本文選題：高強鎂合金　切入點：LPSO相　出處：《重慶大學》2015年碩士論文　論文類型：學位論文

【摘要】：鎂合金作為目前最輕的金屬結(jié)構(gòu)材料,具有比強度高、減振性好和易回收等優(yōu)點,在航天航空、國防軍工、交通運輸和電子產(chǎn)品等領(lǐng)域都具有廣闊的應用前景。然而鎂合金的絕對強度偏低,制約了鎂合金的應用發(fā)展。近年來,研究開發(fā)的Mg-RE-Zn系變形鎂合金由于LPSO相和時效沉淀相的復合強化作用,強度可以達到500MPa以上,但是關(guān)于Mg-RE-Zn系合金塑性變形規(guī)律的研究還比較缺乏。擠壓和軋制變形能夠有效調(diào)控鎂合金的組織和性能,且能夠應用于棒材、管材、型材和板材的大規(guī)模生產(chǎn),對于促進鎂合金的生產(chǎn)應用具有重大意義。為此本文針對擠壓、軋制變形對高強度Mg-9.23Gd-3.29Y-1.24Zn-0.87Mn(wt%)合金組織性能的影響開展了研究。首先,研究了擠壓比(8,11,27和42)對均勻化退火態(tài)合金組織性能的影響。均勻化退火后,合金中析出大量層狀LPSO相。擠壓比為8和11時,合金的再結(jié)晶程度較低,層狀LPSO相趨于與擠壓方向平行分布,形成大量層狀變形組織,合金的塑性較低。隨著擠壓比的增大,再結(jié)晶程度逐漸增大,塑性逐漸提高,但抗拉強度相差不大。時效處理后,各合金的抗拉強度出現(xiàn)一定的差距。擠壓比為11的棒材時效態(tài)合金具有最高的強度,UTS=502MPa,YTS=410MPa,EL=3.8%。此外,制備了擠壓比為11的擠壓板材,合金中同樣主要為層狀組織,時效后也獲得了不錯的力學性能。然后,研究了軋制變形對合金組織性能的影響。均勻化退火態(tài)合金軋制變形參數(shù)的探索中,發(fā)現(xiàn)由于層狀LPSO相對再結(jié)晶具有強烈抑制作用,在450℃下軋制容易開裂。均勻化退火態(tài)合金在520℃下軋制后,仍存在層狀變形組織,塑性較差。而對鑄態(tài)合金進行“軋制+固溶+軋制”工藝處理后,合金中塊狀LPSO相較小,且分布彌散,合金的晶粒較為均勻,具有較高的塑性。對比來看,“軋制+固溶+軋制”工藝容易進行更大下壓量的軋制。最后,研究了軋制變形對擠壓態(tài)合金組織性能的影響。對于含有大量層狀組織的擠壓合金,軋制變形中,層狀組織逐漸減少,再結(jié)晶組織逐漸增多,但晶粒尺寸無明顯變化。對于以等軸晶組織為主的擠壓合金,軋制變形后,晶粒略微細化。對擠壓合金進行軋制變形后,合金的屈服強度都有所提高,但是塑性急劇降低。擠壓比11的棒材合金在“軋制(下壓量50%)+時效”處理后,具有較高的強度,UTS=511MPa,YTS=430MPa,EL=2.6%。
[Abstract]:As the lightest metal structure material at present, magnesium alloy has the advantages of high specific strength, good vibration absorption and easy recovery. Transportation, electronic products and other fields have broad application prospects. However, the absolute strength of magnesium alloy is low, which restricts the development of magnesium alloy application in recent years. The strength of the developed Mg-RE-Zn wrought magnesium alloy can reach above 500MPa due to the composite strengthening effect of LPSO phase and aging precipitation phase. However, the study on the plastic deformation of Mg-RE-Zn alloys is still lacking. Extrusion and rolling deformation can effectively control the microstructure and properties of magnesium alloys, and can be used in large-scale production of bars, pipes, profiles and plates. Therefore, the effect of extrusion and rolling deformation on the microstructure and properties of high strength Mg-9.23Gd-3.29Y-1.24Zn-0.87Mnwtmeter alloy is studied. The effect of extrusion ratio of 8 / 11 / 27 and 42) on the microstructure and properties of homogenized annealed alloy was studied. After homogenization annealing, a large number of layered LPSO phases were precipitated in the alloy. The recrystallization degree of the alloy was lower when the extrusion ratio was 8 and 11:00. The lamellar LPSO phase tends to distribute parallel to the extrusion direction, forming a large number of lamellar deformed microstructure, and the plasticity of the alloy is lower. With the increase of extrusion ratio, the recrystallization degree and plasticity gradually increase, but the tensile strength of the alloy increases gradually, but the tensile strength is not different. The tensile strength of each alloy has a certain gap. The aging alloy with extrusion ratio of 11 has the highest strength. In addition, the extruded sheet with extrusion ratio of 11 is also mainly layered structure. The effect of rolling deformation on the microstructure and properties of the alloy was studied. In the exploration of rolling deformation parameters of homogenized annealed alloy, it was found that the relative recrystallization of layered LPSO was strongly inhibited. It is easy to crack after rolling at 450 鈩，

本文編號：1652761