申坤汪明朴郭明星李树梅
金属学报
利用Gleeble--1500热模拟机、金相以及透射电镜对Cu--0.23%Al2O3(体积分数)合金高温塑性变形过程中的流变应力和显微组织变化规律进行了研究. 研究结果表明, Cu--0.23%Al2O3合金在热压缩过程中,热压缩条件不同流变应力变化规律会有所差异. 此外, 还求得了该合金高温变形的平均激活能和其他相关材料常数, 据此建立了峰值屈服应力--应变速率--温度之间的本构方程. 随热压缩温度的升高, 基体内动态再结晶晶粒尺寸和数量不断增加, 而在同一温度压缩时, 随应变速率的增加,组织分布不均匀性有所增加, 亚晶尺寸不断减小, 位错密度先增加后降低.
关键词:
Cu--Al2O3合金
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high temperature deformation
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constitutive equation
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dynamic recovery
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dynamic recrystallization
Author M. AbdelKarim
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M. Mizuno and N. Ohno\= Department of Mechanical Engineering
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Nagoya University Chikusaku
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Nagoya 4648603
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Japan Manuscript received 18 October 1998
金属学报(英文版)
In the previous paper, in order to express steadystate ratchetting, the present authors extended the cyclic plasticity model proposed by Ohno and Wang (1993), and the validity of the extended model was discussed on the basis of uniaxial ratchetting experiments of 316FR steel at room temperature. In the present paper, the validity of the extended model is discussed further on the basis of nonproportional experiments of IN738LC at 850 such as multiaxial ratchetting, multiaxial cyclic stress relaxation, circular cyclic straining with strain hold, and so on. Predictions based on the OhnoWang model as well as the ArmstrongFrederick model are also given for the sake of comparison. It is shown that the extended model is capable of simulating the nonproportional experiments accurately, and especially that the extended model can predict much less steadystate ratchetting than the ArmstrongFrederick model. It is also shown that the extended model provides almost the same predictions as the OhnoWang and th
关键词:
dynamic recovery
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null
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null
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null
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null
赵鹏程
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俞树荣
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李淑欣
,
何燕妮
材料科学与工艺
doi:10.11951/j.issn.1005-0299.20160606
为了加深对风机轴承失效的进一步理解,从而提高其服役寿命,本文提出并研究了轴承钢GCr15在动载荷下的失效模式,采用分离式霍普金森压杆(SHPB)对轴承钢GCr15进行动态冲击试验,借助光学显微镜、SEM和FIB/TEM研究动态载荷下绝热剪切带的形成机理和组织变化.研究表明:冲击载荷下GCr15内部产生致密的绝热剪切带,且裂纹伴随着剪切带产生.剪切带中的晶粒被严重细化,由亚结构和纳米等轴晶组成.带中心部位大量位错缺陷的存在说明晶粒是在动态回复和不完全动态再结晶主导机制下逐步被细化的过程.细化的晶粒使得ASB内显微硬度值显著升高.
关键词:
GCr15
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轴承钢
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高速冲击
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绝热剪切带
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纳米晶
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SHPB
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动态再结晶
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动态回复
GAO Weilin.BAI Guangrun
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ZHOU Zhimin
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LUAN Guifu Northeast University of Technology.Shenyang
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ChinaLONG Chunman Anshan Iron and Steel Company
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China Lecturer
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Post Box No.92.Northeast University of Technology.Shenyang 110006
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China
金属学报(英文版)
Experimental investigation of hot deformation behaviour of Nb-bearing low carbon steel 14MnNb was carried out by Gleeble 1500 simulator.Regressive analysis was made of the re- lationship between deformation onditions and steady state flow stress during hot deformation and the peak fliw stress corresponding to dynamic recrystallization.Clarification was also described for the influence of strain-induced Nb(C.N)precipitation on the activation energy of deformation.On the basis of analyzing the processes of dislocation multiplication and re- coveries from cross-slip of screw dislocation and from climb of edge dislocation during plastic deformation of metals.the theoretical mpdel to predict flow stress under the condiltions of dy- namic recorery and recrystallization occirred simultancously was developed,The prediction about flow stress in practice,under various deformation conditions by the model seems in fair agreement with the experimental results.
