刘东升
,
王国栋
,
刘相华
,
甄立冬
,
苏永科
,
徐辉
金属学报
采用膨胀法结合金相分析建立了P20钢的CCT曲线,根据动态CCT曲线，提出P20钢轧后控冷预硬化工艺．与常规热处理条件相比，形变热处理条件下的奥氏体具有较高的稳定性.变形后以0．2—0．02℃／s连续冷却时，主要发生贝氏体相交，而多边形铁素体相变被抑制．变形可使奥氏体机械稳定化，阿氏体相变推迟至较低温度下完成.P20钢轧后在贝氏体相变区缓冷获得粒状贝氏体组织，实现在线预硬化，硬度达到35—38．
关键词:
P20塑料模具钢
,
hardening
,
transformation
,
granular bainite
,
deformed austenite
杨军贺志荣王芳王永善
金属学报
doi:10.3724/SP.J.1037.2010.00390
使用示差扫描量热仪(DSC)和拉伸实验研究了Cr掺杂对550℃退火态Ti-50.8Ni(原子分数, %)形状记忆合金相变和循环形变特性的影响. 结果表明, Ti-50.8Ni合金冷却/加热时发生B2→R→M/M→B2型可逆相变, 掺杂0.3%Cr后所得Ti-50.8Ni-0.3Cr合金的相变类型为B2→R→M/M→R→B2, 相变温度大幅度降低. 室温下, Ti-50.8Ni和Ti-50.8Ni-0.3Cr合金的相组成均为母相B2, 前者呈现形状记忆效应, 后者呈现超弹性. 随循环变形次数n的增加, Ti-50.8Ni合金的特性由形状记忆效应演变为线性超弹性, 合金的应力诱发马氏体临界应力和积累残余应变迅速增加; Ti-50.8Ni-0.3Cr合金的特性由非完全超弹性演变为完全超弹性, 超弹性应力-应变曲线形态比较稳定. 随$n$增加, Ti-50.8Ni合金的超弹性残余应变εr减小, 超弹性应变恢复率ηs增加; Ti-50.8Ni-0.3Cr合金的εr和ηs则分别稳定在较低和较高水平, 超弹性稳定.
关键词:
Ti-Ni合金
,
Ti-Ni-Cr alloy
,
shape memory alloy (SMA)
,
transformation
,
cycling deformation
胡亮
,
郭顺
,
孟庆坤
,
赵新青
稀有金属材料与工程
采用X射线衍射、透射电镜和力学性能测试等手段,系统研究了热-机械处理对亚稳βTi-25Nb-2Mo-4Sn合金微观组织和力学性能的影响.结果表明:由于合金中β稳定化元素含量不足,固溶处理后的合金中含有大量的α”马氏体,合金呈现低屈服强度.经过相同的时效处理(400℃/2 h),固溶态和冷轧态样品的相组成分别为β+ω和β+α相.冷变形引入的大量位错和晶界可有效抑制时效过程中ω相的形成,并促进α相的析出.冷轧态样品经475℃时效15 min后弹性模量为65 GPa,屈服强度和抗拉强度分别为1033和1113MPa,实现了低模量和高强度的良好匹配.
关键词:
亚稳β钛合金
,
热-机械处理
,
相变
,
力学性能
方琪
,
李春龙
,
勤牧
,
白海瑞
,
董元
,
孙伟
稀土
利用L78RITA热膨胀相变仪研究了不同冷速下稀土对低碳高铌钢相变行为的影响,并结合金相法绘制了加稀土和未加稀土两种成分试验钢的连续冷却相变曲线,分析了稀土对连续冷却组织的影响规律.试验结果表明,稀土加入低碳高铌钢后使连续冷却相变曲线向右移动,在相同冷速下显著降低了奥氏体向铁素体转变的开始温度,并且随着冷速的增加使降低程度增大.冷速从0.1℃/s增加到15℃/s时,加稀土的低碳高铌相变开始温度点下降了90℃,而未加稀土的下降了52℃;另一方面,稀土对低碳高铌钢在0.1℃/s到1℃/s冷速下的组织有较大影响,促进了针状铁素体的转变,并能在冷速增至5℃/s后使其更易获得板条状贝氏体组织.
