纳米晶W-Ni-Fe粉末的流变行为和烧结特性

研究了W-Ni-Fe纳米晶粉在注射成形中喂料的流变行为.纳米晶W-Ni-Fe粉采用机械合金化(MA)的方法制备，并将其与蜡基粘结剂混合形成1种喂料.讨论了MA球磨时间、纳米晶粉末体积和温度对喂料流变性的影响及采用MA制备的W-Ni-Fe纳米粉末的烧结特性.结果表明随着球磨时间增加，喂料的粘度以及粘度对剪切速率的敏感性降低，因此，在较长的球磨时间下，这种粉末喂料的流动性和成形性较好；随着粉末体积的增加，喂料的粘度遵循公式η=ηοA1-(φ/φm)]

Rheologic behavior and sintering characteristic of nanocrystal W-Ni-Fe powder

The rheologic behavior of the nanocrystal W-Ni-Fe powder feedstock in MIM process was studied. The nano-crystal W-Ni-Fe powder was prepared by mechanical alloying (MA), and then was mixed with wax-based binder to formthe feedstock. The effects of MA time, powder volumn and temperature on the rheologic behavior of the feedstock werediscussed. The feedstock viscosity and its sensitivity to the shear rate decreased with increasing milling time. Therefore,the flowability and compactability of the feedstock were proved to be good after milling for a long time. With the volumncontent of the powder increasing, the viscosity of the feedstock increased nonlinearly according to the following formula:η=η0 A 1-( φ/φm )]-n ( where n = 0. 68). The viscosity of the MA powder feedstock was influenced a little by the tem-perature and the shear rate, so the injection temperature and rate had little influence on this kind of green parts. The sin-tering characteristics of this MA-prepared W-Ni-Fe powder were also studied. The results showed that milling had led toa high alloy density when sintering below liquid phase temperature, and the sintering rate was accelerated by large crystaldistortion, grain refining and supersaturated sosoloid.