(中南大學(xué) 粉末冶金研究院，長(zhǎng)沙 410083)
摘 要: 通過Gleeble-3180熱模擬機(jī)對(duì)具有細(xì)晶組織的鎳基粉末高溫合金U720Li進(jìn)行高溫?zé)釅嚎s變形實(shí)驗(yàn)，分析該合金在1000~1150 ℃、0.001~1 s-1應(yīng)變速率的變形條件下的流變行為。利用采集的應(yīng)力-應(yīng)變數(shù)據(jù)計(jì)算材料的熱變形激活能，構(gòu)建材料的本構(gòu)方程，建立合金的熱加工圖，并通過微觀組織觀察對(duì)熱加工圖進(jìn)行解釋。結(jié)果表明：失穩(wěn)區(qū)主要位于低溫高應(yīng)變速率區(qū)域，合金未發(fā)生明顯動(dòng)態(tài)再結(jié)晶現(xiàn)象，晶界處的應(yīng)力集中導(dǎo)致沿晶裂紋的產(chǎn)生。在1150 ℃、0.01 s-1條件下，晶粒明顯長(zhǎng)大；在1100 ℃、0.001 s-1條件下，變形能夠獲得細(xì)小均勻的晶粒組織。
關(guān)鍵字: 鎳基粉末高溫合金；本構(gòu)方程；熱加工圖；微觀組織
（Research Institute of Powder Metallurgy, Central South University, Changsha 410083, China）
Abstract:Hot deformation on a fine-grained P/M superalloy U720Li was performed at 1000-1150 ℃ and strain rate of 0.001-1 s-1 by the Gleeble-3180 simulator. The deformation activity energy and constitutive equations were established by the true stress and true strain data. Processing maps for hot working were established on the basis of the variations of power dissipation efficiency, and related them with the microstructure observation. The results show that the major instability domain locates at low temperature and the high strain rate region, which is mainly caused by intergranular cracks, and the dynamic recrystallization doesn’t occurred. The grain growth is remarkably triggered under 1150 ℃, 0.01 s-1. Optimum hot working condition for U720Li is determined as 1100 ℃ and 0.001 s-1, where the refined and uniform grains are observed.
Key words: nickel-based powder superalloy; constitutive model; hot processing map; microstructure
