends on the ion beam parameters used for ion milling. This indicates that the ion beam could introduce surface fluctuation to metallic glasses during ion milling.
关键词:
room-temperature
刘叔仪
金属学报
<正> 作为固体脆性断裂判据的J积分,其数值与其积分路径无关,这在文献中叫“守恒性”。这个守恒性已被推广到塑性断裂,这到底有否根据?本文目的是作这个问题的证明。未用原作者的方法,但由两个旋度判据得到应力应变函数行列式给出的一些否定结论,希望这对J积分应用条件的了解有所助益。1.弹塑性J积分守恒的条件 J积分
关键词:
朱杰武
,
柳永宁
,
许雁
,
冯耀荣
机械工程材料
doi:10.3969/j.issn.1000-3738.2005.06.007
在不同温度下测试了X70管线钢动态断裂韧度K1d、J1d和止裂韧度K1a以及夏氏V型缺口冲击韧度Ak,对三者的关系进行了分析.结果表明:温度和加载速率都对断裂韧度产生影响;加载速率变化引起的韧-脆断裂转变具有热激活特征,在热激活分析基础上,在应力强度因子速率K=15 MPa·m1/2s-1条件下,得出断裂韧度、止裂韧度和冲击韧度三者的关系:Ak=4.84×106T-2.8K1d(或K1a).可以用小试样Ak数据计算得到K1d和K1a.
关键词:
管线钢
,
断裂韧度
,
止裂韧度
,
韧-脆断裂转变
Journal of Physics-Condensed Matter
The temperature dependences of the magnetization, internal energy and specific heat in a three-sublattice ferrimagnet or ferromagnet with /J(ab)/ = /J(bc)/ not equal /J(ca)/ are calculated within the framework of the linear spin-wave approximation, by employing retarded Green's functions. For both the ferromagnet and the ferrimagnet, the internal energy and the specific heat decrease with increasing J ' /J and/or the value of the spins. For fixed values of S,, Sb, S, and J ' /J, the internal energy and the specific heat increase, whereas the sublattice magnetization decreases with increasing temperature theta. The three-sublattice ferrimagnet has some particular characteristics which are not shown by the systems with two sublattices. For ferrimagnets, the antiferromagnetism of the system becomes weaker with increasing J ' /J. The sublattice magnetization at low temperatures (also the magnetization M(0) at 0 K) of a ferrimagnet increases with increasing J ' /J for fixed values of S(a), S(b) and S(c). The effects of the spins S(a) (S,) and Sb On the magnetizations of other sublattices differ. The characteristics of the a-sublattice are the same as those of the c-sublattice, due to their similarity as well as the symmetry of the system. The behaviours of the b-sublattice are different from those of the a- and c-sublattices, due to the asymmetry of the three-sublattice system. The spin-value dependences of the spin deviation Deltam per spin land also the energy for the zero-point quantum fluctuation) of the system are different for different sublattices. These differences are ascribed to the asymmetry of the three-sublattice systems, which leads to the new intrinsic properties of the systems.
关键词:
layered heisenberg ferrimagnets;spin-wave theory;elementary;excitations;superlattices;systems;magnetoresistance;antiferromagnet;interfaces
Physical Review B
The Hamiltonian for a four-sublattice Heisenberg ferrimagnet or ferromagnet with different exchange constants (J(ab) = J(cd) not equal J(bc) = J(da)) was established. An extended Bogoliubov transformation was developed by solving an equation group, consisting of 20 equations and 20 unknowns. The procedure for solving the equation group was carried out by introducing a simple way of reducing the numbers of the equations and the unknowns. The spin-wave spectra in the present system have been determined by performing the standard Holstein-Primakoff transformation and the Bogoliubov one. It has been found that the spin-wave spectra of the present system depend on the exchange constants and that the degeneracy of the spin-wave spectra remains. The results for a special case (J(ab) = J(bc)) i.e., an antiferromagnet are discussed briefly. The spin-wave spectra of the four-sublattice Heisenberg antiferromagnet are found to be degenerative also and they are linear in k for small k.
关键词:
model
Physical Review B
The quadratic Holstein-Primakoff spin-wave Hamiltonian for three-sublattice Heisenberg systems with different exchange constants (J(ab)=J(bc)not equal J(ca)) was diagonalized by a three-step procedure. The classical ground state was examined and the effects of quantum fluctuation on the ground state were discussed. The 0 K spin reorientation angles due to quantum fluctuations were found to originate from the asymmetry of the system. As an extended application of the spin-wave study of the multisublattice systems, the spin-wave spectra of a Heisenberg superlattice, which has four or three magnetic atoms or spins, in each magnetic unit cell in the x direction, were solved analytically in terms of creation and annihilation operators. It has been found that the spin-wave spectra of the present superlattice systems depend on the exchange constants J and J(1), and that the degeneracy of the spin-wave spectra remains for the superlattice of four atomic layers and is partially removed for the superlattice of three atomic layers mainly due to the asymmetry of the system. Another type of splitting of the energy level occurs which differs for those levels with different degeneracies. The mixing of the interface and the bulk modes were found for the spin-wave dispersion of the superlattices. It was predicted that even for different superlattices having the same exchange constants (either J or J'), i.e., without the oscillation of the exchange coupling, the asymmetry can lead to the oscillation of magnetic properties, such as magnetization and giant magnetoresistance.
关键词:
ferromagnetic superlattices;reorientation transitions;magnetic;superlattices;modes;temperatures;film
Ieee Transactions on Magnetics
The microstructure, magnetic properties and magnetostriction of Tb0.2Pr0.8(Fe0.4Co0.6)(infinity) (1.65 less than or equal to x less than or equal to 1.90) alloys has been studied. The Curie temperatures for the 1:2 and 1:3 phases decrease with increasing x, whereas the saturation magnetization increases with increasing cc. The remanent magnetization remains almost constant for all the samples and the coercivity decreases with increasing x. The spontaneous magnetostriction (lambda (111)) estimated from the splitting of the (440) lines is found to decrease with increasing x. The largest lambda (111) recorded for Tb0.2Pr0.8(Fe0.4Co0.6)(1.65) is 2900 ppm at room temperature.
关键词:
Laves phase;microstructure;spontaneous magnetostriction;alloys
