球化时间对AZ80镁合金组织及力学性能的影响

Effect of Spheroidizing Time on Morphology of β-Mg_(17)Al_(12) Phase and Mechanical Properties of AZ80 Magnesium Alloy

通过光学显微镜、场发射扫描电镜、X射线衍射(XRD)、硬度测试及拉伸试验等手段,研究了球化处理时间对AZ80析出相β-Mg17Al12及力学性能的影响。结果表明,铸态AZ80合金经退火处理后,晶间粗大的网状共晶β相消失,得到细小层片状脱溶β相均匀分布于α-Mg基体中。随球化时间延长,层片状β相开始溶断,先出现短棒状,然后向球状过渡,球化16h时镁基体上弥散分布大量细小颗粒状β相。继续延长时间,颗粒状β相出现溶解,数量减少,合金的综合性能最佳,屈服强度、抗拉强度和伸长率分别是132.5 MPa、252.4 MPa和9.56%。合金硬度随球化时间延长呈先升后降的变化规律,且均高于铸态合金。

The morphology ofβ-Mg17 Al12 phase and mechanical properties of as-cast AZ80 magnesium al-loy after spheroidizing treatment were investigated by means of optical microscope（OM）,field emission scanning electron microscopy（FESEM）,X-ray diffraction（XRD）,hardness and tensile testing.The re-sults reveal that the coarse divorced eutectic phaseβ-Mg17 Al12 phase in the AZ80 cast magnesium alloy is fully dissolved into Mg matrix during isothermal process at 415 ℃,and the perlite-type lamellerβphase with dense structure is precipitated from magnesium solid solution during the slow cooling.And then, the spheroidizing treatment was carried out,and the lamellerβphase was spheroridized by dissolved themselves.With the increase of spheroidizing time,the lamellarβphase began to fusing to generate short rod firstly,then transform to spheroidization.After spheroidizing treatment at 320 ℃ for 16 h, lots of small granularβphases are distributed dispersedly in the magnesium matrix.However,when the spheroidizing time is further increased,dissolution of the granularβphase appears in the alloy,and the number ofβphase is reduced.And after spheroidizing treatment at 320 ℃ for 16 h,yield strength,ten-sile strength and elongation of AZ80 magnesium alloy reach 132.5 MPa,252.4 MPa and 9.56% ,respec-tively.The brinell hardness of the alloy are increased firstly,and then declined with prolongation of spheroidizing time,however,the hardness value is higher than that of the as-cast alloy.