材料期刊网

铁基合金的贝氏体基元及其生长演化

徐启昆 , 周正

材料研究学报

用透射电镜研究了Fe-C-Mo 和Fe-C-Si-Mn 合金中温转变早期产物的组织形态,发现在整个中温转变范围非平衡先析型转变都是按贝氏体铁素体相变基元形成及其扩散生长演化方式进行,说明经生长演化一些时间后的基元难于作为判断贝氏体形核机制的形态学依据。从基元生长演化进程区分了低碳贝氏体和板条马氏体。

关键词: 贝氏体组织 , bainite transformation , basic unit of baintite , morphology of bainite , formation mechanism of baintite

IN SITU OBSERVATION OF LOWER BAINITIC CARBIDES PRECIPITATION

KANG Mokuang SUN Jialin Northwestern Polytechnical University , Xi'an , China Dept.of Materials Science and Engineering Northwestern Polytechnical University , Xi'an , 710036 , China

金属学报(英文版)

The lower bainitic carbides precipitation in 40CrMnSiMoV steel previously austempered at 310℃ was observed in situ by employing a high temperature stage of an ultra high voltage TEM(JEM-1000).The typical lower bamitic carbides were found to have precipitated from within the carbide-free bainitic ferrite after tempering for certain period at a temperature higher than that of the isothermal transformation.This revealed that the lower bainitic ferrite is supersaturated with carbon to some extent.The carbide may also precipitate from austenite, but they have no typical morphological features of lower bainitic carbide.

关键词: bainite transformation , null , null , null

SUBSTRUCTURAL AND CRYSTALLOGRAPHIC FEATURES OF LOWER BAINITE

SUN Jialin Kunming Institute of Technology , Kunming , ChinaKANG Mokuang Northwestern Polytechnical University , Xi'an , China

金属学报(英文版)

Based on the TEM analysis of substructures of lower bainite in two steels containing Si,the lattice invariant shear elements were determined and a plastic accommodation double-shear model of phenomenological crystallography was proposed.The theoretical predictions about crystallography given by the model are in good agreement with the experimental data for the steels tested.

关键词: bainite transformation , null , null

A Crystallography Study of Bainitic Transformation in a Cu-Zn-Al Alloy

AN Jiangying , ZHU Min , YANG Dazhi Department of Materials Engineering , Dalian Institute of Technology , China.

材料科学技术（英文）

The crystallographic nature of initial isothermal phase transformation in Cu-26Zn-4Al (wt-%) was investigated. The kinetic transforma- tion curve, morphology, crystal structure, substructure, orientation relationship and twin relationship of bainite plates have been studied by means of optical and transmission electron microscopy. The experimental results showed that the characteristics of initial 8→bainite transformation are not exactly consistent with that found in martensite transformation, for example, orientation relationship between matrix and bainite does not exist in martensite transformation.

关键词: bainite transformation , null , null

INVESTIGATION ON LATER STAGE OF INTERMEDIATE TRANSFORMATION IN Fe-C-Mo ALLOYS

XU Qikun WANG Dongya Chongqing University , Chongqing , China XU Qikun , Dept.of Metallurgy and Materials Engineering , Chongqing University , Chongqing , Sichuan , China

金属学报(英文版)

The transformation process and the products of long term isothermal transformation around the kinetic B_s temperature(the bay temperature in TTT diagram)in Fe-C-Mo alloys have been investigated.It was found that,at the final stage of intermediate transformation,a kind of granular structure formed accompanying the growth of bainitic ferrite.In comparison with the carbide Mo_2C in the bainitic ferrite plates or blocks,the carbide m granular eutectoid has been determined to be cementite containing a tiny bit of molvbdenum,(Fe,Mo)_3C.

