Z.M. Zhang
,
C.J. Xu
,
X.F. Guo
,
S.Z. Jia
金属学报(英文版)
Mg 2 Si reinforced Mg-Al based composite with
high amount of silicon was prepared by permanent mould casting, and
then extruded by reciprocating extrusion (RE) after the composite
was processed by homogenization heat treatment. The effect of RE
processing on the morphology and size of Mg 2 Si and the
mechanical properties of the composite were investigated, to develop
new ways to refine the Mg 2 Si phase and improve its shape. The
result showed that RE was very useful in refining the Mg 2Si
phase. The more the RE processing passes, the better the refining
effect would be. Moreover, the uniform distribution of Mg 2 Si
phases would be more in the composite. After the composite was
processed by RE for 12 passes, most Mg 2 Si phases were equiaxed,
with granular diameter below 20 um, and distributed uniformly in
the matrix of the composite. The mechanical properties of the
composite could be increased prominently by RE processing, and were
much higher than that in the as-cast state. As the temperature
rises, the tensile strength is reduced. For the composite RE
processed for 12 passes, the tensile strength, yield strength, and
elongation are 325.9 MPa, 211.4 MPa, and 3.3 % at room temperature,
whereas, 288.2 MPa, 207.7~MPa, and 7.8 %, respectively, at
150 C. In comparison with the properties at room
temperature, the tensile strength and yield strength are high and
only decrease by 11.6 and 1.8 at 150 C. The Mg 2 Si
reinforced Mg-Al based composite possesses good heat resistance at
150 C. The excellent resistance to effect of heat is
attributed to the high melting temperature and good thermal
stability of fine Mg 2 Si phases, which are distributed uniformly
in the composite, and effectively hinder the grain boundary gliding
and dislocation movement.
关键词:
Reciprocating extrusion
,
null
,
null
,
null
Z.M. Zhang
,
T. Lu
,
C.J. Xu
,
X.F. Guo
金属学报(英文版)
Directionally solidified binary Mg-Al eutectic
alloy wires of approximately 5mm in diameter were produced by the
Ohno continuous casting (OCC) process and the microstructure was
examined. It was found that the wires possess obvious unidirectional
growth characteristic along its axial direction. The microstructure
consists of parallel columnar grains that resulted from the
competitive growth of equiaxed grains solidified on the head of
dummy bar. Each columnar grain comprises regular eutectic
α-Mg and β-Mg17Al2 phases, which grew along the axial direction of the wires. The morphology of the eutectic ismainly lamellar, meanwhile rod eutectic exists. The formation of rod eutectic was attributed to the ``bridging effect" caused by
incidental elements in the alloy.
关键词:
Mg-Al alloy
,
null
,
null
,
null
Z.M. Zhang
,
*
,
C.J. Xu
,
J.C. Wang
金属学报(英文版)
Ultrafine-grained pure aluminum L2 with a mean grain size of 1.0μm was produced by equal channel angular pressing (ECAP) and annealing at 150℃ for 2h. Damping behavior of the alloy was measured using a dynamic mechanical thermal analyzer. The alloy had an excellent damping capacity Q-1 with the ambient value being 9.8×l0-3 at 1.0Hz when the strain amplitude was 2.0×l0-5. The damping behavior of the alloy showed a non-linear damping variation tendency, that is, with an increase in temperature and a decrease of frequency, the damping capacity of the alloy increased. The damping capacity increased with the strain amplitude when the strain amplitude was less than 4.6×l0-5. When the strain amplitude was higher than 4.6×10-5, the damping capacity became a constant and independent of strain amplitude. The high damping capacity was attributed to dislocation unpinning and a drag of dislocation on pinning points.
关键词:
ECAP
,
超细晶
,
阻尼
,
铝合金
Z.M. Zhang
,
C.J. Xu
,
X.F. Guo
金属学报(英文版)
As an icosahedral Mg3YZn6 quasicrystalline phase can be produced in Mg-Zn-Y system alloys when a proper amount of Zn and Y is contained, it is feasible to prepare the quasicrystal phase-reinforced low-density magnesium alloy. The purpose of this paper is to analyze phase constituents and the effect of reciprocating extrusion on microstructures and properties of the as-cast Mg-6.4Zn-1.1Y alloy. The microstructure of as-cast Mg-6.4Zn-1.1Y alloy consists of the α-Mg solid solution, icosahedral Mg3YZn6 quasicrystal, and Mg3Y2Zn3 and MgZn2 compounds. After the alloy is reciprocatingly extruded for 4 passes, grains were refined, Mg3Y2Zn3 and MgZn2 phase dissolved into the matrix, whereas Mg3YZn6 precipitated and distributed uniformly. The alloy possesses the best performance at this state, the tensile strength, yield strength, and elongation is 323.4MPa, 258.2MPa, and 19.7%, respectively. In comparison with that of the as-cast alloy, the tensile strength, yield strength, and elongation of the reciprocatingly extruded alloy increase by 258.3％, 397.5％, and 18 times, respectively. It is concluded that reciprocating extrusion can substantially improve the properties of as-cast Mg-6.4Zn-1.1Y alloy, particularly for elongation. The high performance of the Mg-6.4Zn-1.1Y alloy after reciprocating extrusion can be attributed to dispersion strengthening and grain-refined microstructures.
