本文選題：Mg-Sn-Zn-Al + 變形　； 參考：《重慶大學(xué)》2015年碩士論文

【摘要】：隨著鎂合金的應(yīng)用不斷增多,特別是交通業(yè)、航空航天、3C產(chǎn)品的需求,迫切需要開發(fā)出新型鎂合金。Mg-Sn是典型的時效強化型合金,其存在偏析嚴重、Mg2Sn易粗化以及時效硬化需時較長等問題,所以關(guān)于Mg-Sn體系合金的研究有待進一步深入。本文擬以Mg-Sn合金為基礎(chǔ),采用電磁感應(yīng)熔煉爐在氬氣保護下制備出了Mg-3Sn-x Zn-1Al(x=0.5~2.0wt.%)、Mg-x Sn-2Zn-1Al(x=3.0~10.0wt.%)和Mg-5Sn-2Zn-1Al-0.1Ba合金,通過X射線熒光光譜儀(XRF)、金相顯微鏡(OM)、X射線衍射儀(XRD)、掃描電鏡(SEM)、透射電鏡(TEM)、維氏顯微硬度計及力學(xué)性能測試儀器等手段方法研究了合金的顯微組織和力學(xué)性能,研究合金中析出相的成分、結(jié)構(gòu)及組織演變規(guī)律,擴大鎂合金的應(yīng)用范圍,對建立一種新型高強高韌的Mg-Sn系合金具有重要的意義。研究了Mg-3Sn-x Zn-1Al合金的顯微組織與力學(xué)性能,發(fā)現(xiàn)0.5-2.0 wt.%Zn的添加可以逐漸細化Mg-3Sn-1Al合金的晶粒,使Mg2Sn相增多,但會使Mg2Sn相粗化。在凝固過程中,固相中高濃度的Sn元素能夠阻止Mg原子的擴散,進而阻礙晶粒的長大。隨Zn含量的增加,擠壓態(tài)合金晶粒顯著地細化,力學(xué)性能有了顯著的提高,且塑性都出現(xiàn)了一定程度的增加。特別是合金的加工硬化能力(1/YR)也隨Zn含量的增加而略有提高,這意味著Zn元素能改善合金的強度和塑性變形能力,其主要原因是晶粒細化效應(yīng)和第二相的彌散均勻分布。在對合金進行時效處理后,Zn的存在可以縮短合金到達時效峰值時間,提高峰值硬度。Zn的添加會增加Mg2Sn相的數(shù)量,其阻礙晶界滑移和位錯的運動,有利于提高合金的強度,但卻降低了塑性。研究了Mg-x Sn-2Zn-1Al合金的顯微組織與力學(xué)性能。隨著Sn量的增加,合金枝晶逐漸細化,并且樹枝晶形態(tài)更加明顯,即Sn元素發(fā)生了明顯的偏析,且Mg2Sn相逐漸增加,呈斷續(xù)網(wǎng)狀分布于晶界處,但Sn含量增加至7%后,Mg2Sn的數(shù)量和尺寸都大幅度增加,在晶界上呈半網(wǎng)絡(luò)狀分布。經(jīng)熱擠壓后,合金發(fā)生動態(tài)再結(jié)晶,再結(jié)晶晶粒尺寸較為均勻,擠壓過程中析出的Mg2Sn相也逐漸增多。合金在經(jīng)過180℃×60h時效后,合金達到峰值硬度,隨Sn含量的增加,其到達峰值的時間未發(fā)生明顯的變化,但是硬度峰值從74.5增至78.9。經(jīng)T5時效處理,合金具有較高的強度和延伸率,其強化效果主要源于Mg2Sn相的增多。擠壓態(tài)Mg-5Sn-2Zn-1Al和Mg-10Sn-2Zn-1Al合金經(jīng)過軋制后,合金具有細小的晶粒,低的織構(gòu)和部分孿晶,盡管合金塑性有所下降,但合金仍然顯示較高的強度,其中,Mg-10Sn-2Zn-1Al合金的抗拉強度、屈服強度和延伸率分別達到369Mpa,263Mpa和8.4%。經(jīng)過300℃下退火1h后,合金發(fā)生完全再結(jié)晶,孿晶消失,晶粒大小均勻,強度,特別是屈服強度急劇下降,但塑性有很大的提高。研究了Mg-5Sn-2Zn-1Al-0.1Ba合金的顯微組織與力學(xué)性能,結(jié)果表明:微量Ba的添加顯著地細化了合金的枝晶,并且形成了Sn3Ba5和Sn Ba2相。經(jīng)過擠壓變形后,合金發(fā)生了晶粒的再結(jié)晶,晶粒轉(zhuǎn)變?yōu)榫鶆虻牡容S晶,尺寸較小,合金組織較為均勻,合金的力學(xué)性能得到進一步改善。合金在經(jīng)過180℃時效后,微量的Ba使Mg-5Sn-2Zn-1Al的峰值時效硬化時間從60h縮短到20h,促進了Mg2Sn相的析出,合金的力學(xué)性能有所提高,特別是屈服強度提升較為明顯。
[Abstract]:With the increasing application of magnesium alloys, especially the demand of transportation, aerospace and 3C products, it is urgent to develop a new type of magnesium alloy.Mg-Sn as a typical aging hardening alloy, which has many problems such as serious segregation, easy to coarsening of Mg2Sn and longer time hardening. So the research on Mg-Sn alloy needs further research. In this paper, based on Mg-Sn alloy, Mg-3Sn-x Zn-1Al (x=0.5~2.0wt.%), Mg-x Sn-2Zn-1Al (x=3.0~10.0wt.%) and Mg-5Sn-2Zn-1Al-0.1Ba alloy are prepared under the protection of argon gas by electromagnetic induction melting furnace. The X ray fluorescence spectrometer (XRF), metallographic microscope (OM), X ray diffractometer, transmission electron microscope, and dimension are used. The microstructure and mechanical properties of the alloy are studied by means of microhardness tester and mechanical properties testing instrument. The composition, structure and microstructure evolution of the precipitated phase in the alloy are studied, and the application range of the magnesium alloy is expanded. It is of great significance for the establishment of a new type of Mg-Sn alloy with high strength and high toughness. The study of Mg-3Sn-x Zn-1Al combined with the alloy is of great significance. The microstructure and mechanical properties of gold show that the addition of 0.5-2.0 wt.