熱處理工藝對(duì)Mg-6Zn-2Sm-0.4Zr鎂合金顯微組織和力學(xué)性能的影響

熱處理工藝對(duì)Mg-6Zn-2Sm-0.4Zr鎂合金顯微組織和力學(xué)性能的影響Effects of heat-treatment technology on microstructure and mechanical properties of Mg-6Zn-2Sm-0.4Zr magnesium alloy

通過(guò)在Mg-6Zn合金中添加0.4%Zr和2%Sm(質(zhì)量分?jǐn)?shù))制備出一種新型Mg-6Zn-2Sm-0.4Zr合金；利用光學(xué)顯微鏡(OM)、掃描電鏡(SEM)及能譜儀(EDS)、X射線衍射儀(XRD)、顯微硬度及力學(xué)性能測(cè)試研究鑄造Mg-6Zn-2Sm-0.4Zr合金在鑄態(tài)、固溶、時(shí)效處理下的顯微組織和力學(xué)性能的變化。結(jié)果表明：合金鑄態(tài)組織主要由基體α-Mg、晶界處呈連續(xù)或半連續(xù)分布的(α-Mg+Mg2Zn3+Mg41Sm5)共晶和晶內(nèi)孤立的點(diǎn)狀相組成。合金在440和450 ℃固溶12~36 h時(shí)間范圍內(nèi)，隨著時(shí)間和溫度的增加，固溶效果逐漸增強(qiáng)。當(dāng)在450℃固溶28 h時(shí)獲得了較好的顯微組織，抗拉強(qiáng)度為230 MPa，伸長(zhǎng)率為9.58%。隨后經(jīng)200 ℃時(shí)效6~48 h后，合金的力學(xué)性能明顯提高，時(shí)效強(qiáng)化效應(yīng)隨時(shí)間的延長(zhǎng)呈先增加后減小的趨勢(shì)，其中時(shí)效12 h時(shí)同時(shí)出現(xiàn)了抗拉強(qiáng)度和伸長(zhǎng)率的峰值258 MPa和14.43%，比鑄態(tài)的分別提高44 MPa和90.80%。

A new type Mg-6Zn-2Sm-0.4Zr alloy was fabricated by adding 0.4%Zr and 2%Sm (mass fraction) in Mg-6Zn alloy, and the microstructure and mechanical properties of the cast alloy under the conditions of as-cast, solution and aging treatment were investigated by optical microscopy (OM), scanning electron microscopy (SEM) with equipped energy dispersive spectrometry (EDS), X-ray diffractometry (XRD), micro-hardness and mechanical tests. The results indicate that the as-cast alloy is mainly composed of matrix α-Mg, eutectic phases (α-Mg+Mg2Zn3+Mg41Sm5) with continuous or semi-continuous morphology distributed along grain boundaries and a few isolated particles inside grains. The alloy is solutionized at 440 ℃ and 450 ℃ for 12-36 h, with the increment of solution temperature and time, the solution effect gradually increases. When the alloy is treated at 450 ℃ for 28 h, the alloy exhibits relatively homogeneous microstructure and attains mechanical performance with ultimate tensile strength (UTS) of 230 MPa and elongation (EL) of 9.58%, respectively. After the alloy being aged at 200 ℃ for 6-48 h, the mechanical properties of alloy increase obviously, and the aging strengthening effect increases firstly and then decreases, the peak values of UTS (258 MPa) and EL (14.43%) of the alloy aged at 200 ℃ for 12 h are simultaneously obtained, which are increased by 44 MPa and 90.80% compared with those of the as-cast alloy, respectively.

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