稀土La对细晶93W-4.9Ni-2.1Fe合金致密化与显微组织的影响  

Effect of rare-earth element La on densification and microstructure of fine-grained 93W-4.9Ni-2.1Fe alloy

作　　者：丁飞[1] 范景莲[1] 曾毅[1] 龚星[1] 田家敏[1] 

机构地区：[1]中南大学粉末冶金国家重点实验室,长沙410083

出　　处：《粉末冶金材料科学与工程》2011年第4期517-522,共6页Materials Science and Engineering of Powder Metallurgy

基　　金：国家自然科学基金资助项目(50674106);国家自然科学基金创新群体资助项目(50721003);国家杰出青年科学基金资助项目(50925416)

摘　　要：采用溶胶-喷雾干燥-氢还原法制备超细/纳米晶93W-4.9Ni-2.1Fe和93W-4.9Ni-2.1Fe-0.4La的复合粉末,对比研究烧结过程中稀土La对合金致密化与显微组织的影响,并讨论其作用机理.。结果表明:添加稀土La对合金致密化及晶粒长大均具有一定的抑制作用,在1 420℃烧结时,由93W-4.9Ni-2.1Fe复合粉末制备的合金晶粒长大速率常数为247.1μm3/min,而添加0.4%La后合金晶粒长大速率常数仅为83.3μm3/min。此外,添加稀土La的93W-4.9Ni-2.1Fe合金具有更高的W-W临接度。扫描电镜及能谱分析结果表明,稀土La在合金中会形成成分复杂的二次相,并偏聚在相界或晶界处,阻止W原子在粘结相中的扩散。同时,与稀土La有关的一系列相变可干扰溶解-析出过程,从而有效抑制W晶粒的长大。这些二次相颗粒的存在,降低了液相对钨颗粒的润湿性,并会阻碍钨颗粒的重排,使得W-W临接度增大。Ultrafine/Nanocrystalline 93W-4.9Ni-2.1Fe and 93W-4.9Ni-2.1Fe-0.4%La composite powders have been synthesized by sol-spray drying and subsequent hydrogen reduction process.The effect of La addition on densification behavior and microstructure of the alloy in sintering process were investigated systematically,and its function mechanism was also discussed.The results show that La addition can inhibit the densification and grain growth of the fine-grained alloys.The grain coarsening rates of 93W-4.9Ni-2.1Fe and 93W-4.9Ni-2.1Fe-0.4%La alloys when sintered at the temperature of 1 420 ℃ are approximately 247.1 μm3/min and 83.3 μm3/min,respectively.In addition,the W-W contiguity of 93W-4.9Ni-2.1Fe-0.4%La alloys is higher than that of 93W-4.9Ni-2.1Fe alloys.The fractograph of 93W-4.9Ni-2.1Fe-0.4%La alloys characterized by Scanning Electron Microscope（SEM） and EDS analysis shows that the La-containing particles consisting of various elements are formed and segregate along the grain boundaries,which inhibits the diffusion of the tungsten atoms to γ-（Ni,Fe） phase.A series of the phase transition associated with La is responsible for the disturbance of the solution-precipitation process.As a consequence,the grain growth of the 93W-0.4%La is inhibited significantly.In addition,these La-containing particles reduce the wettability of γ-（Ni,Fe） phase on tungsten particles and hinder the particles rearrangement,resulting in the increase of W-W contiguity in the 93W-0.4%La alloys.

关 键 词：稀土La 细晶W-Ni-Fe合金 致密化 晶粒长大 

分 类 号：TG149.411[一般工业技术—材料科学与工程]