強織構AZ31鎂合金板材深低溫軋制過程中微觀組織演變及力學性能控制研究

強織構AZ31鎂合金板材深低溫軋制過程中微觀組織演變及力學性能控制研究Study on the Microstructural Evolution and Mechanical Properties Control of a Strong Textured AZ31 Magnesium Alloy Sheet During Cryorolling

取初始織構為c軸與板面法向垂直的強織構AZ31鎂合金板材為初始樣品,經液氮溫度深低溫軋制多道次至不同變形量,研究所得軋制板材的顯微組織與織構演變,及其對軋制力學性能的影響。利用SEM、EBSD和XRD表征分析了軋制板材的顯微組織和織構,應用準靜態單軸拉伸實驗分別測試了深低溫軋制板材沿軋向(RD)和橫向(TD)的室溫力學性能。研究表明,{101?2}拉伸孿晶是深低溫軋制強織構AZ31鎂合金板材中的主導孿晶類型,其對軋制板材的微觀組織和織構影響較為顯著。軋制變形后,大量的拉伸孿晶晶界不但對晶粒起到了分割碎化作用,并且由于孿晶對取向的劇烈改變,使得板材在軋制變形后c軸平行于ND的織構組分加強。深冷軋制板材的強度有所提高,但是延伸率卻急劇下降,沿著RD方向的強度要高于TD方向的強度。

A strongly basal textured AZ31 magnesium alloy sheet with the normal direction (ND) perpendicular to the c-axis has been cryorolled at the liquid-nitrogen temperature to the strain of different amount to analyze the influence of cryogenic rolling temperature. The microstructure and texture of the cryorolled samples have been investigated by using SEM, EBSD and XRD. And the mechanical properties of the cryorolled sheets have also been tested under quasi-static uni-axial tension at the ambient temperature along the rolling direction (RD) and transverse direction (TD) respectively. The microstructural and textual evolutions of the strongly basal textured AZ31 magnesium alloy sheets during cryorolling and the relationship between mechanical properties and the microstructural and textural evolutions of cryorolled samples has also been discussed in this work. The results show that a lot of twins have been observed in cryorolled sheets, and they were found to be {101?2} tension twins. {101?2} tension twins were the dominant twinning type of the AZ31 magnesium alloy sheet during cryogenic rolling. With the increase of cryogenic rolling pass, new texture component with the c-axis paralleled to the normal direction (ND) was strengthened and the breadth of {101?2} tension twins was also increased. Grains were separated by the twin grain boundaries after cryorolling. The mechanical test results show that the strength of the sheets increased while the ductility decreased after cryogenic rolling. The strength of the sheets along RD was higher than that along TD.

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