共查询到20条相似文献,搜索用时 187 毫秒
1.
对Ag-Ni偏晶合金开展了快速/亚快速凝固实验,获得了富Ni相粒子均匀弥散分布于Ag基体的合金样品,Ag-Ni合金显微硬度随着合金Ni含量增加和试样凝固过程冷却速率升高而增大,当Ag-4.0%Ni合金液-液相变开始阶段熔体冷却速率达1800 K/s时,其显微硬度接近粉末冶金生产的Ag-10.0%Ni片状电触头的硬度。建立了描述Ag-Ni合金凝固组织演变的动力学模型,模拟计算了Ag-Ni合金凝固组织形成过程,分析讨论了合金成分和试样直径(冷却速率)对Ag-Ni合金凝固组织形成过程的影响。结果表明:富Ni相液滴/粒子形核阶段熔体的冷却速率对合金凝固组织弥散度具有决定性影响;合金的Ni含量越高、试样冷却速率越低,凝固组织中富Ni相粒子平均尺寸越大;Ag-Ni合金熔体冷却凝固时,富Ni相液滴/粒子的尺寸主要受形核和长大控制,Ostwald粗化作用很弱。 相似文献
2.
3.
急冷条件下Ni-Pb偏晶合金的相分离研究 总被引:1,自引:1,他引:0
采用单辊法实现了Ni-Pb偏晶合金的快速凝固,分别制备出直径40~400μm的合金粒子和宽约4mm、厚30~50μm的合金条带.在急冷快速凝固条件下,Ni-8%Pb亚偏晶合金由Ni和富Pb相组成.Ni以枝晶方式生长,富Pb相分布于枝晶间隙.随着冷却速率的增大,凝固组织显著细化,晶体形态经历由粗大枝晶向细小等轴晶的转变.在快速凝固过程中,Ni-60%Pb过偏晶合金的液相分离在很大程度上被抑制,合金粒子和条带均可获得均匀弥散的快速凝固组织.在冷却速率相近的条件下,合金粒子和条带的凝固组织与晶粒尺寸具有相似相近性,冷却速率是决定合金凝固组织的本征物理参量. 相似文献
4.
在落管中进行Cu—Co合金的快速凝固试验,分析了液滴尺寸与合金成分对微观组织演变过程的影响。结果表明,液滴尺寸越小,其内部的富Co粒子越弥散;Co含量越接近亚稳液态组元不混溶区的临界成分,合金熔体越容易发生液-液相变,凝固组织中富Co粒子平均半径越大。液-液相变过程中富Co相液滴在液滴内部形核,并在温度梯度作用下向液滴中心高温区做Marangoni迁移,这最终导致在粉末表面形成贫Co层。 相似文献
5.
6.
采用合金化的方法得到快速凝固Cu75-xCr25Nix(X=0.5,1和3) 合金的凝固组织.利用带有能谱(EDS)的扫描电子显微镜(SEM)分析了富Cr相的形态、成分以及形成机制.结果显示,合金元素Ni扩大了Cu、Cr之间的固溶度; Cu75Cr25合金快速凝固过程中的液相分解得到抑制.Cu75-xCr25Nix合金富Cr液相分解组织的数量、尺寸、形貌较Cu75Cr25合金富Cr液相分解组织均有较大的变化.在Cu75-xCr25Nix组织中发现,除富Cr液相分解组织之间有聚集现象以外,还存在富Cr液相分解组织与富Cr枝晶间的聚集. 相似文献
7.
An Experimental Study of the Rapid Continuous Solidification of Al—Bi Immiscible Alloy 总被引:2,自引:0,他引:2
采用Al-(3.4—15)%Bi(质量分数)难混溶合金进行了快速连续凝固实验,研究了Bi含量和凝固速率对快速连续凝固组织的影响.结果表明,少量富Bi相粒子尺寸随着Bi含量的增加而增大,提高凝固速率有助于制备少量富Bi相粒子均匀分布的难混溶合金.通过分析富Bi粒子尺寸分布,发现沿试样轴向和径向方向粒子平均直径变化不大,试样表层处粒子尺寸较小.研究表明,快速连续凝固是制备均质难混溶合金的有效途径. 相似文献
8.
