【摘要】：基于節(jié)能減排的迫切需求,鎂合金作為輕質(zhì)結(jié)構(gòu)材料在航空、汽車、電子器件等領(lǐng)域受到了海內(nèi)外學(xué)者的廣泛關(guān)注。鑒于鎂合金本身極限抗拉強(qiáng)度較低,上個(gè)世紀(jì)以來,大量研究聚焦在大變形超細(xì)晶鎂合金上,大變形超細(xì)晶鎂合金強(qiáng)度較傳統(tǒng)粗晶材料有大幅度提高,但其室溫延伸率一般較低。目前,金屬領(lǐng)域科研工作者陸續(xù)制備了高強(qiáng)塑性混晶結(jié)構(gòu)金屬材料,然而針對(duì)混晶結(jié)構(gòu)鎂合金強(qiáng)塑性同時(shí)提高方面的研究甚少。本人所在課題組在前期研究中開發(fā)了大壓下量襯板軋制(HPR)技術(shù),該技術(shù)不僅制樣簡(jiǎn)單、軋制道次少、效率高,能夠大大降低鎂合金板材軋制成本,具有良好的工業(yè)應(yīng)用潛力;而且利用該技術(shù)獲得了室溫力學(xué)性能優(yōu)異的、具有混晶結(jié)構(gòu)的AZ91鎂合金,但對(duì)混晶比例的調(diào)控尚未完全掌握、對(duì)混晶的形成機(jī)制尚未清晰。因此,本文以Mg-9Al-1Zn(AZ91)鎂合金為研究對(duì)象,采用HPR技術(shù),通過改變襯板軋制參數(shù)(溫度、壓下量、軋制道次)、再結(jié)晶退火參數(shù)(溫度、時(shí)間),獲得具有不同結(jié)構(gòu)特性(尺寸、比例、織構(gòu))的混晶鎂合金或細(xì)晶鎂合金;為強(qiáng)塑性同時(shí)提升的混晶鎂合金、力學(xué)性能媲美傳統(tǒng)軋制但更節(jié)約環(huán)保的細(xì)晶鎂合金的可控制備奠定基礎(chǔ),并對(duì)混晶的形成機(jī)制進(jìn)行初步了解。另外,對(duì)單道次襯板軋制工藝制備的混晶AZ91鎂合金的高溫拉伸變形行為進(jìn)行了研究。得出主要結(jié)論如下:(1)研究了軋制溫度、壓下量軋制參數(shù)對(duì)雙襯板單道次軋制AZ91鎂合金組織、力學(xué)性能的影響規(guī)律。優(yōu)化出雙襯板單道次350℃/55%壓下量的軋制參數(shù),該軋制工藝可制備具有混晶結(jié)構(gòu)且力學(xué)性能(σ0.2-152MPa,σb-374MPa,δp-19.6%)較佳的AZ91鎂合金薄板。(2)探索了350℃/75%壓下量單道次軋制工藝制備的混晶AZ91鎂合金在175℃、200℃、300℃及350℃的高溫拉伸變形行為;發(fā)現(xiàn)混晶AZ91試樣可以在200℃以上溫度、1×10-3s-1應(yīng)變速率拉伸條件下,表現(xiàn)出超塑性,且該混晶板材在300℃下拉伸時(shí)的斷裂延伸率高達(dá)505%。分析認(rèn)為在300℃、1.0×10-3s-1應(yīng)變速率下拉伸變形的超塑性主要為動(dòng)態(tài)再結(jié)晶及第二相輔助晶界滑移共同作用的結(jié)果。(3)優(yōu)化了再結(jié)晶退火工藝(溫度、時(shí)間)對(duì)兩道次雙襯板同溫軋制和降溫軋制AZ91鎂合金組織、力學(xué)性能的影響。發(fā)現(xiàn)經(jīng)過降溫軋制及再結(jié)晶退火后,可以獲得晶粒尺寸較為細(xì)小均勻(~3.2μm)的鎂板。(4)實(shí)現(xiàn)了用波浪襯板軋制(WDR)技術(shù)制備邊緣無明顯開裂的AT63鎂合金板材,發(fā)現(xiàn)WDR技術(shù)可以有效弱化鎂合金軋板基面織構(gòu),揭示了弱化軋板基面織構(gòu)可以提高板材加工硬化能力的作用機(jī)制,由于織構(gòu)弱化導(dǎo)致波浪襯板軋制試樣具有更高的斷裂延伸率(22.5%)。
[Abstract]:Due to the urgent need of energy saving and emission reduction magnesium alloys as lightweight structural materials have been widely concerned by scholars at home and abroad in the fields of aviation automotive electronic devices and so on. In view of the low ultimate tensile strength of magnesium alloys, since last century, a large number of studies have focused on large deformation superfine grained magnesium alloys, and the strength of large deformation ultrafine grained magnesium alloys has been greatly improved compared with traditional coarse grained materials. But the elongation at room temperature is generally low. At present, researchers in metal field have prepared high strength plastic mixed crystal structure metal materials one after another. However, there is little research on the enhancement of high strength plasticity of mixed crystal magnesium alloy. In the previous research, my research group developed the (HPR) technology of large volume liner rolling. This technology is not only simple in sample preparation, less pass rolling, high efficiency, can greatly reduce the rolling cost of magnesium alloy sheet, and has a good potential for industrial application. Moreover, AZ91 magnesium alloys with excellent mechanical properties at room temperature and mixed crystal structure have been obtained by using this technique, but the control of the proportion of mixed crystals has not been fully grasped, and the formation mechanism of mixed crystals has not been clearly understood. Therefore, taking Mg-9Al-1Zn (AZ91) magnesium alloy as the research object, using HPR technology, by changing the rolling parameters (temperature, reduction, rolling pass) and recrystallization annealing parameters (temperature, time) of lining plate, different structural characteristics (size, proportion) are obtained. Texture) or fine-grained magnesium alloy, and lay a foundation for the controllable preparation of high-plasticity, simultaneous lifting, fine-grained magnesium alloy with mechanical properties comparable to that of conventional rolling but more economical and environmentally friendly. The formation mechanism of mixed crystals was also preliminarily understood. In addition, the high temperature tensile deformation behavior of mixed AZ91 magnesium alloy prepared by single pass liner rolling process was studied. The main conclusions are as follows: (1) the effects of rolling temperature and rolling parameters on the microstructure and mechanical properties of AZ91 magnesium alloy were studied. The rolling parameters of single pass 350 鈩，

本文編號(hào)：2148651