郑运荣
,
蔡玉林
,
阮中慈
,
马书伟
航空材料学报
doi:10.3969/j.issn.1005-5053.2006.03.006
在高温合金中,元素Hf和Zr可以促进γ+γ′共晶、MC(2)碳化物、M2SC碳硫化物和Ni5M相的形成,改变草书状MC和M3B2成为块状并且通过净化晶界或枝晶间自由态的S来提高这些薄弱部位的结合强度,从而延迟裂纹的形成和扩展.Hf和Zr可提高铸造高温合金室温拉伸和中温持久的强度和塑性.Hf,Zr抑制次生碳化物M23C6和M6C的生成,从而提高了合金在高温长时热暴露时的显微组织稳定性.Hf,Zr降低合金的初熔温度,Ni5Hf和Ni5Zr相的初熔被认为是Hf,Zr影响初熔的主要原因.通过1150℃/8h的预处理,Ni5Hf以Ni5Hf+γ(C)→MC(2)+γ反应或者固溶两种方式被消除.元素Hf可以缩小枝晶间失去毛细管补缩能力和固相线之间的温度范围,还能降低枝晶间液池沟通所需的液体量.在凝固后期枝晶间的富Hf熔体具有很好的流动性、浸润性和趋肤效应,这些都是降低合金热裂倾向、提高合金可铸性和焊接性能的有利因素.具有高的化学活性的富Hf液膜容易在铸件表面形成Hf2O薄层.Hf和Zr是钎焊用中间层合金的降熔点元素.根据凝固过程中富Hf,Zr熔体的成分最终发展出Ni-18.6Co-4.5Cr-4.7W-25.6Hf和Ni-10Co-8Cr-4W-13Zr两种中间层合金,使单晶高温合金的无Si、B连接成为现实.还发展出了定向凝固片状Ni3Al/Ni7Hf2共晶合金,成分为Ni-5.8Al-32Hf和Ni-4Al-26Hf-8Cr-4W.Ni-5.8Al-32Hf合金的最佳凝固条件为温度梯度G=250℃·cm-1和凝固生长速率R=5μm·s-1;Ni-4Al-26Hf-8Cr-4W,凝固条件为G=350℃·cm-1和R=1μm·s-1.
关键词:
高温合金
,
相变
,
铪
,
锆
,
凝固
,
初熔
,
TLP连接
,
Ni3Al/Ni7Hf2共晶
,
显微组织
,
MC(2)碳化物
,
Ni5Hf相
,
力学性能
Guofeng Wang Kaifeng Zhang
材料科学技术（英文）
Ni-Mn nanocomposite reinforced by Al2O3 particles was fabricated by pulse electrodeposition. The average grain size is 60 nm and the content of Mn and Al2O3 particles is 0.3 and 0.6 wt pct, respectively. The superplastic deformation behavior was further studied at the temperatures ranging from 673 to 873 K. A maximum elongation of 530% is obtained in the tension test at a temperature of 773 K and at a strain rate of 1.67×10-3 s-1. The curves of the flow stress vs strain rate have features similar to the trend of conventional superplastic materials. The test temperature (773 K) equals to 0.35Tm, which means the material obtains low temperature superplasticity. The microstructures of the composite were examined and grain growth was observed during deformation.
关键词:
Electrodeposition
,
纳米复合材料
,
低温超塑性
,
显微组织
Li Ma Dingyong He Xiaoyan Li Jianmin Jiang
材料科学技术（英文）
In order to join the similar magnesium alloy, a novel Zn-Mg-Al filler metal was designed and applied to braze AZ31B plates by using high-frequency induction brazing technique. The microstructure, phase constitution and fracture morphology of the brazed joint were investigated. The experimental results show that MgZn2 phase in the original filler metal is completely consumed in the brazing process. Moreover, α-Mg solid solution and α-Mg+MgZn eutectoid structure formed in the brazing region due to the intensive alloying between the molten filler metal and the base metal in the brazing process. Test results indicate that the shear strength of the brazed joint is 56 MPa. The fracture morphology of the brazed joint shows intergranular fracture mode, where crack originates from the hard α-Mg+MgZn eutectoid structure.
