陈卫中
,
徐祖耀
,
陈树川
,
张骥华
材料研究学报
通过研究三种Fe-Ni-C 合金中珠光体、贝氏体及马氏体的低频相变内耗,发现马氏体相变内耗遵守相界面位错的静滞后损耗机制,珠光体和贝氏体相变内耗不遵守这种机制。在频率基本不变时,随着冷却速度的增加珠光体和贝氏体的相变内耗峰增高,峰温降低,且Q(?)和(?)/fm 件·T_m 呈正比线性关系;频率增加时,珠光体和贝氏体的内耗峰明显降低,峰温上串。在连续冷却条下,Fe-Ni-C 合金中开始珠光体及贝氏体相变时并不存在点阵软化现象。
关键词:
珠光体相变
,
bainitic transformation
,
martensitic transformation
,
internal friction
C.C. Liu
,
Z. Liu and G.X. Chen (Department of Mechanical Engineering
,
Tsinghua University
,
Beijing 100084
,
China)(Department of Mechanical Engineering
,
Tsinghua University
,
Beijing 100084
,
China)(Department of Mechanical Engineering
,
Tsinghua University
,
Beijing 100084
,
China)
金属学报(英文版)
ZBainitic transformation is analyzed in detail according to the factors such as morphology,crystallography,mechanical property of bainite and transformation kinetics,and conclusion is drawn that bainitic transformation is controlled by displacive mechanism and self-fempering of displacive microstructure.That is to say,bainite is the product of such procedure during which undercooled austemite first transforms into one certain displacive microstructure by displacive mechanism and then this microstructure experiences self-fempering.With this idea,several questions,which cannot be illustrated only by displacive transformation mechanism,can be explained successfully.
关键词:
bainitic transformation
,
null
,
null
徐祖耀
,
周晓望
金属学报
对x_(Al)=0.24合金贝氏体相变的两种机制的相变驱动力ΔG~(p_1→a’)及ΔG~(β_1→β_2~(+a))进行了热力学计算,结果表明,在贝氏体相变温度范围680—750K内,ΔG~(β_1→α’)>0,这说明贝氏体相变的开始不可能按β_1→α’的切变型机制进行,在700K只产生5％的α时,α的成分至少降到x_(Al)~α=0.204,才能使ΔG~(β_1→β_2~(+α))<0,而在750K,则至少需满足x_(Al)~α≤0.209,才有ΔG~(β_1→β_2~(+α))<0,说明贝氏体相变须按β_1→β_2+α扩散型机制进行,且转变温度不同,所需扩散量也不同。
关键词:
Cu-Al合金
,
bainitic transformation
,
thermodynamics
张志宏
,
薛向欣
材料热处理学报
利用热模拟实验研究了一种含硼微合金钢未变形和900℃变形40%的奥氏体CCT曲线,利用光学显微镜和电镜研究冷却速度、变形对实验钢显微组织的影响。结果表明：微量硼提高实验钢过冷奥氏体的稳定性;未变形及变形试样分别在冷速2℃/s和5℃/s以上为贝氏体组织,变形提高贝氏体开始转变温度,但冷速在20℃/s以上时变形与未变形Bs温度相差较小;并且随冷速增加,显微硬度显著增加。
关键词:
含硼微合金钢
,
连续冷却转变
,
显微组织
,
贝氏体转变
张志宏
,
薛向欣
,
杨合
钢铁研究学报
利用热模拟试验技术对实验室制备的含硼微合金钢连续冷却转变形为进行了试验研究,利用光学显微镜研究冷却速度、变形对试验钢显微组织的影响,探讨了硼对转变行为的影响规律。结果表明：适量硼延缓多边形铁素体生成,有利于获得贝氏体组织;无硼及wB=0.002 0%时,分别在1～25及0.5～25℃/s的冷速都能得到贝氏体组织;wB=0.003 0%时,冷速在2℃/s以上能得到贝氏体组织;与未变形相比,变形导致试验钢贝氏体冷速区间变窄。在同一冷速下,随硼含量增加贝氏体开始转变温度先降低再升高,显微硬度随硼含量增加先增加而后降低。
关键词:
含硼微合金钢
,
连续冷却转变
,
显微组织
,
贝氏体转变
ZHAO Zengqi CHEN Feixia YANG Dazhi BAO Er ** Physical Laboratory
,
Baotou Research Institute of Rare Earth
,
Baotou
,
014010
,
China*** Dept.of Materials Engineering
,
Dalian University of Technology
,
Dalian
,
116024
,
China**** Dept.of Materials Engineering
,
Yanshan Uni
材料科学技术（英文）
The present investigation showed that the re- laxation peak at about 200℃ (f≈1Hz) was related to bainitic transformation in a CuZnAl alloy.The peak decreased when bainite precipitated.The activation energy of the peak was the same as the apparent activation energy of bainitic transforma- tion.According to the relations between the peak and the bainitic transformation,the mechanism of the peak has been discussed.
关键词:
internal friction
,
null
,
null
,
null
Zengqi ZHAO Lab.of Physics
,
Baotou Research Institute of Rare Earth
,
Baotou
,
014010
,
ChinaFeixia CHEN Dazhi YANG Dept.of Mater.Eng.
,
Dalian University of Technology
,
Dalian
,
116024
,
ChinaEr BAO Dept.of Mater.Eng.
,
Yanshan University
,
Qinhuangdao
,
066004
,
China
材料科学技术（英文）
Isothermal aging behaviours of a CuZnAl shape memory alloy have been investigated by means of dilatometry.The length of the specimens during isothermal aging from 190 to 280℃ increases with the aging time at each temperature.The isothermal aging kinetics fits in Avrami equation and the time exponent n decreases with the increase in aging temperature.The apparent activation energy for the isothermal aging process was measured to be 109.0kJ/mol,which is about equal to that of a relaxation internal friction peak at about 200℃ (f≈1 Hz) in the alloy.
关键词:
isothermal aging kinetics
,
null
,
null
,
null
,
null
徐祖耀
金属学报
外加应力使贝氏体相变形核率增大, 等温孕育期缩短, 即使所加应力远低于母相的屈服强度. 由于钢
中γ→α＋γ‘的形核驱动力较大(约为kJ/mol数量级), 贝氏体相变的膨胀应变能很小, 过小的外加应力对形核率的影响甚微. 考虑在外加应力的影响下, 会使界面能量有所下降, 也可能发生碳原子的再分布, 偏聚在晶界或其它缺陷, 甚至碳化物析出都会显著地增大形核率和缩短孕育期, 有待进一步实验给予证明. 无应力下, 贝氏体相变动力学可以用Avrami的等温相变方程来表述; 应力下则符合应力下铁素体及珠光体相变的动力学模型(经修改的Avrami方程). 形变奥氏体促发贝氏体相变, 但随后会发生奥氏体的力学稳定
化, 其机制可能和马氏体相变时的奥氏体力学稳定化不完全相同, 仅形变形成的位错阻碍贝氏体以一定位向长大, 使相变动力学迟缓. 贝氏体相变时奥氏体力学稳定化的模型有待建立.
关键词:
贝氏体相变
,
transformation under stress
,
transformation kinetics
