發(fā)布時間：2018-06-19 23:45

  本文選題：非晶復合材料 + 形狀記憶晶相��； 參考：《蘭州理工大學》2016年碩士論文

【摘要】：本文選擇具有形狀記憶效應和較強非晶形成能力的(Ti_(0.5)Ni_(0.5))100-xCux系合金,研究了銅含量變化(x=0,10,15,20,25,30,35,40)對(Ti_(0.5)Ni_(0.5))100-xCux合金系組織和力學性能的影響,優(yōu)化出綜合力學性能優(yōu)異的(Ti_(0.5)Ni_(0.5))80 Cu20合金,其斷裂強度為2246MPa,壓縮塑性達到12.2%,組織中僅為非晶基體和過冷奧氏體相B2-Ti(Ni,Cu)和熱致馬氏體相B19’-Ti(Ni,Cu),而無其他金屬間化合物相,應力加載形變過程中通過形狀記憶晶相TRIP效應對非晶基體增韌,并表現(xiàn)出強烈加工硬化行為。在此基礎上,研究了(Ti50Ni50-y My)_(80)Cu_(20)合金體系,M=Zr或Co,其中,Zr為提高馬氏體相變溫度元素,促進凝固組織中馬氏體的相轉變,但能夠明顯提高非晶形成能力;Co為降低馬氏體相變溫度元素,穩(wěn)定凝固組織中奧氏體相析出。當M=Co,y=0.02時,非晶復合材料的壓縮斷裂強度為2582MPa,塑性應變?yōu)?5%。在前述成分優(yōu)化的基礎上,分別設計了半固態(tài)處理工藝和預變形退火工藝,進一步優(yōu)化組織結構并提高力學性能,本文得出結論如下:(1)隨著銅含量的增大,(Ti_(0.5)Ni_(0.5))100-x Cux合金的非晶形成能力呈現(xiàn)一個從上升、降低再到上升的波形變化,但總體呈現(xiàn)降低趨勢。優(yōu)化出具有綜合力學性能最優(yōu)的成分點,即在x=20時,合金有最高的斷裂強度2246MPa,且其產(chǎn)生了12.2%塑性應變。(2)隨著Zr的不斷添加,此系列非晶合金非晶形成能力先提高后降低,凝固過程的溫度梯度決定了復合材料的組織梯度,由表及里,主要為非晶相、馬氏體相和奧氏體樹枝晶相。隨著非晶形成能力提高,非晶相體積分數(shù)增加。而整個研究成分體系中,隨著Zr的添加,奧氏體含量不斷下降,相變誘發(fā)塑性減弱,從而塑性逐級遞減,強度先升高后降低。(Ti0.5Ni0.48Zr0.02)_(80)Cu_(20)的斷裂強度達到2345MPa,塑性應變達10.1%;隨著鈷的不斷添加,奧氏體含量不斷升高,相變誘發(fā)塑性增強,從而塑性逐漸上升致奧氏體達到飽和時下降,強度先升高后下降,(Ti0.5Ni0.48Co0.02)80 Cu20的綜合性能最佳,斷裂強度達到2582MPa,塑性應變達15%。加載時形變誘導相變對非晶基體同時增強增韌,復合材料的綜合力學性能優(yōu)異,以連續(xù)屈服和強烈的加工硬化為主要特征。(3)(Ti_(0.5)Ni_(0.5))_(80)Cu_(20)和(Ti0.5Ni0.48Co0.02)80 Cu20試樣的組織為晶相和非晶相的復合結構,晶相為過冷奧氏體和熱致馬氏體結構,應力加載誘發(fā)奧氏體相轉變?yōu)轳R氏體并擇優(yōu)取向,使復合材料強度和塑性同時提高并出現(xiàn)加工硬化行為。鑄態(tài)試樣的心部組織為較粗大的樹枝晶,且生長不均勻,經(jīng)半固態(tài)處理后,復合材料組織得到有效優(yōu)化,獲得奧氏體相晶粒細小、圓整度高、組織致密;隨著預變形程度的增加,(Ti_(0.5)Ni_(0.5))80 Cu20合金中馬氏體相和奧氏體相均增加,而馬氏體相增加的更快,復合材料的屈服強度提高,塑性減小,塑形階段預變形能夠實現(xiàn)屈服強度可控。
[Abstract]:In this paper, we have studied the effect of the change of copper content on the microstructure and mechanical properties of TiTiG 0.5Nix 100-xCux alloy system with shape memory effect and strong amorphous formation ability. The effect of copper content change on the microstructure and mechanical properties of TiTiG 0.5NiU 0.5NiCX alloy system has been studied, and the excellent comprehensive mechanical properties have been optimized. The fracture strength is 2246MPa, the compressive plasticity reaches 12.2mm, the microstructure is composed of amorphous matrix and undercooled austenite phase B2-TiTiNiNiCuCu) and thermally induced martensite phase B19-TiNiNiNiCU, but there are no other intermetallic compound phases. During stress loading and deformation, the amorphous matrix is toughened by shape memory crystal phase trip effect and shows strong work hardening behavior. On the basis of this, the alloy system of Ti50Ni50-y Myai _ (80) / C ~ (+) / C _ (20) is studied, in which Zr is used to increase the martensite transformation temperature element and to promote the martensite phase transformation in solidified microstructure, but the amorphous formation ability and Co is the decreasing martensite transformation temperature element. Austenitic phase precipitates in stable solidified microstructure. The compressive fracture strength of the amorphous composite is 2582 MPA and the plastic strain is 15%. On the basis of the composition optimization mentioned above, the semi-solid treatment process and pre-deformation annealing process were designed respectively to further optimize the microstructure and improve the mechanical properties. The