【摘要】：本文通過采用Cu和Cu-30%Zn金屬作為兩種研究材料,采用一種設(shè)計(jì)多級(jí)構(gòu)筑納米金屬結(jié)構(gòu)的思路,即首先通過大塑性變形細(xì)化晶粒,隨后再利用部分再結(jié)晶退火引入部分再結(jié)晶晶粒,以此來獲得一種非均質(zhì)的納米金屬結(jié)構(gòu)材料。通過大塑性變形技術(shù)和熱處理工藝的參數(shù)調(diào)控來獲得最佳拉伸強(qiáng)度與均勻延伸率的匹配。對(duì)變形機(jī)理的研究思路為結(jié)合位錯(cuò)理論與包申格效應(yīng),再通過微結(jié)構(gòu)表征,對(duì)非均質(zhì)納米金屬的拉伸應(yīng)變硬化行為進(jìn)行分析。(1)Cu:粗晶組織Cu經(jīng)過2道次的ECAP剪切變形,晶粒得到有效細(xì)化,再采用短時(shí)退火引入部分再結(jié)晶,以獲得非均質(zhì)納米結(jié)構(gòu)。利用室溫準(zhǔn)靜態(tài)拉伸實(shí)驗(yàn)得到不同結(jié)構(gòu)的應(yīng)力應(yīng)變響應(yīng)。通過循環(huán)加卸載拉伸試驗(yàn)研究非均質(zhì)納米Cu中的包申格效應(yīng),對(duì)粗晶和非均質(zhì)結(jié)構(gòu)所表現(xiàn)出來的不同背應(yīng)力硬化行為對(duì)比研究。循環(huán)應(yīng)力松弛拉伸試驗(yàn)可以有效表征納米金屬在準(zhǔn)靜態(tài)拉伸變形過程中的激活體積和可動(dòng)位錯(cuò)密度演化,進(jìn)而將納米金屬的林位錯(cuò)行為及其硬化機(jī)制進(jìn)行闡明。對(duì)粗晶和非均質(zhì)結(jié)構(gòu)Cu的循環(huán)應(yīng)力松弛拉伸結(jié)果進(jìn)行對(duì)比,各自給出林位錯(cuò)硬化機(jī)制與微結(jié)構(gòu)的演化關(guān)系。最后對(duì)粗晶和非均質(zhì)Cu進(jìn)行DIC全場應(yīng)變測量,從宏觀變形的角度,完整地把各自不同的應(yīng)變硬化行為展現(xiàn)出來。(2)Cu-30%Zn:通過大應(yīng)變冷軋將粗晶Cu-30%Zn的屈服強(qiáng)度從100MPa提高到了750 MPa。加部分再結(jié)晶退火后,對(duì)熱處理工藝進(jìn)行不同嘗試,以獲得了較好的強(qiáng)度塑性匹配。在300℃退火30 min后材料可以達(dá)到最好的強(qiáng)度塑性匹配,屈服強(qiáng)度為約600 MPa,均勻拉伸塑性為20%。同樣對(duì)其做循環(huán)加卸載拉伸試驗(yàn)探究非均質(zhì)的低層錯(cuò)能材料在拉伸變形過程中的包申格效應(yīng)與背應(yīng)力硬化,以研究背應(yīng)力硬化對(duì)加工硬化能力的提升作用。通過EBSD表征證明該材料在拉伸變形過程中發(fā)生了孿生變形,進(jìn)一步證明低層錯(cuò)能材料在拉伸變形的過程中不再是單純以位錯(cuò)的滑移為主導(dǎo)的變形機(jī)制,而是變成了以孿生為主導(dǎo)的變形機(jī)制。另外,通過低溫下的準(zhǔn)靜態(tài)拉伸性能結(jié)果與室溫準(zhǔn)靜態(tài)拉伸對(duì)比,結(jié)合EBSD表征,分析低溫下Cu-30%Zn的強(qiáng)韌化效果與應(yīng)變硬化行為。此外,高應(yīng)變速率下的拉伸應(yīng)力應(yīng)變響應(yīng)研究了其對(duì)應(yīng)變速率敏感性。
[Abstract]:In this paper, Cu and Cu-30%Zn metals are used as two kinds of research materials, and a multi-level design method is used to construct nanocrystalline structure. Firstly, grain refinement is made by large plastic deformation, and then partial recrystallization grain is introduced by partial recrystallization annealing, and then part recrystallization grain is introduced by partial recrystallization annealing. In order to obtain a heterogeneous nanometallic structure material. The best match of tensile strength and uniform elongation is obtained by means of large plastic deformation technique and parameter control of heat treatment process. The research idea of deformation mechanism is to combine dislocation theory with Bauschinger effect, and then analyze the tensile strain hardening behavior of heterogeneous nanometers by microstructure characterization. (1) Cu of Cu: coarse grain structure has undergone two ECAP shearing deformation. The grain was refined effectively and the partial recrystallization was introduced by short time annealing to obtain heterogeneous nanostructures. The stress-strain response of different structures was obtained by quasi-static tensile test at room temperature. The Bauschinger effect in heterogeneous nanocrystalline Cu was studied by cyclic loading and unloading tensile tests. The different back stress-hardening behaviors of coarse crystal and heterogeneous structure were compared. Cyclic stress relaxation tensile test can effectively characterize the evolution of activation volume and movable dislocation density of nanometallic metals during quasi-static tensile deformation, and then explain the stand dislocation behavior and hardening mechanism of nanometallic materials. The cyclic stress relaxation and tensile results of coarse grained and heterogeneous Cu were compared and the relationship between dislocation hardening mechanism and microstructure evolution was given. Finally, the DIC full-field strain measurement of coarse grain and heterogeneous Cu is carried out. From the angle of macroscopic deformation, the different strain-hardening behaviors of Cu-30%Zn: are presented completely. (2) the yield strength of coarse grain Cu-30%Zn is increased from 100MPa to 750 MPa. by Cu-30%Zn: cold rolling with large strain. After partial recrystallization annealing, different attempts were made on the heat treatment process to obtain a better strength and plasticity match. After annealing at 300 鈩，

本文編號(hào)：2248221