(1. 蘭州理工大學(xué)省部共建有色金屬先進(jìn)加工與再利用國家重點(diǎn)實(shí)驗(yàn)室，蘭州 730050；
2. 蘭州理工大學(xué)材料科學(xué)與工程學(xué)院，蘭州 730050；
3. 蘭石鑄造有限公司，蘭州 730050)
摘 要: 采用光學(xué)顯微鏡(OM)、掃描電子顯微鏡(SEM)、透射電子顯微鏡(TEM)、X射線衍射儀(XRD)、維氏硬度計(jì)和萬能試驗(yàn)機(jī)，研究了擠壓和時(shí)效態(tài)Mg-6.8Y-2.5Cu(質(zhì)量分?jǐn)?shù)，%)合金的顯微組織和力學(xué)性能。結(jié)果表明：擠壓合金主要由α-Mg基體、沿?cái)D壓方向分布的片層狀和塊狀18R類型的長周期堆垛有序相(18R-LPSO)、Mg2Cu相以及晶粒內(nèi)細(xì)小條紋狀的14H-LPSO相組成。180 ℃等溫時(shí)效后，亞穩(wěn)18R-LPSO相分解，晶內(nèi)析出新的14H-LPSO相。合金在58 h和130 h處分別出現(xiàn)兩個(gè)硬度峰值，其硬度值分別為69.2 HV和70.2 HV。第一個(gè)時(shí)效峰的出現(xiàn)主要源于大量18R-LPSO相和部分14H-LPSO相的析出。第二個(gè)時(shí)效峰的出現(xiàn)源于晶粒內(nèi)部高體積分?jǐn)?shù)14H-LPSO相的析出。拉伸測試結(jié)果表明：時(shí)效130 h的擠壓合金在室溫下具有最高的極限抗拉強(qiáng)度(276.8 MPa)和伸長率(25.9%)。合金高的抗拉強(qiáng)度主要?dú)w因于14H-LPSO相的析出強(qiáng)化及18R-LPSO相的彌散強(qiáng)化。
關(guān)鍵字: 擠壓Mg-Y-Cu合金；LPSO相；顯微組織；力學(xué)性能
（1. State Key Laboratory of Advanced Processing and Recycling of
Nonferrous Metals,Lanzhou University of Technology, Lanzhou 730050, China;
2. School of Materials Science and Engineering,
Lanzhou University of Technology, Lanzhou 730050, China;
3. Lanshi Foundry Co., Ltd., Lanzhou 730050, China）
Abstract:The microstructure and mechanical properties of the extruded and aged Mg-6.8Y-2.5Cu alloys were investigated by optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD), Vickers micro-hardness tester and tensile testing machine. The results show that the extruded alloy is mainly composed of α-Mg matrix, lamellar and block 18R type long-period stacking ordered (18R-LPSO) phase distributes along the extrusion direction, Mg2Cu phase and the fine striped 14H-LPSO phase in the grain interior. During the 180 ℃ isothermal aging process, parts of metastable 18R-LPSO phases occurrs to dissolve and the new 14H-LPSO phase precipitated in Mg matrix. Two hardness peaks of the extruded alloy appear at 58 h and 130 h, and hardness values are 69.2 HV and 70.2 HV, respectively. The first ageing peak arises from a great number of 18R-LPSO phases and small amounts of 14H-LPSO phases. The second aging peak originates from the precipitation of a large number of 14H-LPSO phases in the grain interior. The tensile test results show that the extruded alloy aged for 130 h exhibits the highest ultimate tensile strength (276.8 MPa) and elongation (25.9%) at room temperature. The good tensile strengths of the alloy are mainly attributed to the precipitation strengthening of the 14H-LPSO phase and the dispersion strengthening of the 18R-LPSO phase.
Key words: extruded Mg-Y-Cu alloy; LPSO phase; microstructure; mechanical property
