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)
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
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
,
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
刘永
,
宋耀祖
工程热物理学报
本文采用M-Z干涉测量的方法,研究了半三角形翼片纵向涡发生器强化换热方案对矩形通道内气体流动换热的影响,获得了安装纵向涡发生器前后对流换热温度场的M-Z干涉图像.通过对实验获得的干涉图像进行分析处理,表明安装纵向涡发生器后,通道内入口段流动的热边界层明显变薄,反映了纵向涡对流动换热的强化作用,验证了将M-Z干涉测量方法应用于纵向涡强化换热研究的可行性.
关键词:
纵向涡
,
强化换热
,
M-Z干涉
,
热边界层
陆永浩
,
陈子瑞
,
朱晓锋
材料科学与工艺
为了研究敏化处理对Z3CN20-09M不锈钢高温水应力腐蚀行为的影响，使用敏化处理的Z3CN20-09M不锈钢制成U弯试样，并置于250、290及320℃的高温水中进行应力腐蚀开裂实验，采用扫描电镜观察了高温水实验后试样的氧化膜厚度以及应力腐蚀裂纹的萌生及扩展行为。结果表明：敏化处理增加了氧化膜的厚度，降低了耐蚀能力，使SCC敏感性增大；温度较高时，敏化处理的影响较大；铁素体相容易被侵蚀，大多数点蚀坑产生于铁素体中；SCC裂纹优先在点蚀坑底部和奥氏体/铁素体相界位置处形成；相界面对SCC裂纹的影响取决于SCC裂纹相对于相界面的取向，SCC裂纹扩展方向平行于相界面时裂纹易沿着相界扩展，SCC裂纹扩展垂直于相界面方向时相界面对裂纹扩展起阻碍作用。
关键词:
Z3CN20-09M
,
敏化处理
,
SCC裂纹
,
萌生和扩展
,
相界面
王玮
,
罗奎林
,
陆永浩
材料研究学报
用光学显微镜和扫描电镜等手段研究了核级不锈钢Z3CN20-09M焊缝组织特征,用原位拉伸和EBSD等方法研究了焊缝组织对裂纹扩展的影响.结果表明,焊缝区主要由板条状组织和岛状组织构成.不同的组织对裂纹扩展的阻力不同,岛状组织对裂纹的扩展具有阻碍作用且使裂纹发生偏转,而板条状组织对裂纹扩展无阻碍作用,裂纹可在片层组织中迅速通过.
关键词:
金属材料
,
核级不锈钢
,
焊缝
,
组织裂纹
朱晓锋
,
陆永浩
,
杨海波
材料科学与工艺
为研究国产核级主管道不锈钢Z3CN20-09M中奥氏体/铁素体相界面在裂纹萌生与扩展过程中的作用,通过扫描电镜原位拉伸技术对核级主管道不锈钢在拉伸过程中的组织形变、微裂纹的萌生与扩展进行原位观察,对断口进行了分析.研究表明,在拉伸过程中,微裂纹优先在杂质颗粒和相界位置萌生.当铁素体/奥氏体界面垂直于拉伸方向时,裂纹倾向于沿相界萌生,并沿相界扩展;当铁素体/奥氏体界面平行于拉伸方向时,微裂纹在相界开裂,并垂直于界面扩展,主裂纹发生偏折,界面在裂纹扩展过程中起阻碍作用.
关键词:
核级不锈钢
,
原位拉伸
,
奥氏体/马氏体相界
,
裂纹萌生与扩展
