La_2O_3对超细钨复合粉末烧结性能与钨合金显微组织的影响

Influence of La_2O_3 on sintering performance of ultrafine W composite powders and micro-structure of W alloy

采用溶胶喷雾干燥-煅烧还原方法制备超细/纳米W-La2O3复合粉末,将粉末压制成形后在1 950℃烧结,制备La2O3弥散强化钨合金,检测合金的密度与强度,并采用SEM对超细粉末形貌、合金的组织结构、断口形貌进行分析,结果表明:随La2O3加入量增加,粉末颗粒显著细化,W-0.7%La2O3复合粉末的粒径仅为0.1μm;制备的W-La2O3超细/纳米复合粉末具有很高的烧结活性,烧结后,合金最高相对密度达到99.1%;La2O3均匀弥散分布于钨晶界,抑制钨合金的晶粒长大,提高材料的强度,W-0.7%La2O3合金中钨平均晶粒尺寸仅为8.7μm,抗弯强度达到548 MPa;合金的断裂形式表现为穿晶-沿晶共有的复合断裂形式。

Ultrafine/nano composite powders of W-La2O3 were prepared by Sol-spray drying-calcination-hydrogen reduction process, and sintered at 1 950 ℃ to form La2O3 dispersion strengthened tungsten materials and obtain high density after molding under the press of 275 MPa. The density and mechanical properties of the alloy were studied. Morphologies of superfine powder, microstructure and fracture morphology of the sintered materials were investigated by SEM. The results show, with increasing the amount of La2O3, particles size of the powder decreases. The BET particle size of W-0.7%La2O3 composite powder is 0.1μm. The highest relatively density can reach 99.1%after sintering due to high sintering activity of W-La2O3 ultrafine/nano composite powders. La2O3 uniformly disperses on the tungsten grain boundary and inside, which can restrain the grain growth process. As a result, the average grain size of W-0.7%La2O3 is 8.7μm. The property of La2O3 dispersion strengthened tungsten materials is greatly improved , the flexural strength of W-0.7%La2O3 is 548 MPa. The morphologies of fracture surface of W-La2O3 alloy show a mixed mode of transgranular and intergranular fracture.