在Al-Pb二元难混溶合金的基础上添加其它的合金元素Ni,Y和Co,优化设计了新的Al_(82.87)Pb_(2.5)Ni_(4.88)Y_(7.8)Co_(1.95)多元难混溶合金。开展了该多元难混溶合金的快速凝固实验,对制备的薄带样品进行了结构表征、热稳定性分析以及显微组织形成的研究。结果表明,合金熔体在快速冷却过程中发生了液-液相分离,生成富Al和富Pb两液相;随后,富Al基体液相发生玻璃转变,形成铝基非晶合金基体,而富Pb液相凝固结晶后以球形晶态粒子形式均匀分布于铝基非晶基体中。研究表明,利用难混溶合金液-液相变原理,通过快速凝固技术可以设计和制备原位球晶粒子/非晶合金基复合材料。 相似文献
9.
10.
在Al--Pb二元难混溶合金的基础上添加其它的合金元素Ni, Y和Co, 优化设计了新的 Al82.87Pb2.5Ni4.88Y7.8Co1.95多元难混溶合金. 开展了该多元难混溶合金的快速凝固实验, 对制备的薄带样品进行了结构表征、热稳定性分析以及显微组织形成的研究. 结果表明, 合金熔体在快速冷却过程中发生了液-液相分离, 生成富Al和富Pb两液相; 随后, 富Al基体液相发生玻璃转变, 形成铝基非晶合金基体, 而富 Pb液相凝固结晶后以球形晶态粒子形式均匀分布于铝基非晶基体中. 研究表明, 利用难混溶合金液-液相变原理, 通过快速凝固技术可以设计和制备原位球晶粒子/非晶合金基复合材料. 相似文献
11.
铸型材质不同,其冷却速度不同,它影响液态金属凝固过程及形成的组织,进而影响材料的性能。用铸造法制备复合材料时,铸型材质还会对增强体颗粒的分布产生影响。采用液态搅拌法制备了SiCp/ZAlSi5CuMg复合材料,研究了不同铸型材质、相同材质不同壁厚对SiCp/Al复合材料微观组织均匀性的影响规律。试验结果表明,在其他条件相同的情况下,采用冷却能力较快的铸型,可以明显改善SiC颗粒在ZAlSi5CuMg基体中分布的均匀性。冷却速度较快,凝固过程中金属液粘度迅速增大,使SiC颗粒聚集及下降时的阻力增大,难以聚集或下降,进而使SiC颗粒在ZAlSi5CuMg基体中分布的均匀性得到改善。 相似文献
12.
超音速电弧喷射雾化制备的非互溶Ag-10Ni合金粉末的凝固特征 总被引:2,自引:0,他引:2
采用超音速电弧喷射气雾化制粉设备制备了难固溶Ag-10Ni合金粉末。研究了粉末粒度分布、形貌及凝固组特征,并对雾化熔滴的冷却速率及过冷度、凝固组织的凝固次序、形成机制进行了分析。结果表明:粉末分散性好、粒度主要集中在20pm~45μm、平均粒度32μm、形貌主要为球形和近球形;粉末颗粒凝固组织为富Ag基体+弥散分布于基体中的细Ni相+位于芯部的大直径初晶富Ni相,在大直径初晶富Ni相中弥散分布析出Ag相;富Ag基体的凝固组织为树枝晶组织,小颗粒粉末(〈20μm)枝晶间距小于0.2μm。 相似文献
13.
采用熔体快淬Al-Ce中间合金对ZL108活塞合金进行了变质处理,然后对变质后的ZL108合金试样进行了显微组织观察和性能检测,并与加入普通块状Al-Ce合金变质的ZL108合金进行了对比.结果表明,与加入块状Al-Ce变质剂相比,加入熔体快淬Al-Ce变质处理的ZL108合金,组织中的共晶硅得到了更好的细化,室温和高温力学性能得到了很大的提高.因此熔体快淬Al-Ce合金变质处理可更好的提高ZL108合金的综合力学性能. 相似文献
14.
