(1. 東南大學(xué) 材料科學(xué)與工程學(xué)院，南京 211189；
2. 南京云海特種金屬有限公司，南京 211221)
摘 要: 在鑄鋼坩鍋中熔煉制備了Mg-2Nd二元鎂合金，試樣經(jīng)不同熱處理工藝處理后，測(cè)試合金的室溫拉伸性能，采用光學(xué)顯微鏡(OM)、掃描電鏡(SEM)及透射電鏡(TEM)觀察合金的顯微組織，通過X射線衍射法(XRD)和能譜分析(XEDS)及選區(qū)電子衍射花樣進(jìn)行合金中的物相鑒別和微觀成分分析。結(jié)果表明：Mg-2Nd合金的鑄態(tài)組織由α-Mg基體和呈離異共晶形貌的Mg12Nd相組成；熱擠壓后，Mg12Nd相沿?cái)D壓方向呈纖維或顆粒狀分布；擠壓過程中發(fā)生動(dòng)態(tài)再結(jié)晶，合金的抗拉強(qiáng)度(σb)由鑄態(tài)的148.8 MPa提高到擠壓態(tài)的210.2 MPa，伸長(zhǎng)率(δ) 由鑄態(tài)的2.8%提高到擠壓態(tài)的19.9%；熱擠壓和熱軋成形的Mg-2Nd合金，直接時(shí)效T5(extruded、rolled)處理能產(chǎn)生形變強(qiáng)化和時(shí)效硬化雙重作用，其中T5(rolled)態(tài)合金σb高達(dá)276.4 MPa，δ較熱軋態(tài)提高了64%；T5(rolled)態(tài)組織中出現(xiàn)了β′和β沉淀，尺度均在50 nm左右，對(duì)合金產(chǎn)生了明顯的時(shí)效強(qiáng)化作用。
關(guān)鍵字: Mg-2Nd合金；微觀組織；力學(xué)性能；時(shí)效硬化；形變強(qiáng)化
（1. School of Materials Science and Eengineering, Southeast University, Nanjing 211189, China;
2. Nanjing Welbow Metals Co. Ltd., Nanjing 211221, China）
Abstract:The Mg-2Nd alloy was melted in a mild steel crucible. After heat treatment, the tensile properties of specimens were tested at room temperature, the microstructures were observed by using optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the microanalysis and characterization of second phase particles were carried out using X-ray diffraction (XRD), X-ray energy dispersive spectroscopy (XEDS) and selected area electron diffraction(SAED). The results show that the as-cast Mg-2Nd alloy consists of the α-Mg matrix and divorced eutectic phase Mg12Nd. After hot extrusion the Mg12Nd phase shows fibrous and granular morphology and is distributed along the extrusion direction. The dynamic recrystallization during hot extrusion significantly improves the tensile strength and elongation of alloys, which increase from 148.8 MPa and 2.8% to 210.2 MPa and 19.9%, respectively. For the extruded and rolled Mg-2Nd alloys, the direct aging(T5) has the combined effect of work hardening and age hardening. The tensile strength of as rolled sample is raised to 276.4 MPa and the elongation is enhanced by 64% compared with that of extruded sample. After the direct aging(T5) treatment, the α-Mg matrix of hot rolled sample has β′ and β precipitates with average sizes of 50 nm in length, which play important roles in age hardening.
Key words: Mg-2Nd alloys; microstructures; mechanical properties; age hardening; work hardening
