晏井利
,
孙扬善
,
薛烽
,
陶卫建
金属学报
不同状态纯Mg试样在75-200 ℃, 15-40 MPa条件下的蠕变实验表明: 在等同条件下, 铸态试样的晶粒粗大, 蠕变速率较低; 挤压态试样由于动态再结晶, 晶粒变细, 蠕变速率大幅上升; 退火后由于晶粒长大, 蠕变速率又呈下降趋势. 根据应变速率幂指数公式, 铸态纯Mg试样在较低应力时, 应力指数n处于4.3-4.9的范围, 在较高应力时, n>7; 激活能在76.0-89.4 kJ/mol的范围. 根据应力指数和激活能并结合蠕变过程中的组织分析, 纯Mg的蠕变受位错攀移、晶界滑移以及孪生的共同作用, 其中位错攀移和晶界滑移占主导地位.
关键词:
纯Mg
,
Creep
,
Dislocation Climb
,
Grain boundary sliding
喻吉良李中奎郑欣张建军刘辉王晖王文生
金属学报
采用机械合金化(MA)+热压烧结制备Mo-9Si-8B-3Hf难熔合金，研究了球磨时间对热压合金致密度的影响。采用真空高温拉伸评价了该材料的高温性能。结果表明，材料的致密度随着球磨时间的延长而增大；X射线衍射(XRD)分析表明：制备的合金由连续分布的钼固溶体(α-Mo)相、金属间化合物Mo3Si相、Mo5SiB2相组成。各物相的平均晶粒尺寸大约为3μm，并且呈等轴状。在1400~1560℃、应变速率为3×10-4s-1条件下，该合金具有极大的塑性或超塑性。在1560℃由于行程限制尽管试样没有断裂，拉伸延伸率达到410%，表现出优异的超塑性。晶界滑移是塑性变形的主要机制。在塑性变形过程中连续分布的软化的α-Mo协调晶界滑移，减小了三角晶界处的应力集中，从而导致了大的延伸率。
关键词:
晶界滑移
Jitai NIU
,
Lihong HAN
,
Chonghao WOO
材料科学技术（英）
Grain growth and grain boundary sliding are the two main superplastic deformation mechanisms. In the paper, simulation work is focused on the sliding of a Σ13 (111) symmetric twist coincidence grain boundary, a Σ13 (110) asymmetric tilt coincidence grain boundary, and a Σ3 (110) symmetric tilt coincidence grain boundary in Al, and the energies of grain boundary for each of equilibrium configurations are computed. An embedded atom method (EAM) potential was used to simulate the atomic interactions in a bicrystal containing more than 2000 atoms. At 0 K, the relationships between total potential energy and time steps for 3 (111) symmetric twist coincidence grain boundary and Σ3(110) symmetric tilt coincidence grain boundary during sliding at 2 m/s represent the periodic characteristic. However, the relationship between total potential energy and time steps for Σ13 (110) asymmetric tilt coincidence grain boundary represents the damp surge characteristic. It is found that grain boundary sliding for Σ3 (110) symmetric tilt coincidence grain boundary is coupled with apparent grain boundary migration.
关键词:
Aluminum
,
null
,
null
,
null
Yinong WANG
,
J.C.Huang
材料科学技术（英）
A two-stage strain rate deformation method is proposed to enhance the superplasticity in a hot extruded AZ61 alloy. In the stage-one of deformation, a relatively high strain rate was applied in order to obtain fine grains through dynamic recrystallization. The optimum strain rate for DRX at 300℃ was identified as ～5×10-3 s-1. Stage-two is conducted at relatively low strain rate in order to utilize the fine grains refined by DRX during stage-one to make the grain boundary sliding operate more smoothly, which resulting in enhanced superplastic elongation from 350% to 440%.
关键词:
AZ61 magnesium alloy
,
null
,
null
,
null
