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
B.Y. Yu*
,
C.L. Bao
,
H.W. Song
,
Z. Liu
金属学报(英文版)
The effect of extrusion ratio on microstructures and mechanical properties of magnesium alloy AZ91D extruded tube at 430℃ has been studied. After the evolution of microstructure and mechanical properties of AZ91D during extrusion were studied, the following parameters were obtained: tensile strength reached the climax value of 306.9MPa and elongation peak value of 10.1% at an extrusion ratio of 7.125, and with the increase of the extrusion ratio to 7.45, yield strength reached a top value of 285.795MPa with decreased tensile strength and elongation. It was concluded that mechanical properties of magnesium alloys AZ91D could be enhanced by adjusting the extrusion ratio near recrystallization.
关键词:
magnesium
,
挤压
,
管材
,
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
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
尹志民
,
邓英
,
赵凯
,
段佳琦
,
唐蓓
,
何振波
,
彭勇宜
,
姜锋
,
潘清林
中国有色金属学报
采用力学性能测试和电子显微分析技术研究了不同加工处理条件下Al-5.4Zn-2.0-Mg-0.25Cu-0.1Sc-0.1Zr合金的显微组织及性能演变.结果表明:在半连续激冷铸造条件下,铸锭存在晶界偏析,形成了富Zn、Mg的非平衡相和富Fe、Si、Mn的杂质相；经470℃、12 h均匀化处理后,富Zn、Mg的非平衡相溶入基体,仅剩下少量富Fe、Si、Mn的杂质相；与此同时,铸锭合金固溶体分解析出纳米级的Al3(Sc,Zr)相,470℃、12h是研究合金合适的铸锭均匀化制度；铸锭热变形过程中,随试验温度升高合金强度逐渐降低,伸长率则先增加而后降低,350～400℃的温度范围内合金具有较稳定的热变形抗力和塑性,是合宜的热变形温度范围；合金冷轧板材经470℃、1h固溶处理后,热变形过程中形成的大量非平衡相溶入基体形成过饱和固溶体,时效过程中脱溶顺序为asss(α过饱和固溶体)→GP区→η’相→η相.合金板材最佳固溶-时效工艺为(470℃,1h)固溶+(120℃,24 h)时效,在此条件下,试验合金的抗拉强度、屈服强度和伸长率分别可达533MPa、494 MPa和15％.试验合金的高强度主要来源于η’相析出强化、添加微量Sc和Zr引起的亚晶强化和亚结构强化以及Al3(Sc,zr)相的弥散强化.
关键词:
Al-Zn-Mg-Sc-Zr合金
,
板材
,
铸锭均匀化
,
热塑性
,
固溶-时效
,
组织
,
力学性能
,
演变