A new method to modify the solidification microstructure of titanium alloys, named melt hydrogenation, by adding TiH2 as additive into the melt of titanium alloys during induction skull melting process (ISM), is put forward and the refining effect of this method on the solidification microstructure of Ti-6Al-4V alloy was studied experimentally. After melt hydrogenation, the grain sizes of as-cast Ti-6Al-4V alloy decreased to 612 μm from 1,072 μm, lath-shaped α phase was also refined and fine α/β lamellar microstructure was formed when 1.0 wt.% TiH2 was added. δ-hydride was found in the X-ray diffraction (XRD) spectra of Ti-6Al-4V alloy that prepared with 1.0 wt.% TiH2 added and the δ-hydride distributes in α phase as acicular precipitations. 相似文献
15.
Yao-Yao Xi Jie He Xiao-Jun Sun Wang Li Jiu-Zhou Zhao Hong-Ri Hao Ting Xiong 《金属学报(英文版)》2018,31(11):1130
In this work, a quaternary Ni–Cu–Nb–Ta system has been designed to obtain composite microstructure with spherical crystalline Cu-rich particles embedded in amorphous Ni-rich matrix. The alloy samples were prepared by using singleroller melting-spinning method. The microstructure and thermal properties of the as-quenched alloy samples were characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and differential scanning calorimetry. It shows that the spherical crystalline Cu-rich particles are embedded in the amorphous Ni-rich matrix. The average size of the Cu-rich particles is strongly dependent upon the Cu content. The effect of the alloy composition on the behavior of liquid–liquid phase separation and microstructure evolution was discussed. The phase formation in the Ni-based metallic glass matrix composite was analyzed. 相似文献
16.
The effects of a pulsed magnetic field on the solidified microstructure of an AZ31 magnesium alloy were investigated. The experimental results show that the remarkable microstructural refinement is achieved when the pulsed magnetic field is applied to the solidification of the AZ31 alloy. The average grain size of the as-cast microstructure of the AZ31 alloy is refined to 107 μm. By quenching the AZ31 alloy, the different primary α-Mg microstructures are preserved during the course of solidification. The microstructure evolution reveals that the primary α-Mg generates and grows in globular shape with pulsed magnetic field, contrast with the dendritic shape without pulsed magnetic field. The pulsed magnetic field causes melt convection during solidification, which makes the temperature of the whole melt homogenized, and produces an undercooling zone in front of the liquid/solid interface, which makes the nucleation rate increased and big dendrites prohibited. In addition, the Joule heat effect induced in the melt also strengthens the grain refinement effect and spheroidization of dendrite arms. 相似文献
17.
18.
19.
The effects of pulsed magnetic field on the solidified microstructure of an AZ91D magnesium alloy were investigated. The experimental results show that the remarkable microstructural refinement is achieved when the pulsed magnetic field is applied in the solidification of AZ91D alloy. The average grain size of the as-cast microstructure of AZ91D alloy is refined to 104 μm. Besides the grain refinement, the morphology of the primary α-Mg is changed from dendritic to rosette, then to globular shape with changing the parameters of the pulsed magnetic field. The pulsed magnetic field causes melt convection during solidification, which makes the temperature of the whole melt homogenized, and produces an undercooling zone in front of the liquid/solid interface by the magnetic pressure, which makes the nucleation rate increased and big dendrites prohibited. In addition, primary α-Mg dendrites break into fine crystals, resulting in a refined solidification structure of the AZ91D alloy. The Joule heat effect induced in the melt also strengthens the grain refinement effect and spheroidization of dendrite arms. 相似文献
20.
采用单辊旋铸法分别制备了Al-5%Pb, Al-8%Pb和Al-15%Pb三种合金条带, 并利用TEM分析其显微组织. 结果表明 在快速凝固下, Al-Pb合金中的第二相(f.c.c. Pb)在基体中分布均匀, Pb颗粒尺寸随Pb含量增加而增加, 随冷却速度的增大而减小, Pb颗粒的尺寸呈双峰或三峰分布特征. 此外, 还分析了快速凝固下偏晶合金的凝固过程, 对上述现象进行了解释. 相似文献