%Zn can gradually refine the grain of Mg-3Sn-1Al alloy, make the phase of Mg2Sn increase, but make the Mg2Sn phase coarsened. In the solidification process, the high concentration of Sn elements in the solid phase can prevent the diffusion of Mg atoms, and then obstruct the grain growth. With the increase of Zn content, the extruded alloy grains are increased. The mechanical properties have been significantly improved and the plasticity of the alloy increased to a certain extent. Especially, the working hardening ability (1/YR) of the alloy increased slightly with the increase of the content of Zn, which means that the Zn element can improve the strength and plastic deformation ability of the alloy. The main reason is the grain refinement effect and the dispersion of the second phase. After aging treatment, the existence of Zn can shorten the peak time of aging and increase the number of Mg2Sn phase with the increase of the peak hardness.Zn. It hinders the movement of grain boundary slip and dislocation, which is beneficial to improve the strength of the alloy, but reduces the plasticity. The microstructure of Mg-x Sn-2Zn-1Al alloy is studied and the microstructure of the alloy is studied. With the increase of Sn, the dendrite gradually refined, and the dendrite morphology is more obvious, that is, the Sn element has obvious segregation, and the Mg2Sn phase increases gradually, showing a intermittent network distribution at the grain boundary. But after the increase of the Sn content to 7%, the number and size of Mg2Sn increase greatly, and the grain boundary is distributed in a semi network shape. Hot extrusion has been made. After pressure, the alloy has dynamic recrystallization, the recrystallized grain size is more uniform and the precipitated Mg2Sn phase increases gradually during the extrusion process. The alloy reaches the peak hardness after 180 C 60H aging. With the increase of Sn content, the peak time has not changed obviously, but the peak of hardness increases from 74.5 to the aging place of T5. The alloy has high strength and elongation, and its strengthening effect is mainly due to the increase of Mg2Sn phase. After rolling, the alloy has fine grain, low texture and partial twins after the extrusion of Mg-5Sn-2Zn-1Al and Mg-10Sn-2Zn-1Al alloy. Although the alloy plasticity decreases, the alloy still shows high strength, of which, Mg-10Sn-2Zn-1Al The tensile strength, yield strength and elongation of the alloy reached 369Mpa, respectively, when 263Mpa and 8.4%. were annealed at 300 C for 1h, the alloy was completely recrystallized, the twins disappeared, the grain size was uniform, the strength, especially the yield strength decreased sharply, but the plasticity was greatly improved. The microstructure and mechanical properties of the Mg-5Sn-2Zn-1Al-0.1Ba alloy were studied. The results show that the addition of trace Ba significantly refines the dendrite of the alloy and forms the phase of Sn3Ba5 and Sn Ba2. After the extrusion, the alloy has the recrystallization of the grain, the grain is transformed into uniform equiaxed crystal, the size is smaller, the alloy structure is more uniform, and the mechanical properties of the alloy are further improved. The alloy is at 180 C. After the effect, the micro Ba shortens the time of peak hardening of Mg-5Sn-2Zn-1Al from 60H to 20h, which promotes the precipitation of Mg2Sn phase and improves the mechanical properties of the alloy, especially the increase of yield strength.

【學(xué)位授予單位】：重慶大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TG146.22

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