- 學位論文
含硼粉末合金鋼之液相燒結行為研究
Liquid Phase Sintering of Boron-containing Powder Metal Steel
摘要
現今粉末冶金鋼多用於汽機車零組件，歸功於快速的製程並且成品完成後已為近淨形(net-shape)，相較鑄造後產品額外的形狀加工，因而省去較多的成本，但因粉末冶金製程後成品本身約帶10%孔隙率，而此孔隙率往往為破裂的起始點，導致強度及韌性較鑄件來得差。為此本研究探討各合金元素對含硼粉末合金鋼之液相燒結行為之影響，已瞭解其液相與合金元素間的交互作用，和對緻密化過程的影響。 研究結果顯示不論鉬與鉻是否存在於對含硼粉末合金鋼中，碳的添加都可使含硼粉末合金鋼中產生二次液相而促進燒結緻密化。為了解試片內部之元素分佈，本研究也利用EPMA分析探討其元素分佈情形，結果發現Cr、Mo、C與B等原子皆易集中在硼化物內，藉由定量分析確定各合金系統內之硼化物成分。由DSC分析可鑑定出液相的生成溫度，進而理解合金元素對於液相形成的影響。
並列摘要
Powder metallurgy (PM) steels are widely applied in the automobile parts due to their versatile near net-shaped processes. The production of PM steels can reduce the additional machining and the cost. However, PM steels consist of about 10 vol% porosity, which result in the inferior strength and toughness. The aim of this study was to investigate the influences of different alloying elements on the liquid phase sintering and interactions between various elements in the boron-alloyed PM steels. The results showed that the addition of carbon can induce the formation of secondary liquid phase and thus improve the densification, irrespective of the alloying systems. To understand the distribution of alloying elements in the steels, EPMA was used to identify the alloying distributions. The findings showed that Cr, Mo, and B concentrate on the region of boride. The compositions of the boride in various systems were also examined. Moreover, the temperature for liquid formation and the effects of alloying elements on the liquid formation were also studied by DSC analyses.