合金元素铜和镍对铸铁短纤维烧结特性的影响
INFLUENCES OF ALLOYING ELEMENTS Cu AND Ni ON SINTERING CHARACTERISTICS OF SHORT CAST IRON FIBRES
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摘要: 研究了1100℃烧结温度下合金元素铜、镍含量对铸铁短纤维烧结特性的影响规律,结果表明:与铁-铜粉末压坯相比,铸铁短纤维-铜压坯烧结后的最大膨胀率及相对应的铜含量均明显减少。产生膨胀的主要原因是铜熔化后,富铜液相向奥氏体中扩散,在原位留下空隙,而液相沿界面流动不明显。镍显著加快了铸铁短纤维烧结体的致密化。在镍含量高于4.5%时,显微组织中出现奥氏体相,在奥氏体与珠光体边界析出网状渗碳体,在奥氏体晶内析出魏氏碳化物及游离石墨,引起致密化速率下降,断裂方式由延性断裂转化为脆性断裂。Abstract: The law of influences of alloying elements copper and nickel contents on the sintering characteristics of short cast iron fibres sintered at 1100℃ was studied. Results have shown that in comparison with ironcopper powder compacts, short cast iron fibre-copper compacts obviously decrease maximum expansion rate and corresponding copper contents. The main reason of expansion consists in that the liquid phase riched in copper diffuses into austenite after copper melting and pores remain in situ and there is no clear flow of liquid phase along interface.Nickel obviously speeds up the densification of sintered compacts with short cast iron fibres, When nickel content is more than 4.5%, austenitic phase is presented in microstructure, uncontinuous network-shaped cementite is precipitated in the interface between austenites and pearlites, and widmanstatten carbides and free graphites are precipitated in austenitec grains. Therefore densification rate decreases and the ductility fracture mode changes into brittleness.