关键词:
稀土
,
低碳高铌钢
,
连续冷却转变曲线
,
相变
L. W. Zhang
,
J. Th.M.De Hosson
,
Y.L. Xia and F. G. Wang 1)The State Key Lab. for Materials Modification by Laser
,
Ion and Beams
,
Dalian University of Technology
,
Dalian 116023
,
China 2)Department of Applied Physics
,
University of Froningen
,
The Netherlands
金属学报(英文版)
In this paper,a thermal elastic-plastic 2-D finite element model of stress generation during laser transformation hardening process was developed. In this model, the mechanical properties of the material, Young's modules E, Poisson's ratio v, yield limit s, and thermal expansion coefficient α, are all change with temperature. The equivalent expansion method was used to deal with the problem with phase transformation. Based on this model, a program to calculate the residual stress field was developed using FORTRAN language. The residual stress fields in CO2 laser transformation hardened MoCu nodular iron were calculated. The calculated results showed that in the transformation hardened zone, the residual stress state is compress,whereas adjacent to this zone the residual stress state is tensile, and there is a tensile stress peak close to the transformation hardened zone. To verify this model, the residual stress fields were measured using X-ray diffraction method. The calculated results of residual stress fields are in good agreement with the experimental results.
关键词:
laser
,
null
,
null
,
null
,
null
Z.D. Wang
,
J.B. Qu
,
X.H. Liu and G.D. Wang(State Key Lab of Rolling and Automation
,
Northeastern University
,
Shenyang 110006
,
China)
金属学报(英文版)
The influence of hot deformation conditions on continuous cooling bainitic transformation has been investigated for a low carbon microalloyed steel. The CCT diagrams show that deformation in unrecrpstallized austcnite ation can accelerate transformation process. Bainitic transformation in intermediate transformation temperature region is prominent, and the proeutectoid polygonal ferrite transformation at evelated high temperature is suppressed. According to optical and TEM analyses, low carbon bainitic ferrite is characterized by granular and lathlike ferrite, based on the cooling rate and deformation conditions. For nondeformation, groaps of coarse parallel ferrite lath form from the prior austenite grain boundaries with the same crystallographic orientation. For heavy deformaton, cell structure within the austenite grains due to the high dislocation density formed, which provides more nucleation sites for bainite ferrite. So deformation can discontinue the growth of ferrite laths and decrease the length of ferrite laths.
关键词:
bainite
,
null
,
null
,
null
,
null
丁国
,
黄丽颖
,
定巍
,
龚志华
,
王宝峰
材料热处理学报
利用光学显微镜、透射电镜、X射线衍射和相变仪对热镀锌TRIP钢的微观组织进行了定性观察和定量计算,在此基础上对热镀锌TRIP钢残留奥氏体的演变规律和马氏体的精细结构进行了研究.定性观察表明热镀锌TRIP钢的微观组织由铁索体,贝氏体,残留奥氏体和马氏体构成,在贝氏体相变结束后的冷却过程中还存在马氏体相变;通过对微观组织计算发现,受贝氏体等温相变时间影响,热镀锌TRIP钢中的马氏体碳含量在0.80％～1.0％之间,贝氏体等温时间越长,最终组织中马氏体碳含量越高,Ms点越低;在贝氏体相变结束后,部分碳含量不高的奥氏体在随后的冷却过程中发生马氏体相变,以马-奥岛的形式存在,马氏体的精细结构以孪晶马氏体为主,存在少量位错马氏体.
关键词:
热镀锌TRIP钢
,
微观组织
,
相变
李强
,
金明江
,
应仁龙
,
金学军
金属功能材料
通过DSC热分析技术研究了成分和升降温速率对GaInSn三元合金和GaIn二元合金的固-液相变行为的影响.结果表明,GaInSn三元合金和GaIn二元合金升温过程中的固-液转变(熔化)温度十分稳定,对成分波动不敏感;而降温过程中的液-固转变(凝固)温度则随成分的波动而显著变化.此外,讨论了Ga基合金过冷度与Ga含量和冷却速率之间的关系.
关键词:
镓基合金
,
过冷度
,
相变
