粉末热压烧结NiAl高温变形及动态再结晶行为演化研究
发布时间：2018-10-19 08:48
【摘要】：随着航天工业的快速发展,对于超高声速飞行器具有迫切的需求。寻找在高温下服役具有优异性能的轻质金属材料是解决航空飞行器瓶颈问题的有效手段。NiAl金属间化合物具有优异的高温性能和较低的密度,被认为是最有前景的高温结构材料之一。但是,差的室温塑性阻止了NiAl金属间化合物的大规模应用。塑性热成形是实现其室温强度和塑性协同提升的最有效方法之一。但是由于变形参数与微观组织密切相关(即与性能密切相关),因此建立变形参数与微观组织的关系非常重要。并且,变形诱导织构对于构件成形性能会产生显著影响。因此,为了获得具有理想微观组织的构件,需要考虑材料变形过程中产生的织构。本文采用Ni和Al元素粉末作为初始材料,基于Al-Ni二元相图制定出热压反应烧结工艺曲线。通过热压烧结工艺制备块状NiAl材料。在变形温度区间1100~1300℃,应变速率区间1×10-3~1s-1进行Gleeble高温压缩模拟实验。通过分析单向压缩变形材料的力学响应确定NiAl的高温变形行为,并且构造Arrhenius型本构方程。采用Zenner-Hollomon参数验证所建立本构方程的有效性。此外,通过原位拉伸实验进一步了解NiAl材料的高温变形行为。原位拉伸实验结果揭示了应变速率改变时材料的力学响应,说明了材料良好高温塑性的原因。基于高温变形行为,根据动态材料模型构造了热加工图。通过热加工图确定了理想的热加工窗口。根据热加工图优化的热加工窗口进行了高温锻造,在高温锻造后,NiAl延伸率显著上升。此外,高温拉伸材料断裂形貌分析揭示在高温拉伸,应变速率为10-3s-1时,高温锻造后断裂模式由脆性沿晶断裂向塑性断裂转变。而应变速率为10~(-2)s~(-1)时,高温锻造后断裂模式由脆性解理断裂向塑性断裂转变。室温拉伸断口在材料高温锻造后由脆性穿晶断裂向脆性解理断裂和塑性断裂的混合模式转变。通过晶界形貌、晶粒取向差梯度和GOS值表征了微观组织演变过程。结果显示在高应变速率,中等变形温度下,软化过程主要是连续动态再结晶和非连续动态再结晶的混合模式。在高变形温度,中等应变速率条件下,软化过程主要是非连续动态再结晶。并且发现,由于连续亚晶转动,连续动态再结晶会导致材料织构强度上升,而由于动态再结晶晶粒替代初始形变晶粒,非连续动态再结晶会导致材料织构强度下降。初始热压烧结产物具有弱{111}uvw织构。在1100℃/10~(-2)s~(-1)条件下进行高温变形,织构主要由{110}111和{112}111组分构成。
[Abstract]:With the rapid development of aerospace industry, there is an urgent need for UHV. Finding light metal materials with excellent performance at high temperature is an effective way to solve the bottleneck problem of aeronautical aircraft. NiAl intermetallic compounds have excellent high temperature performance and low density. It is considered to be one of the most promising high temperature structural materials. However, poor room temperature plasticity prevents large-scale applications of NiAl intermetallics. Plastic hot forming is one of the most effective methods to realize the synergistic enhancement of room temperature strength and plasticity. However, because deformation parameters are closely related to microstructure (that is, closely related to properties), it is very important to establish the relationship between deformation parameters and microstructure. In addition, deformation-induced textures have a significant effect on the formability of the components. Therefore, in order to obtain the components with ideal microstructure, the texture produced in the process of material deformation should be considered. In this paper, Ni and Al powders are used as the initial materials, and the hot pressing reaction sintering process curves are worked out based on the binary phase diagram of Al-Ni. Bulk NiAl materials were prepared by hot pressing sintering process. The Gleeble high temperature compression simulation experiment was carried out in the deformation temperature range of 1100 鈩，
本文编号：2280669
[Abstract]:With the rapid development of aerospace industry, there is an urgent need for UHV. Finding light metal materials with excellent performance at high temperature is an effective way to solve the bottleneck problem of aeronautical aircraft. NiAl intermetallic compounds have excellent high temperature performance and low density. It is considered to be one of the most promising high temperature structural materials. However, poor room temperature plasticity prevents large-scale applications of NiAl intermetallics. Plastic hot forming is one of the most effective methods to realize the synergistic enhancement of room temperature strength and plasticity. However, because deformation parameters are closely related to microstructure (that is, closely related to properties), it is very important to establish the relationship between deformation parameters and microstructure. In addition, deformation-induced textures have a significant effect on the formability of the components. Therefore, in order to obtain the components with ideal microstructure, the texture produced in the process of material deformation should be considered. In this paper, Ni and Al powders are used as the initial materials, and the hot pressing reaction sintering process curves are worked out based on the binary phase diagram of Al-Ni. Bulk NiAl materials were prepared by hot pressing sintering process. The Gleeble high temperature compression simulation experiment was carried out in the deformation temperature range of 1100 鈩，
本文编号：2280669
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