基于t-HPS加工的Pb-Sn合金室温下超塑性研究
Study on Superplasticity of Pb-SnAlloy Processed by t-HPS at RoomTemperature

晶粒尺寸对金属实现超塑性变形有很大的影响，传统的剧烈塑性变形该方法对金属的晶粒细化程度有限， 需要新的加工技术和方法来改善。超塑性变形过程中晶粒的过快长大，往往会破坏超塑性材料的组织稳 定性进而降低断裂延伸率。如何有效的抑制晶粒长大，是超塑性研究的重点之一。本文对特定成分点的 铅锡合金在进行周向高压剪切(t-HPS)加工后的组织和室温超塑性性能进行了研究，结果显示Pb-40% Sn 的断裂延伸率最高，达到1150%。EBSD图显示：t-HPS加工后的样品的平均晶粒尺寸在1.5 μm左右，t-HPS 的晶粒细化效果显著，在wt% Sn < 40%后，相比例(Pb相:Sn相)从46:54增加至59:41，即两相界面数量 有一个先增加后减少的过程，拉伸实验中Pb-40% Sn的断裂延伸率达到了1150%，但Pb-30% Sn的断裂 延伸率仅690%，结合文献中两相晶粒互相抑制晶粒长大理论和实验中两相界面数量的变化，推测铅锡 合金室温下超塑性最好的成分点在铅质量占比60%~70%的区间内。
The grain size has a great influence on the superplastic deformation of metal. The traditional severe plastic deformation method has limited grain refinement of metal, which needs new processing technologies and methods to improve. The rapid growth of grains in the process of superplastic deformation often destroys the structural stability of superplastic materials, and then reduces the fracture elongation. How to effectively inhibit grain growth is one of the key points of superplasticity research. In this paper, we studied the microstructure and room temperature superplasticity of the lead-tin alloy with specific composition points which through circumferential high pressure shearing (t-HPS). The results show that the fracture elongation of pb-40% Sn is the highest, reaching 1150%. EBSD diagram shows that the average grain size of the sample processed by t- HPS is 1.5 μm, the grain refinement effect of t-HPS is significant; When wt% Sn < 40%, the phase ratio (Pb:Sn) increases from 46:54 to 59:41, that is, the number of two-phase interfaces increases first and then decreases. In the tensile test, the fracture elongation of pb-40% Sn reached 1150%, but the fracture elongation of pb-30% Sn was only 690%. Combined with the theory of mutual inhibition of grain growth in the literature and the change of the number of two-phase interfaces in the experiment, it is speculated that the component point with the best superplasticity of lead tin alloy at room temperature is in the range of 60%~70% of lead mass.