关键词:
flow stress
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null
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null
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null
J. Shen
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S. S. Xie and J. H. tang (General Research Institute for Non - ferrous Metals
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Beijing 100088
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China)
金属学报(英文版)
Dynamic recovery and dynamic recrystallizatin behaviors of AA7005 aluminium alloy (Al - Zn - Mg) during hot compression are investigated by isothermal compression testing.The interdependence of flow stress,stress, strain rate,true strain and deformation temperature for the alloy is analyzed by introduc- ing Zener-Hollomon parameter. A steady - state flow of the 7005 alloy is confirmed to be a thermal- ly activated process.which is governed by rate-controlling mechanisms of dislocations.A hyperbolic sine relationship can satisfactorily correlate temperature, strain rate with flow stress through an Arrhe- nius term that involves thermal activation parameters. The dynamic recovery mechanisms of the alloy are discussed.Cross- slip of jogged screw dislocations is the main dynamic recovery mechanism over the deformation temperatures and strain rates.Subgrains are highly developed in the originally elongat- ed grains.The size of the subgrain increases with decrease of the natural logarithm of Zener- Hol - lomon parameter.Local dynamic recrystallization is operative when the alloy is deformed at temperature of 500℃ and strain rate of 0. 001s - 1.
关键词:
compression
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null
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null
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null
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null
孙述利
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何文武
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张敏刚
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柴跃生
稀有金属
doi:10.3969/j.issn.0258-7076.2013.04.008
对9Cr-2W耐热合金进行了热变形温度900～1300℃和应变速率0.005 ～5.000s-1条件下热压缩模拟实验,分析该合金热变形应力应变曲线、热变形组织演变,并测试1150和1300℃下的热变形织构.结果表明,9Cr-2W耐热合金热变形软化方式主要与温度有关,在应变速率0.500 s-1时,900～1050℃出现明显加工硬化,为动态回复型；1100 ～ 1200℃动态再结晶新晶粒沿原晶界分布,为不连续动态再结晶型；1250～1300℃沿原晶界出现锯齿形,为几何动态再结晶型.同时,应变速率对热变形软化方式也有一定的影响,随着应变速率的提高,发生不连续动态再结晶温度范围变宽,细化晶粒效果明显.结合9Cr-2W耐热合金变形织构特征,1150℃热变形组织以动态回复为主,织构相对集中,晶粒择优取向强一些；而1300℃℃热变形组织基本为等轴晶粒,发生了完全动态再结晶,相对应织构漫散,择优取向相对弱一些.
关键词:
9Cr-2W耐热合金
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动态回复
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几何动态再结晶
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变形织构
宋剑锋
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张文志
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董永刚
材料科学与工艺
为了获得高温加工过程中41Cr4钢的动态再结晶体积百分数、真应力、真应变以及稳态应力和稳态应变,在不同变形温度、变形量和变形速度条件下,在GLEEBLE 3500试验机上完成了物理模拟试验.实验结果表明:变形刚开始时位错密度增大较快,因此应力迅速增大,产生加工硬化过程,随着应变的累积,动态回复的发生导致应力增加速度减慢,当应变进一步增大到超过临界应变时,动态再结晶软化导致流变应力降低.在此基础上建立41Cr4钢的流变应力模型时,考虑了加工硬化、动态再结晶以及动态回复对流变应力的影响,给出了与实验值比较接近的41Cr4钢的流变应力模型.
关键词:
流变应力
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物理模拟
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41Cr4钢
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加工硬化
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动态回复
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动态再结晶
周家林
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史密
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张陪毅
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杨光宇
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余茹
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代元
钢铁
doi:10.13228/j.boyuan.issn0449-749X.20140001
利用Gleeble-1500热模拟试验机研究了不同变形条件对45钢低温区热变形行为的影响。试验结果表明：峰值应力随变形温度的降低和应变速率的提高而增大；当应变速率ε?≥0.01s-1、变形温度 t＜500℃时，发生动态回复；当应变速率ε?≤1s-1、变形温度t≥500℃时，发生动态再结晶。在Sellars-Tegart方程的基础上，建立了45钢低温区加工硬化-动态回复、动态再结晶2阶段流变应力模型；根据试验结果计算拟合了模型中各参数。采用建立的流变应力模型成功预测了动态回复、动态再结晶型应力-应变曲线。利用上述模型对45钢中厚板轧后低温工业热矫直的矫直力进行了预测，其结果与实测值吻合良好。
关键词:
45钢
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低温热变形
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动态回复
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动态再结晶
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流变应力
