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1.
金属熔体在超声场中凝固的研究   总被引:30,自引:0,他引:30  
本文综述了超声场对金属凝固过程的影响,着重总结了声空化、声流所起的作用,同时介绍了超声在新材料制备中的应用。  相似文献   

2.
金属熔体在超声场中凝固的研究   总被引:3,自引:0,他引:3  
本文综述了超声场对金属凝固过程的影响,着重总结了声空化、声流所起的作用,同时介绍了超声在新材料制备中的应用。  相似文献   

3.
本文根据耗散结构理论所建立的凝固模型,推导出的过冷度方程,指出金属的凝固与结晶凝固系数β是密切相联系的。其中结晶凝固系数为并且讨论了ρ值在不同情况下的物理意义以及β值在金属凝固中的作用。  相似文献   

4.
磁场作用下的金属凝固研究进展   总被引:4,自引:0,他引:4  
磁场作用下的金属凝固已成为金属材料基础研究和开发制备新技术的重要领域.综述了交变/旋转磁场、直流磁场作用下金属凝固的研究历史及现状,运用电磁学及金属凝固原理,揭示了磁场对凝固组织形貌及凝固过程产生的影响及主要机制,并对以后的理论研究工作提出了建议.  相似文献   

5.
研究了ZnAl4Cu3合金在常规铸造和液态模锻时的凝固过程,探讨了压力对液态金属凝固过程温度场的影响。给出了在压制过程中不同比压和冲头温度下模具与制件不同位置的温度变化情况,根据实验结果计算得出液态模锻下冷却速度较之自由凝固提高近10倍,并由此分析了液态模锻的凝固特征。  相似文献   

6.
一种细化金属凝固组织的新方法   总被引:1,自引:0,他引:1  
提出了用强脉冲磁场改善金属凝固组织的新技术。实验结果表明,强脉冲磁场能把铝合金的凝固组织从粗大的树枝晶细化为等轴晶,而且磁场愈强,细化效果愈显著。强脉冲磁场细金属凝固组织的新技术可应用于各金属材料,并可在工业上推广应用。  相似文献   

7.
分析了颗粒增强金属基复合材料凝固过程的特点,分析评述了复合材料凝固过程中增强颗粒对基体金属凝固特性的影响和增强颗粒与基体金属固/液界面之间相互作用这两个方面的研究进展。  相似文献   

8.
为改善7055铝合金的凝固组织,在合金凝固过程中施加超声振动.采用光学显微镜观察和室温压缩试验等手段研究了超声振动对7055铝合金凝固组织及力学性能的影响,并对超声细化机理进行了探讨.结果表明:未施加超声时,7055合金中形成粗大枝晶组织;施加超声振动后,可获得细小均匀的非枝晶组织.由于超声振动的空化和声流效应,凝固前对熔体施加超声,产生大量微泡核心,这些微泡核心保留下来而成为形核核心,使凝固组织得到细化;凝固过程中导入超声,枝晶出现断裂,导致了细小均匀组织的形成.此外,超声振动的7055合金铸锭显示了较好的室温压缩性能,压缩屈服强度、抗压强度及其对应的工程应变分别为165、729.2 MPa和34.8%.  相似文献   

9.
首先回顾了定向凝固的发展历史,重点分析了液态金属冷却定向凝固的技术特点。总结了高温度梯度下制备的定向凝固法单晶高温合金在组织和性能方面的研究现状,结合作者在本领域的研究,着重分析了定向凝固温度梯度、凝固速率、晶体取向、熔体超温处理、熔体对流控制对组织和性能的作用规律和机制,认为高温度梯度定向凝固是细化组织、减少缺陷、提高合金性能的重要途径。最后展望了高温合金定向凝固的发展趋势。  相似文献   

10.
综合分析了直流电场和交流电场对合金凝固组织、溶质再分配及过冷度的影响.运用电学和金属凝固理论,归纳和总结了连续电流场在金属凝固过程中的主要作用机制,从理论上探讨了连续电流场细化合金枝晶间距的机理,为今后连续电流场在实际生产中的应用提供了指导.  相似文献   

11.
Effect of high-intensity ultrasound irradiation in modifying complex solidification microstructure is explored in a high Si containing Al–Si alloy and the origin of microstructural changes explained on the basis of nucleation and growth behaviour. Complete suppression of dendritic growth and dramatic refinement to globular morphology were observed for primary α-Al grains. Strong supportive evidence is presented towards enhanced and prolonged heterogeneous nucleation triggered by cavitation induced increase in the equilibrium melting point and effective dissipation of latent heat at the solidification front. Morphological evolution of eutectic Si and intermetallic particles is found to be dominated by coarsening and spherodisation from strong fluid flow in areas of intense cavitation near the ultrasonic radiator. Outside the region of direct energy transfer, Si particle morphology appears to be controlled predominantly by the imposed cooling conditions. Extremely fine and short Si-platelets observed in the intergranular spaces near the radiator are explained on the basis of probable rapid cooling of final liquid pockets of small volume and large surface area, rather than refinement through ultrasound.  相似文献   