conclusion is as follows: (1) with the increase of copper content, the amorphous forming ability of titips 0.5 / Nix / x Cux alloy shows a waveform change from rising, decreasing to rising, but the overall trend is decreasing. The optimum composition point with comprehensive mechanical properties is optimized, that is, at x = 20:00, the alloy has the highest fracture strength of 2246MPa, and it produces a plastic strain of 12.2wt%.) with the addition of Zr, the amorphous forming ability of this series of amorphous alloys increases first and then decreases. The temperature gradient of the solidification process determines the microstructure gradient of the composite, which is mainly amorphous phase, martensite phase and austenitic dendritic phase from surface to interior. The volume fraction of amorphous phase increases with the increase of amorphous forming ability. In the whole composition system, with the addition of Zr, the content of austenite decreases and the ductility induced by transformation weakens, and the plasticity decreases gradually. The fracture strength of Ti0.5Ni0.48Zr0.02C _ (+) and the plastic strain reaches 2345MPa, and the plastic strain reaches 10.1.The austenite content increases continuously with the addition of cobalt, and the ductility is enhanced by transformation, so the plasticity increases gradually, and the austenite decreases when the austenite reaches saturation, and the ductility increases gradually, and the ductility decreases when the austenite reaches saturation, with the addition of cobalt, the austenite content increases continuously, and the ductility increases. The comprehensive properties of Ti0.5Ni0.48Co0.02Cu20 are the best, the fracture strength is 2582MPa, and the plastic strain is 15%. Under loading, deformation induced phase transformation strengthens and toughens the amorphous matrix at the same time. The composite material has excellent comprehensive mechanical properties. The main characteristics of the composites are continuous yield and strong work hardening. The main features of the composites are continuous yield and strong work hardening. The microstructure of the Ti0.5Ni0.48Co0.02O80Cu20 and Ti0.5Ni0.48Co0.02O80Cu20 specimens are the composite structures of the crystalline phase and the amorphous phase. The crystal phase is supercooled austenite and thermo-induced martensite structure. The austenite phase is transformed into martensite and preferred orientation by stress loading. The strength and plasticity of the composites increase and work hardening behavior occurs. The core structure of the as-cast sample is a coarse dendrite with uneven growth. After semi-solid treatment, the microstructure of the composite is optimized effectively, and the austenitic phase is obtained with fine grain size, high roundness and dense microstructure. With the increase of predeformation degree, both martensite phase and austenitic phase increase, but martensite phase increases more rapidly, the yield strength increases and the plasticity decreases. The yield strength can be controlled by pre-deformation in the plastic stage.
【學位授予單位】：蘭州理工大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TB33

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