發(fā)布時(shí)間：2018-07-05 14:42

  本文選題：Mg-Li-Zn-Y合金 + 拉伸�。� 參考：《沈陽航空航天大學(xué)》2017年碩士論文

【摘要】：本文以Mg-7Li合金、Mg-7Li-3Zn-6Y合金、Mg-3Zn-6Y合金為研究對象,結(jié)合金相顯微鏡(OM)、掃描電子顯微鏡(SEM)、X射線衍射儀(XRD)、熱分析差示掃描量熱法(DSC)等表征手段,利用電子拉伸試驗(yàn)機(jī)對鑄態(tài)和擠壓態(tài)Mg-Li-Zn-Y合金進(jìn)行拉伸實(shí)驗(yàn),研究Mg-Li-Zn-Y合金拉伸變形行為及其應(yīng)變率效應(yīng),并探討了熱處理制度對Mg-Li-Zn-Y合金顯微組織和性能的影響。結(jié)果表明:隨著應(yīng)變速率的提高,鑄態(tài)Mg-7Li合金拉伸性能表現(xiàn)為應(yīng)變率強(qiáng)化效應(yīng);合金微觀斷裂機(jī)制主要為微孔聚合型斷裂與沿晶斷裂和解理斷裂相結(jié)合的混合斷裂機(jī)制。添加Zn、Y后,鑄態(tài)Mg-7Li-3Zn-6Y合金除α相和β相外還生成了ZnY相和Mg12YZn相,合金強(qiáng)度升高,但塑性降低明顯,合金的微觀斷裂機(jī)制主要為沿晶斷裂。與Mg-7Li-3Zn-6Y合金相比,鑄態(tài)Mg-3Zn-6Y合金屈服強(qiáng)度有所升高,但塑性變化不明顯,合金的微觀斷裂機(jī)制主要為解理斷裂。400℃固溶處理后,Mg-7Li-3Zn-6Y合金顯微組織中并未形成LPSO相,當(dāng)固溶溫度達(dá)到450℃和500℃,該合金中生成LPSO相,且450℃×8h固溶處理后,合金的硬度達(dá)到最大值;Mg-3Zn-6Y合金固溶處理后顯微組織中形成了細(xì)長條狀的LPSO相,并在固溶制度為470℃×8h時(shí)合金的性能達(dá)到最佳。與固溶處理相比,時(shí)效處理后合金中LPSO相的形成沒有進(jìn)一步的改善合金的硬度,致使合金的硬度有所降低。在熱擠壓過程中,Mg-7Li合金發(fā)生了動態(tài)再結(jié)晶,與α相相比,β相再結(jié)晶較為充分;添加Zn、Y后,Mg-7Li-3Zn-6Y合金的晶粒明顯細(xì)化,平均晶粒尺寸不足5μm;隨著應(yīng)變速率的升高,兩種合金的拉伸性能均表現(xiàn)為應(yīng)變率強(qiáng)化效應(yīng),同時(shí)發(fā)生了塑性不穩(wěn)定現(xiàn)象,且添加Zn、Y后,合金塑性不穩(wěn)定現(xiàn)象受到抑制。
[Abstract]:In this paper, the Mg-7Li-3Zn-6Y alloy, Mg-7Li-3Zn-6Y alloy, was studied by means of metallographic microscope (OM), scanning electron microscope (SEM) X-ray diffraction (XRD), differential scanning calorimetry (DSC), etc. The tensile deformation behavior and strain rate effect of Mg-Li-Zn-Y alloy in as-cast and extruded Mg-Li-Zn-Y alloys were studied by means of electronic tensile testing machine. The effect of heat treatment on microstructure and properties of Mg-Li-Zn-Y alloy was discussed. The results show that the tensile properties of as-cast Mg-7Li alloy show strain rate strengthening effect with the increase of strain rate, and the microfracture mechanism is mainly the mixed fracture mechanism of microporous polymeric fracture and intergranular fracture. In addition to 偽 phase and 尾 phase, ZnY and Mg12YZn phases were formed in as-cast Mg-7Li-3Zn-6Y alloy, the strength of the alloy increased, but the plasticity decreased obviously. The microfracture mechanism of the alloy was mainly intergranular fracture. Compared with Mg-7Li-3Zn-6Y alloy, the yield strength of as-cast Mg-3Zn-6Y alloy increased, but the plastic change was not obvious. The microfracture mechanism of Mg-7Li-3Zn-6Y alloy was mainly cleavage fracture. After solution treatment at 400 鈩，

本文編號：2100549