本文選題：AZ80鎂合金　切入點：負重輪　出處：《中北大學》2017年碩士論文

【摘要】：負重輪作為履帶車輛的主要組成部件,對履帶式車輛的安全性、舒適性、平穩(wěn)性起著決定性作用,因此可以通過降低負重輪的重量來達到武器系統(tǒng)輕量化設計的目的,鎂合金因其優(yōu)越的性能作為生產(chǎn)負重輪的首選材料。在行駛過程中負重輪受到多種交變載荷的作用,而這種載荷的作用易引起構件疲勞失效,所以提高鎂合金負重輪的疲勞性能、增加其疲勞壽命是促進負重輪廣泛應用的必要前提,而成形工藝直接影響著負重輪的性能,因此針對提出的徑向-反向復合擠壓工藝,系統(tǒng)分析研究該工藝成形的AZ80鎂合金負重輪的疲勞性能,對成形工藝的改進以及促進鎂合金負重輪的應用具有顯著的實際意義。本文首先簡單介紹了成形負重輪的新工藝——徑向-反向復合擠壓工藝的工藝流程,其次在負重輪壁部和底部平行擠壓方向截取試樣,使用ZEISS金相顯微鏡觀察其顯微組織,利用INSTRON 3382試驗機進行拉伸試驗。最后在負重輪的壁部沿擠壓方向截取試樣,采用INSTRON 8801試驗機進行高周疲勞試驗和裂紋擴展速率試驗,測試其疲勞強度和斷裂韌性,并利用SU5000掃描電鏡對疲勞裂紋斷口形貌進行分析。AZ80鎂合金負重輪壁部和底部的晶粒細小呈等軸狀,壁部第二相析出呈點狀、棒狀和片層狀,底部第二相析出呈顆粒狀。壁部試樣抗拉強度為301Mpa,延伸率為9.8%,底部試樣的抗拉強度為285Mpa,延伸率為9.3%。結(jié)果表明壁部強度偏大、塑性較好,相差百分比分別為5.3%、5.1%。說明該新工藝成形的負重輪實現(xiàn)了壁部和底部的組織性能均勻化。高周疲勞試驗結(jié)果表明:繪制S-N曲線和利用公式計算后均可得負重輪壁部的疲勞強度值約為102Mpa,與曾榮昌等的研究相比,疲勞強度值提高10Mpa左右,說明徑向擴-收復合擠壓工藝可以改善負重輪的疲勞強度。從斷口形貌可知:裂紋萌生于試樣表面;擴展區(qū)存在疲勞輝紋、二次裂紋、解理臺階及羽毛狀花樣形貌;瞬斷區(qū)存在二次裂紋、韌窩、解理及準解理臺階和撕裂棱形貌。裂紋擴展試驗結(jié)果表明:采用COD法測定的試樣斷裂韌性值KIC=10.01MPa。從da/dN-ΔK曲線可得,過時效處理使負重輪抵抗裂紋擴展的能力降低。從斷口形貌可以看出:疲勞斷口呈多源萌生,過時效試樣的預制裂紋源區(qū)呈光滑平整形貌,峰值時效試樣呈河流狀類解理形貌;與峰值時效試樣相比,過時效試樣擴展區(qū)的疲勞條帶擴展痕跡間隔較大,瞬斷區(qū)的韌窩少且淺,說明過時效處理后負重輪的疲勞壽命降低。
[Abstract]:As the main component of tracked vehicle, load-bearing wheel plays a decisive role in the safety, comfort and smoothness of tracked vehicle, so the lightweight design of weapon system can be achieved by reducing the weight of load-bearing wheel.Magnesium alloys are the preferred materials for the production of load-bearing wheels because of their superior properties.In the course of driving, the load bearing wheel is subjected to many kinds of alternating loads, and this kind of load can easily cause fatigue failure of the components, so the fatigue performance of the magnesium alloy bearing wheel can be improved.Increasing its fatigue life is a necessary prerequisite to promote the wide application of load-bearing wheels, and the forming process directly affects the performance of the load-bearing wheels.The fatigue properties of the AZ80 magnesium alloy bearing wheel formed by this process are analyzed systematically. It is of great practical significance to improve the forming process and promote the application of the magnesium alloy bearing wheel.In this paper, the new technology of radial reverse composite extrusion for forming load-bearing wheel is introduced briefly. Secondly, the specimen is intercepted in the wall and bottom of the wheel, and the microstructure is observed by ZEISS metallographic microscope.Tensile test was carried out with INSTRON 3382 tester.Finally, the specimens were cut off from the wall of the load-bearing wheel along the extrusion direction. High cycle fatigue tests and crack growth rate tests were carried out with INSTRON 8801 tester to test their fatigue strength and fracture toughness.The fracture morphology of fatigue crack was analyzed by SU5000 scanning electron microscope. The fine grains in the wall and bottom of the wheel of AZ80 magnesium alloy were equiaxed, the second phase in the wall was punctate, the second phase was in the shape of rod and lamellar, and the second phase in the bottom was granular.The tensile strength of the wall specimen is 301 Mpaand the elongation is 9.8. The tensile strength of the bottom specimen is 285 Mpaand the elongation of the bottom specimen is 9.3.The results show that the strength of the wall is larger, the plasticity is better, the difference percentage is 5.3% and 5.1% respectively.The results show that the new process can homogenize the structure and properties of the wall and bottom.The results of high cycle fatigue test show that the fatigue strength of the wall of the load-bearing wheel can be obtained by drawing S-N curve and calculating by the formula. Compared with Zeng Rongchang and so on, the fatigue strength is increased by about 10Mpa.It is shown that the fatigue strength of the load wheel can be improved by the radial expansion-retraction composite extrusion process.The fracture morphology shows that the crack originates on the surface of the specimen, the fatigue ripple, the secondary crack, the cleavage step and the feather pattern in the propagating zone, and the secondary crack, dimple, cleavage, quasi cleavage step and tearing edge in the transient fracture zone.The results of crack growth test show that the fracture toughness of the specimen determined by COD method is 10.01 MPa.From the da / dN- 螖 K curve, it is found that aging treatment reduces the resistance of the load-bearing wheel to crack growth.From the fracture morphology, it can be seen that the fatigue fracture surface is multi-source initiation, the prefabricated crack source area of overaged specimen is smooth and smooth, and the peak aging specimen has fluvial cleavage morphology, compared with the peak aging specimen,The fatigue bands in the overaging specimens have a large spread trace interval, and the dimples in the transient fracture zone are small and shallow, which indicates that the fatigue life of the load-bearing wheel decreases after aging treatment.
【學位授予單位】：中北大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG146.22