关键词: allot Fe-C-Mo , null , null , null

金属合金等温相变的体激活能及相变机制 I. 钢的中温(贝氏体)等温相变

康沫狂张明星刘峰朱明

金属学报

钢的中温(贝氏体)等温处理获得的上、下贝氏体和粒状组织, 都具有各自独立的C曲线；在转变初期均能获得单一的组织, 而在转变的中、后期通常可获得相邻两组织的复合体. 必须用单一组织和Arrhenius关系求相变产物的体激活能. 将体激活能、组织形貌和体自由能曲线相结合可诠释下述论点: 下或上贝氏体是碳原子扩散控制下在奥氏体中的贫碳或极贫碳区, 进行“军队型”(队列式)原子无扩散马氏体样切变相变; 而粒状组织是碳原子扩散控制下在奥氏体中的最贫碳区, 发生“平民型”(非队列式)原子无扩散界面控制相变.

关键词: 贝氏体相变 , overall activation energy , granular structure , granular bainite , martensite-like shear , interface control transformation , steel

Dynamic Observation of Bainite Transformation in a Fe-C-Mn-Si Superbainite Steel

HU Haijiang , XU Guang , ZHANG Yulong , XUE Zhengliang , ZHOU Mingxing

武汉理工大学学报-材料科学版(英文版) doi:10.1007/s11595-015-1234-2

关键词:

Fe-C合金贝氏体转变初期的热力学分析

谢朝阳 , 康沫狂

材料研究学报

用Fe-C 合金的规则间隙溶体模型在新的贝氏体转变模式的基础上对Fe-C 合金贝氏体转变初期进行了热力学分析。新的模式中,贝氏体铁素体以非平衡但不完全过饱和的碳量经由切变机制形成,碳的再分配先于贝氏体铁素体的形成。结果表明,在完善奥氏体中形成一定尺寸的贫碳区,其引起的能量升高与马氏体相变的形核垒有相同的数量级;在借助于体系的内部缺陷以及非平衡体系结构驰豫的情况下是可以实现的过程;在贝氏体铁素体碳量为非平衡但不完全过饱和的情况下,贝氏体转变的驱动力足以推动切变相变。

关键词: 贝氏体相变 , thermodynamics , carbon partitioning , driving force , shear

Nb微合金化NM500低合金高强度耐磨钢动态连续冷却转变

张国庆 , 王福明 , 庞瑞朋 , 李天生

材料热处理学报

利用Gleeble-1500热模拟试验机,对国产NM500钢化学成分基础上添加微量的合金元素Nb的实验钢的动态连续冷却转变(CCT)曲线进行了研究,实验结果表明:随Nb含量由0.018％增加到0.059％,实验钢的组织硬度提高;贝氏体转变出现和结束所需要的冷却速度提高,扩大了工艺参数选择的操作性;在冷速为5～8℃/s的情况下,使得马氏体和贝氏体的比例适中,保证试验钢获得NM500所规定的强度和硬度.

关键词: NM500 , 耐磨钢 , 动态CCT , 冲击韧性 , 贝氏体转变

SDP2新型贝氏体模具钢的相变及动力学

段丽丽 , 张铮 , 李晓成 , 吴晓春

材料热处理学报

对新开发大截面贝氏体塑料模具钢SDP2在极低冷速下的过冷奥氏体连续冷却转变过程和相变动力学进行了研究.采用DIL805A高精度差分热膨胀仪测量SDP2钢线膨胀行为,利用SEM分析冷却转变产物;根据JMA公式计算SDP2钢贝氏体相变激活能和Avrami指数.结果表明,SDP2钢过冷奥氏体连续冷却过程包含珠光体、贝氏体和马氏体转变,而无铁素体转变;当冷速大于0.02C/s时,转变产物以下贝氏体或马氏体为主;小于0.02℃/s时,以上贝氏体或粒状贝氏体为主,并出现珠光体.SDP2钢贝氏体转变的激活能为117 k J/mol,SDP2钢在不同冷速下贝氏体转变动力学指数Avrami指数n≈2 ～3,经分析计算所得的Avrami指数值所对应的显微组织形态和实验所观察到的显微组织相符合.

关键词: 塑料模具钢 , CCT , 贝氏体相变 , 热膨胀 , 动力学