(1. 河西學(xué)院 物理與機(jī)電工程學(xué)院，張掖 734000；
2. 河西學(xué)院 先進(jìn)材料成形技術(shù)研究所，張掖 734000)
摘 要: 通過(guò)在Mg-12Zn合金中添加2%Al(質(zhì)量分?jǐn)?shù))制備出一種新型Mg-12Zn-2Al(ZA122)鎂合金，并利用光鏡(OM)、掃描電鏡(SEM)、透射電鏡(TEM)、X射線衍射儀(XRD)和力學(xué)性能測(cè)試研究ZA122合金在鑄態(tài)、T4和T6處理后顯微組織和力學(xué)性能的變化規(guī)律。結(jié)果表明：鑄態(tài)組織主要由α-Mg基體和共晶相(α-Mg+Mg2Zn3+Mg7Zn3+Mg32(Al,Zn)49)組成。合金經(jīng)330 ℃固溶32 h后獲得較均勻的組織和231 MPa抗拉強(qiáng)度及9.23%的伸長(zhǎng)率。合金雙級(jí)時(shí)效的強(qiáng)化效果優(yōu)于單級(jí)時(shí)效的，且提前24 h獲得力學(xué)性能峰值。經(jīng)過(guò)(180 ℃, 48 h)單級(jí)時(shí)效后，抗拉強(qiáng)度和伸長(zhǎng)率的峰值分別為283 MPa和8.03%；采用(90 ℃, 24 h)+(180 ℃, 24 h)雙級(jí)時(shí)效后，同時(shí)出現(xiàn)了抗拉強(qiáng)度和伸長(zhǎng)率的峰值為294 MPa和7.81%。單級(jí)時(shí)效下，合金中沉淀相的形核機(jī)制主要借助于位錯(cuò)、空位、層錯(cuò)、亞晶界和晶界等晶體缺陷實(shí)現(xiàn)異質(zhì)形核。雙級(jí)時(shí)效下，預(yù)時(shí)效時(shí)脫溶析出的G.P.區(qū)或團(tuán)簇原子作為亞穩(wěn)相和平衡相的現(xiàn)成異質(zhì)形核核心實(shí)現(xiàn)異質(zhì)形核。
關(guān)鍵字: Mg-12Zn-2Al鎂合金；雙級(jí)時(shí)效；顯微組織；力學(xué)性能；形核機(jī)制
（1. College of Physics and Electromechanical Engineering, Hexi University, Zhangye 734000, China;
2. Institute of Advanced Material Forming Technology, Hexi University, Zhangye 734000, China）
Abstract:A new type Mg-12Zn-2Al magnesium alloy (ZA122) was fabricated by adding 2% Al (mass fraction) in Mg-12Zn alloy, and the microstructure and mechanical properties of the alloy under the conditions of as-cast, solution and aging treatment were investigated with an OM, SEM, TEM, XRD and mechanical tests, respectively. The results show that the as-cast microstructures are mainly comprised of α-Mg matrix, eutectic phases (α-Mg+Mg2Zn3+ Mg7Zn3+Mg32(Al,Zn)49). After being solutionized at 330 ℃ for 32 h, the alloy reveals relatively homogeneous microstructure and perfectly mechanical performance with an ultimate tensile strength (UTS) of 231 MPa and an elongation (EL) of 9.23%, respectively. The effect of two-step strengthening is better than that of single-aging strengthening of the alloy, and the peak mechanical properties are obtained 24 h in advance. After single-aged by (180 ℃, 48 h), the peak values of UTS and EL are 283 MPa and 8.03%, respectively. While the maximum values of UTS 294 MPa and EL 7.81% are simultaneously achieved from the alloy experienced two-step aging (90 ℃, 24 h)+(180 ℃, 24 h). During single-aging process, the nucleation mechanism of precipitated phases of the alloy is mainly realized by dislocation, vacancy, stacking fault, sub-grain boundary, grain boundary and other crystal defects. In the course of two-stage aging, the generated G.P. zones or clustered atoms during the pre-aging process play ready-made heterogeneous nucleation role in the from process of metastable and equilibrium phases.
Key words: Mg-12Zn-2Al magnesium alloy; two-step aging; microstructure; mechanical property; nucleation mechanism
