彭宁琦
,
唐广波
,
刘正东
,
吴秀月
金属学报
doi:10.3321/j.issn:0412-1961.2009.03.013
根据Aaronson提出的超组元模型,借助Ae3的实验数据,提出了修正的置换型元素Xi(Xi=Si,Mn,Ni,Co,Mo,Al,Cu,Cr)的Zener两参数,修正中考虑了合金元素间的交互作用.修正后的超组元模型的预测精度明显改善:Ae3计算值与实验值的标准差为10.8℃,与Thermo-Calc计算值的标准差为2.35℃;Ae1计算值与实验值的标准差为6.8℃.按照马氏体相变热力学的计算方法,采用经修正的参数计算了马氏体相变开始温度Ms,提高了Ms点的预测精度,计算值与实验值的标准差为25.3℃.
关键词:
相变
,
热力学
,
超组元模型
,
相变平衡温度
HU Zhizhong WU Yusheng CAI Heping MA Lihua Xi′an jiaotong University
,
Xi′an
,
China Senior Engineer
,
Res.Inst.for Strength of Metals
,
Xi′an jiaotong University
,
Xi′an 710049
,
China
金属学报(英文版)
Studies have been made of the torsional fatigue fracture life of notched specimens,the macroscopic fractography and microscopic fracture mechanism of steel 40Cr after various tempering treatments under different stresses,With the increase of stress,the fracture model changes from normal stress fracture to longitudinal shear one,and then transversal shear one. Under same stress,with the increase of strength,the fracture mode transfers from shear to normal stress fracture.The mechanism of normal stress fracture may be:transgranular frac- ture→striation+intergranular fracture→dimple+intergranular fracture,and of shear fracture may be:transgranular fracture→shear trace→dimple.Based on the experimental results,a fracture mechanism map of torsional fatigue has been drawn up.
关键词:
mechanism map
,
null
,
null
CHEN Zheng Northwestern Polytechnical University
,
Xi′an
,
China Lab.No.401
,
Northwestern Polytechnical University
,
Xi′an 710072
金属学报(英文版)
Threshold of fatigue for short through cracks for Al-Li alloy 8090 was evaluated to be lower than that of long cracks,and to decrease with the shortening of the crack length.The correla- tion among the threshold,crack wake,and crack tip shielding of the short fatigue cracks was discussed.The super demarcation length and lowest theoretical threshold of short through fa- tigue cracks were presented.
关键词:
Al-Li alloy
,
null
,
null
,
null
,
null
CHEN Daming KANG Mokuang Northwestern Polytechnical University
,
Xi′an
,
ChinaTAN Ruobing Institute of Metal Research
,
Academia Sinica
,
Shenyang
,
China
金属学报(英文版)
The microstructure,strength,toughness and fatigue properties of an ultra-high strength steel 40CrMnSiMoVA have been investigated.The so-called meta-bainite,composed of thin re- tained austenite films within or between the bainitic ferrite lathes was found in the steel after isothermally quenched at 300℃ for 1h.In comparison with the martensite structure obtained by isothermally quenching in martensite range,the meta-bainite has more excellent strength and plasticity,lower notch sensitivity,stronger strain harden ability,higher fatigue strength, longer strain or impact fatigue life,slower crack propagation rate and more remarkable overload effect on increasing fatigue life.
关键词:
ultra-high strength steel
,
null
,
null
,
null
盛广
,
杨志刚
金属学报
根据Fe--C--Xi合金系的正平衡和准平衡热力学模型，推导了简便的奥氏体--铁素体相变驱动力计算解析式。根据公式, 代入合金原始成分和Ae3温度, 即可准确计算正平衡和准平衡模式下的奥氏体--铁素体相变驱动力。采用这一方法计算了Fe--C--Mn--Si--Ni--Cr--Mo--Cu八元系的正平衡和准平衡奥氏体--铁素体相变驱动力。
关键词:
正平衡
,
null
,
null
,
null
WANG Hongwei MA Jinsheng NAN Junma HE Jiawen Xi′an Jiaotong University
,
Xi′an
,
China
金属学报(英文版)
The surface yield strength(σ_(ms))for various carbon steels was studied by means of X-ray diffraction method.The results showed that it is.far below the bulk yield strength,and is the resistance against plastic deformation in the surface layer.The smooth fatigue limit is associ- ated with crack initiation which is a result of accumulation of plastic deformation.Experimen- tal results showed the relation of smooth fatigue limit for 50% survival with σ_(ms)is σ_(ms)=0.81 tO 1.02 σ_(-1)for different steels.The smooth fatigue limit of a medium carbon steel for 99.9% survival with σ_(ms)is σ_(ms)=0.98 tO 1.10 σ_(-1).It is less expensive and time consuming to measure σ_(ms)than σ_(-1).
关键词:
X-ray
,
null
,
null
WANG Zhaoxia CHAI Donglang LIU Jinghua Xi′an Jiaotong University
,
Xi′an
,
China
金属学报(英文版)
On the basis of stress-strain analysis under cyclic loading,the mechanism,origin and cyclic number of microcraek nucleation of duplex structure materials,saying ferrite plus martensite, have been experimentally studied and calculated.Both results are in fair mutual agreement. The morphology,distribution,size and relative quantities of the constitutional phase,especial ly strengthening phase,as well as the stress-strain distribution and variation in micro-region are directly influential in the origin of microcracks in duplex structure materials.
关键词:
stress-strain analysis
,
null
,
null
