具有柱狀晶組織的鎂合金高溫力學(xué)性能及斷裂機(jī)制

具有柱狀晶組織的鎂合金高溫力學(xué)性能及斷裂機(jī)制High temperature mechanical properties and fracture mechanism of magnesium alloy with columnar crystal structure

利用定向凝固技術(shù)制備具有(11 0)á0001？擇優(yōu)取向的柱狀晶Mg-6.52Zn-0.67Y合金。對(duì)定向凝固Mg-6.52Zn-0.67Y合金進(jìn)行室溫及高溫拉伸實(shí)驗(yàn)，并利用SEM、XRD和EBSD等分析方法研究合金的拉伸斷口、形變過(guò)程中組織演變及斷裂機(jī)制。結(jié)果表明：定向凝固Mg-6.52Zn-0.67Y合金的室溫σ0.2和σb分別為124和196 MPa，δ為13%，表明定向凝固合金室溫下具有一定的均勻塑性變形能力；隨著拉伸溫度的升高，合金的強(qiáng)度降低，塑性升高，150 ℃拉伸時(shí)其σb為146 Ma，δ升至27%；300 ℃拉伸時(shí)其σb降至73 MPa，δ高達(dá)35%。150 ℃和200 ℃拉伸時(shí)其主要形變機(jī)制為錐面、棱柱面滑移及{10 2}孿生和{10 1}孿生等共同作用，合金的斷裂機(jī)制為韌性斷裂和準(zhǔn)解理的復(fù)合斷裂； 300 ℃拉伸時(shí)，主要形變機(jī)制則為錐面滑移和動(dòng)態(tài)再結(jié)晶，合金的斷裂機(jī)制為韌性斷裂。

Columnar crystal Mg-6.52Zn-0.67Y alloy with (11 0)á0001？ preferential orientation was prepared by directional solidification technique. The deformation and fracture mechanism were investigated in directionally solidified alloy through stretch test at room temperature and high temperature by using SEM, XRD and EBSD analysis methods. The results show that, directionally solidified Mg-6.52Zn-0.67Y alloy at room temperature has a certain uniform plastic deformation capacity because its yield strength and tensile strength are 124 MPa and 196 MPa, respectively, and its elongation is 13%. With the increase of the tensile temperature, the strength of the alloy decreases, the plasticity increases. At 150 ℃, the tensile strength is 146 MPa and the elongation increases to 27%. At 300 ℃, the tensile strength is down to 73 MPa and the elongation is up to 35%. The deformation mechanism is not only pyramidal, prismatic slip but also {10 2} and {10 1} twins twin jointly, and the fracture mechanism is a mixture cracking mechanism (ductile fracture and quasi cleavage fracture) at 150 ℃ or 200 ℃. With the tensile temperature reaches to 300 ℃, the deformation mechanism is pyramidal slip and dynamic recrystallization, and the fracture mechanism is ductile fracture.

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