Gang Wang
,
Zbigniew H. Stachurski
金属学报(英文版)
doi:10.1007/s40195-016-0369-2
The homogeneous plastic flow in bulk metallic glasses (BMGs) must be elucidated by an appropriate atomistic mechanism. It is proposed that a so-called concordant shifting model, based on rearrangements of five-atom subclusters, can describe the plastic strain behaviour of BMGs in a temperature range from room temperature to the supercooled liquid region. To confirm the effectiveness of the atomic concordant shifting model, a comparative investigation between the vacancy/atom model and the concordant shifting model is carried out based on the estimation of the strain rate deduced from two models. Our findings suggest that the atomic concordant shifting model rather than the vacancy/atom exchange model can well predict the large strain rate in the superplasticity of BMGs.
关键词:
Bulk
,
metallic
,
glasses
,
Superplasticity
,
Vacancy/atom
,
exchange
,
model
,
Atomic
,
concordant
,
shifting
,
model
,
Strain
,
rate
Ying Yan
,
Wan-Peng Deng
,
Zhan-Feng Gao
,
Jing Zhu
,
Zhong-Jun Wang
,
Xiao-Wu Li
金属学报(英文版)
doi:10.1007/s40195-016-0373-6
To explore the coupled effect of temperature T and strain rate ε˙ε˙ on the deformation features of AZ31 Mg alloy, mechanical behaviors and microstructural evolutions as well as surface deformation and damage features were systematically examined under uniaxial tension at T spanning from 298 to 523 K and ε˙ε˙ from 10-4 to 10-2 s-1. The increase in T or the decrease in ε˙ε˙ leads to the marked decrease in flow stress, the appearance of a stress quasi-plateau after an initially rapid strain hardening, and even to the occurrence of successive strain softening. Correspondingly, the plastic deformation modes of AZ31 Mg alloy transform from the predominant twinning and a limited amount of dislocation slip into the enhanced non-basal slip and the dynamic recrystallization (DRX) together with the weakened twinning. Meanwhile, the cracking modes also change from along grain boundaries (GBs) and at twin boundaries (TBs) or the end of twins into nearby GBs where the DRX has occurred. The appearance of a stress quasi-plateau, the formation of large-sized cracks nearby GBs, and the occurrence of continuous strain softening, are intimately related to the enhancement of the non-basal slip and the DRX.
关键词:
AZ31
,
Mg
,
alloy
,
Uniaxial
,
tension
,
Temperature
,
Strain
,
rate
,
Deformation
,
Damage
,
Twinning
Ya-Qiang Wang
,
Zhao-Qi Hou
,
Jin-Yu Zhang
,
Xiao-Qing Liang
,
Gang Liu
,
Guo-Jun Zhang
,
Jun Sun
金属学报(英文版)
doi:10.1007/s40195-016-0372-7
Cu-Al/Al nanostructured metallic multilayers with Al layer thickness h Al varying from 5 to 100 nm were prepared, and their mechanical properties and deformation behaviors were studied by nanoindentation testing. The results showed that the hardness increased drastically with decreasing h Al down to about 20 nm, whereafter the hardness reached a plateau that approaches the hardness of the alloyed Cu-Al monolithic thin films. The strain rate sensitivity (SRS, m), however, decreased monotonically with reducing h Al. The layer thickness-dependent strengthening mechanisms were discussed, and it was revealed that the alloyed Cu-Al nanolayers dominated at h Al ≤ 20 nm, while the crystalline Al nanolayers dominated at h Al > 20 nm. The plastic deformation was mainly related to the ductile Al nanolayers, which was responsible for the monotonic evolution of SRS with h Al. In addition, the h Al-dependent hardness and SRS were quantitatively modeled in light of the strengthening mechanisms at different length scales.
关键词:
Nanostructured
,
films
,
Cu-Al/Al
,
multilayers
,
Hardness
,
Strain
,
rate
,
sensitivity
,
Layer
,
thickness
,
dependence
Xinhai ZHAO
,
Guoqun ZHAO
,
Guangchun WANG
,
Tonghai WANG
材料科学技术（英文）
A finite element based sensitivity analysis method for preform die shape design in metal forging is developed. The optimization goal is to obtain more uniform deformation within the final forging by controlling the deformation uniformity. The objective function expressed by the effective strain is constructed. The sensitivity equations of the objective function, elemental volume, elemental effective strain rate and the elemental strain rate with respect to the design variables are constituted. The preform die shapes of an H-shaped forging process in axisymmetric deformation are designed using this method.
关键词:
Metal forging
,
null
,
null
,
null
,
null
Hongbo DONG
,
Yonglin KANG
材料科学技术（英文）
With a geometrical model of porous material, a 3D finite-element analysis on the rolling process of spring steel- 60Si2Mn in the semi-solid state is carried out using software MARC. In terms of flat and groove rolling conditions, stress field and strain field are studied. The simulation results show that the rigid-viscoplastic model can accurately describe the semi-solid metal rolling process. Semi-solid slurry has the characteristics of low flow stress and good fluidity. During groove rolling, distribution of stress and strain on the cross-section of deformation zone is more uniform than that during flat rolling. The results of simulation are in good agreement with the experiment data, and show that semi-solid material fits for groove rolling.
关键词:
Finite-element analysis
,
null
,
null
,
null
周伟江
,
廖英强
,
张世杰
,
尤丽虹
宇航材料工艺
doi:10.3969/j.issn.1007-2330.2014.03.026
针对T800HB/环氧复合材料壳体易在封头部位产生复杂的应力状态,导致壳体低压破坏的问题,通过采用金属接头结构优化与封头补强措施,使T800HB/环氧复合材料壳体的爆破压力由28.2 MPa提高到36.4 MPa,纤维强度发挥率由65.7％提升至85.6％.
关键词:
复合材料壳体
,
碳纤维
,
应变
,
纤维强度转化率
曹海建
,
俞科静
,
钱坤
宇航材料工艺
doi:10.3969/j.issn.1007-2330.2015.02.004
利用有限元软件Workbench,建立了三维中空夹芯复合材料结构模型,进行拉伸性能研究.利用该模型,探讨了材料在1 mm拉伸位移栽荷作用下纤维、树脂和复合材料的应力、应变分布.结果表明:三维中空夹芯复合材料在拉伸载荷作用下,“X”形芯材交叉处应力最大,最容易发生拉伸破坏;上下面板应力最小,最不容易发生拉伸破坏;复合材料在承受拉伸载荷作用时,增强体纤维起主要承载作用,基体树脂起次要作用;当拉伸位移栽荷达到1 mm时,材料的破坏模式主要为树脂破裂.
关键词:
三维中空夹芯复合材料
,
有限元软件Workbench
,
拉伸性能
,
应力
,
应变
,
破坏模式
鄢东洋
,
王爱民
,
潘桢
,
王晓博
,
梁晓光
宇航材料工艺
doi:10.12044/j.issn.1007-2330.2017.03.017
针对纵缝采用搅拌摩擦焊、环缝采用VP-TIG熔焊工艺的箱底进行液压试验,并在试验过程中监测各典型焊缝位置的应变响应,结果显示箱底上搅拌摩擦焊缝和熔焊焊缝交叉形成的“T”型接头区域在试验中最先进入屈服,说明该位置材料的屈服强度较低,是箱底承载的薄弱环节.
关键词:
推进剂贮箱箱底
,
FSW
,
VP-TIG
,
液压
,
应变
