Sintering microstructure and properties of copper powder prepared by electrolyzation and atomization

The almost completely dense copper was prepared by ultrafine copper powder prepared with both methods of electrolysis and novel water-gas atomization through cold isostatic pressing(CIP)and sintering under atmospheric hydrogen.Fine copper powder possesses the higher sintering driving force,thereby promoting shrinkage and densification during the sintering process.The grain size of sintered samples by electrolytic copper powder is smaller than that prepared by the atomized copper powder,and the twin crystals are particularly prone to forming in the former sintered microstructure due to the raw powder with low oxygen content and high residual stress originating from the CIP process.The relative density of samples by electrolytic and atomized powder at 1000℃ sintering temperature achieves 99.3%and 97.4%,respectively,significantly higher than that of the powder metallurgy copper parts reported in the literature.Correspondingly,the ultimate tensile strength and yield strength of samples by both kinds of copper powder are approximately similar,while the elongation of the sintered sample by the electrolytic powder(60%)is apparently higher than the atomized powder(44%).The superior performance of samples fabricated by electrolytic powder is inferred from the full density and low oxygen level for there is no cuprous oxide in the grain boundaries.

高球形度非晶软磁合金粉末性能研究

采用水气组合雾化工艺制备了高球形度的非晶软磁合金粉末,结合扫描电镜和X射线衍射仪对粉体的形貌和相组成进行了分析,研究表明合金成分和粉末粒度对非晶粉末球形度和非晶形成能力有很大的影响。通过振动样品磁强计测算了样品的磁滞回线和矫顽力。将非晶样品粉压制成粉心,对粉心的磁导率、直流偏置能力和损耗进行了测试分析。研究发现非晶磁粉的粒度、非晶化程度、饱和磁化强度以及矫顽力等对粉心的磁性能有很大的影响。