锻造粉末冶金Ti6Al4V合金的性能和组织研究

Study on Properties and Microstructure of Forged Powder Metallurgy Ti6Al4V Alloy

摘要:

摘 要: 本文对粉末冶金Ti6Al4V合金进行不同方式的锻造，并对锻造前后的性能和组织进行分析。研究表明，锻造是提高粉末冶金钛合金致密度、提高力学性能的有效手段。一方面，对粉末冶金Ti6Al4V合金在不同温度下进行一次锻造变形，发现960℃锻造后合金塑性最高，延伸率达到15.44%；随着锻造温度升高，组织中等轴α不断减少，逐渐向网篮组织转变，塑性有所降低，但是由于粉末的原始颗粒边界对晶粒长大的阻碍作用，在1150℃锻造后粉末冶金Ti6Al4V合金的晶粒没有明显长大，小于20μm的晶粒约占71%。晶粒尺寸小，有利于材料的塑性，其延伸率仍达到14.30%。因此，粉末冶金Ti6Al4V合金比传统熔铸钛合金具有更宽的锻造温度窗口。另一方面，对粉末冶金Ti6Al4V合金在不同温度下进行二次锻造变形，首先在高温锻造，利用小变形量的高温锻造来提高粉末钛合金的致密度，然后在低温进行二次锻造，获取需要的组织。经过两次锻造变形的Ti6Al4V合金的延伸率均大于17%，抗拉强度大于990MPa，屈服强度大于960MPa。

Abstract:

Abstract: In this study, powder metallurgy (PM) Ti6Al4V alloy was forged in different ways. The properties and microstructure of the alloy before and after forging were also analyzed. The results showed that forging was an effective way to improve the density and mechanical properties of PM titanium alloys. Firstly, the PM Ti6Al4V alloy was performed a once forging deformation at different temperatures. The alloy forged at 960℃ had better ductility with an elongation of 15.44%. With the increasing of forging temperature, the equiaxial α phases decreased, and gradually changed to the basket weave structure, resulting in the plasticity decreasing. However, due to the inhibition of the original powder particle boundary on grain growth, there was no obvious grain growth in the alloy forged at 1150℃. The grain smaller than 20??m accounted for about 71%. As fine grain size was beneficial to the plasticity, the elongation still reached to 14.3%. Therefore, the PM Ti6Al4V alloy had a wider forging temperature window compared to the traditional cast titanium alloy. Besides, the PM Ti6Al4V alloy was performed a twice forging deformation at different temperature. In such case, the alloy was firstly forged at high temperature to improve the density with small deformation, and then was forged at lower temperature to obtain the required microstructure. The Ti6Al4V alloy with twice forging deformation had an elongation of higher than 17%, tensile strength of higher than 990MPa, and yield strength of higher than 960MPa.