(中南大學 材料科學與工程學院，長沙 410083)
摘 要: 通過金相和掃描電鏡等分析手段，研究預(yù)變形和過時效對機械熱處理細化AA2195 鋁鋰合金晶粒的影響。結(jié)果表明：過時效前的預(yù)軋制變形所形成的應(yīng)變區(qū)為第二相提供了均勻的形核位置，提高了第二相粒子的體積分數(shù)；與400 ℃單級過時效相比，預(yù)變形后采用300 ℃+ 400 ℃雙級過時效可使第二相粒子間距由2.09 μm增大到3.43 μm，在軋制過程中有利于形成獨立的高能應(yīng)變區(qū)，為再結(jié)晶提供更多的形核位置，進一步細化、等軸化AA2195鋁鋰合金晶粒，最終晶粒尺寸由12.6 µm細化至8.8 µm，晶粒縱橫比由1.61減小至1.27。
關(guān)鍵字: AA2195鋁鋰合金；機械熱處理；粒子激發(fā)形核；雙級過時效；預(yù)變形
pre-deformation and overaging
（School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract: The effects of pre-deformations and overaging on grain refinement of AA2195 Al-Li alloy in thermo-mechanical processing (TMP) were investigated by means of optical microscopy (OM) and scanning electron microscopy (SEM). The results show that the pre-deformation prior to overaging leads to the formation of strained zones, which provide homogeneous nucleation sites for the second-phase particles, and increases the volume fraction of the second-phase particles that can stimulate nucleation. Compared with overaging at 400 ℃, two-step overaging at 300 ℃+ 400 ℃ following pre-deformatiom results in that the spacing among the particles increases from 2.09 µm to 3.43 µm, and the further refinement and spheroidization of the recrystallization grains are obtained. The grain size decreases from 12.6 μm to 8.80 μm and the respect ratio decreases from 1.61 to 1.27.
Key words: AA2195 Al-Li alloy; thermo-mechanical processing; particle-stimulated nucleation; two-step overaging; pre-deformation