12.
AZ91 alloy matrix composites reinforced with phases formed in situ from the addition of Si particles were fabricated by solidification under ultrasonic vibrations. Application of high-intensity ultrasonic field to the melt resulted in optimized size, morphology and distribution of in situ formed Mg2Si particles. The amount of Mg2Si particles increased, its size was refined and the distribution became uniform. Heterogeneous nucleation from the addition of silicon particles and enhanced nucleation from rapid cooling refined the grain size of the matrix in the composites. Hardness and ultimate compressive strength of the composites increased as compared to that of the cast AZ91 alloy. Composites exhibited improved sliding wear behavior of under varying normal loads. Identified dominant wear mechanism at lower sliding velocities is abrasion. Improvement in mechanical and sliding wear properties of the composites is attributed to the refinement of both matrix and reinforcement phases and improved dispersion of the reinforcement under ultrasonic vibrations.  相似文献   

13.
研究了功率超声对水平连铸Al-1%(质量分数)Si合金凝固过程、合金组织和力学性能的影响,详细探讨了超声空化细化合金组织的机理.结果表明,在合金的凝固过程中施加功率超声可以提高形核率,使合金组织细化,从而提高其力学性能,并且随超声波功率的增加,铸坯的平均晶粒直径减小.  相似文献   

14.
金属/气体共晶定向凝固规则多孔金属的研究进展   总被引:9,自引:0,他引:9  
李言祥  刘源 《材料导报》2003,17(4):1-4,49
金属/气体共晶定向凝固是一种制备规则多孔金属的新工艺。评述了该工艺的发展历程、原理和最新进展,同时介绍了由该工艺制备的规则多孔金属的结构和性能特点及其应用。  相似文献   

15.
Compression waves propagating through molten metals are contributed to degassing, accelerating reaction rate,removing exclusions from molten metals and refining solidification structures during metallurgical processing of materials. In the present study, two electromagnetic methods are proposed to generate intense compression wavesdirectly in liquid metals. One is the simultaneous imposition of a high frequency electrical current field and a staticmagnetic field; the other is that of a high frequency magnetic field and a static magnetic field. A mathematical modelbased on compressible fluid dynamics and electromagnetic fields theory has been developed to derive pressure distributions of the generated waves in a metal. It shows that the intensity of compression waves is proportional to thatof the high frequency electromagnetic force. And the frequency is the same as that of the imposed electromagneticforce. On the basis of theoretical analyses, pressure change in liquid gallium was examined by a pressure  相似文献   

16.
材料电磁加工的现状与未来展望   总被引:6,自引:0,他引:6  
李廷举  金俊泽 《材料导报》2000,14(12):12-13,19
综述了材料电磁加工的研究现状和未来的发展动向。由于在熔化、精炼、铸造、轧制等连续铸造过程中应用了电磁场,连铸坯的表面质量和凝固组织得到改善。在电镀、金属腐蚀、金属凝固等过程中施加强磁场,改变了溶质的质量传输,提高了产品质量。  相似文献   

17.
A number of innovative metallurgical processes and products developed by the All-Russia Institute of Light Alloys (VILS) are discussed. These include rapid solidification, advanced casting, innovative high temperature isostatic pressing, improved inspection techniques, mechanical alloying, diffusion bonding, composite materials, and ultrasonic processing. The latter applied to enhanced processing of molten metal and as a cleaning technique. Consideration is given to both metals, intermetallics and ceramics; and inspection techniques. Implementation into the commercial segment of the economy requires much greater concern over cost considerations than in the past.  相似文献   

18.
Compression waves propagating through molten metals are contributed to degassing accelerating reaction rate,removing exclusions from molten metals and refining solidifcation structures during metallurgical processing of materials,In the present study ,two electromagnetic methods are proposed to generate intense compression waves directly in liquid metals.One is the simultaneous imposition of a high frequency electrical current filed and a static magnetic field ;the other is that of a high frequency magnetic field and a static magnetic field ,A mathematical model based on compressible fluid dynamics and electromagnetic fileds theory has been developed to derive pressure distri-butions of the generated waves in a metal.It shows that the intensity of compression waves is proportional to that of the high frequency electromagnetic force,And the frequency is the same as that of the imposed electromagnetic force,On the basis of theoretical analyses ,pressure change in liquid gallium was examined by a pressure transducer under various conditions.The observed results approximately agreed with the predictions derived from the theoretical analyses and calculations.Moreover,the effect of the generated waves on improvement of solidification structures was also examined .It shows that the generated compression waves can refine solidification structures when they were applied to solidification process of Sn-Pb alloy ,This study indicates a new method to generate compression waves by imposing high frequency electromagnetic force locally on molten metals and this kind of compression waves can probably overcome the difficulties when waves are excited by mechanical vibration in high temperature environments.  相似文献   

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