关键词:
Filler metal
,
钎焊
,
显微组织
,
力学性能
Li Ma Dingyong He Xiaoyan Li Jianmin Jiang
材料科学技术（英文）
In order to join the similar magnesium alloy, a novel Zn-Mg-Al filler metal was designed and applied to braze AZ31B plates by using high-frequency induction brazing technique. The microstructure, phase constitution and fracture morphology of the brazed joint were investigated. The experimental results show that MgZn2 phase in the original filler metal is completely consumed in the brazing process. Moreover, α-Mg solid solution and α-Mg+MgZn eutectoid structure formed in the brazing region due to the intensive alloying between the molten filler metal and the base metal in the brazing process. Test results indicate that the shear strength of the brazed joint is 56 MPa. The fracture morphology of the brazed joint shows intergranular fracture mode, where crack originates from the hard α-Mg+MgZn eutectoid structure.
关键词:
Filler metal
,
钎焊
,
显微组织
,
力学性能
郑亮
,
肖程波
,
张国庆
,
顾国红
,
李鑫
,
刘晓光
,
薛明
,
唐定中
航空材料学报
doi:10.3969/j.issn.1005-5053.2012.3.003
采用金相显微镜、扫描电镜及能谱、电子探针和X射线衍射对高Cr铸造镍基高温合金K4648等轴晶和定向凝固铸件的合金/陶瓷型芯界面反应进行了系统研究,获得反应时间与反应量关系的界面反应动力学曲线、不同反应时间的反应界面形貌及产物的种类.结果表明:高Cr铸造镍基高温合金K4648与铝基型芯不易发生反应,而与硅基陶瓷型芯发生剧烈的界面反应,反应产生金属瘤状凸起物,造成铸件内腔破坏.此外,白色的硅基型芯内部变成黑色,黑色反应区内含有一定量的Cr,Al,Ti元素.在反应的中、后期型芯黑色反应区内还存在着灰色区,该区的Cr,Al,Ti含量远高于黑色反应区.高Cr铸造镍基高温合金K4648合金与硅基陶瓷型芯反应分为:(1)富Cr,Al,Ti熔体向型芯内的渗入阶段;(2)富Cr,Al,Ti熔体与陶瓷型芯SiO2基体的反应;(3)富Cr,Al,Ti的熔体与型芯中Zr-SiO4颗粒反应三个阶段.反应过程中型芯存在局部液化现象.K4648合金/硅基陶瓷型界面反应产物主要为层状或树枝状Al2O3,块状Cr3 Si金属间化合物、ZrO2,富Cr,Zr,Al,Ti的复合氧化物、共晶形态的富Cr,Si,Al,Ti的复合氧化物、块状或树枝状的富Ti,Al,Zr,Cr复合氧化物.反应产物中的Cr,Al,Ti元素来自合金熔体而Zr,Si,O来自陶瓷型芯.
关键词:
镍基高温合金
,
陶瓷型芯
,
界面反应
,
定向凝固
,
显微组织
,
K4648
,
Cr3Si
,
Al2O3
田昊
,
付志斌
,
姜金星
,
李俊
,
范磊
,
王青峰
物理测试
为了弄清t8/5对X90管线钢焊接热影响区组织和硬度的影响,利用Gleeble-3500热模拟试验机对该钢焊接热影响区在t8/5=10～300 s下的热循环过程进行了模拟;结合热膨胀法和金相法建立了SHCCT曲线;针对各模拟样品,采用光学显微镜和透射电镜观察了显微组织,测定了维氏硬度HV0.3.结果表明:随着t8/5的减小,试验钢焊接热影响区相变开始和结束的温度降低,粒状贝氏体数量减少,板条贝氏体数量增多,原奥氏体晶粒和贝氏体铁素体细化,使该区域的硬度值升高.该钢环焊的t8/5宜控制在10～20 s.
关键词:
X90管线钢
,
热模拟
,
SHCCT曲线
,
焊接
,
热影响区
,
t8/5
,
显微组织
,
硬度
