(1. 中國鋁業(yè)鄭州研究院 綠色冶金與材料研究所，鄭州 450041；
2. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長沙 410083)
摘 要: 對Mg-9Gd-4Y-0.6Zr合金擠壓態(tài)和擠壓T5態(tài)在275~350 ℃的高溫下時效0~96 h，測試兩種狀態(tài)在時效過程中的硬度變化，并用透射電鏡觀察析出相的組織演變。結(jié)果表明：合金擠壓T5態(tài)比擠壓態(tài)在275~350 ℃高溫時效中的硬度高，并具有較好的耐熱性。合金擠壓T5態(tài)在275~350 ℃的高溫二次時效過程中產(chǎn)生回歸現(xiàn)象，二次時效的溫度越高，回歸現(xiàn)象越明顯，形成β1相的速度越快，達(dá)到平衡相(β相)所需的時間也越短。β′相向β1相轉(zhuǎn)變所需的相變時間最長；β1相向β相轉(zhuǎn)變所需相變時間最短，組織內(nèi)會出現(xiàn)β′相、β1相和β相三相共存；因此，β′相向β1相的轉(zhuǎn)變一旦完成，合金的硬度和耐熱性急劇地下降。
關(guān)鍵字: Mg-Gd-Y-Zr合金；二次時效；析出相；耐熱性
（1. Green Metallurgy and Materials Division, Zhengzhou Research Institute of Chalco, Zhengzhou 450041, China;
2. School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The as-extruded and extruded-T5 Mg-9Gd-4Y-0.6Zr alloys were aged in the temperature range of 275−350 ℃ for 0−96 h, the hardness was tested and the microstructure evolution was studied by transmission electron microscope. The results show that the extruded-T5 alloy has higher hardness and better heat resistance than the as-extruded alloy during high temperature ageing. The retrogression phenomenon occurs during the secondary ageing of the extruded-T5 alloy. The higher the secondary ageing temperature is, the more significant the retrogression phenomenon is, the faster the β1 formation is, the shorter the time of transforming to the equilibrium phase β is. The time of β′ phase transforming into β1 phase is the longest during secondary ageing, while that of β1 phase transforming to β phase is the shortest and three phases of β′, β1 and β can co-exist in the aged microstructure. The hardness and heat resistance drop sharply once the β′ phase transforms to β1 phase.
Key words: Mg-Gd-Y-Zr alloy; secondary ageing; precipitate; heat-resistance
