摘要
熔体过热和过冷保温处理对合金的组织和性能都有显著的影响。目前过热保温处理的研究较多,由于过冷状态很难控制,所以关于熔体过冷保温处理的研究报道甚少。文中通过传统的玻璃净化和循环过热法使Ni-3.2%B合金熔体得到充分净化,再在降温中通过调节设备的加热功率控制凝固中的温度变化,实现过冷熔体在凝固之前经历一段接近恒温的处理过程,最终获得过冷保温时间长达508s的样品,进而分析不同过冷时间对凝固组织、硬度以及初生相分数的影响。结果发现:随着过冷熔体处理时间的延长,初生相α-Ni相分数逐渐增大,边角形貌变圆,显微硬度下降,从HV289(过冷处理时间9s)降到HV160(508 s);共晶组织从长条层片状变成网状,又变成细小层片状,显微硬度缓慢上升,最高达到HV726;Ni3B相的显微硬度也逐渐上升,最高可达HV1033。
Both superheating and undercooling isothermal treatments have important effects on the structure and properties of materials. At present, there are many studies on the superheating isothermal treatment. Due to the difficulty of controlling the undercooled state, isothermal treatment of undercooled melts has few reports. In the study, the undercooled Ni-3.2 wt.%B melt was fully purified through the traditional glass purification and cyclic superheating methods. Then, the temperature change during the solidification was controlled by adjusting the heating power of the equipment during the cooling, so that the undercooled melt underwent a near-constant temperature treatment process before the solidification. Finally, the undercooled melt with a holding time of up to 508 s was obtained, and the effects of different holding times on the solidification structure, hardness and the fraction of the primary phase were analyzed. The results show that with the extension of holding times of the undercooled melt, the phase fraction of the primary phase α-Ni gradually increased, the morphology of edges and corners became rounded and its microhardness decreased, from HV289(holding 9 s) to HV160(holding 508 s).The eutectic structure changed from strip lamellar to net and then to fine lamellar, and its microhardness gradually increased, reaching HV726 at the highest. The microhardness of Ni3 B phase also increased gradually, and the maximum value was HV1033.
作者
汪肖
许军锋
WANG Xiao;XU Jun-feng(The Shaanxi Key Laboratory of Photoelectric Functional Materials and Devices,Xi'an Technological University,Xran710021,Shannxi,China;State Key Laboratory of Sldification Processing,Nothwesterm Polytechnical University,Xian 710021,Shannxi,China)
出处
《铸造》
CAS
北大核心
2020年第12期1265-1271,共7页
Foundry
基金
陕西省科技新星项目(2016KJXX-87)
国家自然科学基金(51671156)。
关键词
Ni-B合金
过冷
保温处理
显微硬度
相分数
Ni-B alloy
undercooling
isothermal treatment
microhardness
phase fraction