关键词:
Reciprocating extrusion
,
null
,
null
Z.M. Zhang
,
C.J. Xu
,
X.F. Guo
金属学报(英文版)
In order to explore the methods to prepare high-strength quasicrystal-reinforced magnesium alloys, the flakes of rapidly solidified Mg-6.4Zn-1.1Y magnesium alloy with thickness of 50-60冚m were obtained by a melt spinning single-roller device, and then the flakes were processed into rods by reciprocating extrusion and direct extrusion. The microstructure of the alloy was analyzed by optical microscope and SEM, and the constituent phases were identified by XRD. Phase transformation and its onset temperature were determined by differential thermal analyzer (DTA). The analysis result shows that rapid solidification for Mg-6.4Zn-1.1Y alloy can inhibit the eutectic reactions, broaden the solid solubility of Zn in 冄-Mg solute solution, and impede the formation of Mg3Y2Zn3 and MgZn2 compounds, and thus help the icosahedral Mg3YZn6 quasicrystal formed directly from the melt. The microstructure of the flakes consists of the -Mg solid solution and icosahedral Mg3YZn6 quasicrystal. Dense rods can be made from the flakes by 2-pass reciprocating extrusion and direct extrusion. The interfaces between flakes in the rods can be welded and jointed perfectly. During the reciprocating extrusion and direct extrusion process, more Mg3YZn6 compounds are precipitated and distributed uniformly, whereas the rods possesses fine microstructures inherited from rapidly solidified flakes. The rods contain only two phases: 冄-magnesium solid solution as matrix and fine icosahedral Mg3YZn6 quasicrystal which disperses uniformly in the matrix.
关键词:
Magnesium alloy
,
null
,
null
,
null
姜志进
原子核物理评论
在核吸收与随动者吸收理论的基础上,给出了在有QGP相变情况下高能重离子碰撞中的J/Ψ微分产生截面,并用其讨论了CERN的NA50合作组给出的入射动量为158 AGeV/c的Pb-Pb碰撞中的J/Ψ反常抑制现象。理论较好地解释了实验结果。
关键词:
J/Ψ反常抑制
,
核吸收
,
随动者
吉日木图
原子核物理评论
研究自旋和轨道量子数不同的介子之间的质量劈裂对检验夸克势模型非常重要.在以往的夸克势模型计算中,η_c-J/ψ的质量劈裂都很难达到实验的值.用正规化形状因μ~2/(q~2+μ~2),在对完整的动量空间中的Breit夸克势实施一次正规化下研究了η_c-J/ψ和新介子ηb与Υ(1s)之间的质量劈裂.结果表明,正规化形状因子中的屏蔽质量μ应与介子折合质量有关,当将其展开为介子折合质量的三阶多项式时,上述介子质量劈裂可以精确重现实验的结果.另外,由于完整的Breit 势包含有自旋一轨道耦合相互作用的项,因而还可以研究χ_(c0),χ_(c1)和χ_(c2)之间的质量劈裂.
关键词:
夸克势模型
,
矩阵元
,
介子束缚态
,
正规化
,
质量劈裂
董元篪
,
魏寿昆
,
彭(忄育)强
,
朱元凯
金属学报
<正> As一向认为是钢铁中的有害元素。除少数耐腐蚀钢种外,脱As是钢铁冶炼的一个问题。欲脱As必先知As在铁液中的热力学行为。文献中只报道过As的活度相互作用系数e_(As)~C,e_(As)~S及e_(As)~N。本文是继续前文研究As在Fe液中的热力学行为,旨在利用下列反应: 3(CaC_2)+2[As]=(Ca_3As_2)+6[C] (1) 求出Fe-As-C-j熔体中的
关键词:
陈建刚
,
卢凤双
,
张敬霖
,
张建生
,
张建福
金属功能材料
3J33(C)马氏体时效钢是以无碳(或超低碳)铁镍马氏体为基体的时效强化型高弹性合金.采用工业电炉处理合金,高温固溶处理后,再经过4次变温循环相变,基体组织由高温固溶后220 μm的粗大等轴晶细化为15 μm左右的均匀细小晶粒.进一步时效处理后,合金抗拉强度、屈服强度、弹性极限、硬度提高10%以上,断面收缩率、断后伸长率、冲击吸收功提高30%以上.
关键词:
马氏体时效钢
,
变温循环相变
,
时效
,
力学性能
王忠纯
,
沈法华
,
刘成林
量子电子学报
doi:10.3969/j.issn.1007-5461.2011.01.011
研究了腔间有耦合的双J-C模型中原子纠缠的动力学,分析了腔间耦合系数A和原子的初态对原子纠缠的猝灭(ESD)和猝生(ESB)的影响.通过对原子间共生纠缠度的数值分析发现,当原子初态为第一类类Bell态时,不会出现ESD和ESB,腔间的耦合可使原子的纠缠加大,并能使初态为分离态的原子产生纠缠.当原子初态为第二类类Bell态时,A的大小可改变出现ESD与ESB的时间间隔,或决定是否出现ESD,但腔间的耦合不能使初态不纠缠的原子产生纠缠.
关键词:
量子光学
,
耦合谐振腔
,
双J-C模型
,
共生纠缠度
,
纠缠的猝灭
,
纠缠的猝生