【參考文獻】

相關期刊論文 前10條

1 權高峰;劉紹東;;超塑性模鍛鎂合金汽車輪轂應用研究[J];兵器材料科學與工程;2012年04期

2 楊永順;郭俊卿;陳拂曉;;鎂合金汽車輪轂塑性成形研究[J];鍛壓技術;2011年04期

3 朱陽;;鎂合金輪轂低壓鑄造數(shù)值模擬及缺陷預測[J];鑄造技術;2011年05期

4 王強;張治民;張星;李國俊;;New extrusion process of Mg alloy automobile wheels[J];Transactions of Nonferrous Metals Society of China;2010年S2期

5 殷銀銀;楊永順;郭俊卿;;鎂合金輪轂的塑性成形技術[J];熱加工工藝;2010年07期

6 周翔;池成忠;魏云龍;賈春燕;劉瑞林;;汽車用鎂合金車輪的液態(tài)模鍛成形研究[J];鍛壓裝備與制造技術;2009年02期

7 王強;張治民;張星;于建民;;Precision forging technologies for magnesium alloy bracket and wheel[J];Transactions of Nonferrous Metals Society of China;2008年S1期

8 劉艷改;熊守美;黃朝暉;房明浩;袁建路;;合金元素對AM60B鎂合金性能的影響[J];材料科學與工藝;2008年04期

9 楊友;劉勇兵;楊曉紅;陳華;;稀土元素對AZ91D壓鑄鎂合金高周疲勞性能的影響[J];金屬熱處理;2006年07期

10 曹亞強;張治民;王強;王智文;;AZ31鎂合金多次變形工藝及其在汽車輪轂上的應用[J];熱加工工藝(鑄鍛版);2006年03期

相關會議論文 前1條

1 曾榮昌;韓恩厚;劉路;徐永波;鐘偉珍;柯偉;;時效對鎂合金AZ80腐蝕疲勞壽命的影響[A];2002年材料科學與工程新進展（上）——2002年中國材料研討會論文集[C];2002年

相關博士學位論文 前2條

1 鄭三龍;擠壓AZ31B鎂合金及純鎂疲勞裂紋擴展研究[D];浙江工業(yè)大學;2013年

2 鄭潤芬;純鎂及鎂合金大氣腐蝕和化學氧化工藝研究[D];大連理工大學;2007年

相關碩士學位論文 前5條

1 阮發(fā)林;AZ91D鎂合金摩托車輪轂鑄鍛復合成形研究[D];哈爾濱工業(yè)大學;2011年

2 王建軍;AZ80鎂合金車輪擠壓成形數(shù)值模擬與實驗研究[D];中北大學;2011年

3 張愛民;塑性變形對AZ31鎂合金高周疲勞性能影響的研究[D];大連交通大學;2009年

4 周渝慶;鎂合金車輪疲勞壽命預測與優(yōu)化設計[D];重慶大學;2008年

5 龔政;鎂合金AM50、AZ91的疲勞裂紋擴展行為和高溫力學性能的研究[D];沈陽工業(yè)大學;2002年

，

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