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1.
C. D'Amato C. Verdu X. Kleber G. Regheere A. Vincent 《Journal of Nondestructive Evaluation》2003,22(4):127-139
The outstanding mechanical properties of austempered ductile irons (ADI) are linked to the microstructure of the matrix obtained by subjecting a ductile iron with an appropriate composition to a heat treatment called austempering. Then the microstructure of the matrix consists of bainitic ferrite with different volume fractions of retained austenite. The aim of this work is to use the magnetic Barkhausen noise (MBN) as a nondestructive method for characterizing the microstructure of ADI. First, it is shown that the amplitude and position of the peak-shaped MBN response is quite sensitive to the microstructure of the matrix of ductile irons. Thus each type of constituent (equiaxial ferrite, pearlite, martensite or bainite) exhibits a typical response and, in turn, it can be identified from the MBN response. Furthermore, a good correlation is found between MBN signal parameters and ADI heat treatment parameters, indicating that MBN is also quite sensitive to fine evolutions of the microstructure of ADI. MBN peak position is especially sensitive to the type of bainite, whereas peak amplitude is linked to the progress of the bainite reaction. Hence MBN measurements appear to be a powerful tool to assess some important microstructural features of ADI castings. 相似文献
2.
Weihong Xu Wei You Yaxiu Liu Bingzhe Bai Hongsheng Fang 《北京科技大学学报(英文版)》2005,12(5):410-415
The quantitative effect of Ni content on continuous cooling transformation (CCT) diagrams of novel air-cooled bainite steels was analyzed using artificial neural network models. The results showed that Ni may retard the high- and medium-temperature transformation and martensite transformation. The results conform to the materials science theories. 相似文献
3.
Pre-bainitic Transformation in Fe-Ni Alloy 总被引:1,自引:0,他引:1
Thepre-bainiticphenomenonisoneoftheim-portantsubjectsofbainitictransformationwhichisstilcontroversial.Oneviewisthatthesolutea... 相似文献
4.
预转变马氏体对GCr15钢贝氏体转变动力学的影响SCIEI 总被引:2,自引:0,他引:2
本文利用磁性法和膨胀法研究了GCr15钢M_s点以下贝氏体转变动力学以及不同温度预转变马氏体对240℃等温时贝氏体转变动力学的影响。试验结果表明,过冷奥氏体在M_s点以下等温过程中首先形成变温马氏体,继而转变为下贝氏体。随着等温温度的降低和预淬马氏体数量的增加,应力促发作用有助于贝氏体转变的加速,200℃左右其孕育期最短。但是,当温度继续下降、预淬马氏体超过一定数量之后,贝氏体转变却愈趋困难,此外,M_s点以下不同温度的预转变马氏体对随后240℃等温时贝氏体转变动力学影响的研究结果,也具有相同的特性。 相似文献
5.
近年来贝氏体相变理论三个学派的研究工作均有明显进展,有些观点渐趋接近,有些观点依然存在严重分歧,各自都有亟待澄清的难题。各派间在学术上的批判反批判旨在指明探索方向和途径,发展理论,这已充分为当今相变理论研究进展事实所证明。 相似文献
6.
摘要:为探索低温贝氏体钢的断裂行为,研究应变速率对低温贝氏体钢TRIP效应的影响,采用不同应变速率的拉伸试验对低温贝氏体钢的强塑性进行研究。利用扫描电镜(SEM)、透射电镜(TEM)及X射线衍射(XRD)等试验方法对低温贝氏体钢的微观组织、断口形貌及裂纹走向进行表征。结果表明,随着应变速率的提高,试验钢的屈服强度由771MPa上升至806MPa,抗拉强度由1554MPa上升至1606MPa,断后伸长率由13.5%下降至9.0%。主要原因是高应变速率拉伸引发的绝热温升抑制了残余奥氏体的马氏体相变,对试验钢塑性造成负面影响。 相似文献
7.
TEMPERED BAINITE EMBRITTLEMENT IN SOME STRUCTURAL STEELS 总被引:2,自引:0,他引:2
HU Guangli LIU Zhengtang WANG Ping HUA Wenjun KANG Mokuang Northwestern Polytechnical University Xi''''an China HU Guangli Associate Professor Department of Materials Science Engineering Northwestern Polytechnical University Xi''''an China 《金属学报(英文版)》1989,2(5):337-342
The variations of microstructures and mechanical properties of steels 15CrMnMoV,18Mn2CrMoB,18Cr2Ni4W,30CrMnSi,30CrMnSiNi2 and 40CrMnSiMoV,which weretempered at different temperatures after austempering and continuous cooling at given rates,have been investigated.Based on the experimental results,the behaviour and mechanism oftempered bainite embrittlement(TBE)have been discussed.Finally,the theoretical and prac-tical basis for selecting the optimum tempering temperature of steels with bainite structure af-ter heat treatment are proposed. 相似文献
8.
9.
Mingru Zhang Jianqing Qian Haicheng Gu 《Journal of Materials Engineering and Performance》2007,16(5):635-639
Metallographic structures of carbide-free bainite steel wheel rim are mainly composed of supersaturated lath ferrite and retained
austenite film among bainitic ferrite laths. It is suspected that supersaturated ferrite and retained austenite are likely
to decompose under the influence of temperature change and mechanical stress. Stability of wheel rim structure is studied
by means of x-ray diffraction, dye microscopy, and micro-hardness test. When the samples are tempered in the range of 150-350 °C,
the retained austenite films are at the state of relative stability. Fifty percent of retained austenite is decomposed when
the sample is tempered at 400 °C. Microhardness increases when the sample is tempered at 150 °C. The decrease in hardness
is mild when the samples are tempered from 200 to 500 °C. The mechanical stability of retained austenite film is studied with
tensile sample under the effect of tensile stress. The retained austenite appears to be stable in low and middle degree of
deformation, and decomposition occurs at great amount of deformation. Diffraction peak of carbide is not found in all above
experiments. The steel enriched silicon prevents the carbide precipitation during the transformation. It indicates the carbide-free
bainite wheel steels have an excellent thermal and mechanical stability. 相似文献
10.
为了研究Al和P合金元素在TRIP钢固态相变过程中的重要作用,利用热膨胀实验、金相观察、显微硬度测量等方法绘制了4种不同Al和P含量的C-Mn-Al-P TRIP钢的CCT图.结果表明,Al元素强烈缩小奥氏体相区,提高Ac3与Ms,促使CCT图左移和上移.P元素能够阻碍碳化物的生成,当钢中w(P)达到0.14%时,能显著将CCT曲线图中的珠光体区与贝氏体区右移.P元素对先共析铁素体相变和马氏体相变没有显著影响.随着冷却速率的增加,材料的显微硬度增加.对于每一种成分超过其临界冷却速率时将得到完全的马氏体组织.添加固溶强化元素可以强化铁素体基体,增加铁素体基体的硬度,P元素固溶强化能力最强,Mn元素稍弱,Al元素很弱. 相似文献