(1. 華中科技大學(xué) 材料成形與模具技術(shù)國(guó)家重點(diǎn)實(shí)驗(yàn)室，武漢 430074；
2. 浙江大學(xué) 寧波理工學(xué)院 機(jī)電與能源工程分院，寧波 315100)
摘 要: 研究時(shí)效處理對(duì)擠壓態(tài)Mg-15Gd-3Y合金顯微硬度及力學(xué)性能的影響，采用透射電鏡對(duì)時(shí)效析出相的形態(tài)進(jìn)行分析。結(jié)果表明：225 ℃、14 h時(shí)效時(shí)合金獲得最高硬度，為135 HV，此時(shí)，晶內(nèi)彌散析出許多納米β′亞穩(wěn)相，且與基體有著良好的共格匹配性，使合金獲得較高強(qiáng)度和硬度，同時(shí)塑性降低；在225 ℃、70 h過(guò)時(shí)效作用下，納米β′亞穩(wěn)相原位長(zhǎng)大成β穩(wěn)定相，且與基體失去共格匹配性，降低合金的強(qiáng)度和硬度，同時(shí)塑性有所回升；合金的最高強(qiáng)度出現(xiàn)在200 ℃、100 h時(shí)效處，此時(shí)，抗拉強(qiáng)度達(dá)到446.67 Mpa，合金中的β′ 亞穩(wěn)相呈蠕蟲(chóng)狀，沿亞晶界分布，有效地阻礙亞晶界和位錯(cuò)的運(yùn)動(dòng)，從而強(qiáng)化合金。
關(guān)鍵字: 鎂合金；擠壓鎂合金；Mg-15Gd-3Y合金；時(shí)效強(qiáng)化；顯微組織；力學(xué)性能
（1. State Key Laboratory of Material Forming and Mould & Die Designing,
Huazhong University of Science and Technology, Wuhan 430074, China;
2. School of Mechanical and Energy, Ningbo Institute of Technology, Zhejiang University, Ningbo 315100, China）
Abstract:The effects of aging on the Vickers hardness and mechanical properties of the squeezed Mg-15Gd-3Y alloy were investigated, and TEM was used to observe the microstructure of the precipitates. The results show that a maximum hardness of 135 HV can be attained when aged at 225 ℃ for 14 h. The alloy exhibits good strength and hardness but poor plasticity due to the precipitation of the nanoscale β′ metastable phase, which has good coherence with the matrix. The β′ phase transforms into the β stable phase in-situ, and becomes incoherent with the matrix when aged at 225 ℃ for 70 h. This induces the decline of the strength and hardness, and somewhat the recovery of the plasticity. The alloy achieves a maximum tensile strength of 446.67 MPa when aged at 200 ℃ for 100 h, and the β′ phase shows a shape of helminth and distributes along the subgrain boundaries. The β′ phase baffles the movement of the subgrain boundaries and dislocation effectively, and strengthens the alloy.
Key words: magnesium alloy; squeezed magnesium alloy; Mg-15Gd-3Y alloy; aging strengthening; microstructure; mechanical properties
