Wenlin HE
,
Qishan ZANG+
,
Zhongguang WANG
,
State Key Laboratory for Fatigue and Fracture of Materials
,
Institute of Metal Research
,
Academia Sinica
,
Shenyang
,
110015
,
China
材料科学技术（英）
The distributions of plastic strain near grain boundaries induced by fatigue loading were investigated by the fiducial grid method in pure aluminum specimens, and the resulted grain boundary sliding (GBS) was systematically analysed. The results show that the strain field near a grain boundary is nonuniform. GBS is restricted by the junction of grain boundaries and causes discontinuities of both displacement and strain. A peak value of shear strain was created in short-range area across the grain boundary. GBS plays an important role in cyclic softening and secondary hardening. The control fac- tor of GBS is the relative orientation between two grains and the macro orientation of the grain boundary rather than the ∑ value of the boundary.
关键词:
grain boundary sliding
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康志新彭勇辉桑静简炜炜赵海东李元元
金属学报
采用T型通道挤压(TCP)对Mg-1.5Mn-0.3Ce合金(质量分数, %)进行了4道次热挤压变形, 其平均晶粒尺寸由原始轧制态的35 μm细化至2 μm; TEM观察表明, 经TCP变形后细小的第二相粒子Mg12Ce弥散分布于晶内及晶界处. 变形合金在573-673 K及 1×10-1-4×10-4 s-1应变速率范围内显示良好的超塑性变形; 在温度为673 K及3×10-3 s-1条件下, 得到最大的断裂延伸率为604%, 应变速率敏感系数$m$为0.36. 超塑性变形后断裂区域显微组织观察表明, Mg-1.5Mn-0.3Ce合金超塑性变形的主要机制为晶界滑移, 在较高温度、较低应变速率条件下超塑性变形时出现晶内滑移现象, 作为超塑性变形的协调机制促进晶界滑移, 随应变速率的降低或温度的升高晶内滑移越明显.
关键词:
Mg-1.5Mn-0.3Ce合金">
Mg-1.5Mn-0.3Ce合金
,
T-shape channel pressing
,
grain refinement
,
high strain rate
,
superplasticity
,
grain boundary sliding
材料导报
利用扫描电镜(SEM)和超塑性拉伸实验对一次热挤压加工成型的AZ61镁合金薄板(晶粒尺寸～12μm)超塑性变形特征进行了研究.结果显示,在最佳的变形温度(623K)和应变速率(1×10-4s-1)条件下,可获得的最大的超塑性形变量为920%.在523～673 K实验温度和1×10-2～1×10-5s-1应变速率范围内,材料的应变速率敏感指数(m值)随实验温度升高和应变速率的降低而增加.较高的m值(0.42～0.46)对应于晶界滑动机制(GBS),而较低的m值(0.22～0.25)则对应于位错滑移机制.变形温度和应变速率是影响超塑性变形量和变量机制的主要因素.
关键词:
镁合金
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超塑性
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晶界滑动
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位错滑移
CUI Jianzhong MA Longxiang Northeast University of Technology
,
Shenyang
,
China Department of Metals Forming
,
Northeast University of Technology
,
Shenyang
,
China
金属学报(英文版)
The method controlling grain shape in TMT processing and the effect of grain shape on char- acteristic parameters in superplastic deformation were discussed.The accommodation velocity of grahl boundary sliding,which is the dominant mechanism in superplastic deformation,and the contribution of each mechanism to the total strain,as influenced by grain shape,were ana- lyzed.Grain shape has been shown to be an essential structural factor for superplasticity.Then an analysis was made about the effect of grain shape on the region transition strain rate so that a new concept,critical aspect for superplasticity,was worked out.These predictions were compared with the measured results in an Al-Zn-Mg alloy.
关键词:
superplastic deformation
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