标题: | 热处理对铁-9铝-30锰-1碳合金机械性质影响 Influence of Heat-treatment on Mechanical Properties of an Fe-9Al-30Mn-1C Alloy |
作者: | 何春伯 Chun-Bo Ho 刘增丰 Tzeng-Feng Liu 材料科学与工程学系 |
关键字: | 机械性质;破断;铁-铝-锰-碳;mechanical properties;fracture;Fe-Al-Mn-C |
公开日期: | 2003 |
摘要: | 本篇论文的目的是经由光学显微镜、扫描式电子显微镜及穿透式电子显微镜来观察铁-9铝-30锰-1碳合金经不同热处理后的显微结构,并探讨不同显微结构对机械性质和破断机构的影响。合金在经过1100℃固溶热处理之后可以得到完全的沃斯田铁相显微结构,拥有良好的强度和韧性。合金经过550℃、6小时的时效热处理后,细小的κ´-碳化物在沃斯田铁晶粒内析出,造成了析出硬化的效果,且此条件下无析出物在晶界上析出,所以材料在没有明显损失韧性的情况下明显的得到了更佳的强度。随着时效温度的上升,在经过650℃、6小时的时效热处理后,不但在沃斯田铁晶粒内有细小的κ´-碳化物析出物,在晶界上也开始有一些粗大的κ-碳化物异相析出,所以虽然材料因为析出硬化而在强度上达到最佳,但却因为晶界上析出而造成材料靭性稍微下降。而在经过850℃、6小时的时效热处理后,在晶粒内的κ´-碳化物变的很少,而在晶界上析出了大量粗大的κ-碳化物,因而造成材料的强度及靭性都大幅地下降。 本篇论文除了比较不同时效热处理温度下所得到的机械性质外,也可以比较出铸造试片及轧延试片的不同。铸造试片经过各不同时效热处理后,破断模式是比较偏向脆性的穿晶、沿晶破断。而轧延试片在经过各不同时效热处理后,破断行为以延性的酒窝状凹洞为主,随着时效温度上升,辅以稍具脆性的穿晶破断。 The purpose of this study is to examine the microstructural development of the Fe-9Al-30Mn-1C alloy through different heat-treatments by means of optical microscopy, scanning electron microscopy and transmission electron microscopy. Besides, the effects of the microstructures on the mechanical properties and fracture mechanisms were also made. In the as-quenched condition, the microstructure of the alloy was single austenite phase. Therefore, the alloy possesses good strength and toughness. When the alloy was aged at 550℃ for 6 hours, fine κ´-carbides were formed within the austenite matrix and no precipitates could be observed on the grain boundaries. It is thus that the alloy could get better strength without losing much toughness. When the alloy was aged at 650℃ for 6 hours, not only the fine κ´-carbides formed within the austenite matrix but also a few of the coarse κ-carbides started to precipitate heterogeneously on the γ/γ boundaries. This leads the alloy to get the best strength and cause the toughness down slightly. When the alloy was aged at 850℃ for 6 hours, there was deficient κ´-carbides existing within the austenite matrix but much coarse κ-carbides occurred on the grain boundaries. Obviously, the strength and the toughness of the alloy would go down greatly. In the present study, the comparison of the mechanical properties between the cast alloy and the rolled alloy was undertaken. Under the same heat-treatment condition, the cast alloy trended to be more brittle. The main fracture mechanism of the cast alloy was intergranular decohesion with a certain proportion of transgranular cleavage. The main fracture mechanism of the rolled alloy was ductile dimple fracture. With increasing the aging temperature, it would be accompanied with a certain proportion of transgranular cleavage. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#GT009118532 http://hdl.handle.net/11536/51024 |
显示于类别: | Thesis |
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