龚宇
,
梁小军
,
华明建
,
A.J.DeArdo
钢铁钒钛
doi:10.7513/j.issn.1004-7638.2015.01.014
利用连续镀锌模拟设备,研究了微合金化元素Nb、V和V-N加入到低碳高强(980级)双相钢后组织与性能的变化.在基本成分基础上,设计了不同含量的V或Nb、采用高N或正常N含量的钢,经过不同的热浸镀锌(GI)、合金化镀锌(GA)和超快冷处理.此外,还利用石英管炉对模拟镀锌后的钢板进行热处理.结果表明,马氏体—贝氏体—铁素体各相比例受到不同微合金化元素加入量的强烈影响,但是各相强度影响较小.在小于0.1％C～ 1.75％ Mn钢中实测抗拉强度达到1 100 MPa、同时具有良好的塑性和加工硬化性能.
关键词:
微合金化双相钢
,
强度
,
塑性
,
加工硬化
,
n值
,
屈强比
,
临界退火
,
热浸镀锌
,
合金化镀锌
龚宇
,
M.Hua
,
J.Uusitalo
,
A.J.DeArdo
钢铁钒钛
doi:10.7513/j.issn.1004-7638.2016.03.027
探讨如何改善镀锌或镀锌合金化钢板基层,比如在实现高强度的同时,保持高的整体成形性能(拉伸塑性)、局部成形性能(冲裁边部塑性)和良好的点焊性能.众所周知,双相钢的强度受几个因素控制,包括最终组织中的初生(未回火)马氏体量.然丽,仍不完全清楚控制最终组织中马氏体量的因素,面确定这些因素是本研究项目的主要内容.最终组织中测定的新生马氏体量认为等于临界退火时形成的奥氏体量减去当钢在经历从临界退火温度(IAT)冷却至460℃、在460℃等温过程中、最终冷却至室温是转变成其他各种相变产物的奥氏体量以及在室温下保留的残余奥氏体量.最新研究发现,特定钢在临界退火过程中形成的奥氏体量受到退火温度、热轧带钢(卷取温度)和冷轧(冷压下量)等退火前条件的强烈影响.研究了退火前条件和4种退火工艺的组合,确定实现这些更高强度DP钢最佳的强度-成形性能匹配所需的最佳热处理路线.研究用钢包括(i)具有良好点焊性能的低碳钢,(ii)加入Mo提高淬透性和Cr提高强度,(iii)加入V实现细晶、析出强化和抗回火软化.当所采用的工艺适当,这些钢具有良好的综合性能,抗拉强度高达1000 MPa、总伸长率达到25％,面缩率45％,扩孔率达到50％.给出并讨论了这些研究成果.
关键词:
镀锌板
,
高强双相钢
,
钒
,
扩孔
,
高塑性
,
析出
,
储存能
,
加工硬化
龚宇
,
M.Hua
,
J.Uusitalo
,
A.J.DeArdo
钢铁钒钛
doi:10.7513/j.issn.1004-7638.2016.04.026
双相钢具有高强度的同时表现出良好的成形性能,因而被广泛应用.这类钢具有高的n值、均匀伸长率和总伸长率,不过,限制高强度双相钢应用的因素之一是在冲裁边部拉延过程中出现失效.为了开发具有良好冲裁边部塑性的高强双相钢,必须精心控制组织中硬相和软相的比例和硬度.冲裁边部拉延时出现的失效机制与微观组织密切相关(不同相的比例、硬度、尺寸和分布),发现在铁素体-马氏体界面出现裂纹萌生.研究了退火前的条件(热轧和冷轧条件)、不同的连续镀锌线工艺过程以及合金化元素对双相钢冲裁边部成形性能的影响,发现所有这三个参数都对扩孔试验中测定的冲裁边部塑性产生强烈影响.
关键词:
双相钢
,
成形性能
,
热轧工艺
,
冷轧工艺
,
扩孔率
,
钒
,
残余奥氏体
,
回火马氏体
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
Y.G. Cao
,
X.Y. Sun
金属学报(英文版)
J-integral and crack opening displacement δ(COD) were important parameters for characterization of fractures in engineering materials. The relationship between J-integral and COD has been investigated for a long time and was enerally represented as J = m σyδ, where σy is the yield strength and m is a function of specimen geometry and material properties. To determine the value of m, extensive studies and experiments have been performed. The method that used the fracture-surface topography analysis (FRASTA) for determining J-integral from fracture surfaces of materials was introduced. On the basis of the relationship between COD and fracture surface average profile, the relationship between J-integral and COD was deduced and compared with the generally used equation. The method was experimentally confirmed to be able to provide a new way to determine the relationship between J-integral and COD.
关键词:
FRASTA
,
null
,
null
null
,
null
金属学报
在工程上,经常由于应力腐蚀开裂和氢脆引起中强度钢结构件发生滞后破坏。这类脆断往往从结构件中预先存在的疲劳或焊接裂纹处开始,因此,运用传统的光滑试样的检验方法不能反映这类破坏的特点。 本文将弹塑性断裂力学中的J积分概念用于滞后破坏的研究,提出用带预制疲劳裂纹的悬臂弯曲试样测定J积分的临界值J_(Ic)和应力腐蚀开裂阈值J_(Iscc)的方法。测定了40CrNiMo钢的J_(Ic)值及其在硫化氢水溶液中的J_(Iscc)值。通过和三点弯曲方法测定的J_(Ic)值的对比,以及和满足线弹性条件时直接测定的应力强度因子K_I值的对比,说明这种方法的可靠性。最后,对悬臂弯曲方法的特点进行了讨论。
关键词:
平荣刚
原子核物理评论
doi:10.3969/j.issn.1007-4627.2004.02.026
通过J/Ψ→pp-,pN-*,N*N-*衰变,研究了Roper共振态的混杂态结构对衰变角分布和分支比的影响.计算结果表明,如果Roper共振态为纯混杂态,那么J/Ψ→pN-*,N*N-*的角分布几乎相等,而J/Ψ衰变到混杂态的衰变宽度还不到J/Ψ→pp-的1%,给出了Γ(J/Ψ→ N*p-)/Γ(J/Ψ→pp-)和Γ(J/Ψ→ N*N-*)/Γ(J/Ψ→pp-)随混合参数的变化关系,并讨论了在J/Ψ衰变中研究Roper混杂态结构的可能性.
关键词:
Roper共振态结构
,
混杂态
,
J/Ψ
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
