本文選題：工業(yè)純鈦　切入點：表面機械研磨處理　出處：《昆明理工大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：鈦元素在地殼中有著豐富的含量,并且鈦及鈦合金擁有著優(yōu)異的耐蝕性、耐高低溫性、生物相容性、和高于其他金屬的比強度等優(yōu)點,使其被普遍的應(yīng)用于航空航天、船舶、生物醫(yī)療、汽車等行業(yè)及領(lǐng)域,有著“航空材料”、“海洋材料”等佳譽。而對于金屬而言,高強度和高塑性一貫是困擾著材料領(lǐng)域科學(xué)家的一個難題。而使用大塑性變形工藝(Severe Plastic Deformation,SPD)對材料進(jìn)行加工以提高材料的性能是近年來研究的熱門之一。本論文以工業(yè)純鈦TA1為研究對象,研究不同塑性變形工藝如表面機械研磨處理(Surface Mechanical Attrition Treatment,SMAT)、軋制工藝(Rolling)以及低溫軋制后退火處理工藝(Annealing)對試樣的顯微結(jié)構(gòu)和力學(xué)性能的影響。并探討了不同加工工藝下材料的強化原理和變形機制。使用SMAT工藝對試樣進(jìn)行處理,鋼球以任意角度撞擊試樣表面,對試樣產(chǎn)生一個從表及里的應(yīng)變速率和應(yīng)變量梯度,從而導(dǎo)致一個從表面納米晶到心部粗晶晶粒尺寸梯度分布的梯度結(jié)構(gòu)。這種梯度結(jié)構(gòu)使材料優(yōu)異的性能。本文通過在低溫(77 K)和室溫(293 K)環(huán)境下對工業(yè)純鈦進(jìn)行SMAT處理,發(fā)現(xiàn)降低溫度能有效的提高材料內(nèi)部顯微應(yīng)變、位錯密度和孿晶密度,進(jìn)一步細(xì)化晶粒,從而提高材料的強硬度。處理時間選取30 min、60 min、90 min,實驗結(jié)果表示,隨處理時間的延長,試樣的強硬度上升,塑性下降。并且具有最佳力學(xué)性能的為LNSMAT-60min試樣。此外,還對儀器內(nèi)鋼球與試樣間的距離進(jìn)行調(diào)整,發(fā)現(xiàn)距離變短時,材料表層的應(yīng)變量和應(yīng)變速率增加并且表面梯度層的厚度更厚,這也使得材料的強度的得到大幅度的提升。本文對工業(yè)純鈦進(jìn)行低溫和室溫環(huán)境下的軋制處理。發(fā)現(xiàn)在低溫軋制(LNR)的情況下試樣內(nèi)部的位錯密度、顯微應(yīng)變和孿晶密度有顯著提高,晶粒更加細(xì)小。拉伸和硬度實驗結(jié)果表明,低溫軋制能在保持材料塑性的情況下顯著提高材料的強度和硬度。而且,通過分析可知軋制時低溫環(huán)境能促使變形機制由位錯機制主導(dǎo)向?qū)\晶機制主導(dǎo)的轉(zhuǎn)變。采用LNR50%試樣進(jìn)行低溫短時間退火。微觀測試結(jié)果表明,試樣經(jīng)過低溫短時間退火后得到了小晶粒包圍大晶粒的結(jié)構(gòu)。在進(jìn)行拉伸實驗時,因這種特殊結(jié)構(gòu)結(jié)構(gòu)的存在試樣內(nèi)部會產(chǎn)生一個非常復(fù)雜的應(yīng)力狀態(tài),這種應(yīng)力狀態(tài)會促進(jìn)更多的滑移系啟動,從而提高材料的加工硬化。并且退火后能引進(jìn)大量的大角度晶界,這對材料塑性的提高是十分明顯的。拉伸實驗結(jié)果表明,隨著退火時間的延長或退火溫度的升高,材料強度下降,塑性提高。其中具有最佳性能的為LNR1-450℃-10min試樣(LNR50%試樣450℃退火10min),其屈服強度為341 MPa,均勻延伸率為11.6%,屈服強度和均勻延伸率均比粗晶高。通過對比幾種不同的大塑性變形工藝處理后試樣的實驗結(jié)果,發(fā)現(xiàn)軋制后退火工藝對工業(yè)純鈦力學(xué)性能的提高是最顯著的。
[Abstract]:Titanium is abundant in the earth's crust, and titanium and titanium alloys have the advantages of excellent corrosion resistance, high and low temperature resistance, biocompatibility, and higher specific strength than other metals, which make them widely used in aerospace, ship, and so on. Biomedical, automotive and other industries and fields have a good reputation for "aeronautical materials", "marine materials" and so on. But for metals, High strength and high plasticity have always been a difficult problem for scientists in the field of materials. However, the use of large plastic deformation process to process materials to improve the properties of materials is one of the hot topics in recent years. The industrial pure titanium TA1 was used as the research object. The effects of different plastic deformation processes such as surface Mechanical Attrition treatment matting, rolling process rolling and annealing treatment after low temperature rolling on the microstructure and mechanical properties of the specimens were studied. The strengthening principle and deformation mechanism of the material. The SMAT process is used to treat the specimen. When the steel ball strikes the surface of the specimen at any angle, it produces a strain rate and strain gradient from the surface and inside the specimen. As a result, a gradient structure with size gradient distribution from nanocrystalline to coarse-grained grains at the center of the surface. This gradient structure makes the material excellent. In this paper, commercial pure titanium was treated with SMAT at low temperature (77K) and room temperature (293K). It is found that decreasing the temperature can effectively increase the internal microstrain, dislocation density and twin density, further refine the grain size and improve the toughness of the material. The treatment time is 30 min ~ 60 min ~ 90 min. The experimental results show that the treatment time increases with the increase of the treatment time. In addition, the distance between the steel ball and the specimen in the instrument is adjusted to find that the distance becomes shorter, while the toughness of the specimen increases and the plasticity decreases, and the best mechanical properties of the specimen are obtained by adjusting the distance between the steel ball and the specimen in the instrument. The strain and strain rate of the surface layer of the material are increased and the thickness of the gradient layer of the surface is thicker. In this paper, the rolling treatment of commercial pure titanium at low temperature and room temperature is carried out. It is found that the dislocation density of the sample is obtained under the condition of low temperature rolling (LNR) and low temperature rolling (LNR). The results of tensile and hardness experiments show that low temperature rolling can significantly increase the strength and hardness of the material while keeping the plasticity of the material. The analysis shows that low temperature environment can promote the transformation of deformation mechanism from dislocation mechanism to twinning mechanism. LNR50% samples are annealed at low temperature for a short time. The results of microcosmic test show that the deformation mechanism is changed from dislocation mechanism to twinning mechanism. After annealing for a short time at low temperature, the structure surrounded by small grain is obtained. In the tensile experiment, a very complex stress state can be produced in the sample due to the existence of this special structure. This stress state will promote the initiation of more slip systems and thus improve the work hardening of the materials. After annealing, a large number of large angle grain boundaries can be introduced, which is very significant for the improvement of the plasticity of the materials. The tensile test results show that a large number of large angle grain boundaries can be introduced after annealing. With the prolongation of annealing time or the increase of annealing temperature, the strength of the material decreases. The plasticity was improved. The best properties were obtained by annealing at 450 鈩，

本文編號：1635704