本文關(guān)鍵詞：Mg-Gd-Y-Ca-Zr合金的組織和性能研究　出處：《河南科技大學(xué)》2015年碩士論文　論文類(lèi)型：學(xué)位論文

  更多相關(guān)文章： Mg-Gd-Y-Ca-Zr合金 顯微組織 力學(xué)性能 耐蝕性能

【摘要】：稀土鎂合金由于其良好的室溫及高溫力學(xué)性能,受到了人們的廣泛關(guān)注,成為近年來(lái)研究的熱點(diǎn)。但是稀土金屬的價(jià)格一般都比較昂貴,致使其不能得到普遍的推廣應(yīng)用。Ca是堿土元素中的一種,其熔點(diǎn)較低,密度與鎂的相近,且價(jià)格低廉。因此,在稀土鎂合金中添加Ca,利用Ca替代或部分替代鎂合金中的稀土元素,在保證其力學(xué)性能的基礎(chǔ)上,降低其經(jīng)濟(jì)成本,進(jìn)而開(kāi)發(fā)含Ca的新型鎂合金,會(huì)成為一個(gè)重要的研究方向。本文以Mg-5Gd-3Y-0.5Zr合金為基礎(chǔ),Ca元素按0.3wt%、0.6wt%、0.9wt%、1.2wt%的比例加入合金中,研究合金的微觀組織、力學(xué)性能和耐蝕性能。結(jié)果表明:Ca含量不同的Mg-Gd-Y-Ca-Zr合金的鑄態(tài)和固溶時(shí)效態(tài)顯微組織均由α-Mg基體、Mg2Ca、Mg5Gd和Mg24Y5相組成。隨著Ca含量的增加,合金的晶粒得到細(xì)化,但Ca含量的增加也致使合金的第二相明顯增多,在Ca含量為1.2wt%的鑄態(tài)合金中,第二相在晶界上已呈連續(xù)網(wǎng)狀分布,且部分覆蓋晶界,使晶界輪廓不太清晰。經(jīng)過(guò)固溶時(shí)效的熱處理工藝后,在同一溫度下,隨著Ca含量的增加,四種實(shí)驗(yàn)合金的抗拉強(qiáng)度都是先升高后降低,在Mg-5Gd-3Y-0.6Ca-0.5Zr合金時(shí)抗拉強(qiáng)度最高。在合金成分一定時(shí),四種實(shí)驗(yàn)合金的抗拉強(qiáng)度都隨溫度的升高而下降。合金的延伸率隨Ca含量的增加而減小,其斷裂方式都屬脆性斷裂。與Mg-5Gd-3Y-0.5Zr合金相比,加Ca后,無(wú)論是室溫還是高溫,合金的抗拉強(qiáng)度都明顯提高,室溫下Mg-5Gd-3Y-0.6Ca-0.5Zr合金的抗拉強(qiáng)度達(dá)到230MPa,比Mg-5Gd-3Y-0.5Zr合金高出20 MPa以上。Mg-5Gd-3Y-0.6Ca-0.5Zr合金的高溫抗蠕變性能良好。在200-300℃溫度范圍內(nèi)和50MPa-70MPa應(yīng)力范圍內(nèi),其蠕變應(yīng)力指數(shù)n值為1.11-2.92,蠕變激活能Qc的值為147.3-172.7k J/mol,分析其蠕變機(jī)制主要是擴(kuò)散控制機(jī)制向晶界滑動(dòng)和位錯(cuò)滑移控制機(jī)制轉(zhuǎn)變。在室溫下,對(duì)四種實(shí)驗(yàn)合金在不同濃度的Na Cl溶液(濃度為0.5%、2.0%、3.5%)中的腐蝕行為進(jìn)行了研究。合金成分一定時(shí),隨著Na Cl腐蝕液濃度的增加,四種實(shí)驗(yàn)合金的腐蝕速率均增大。在同一濃度的Na Cl腐蝕液中,合金的耐蝕性能隨Ca含量的增加而先增強(qiáng)后減弱,其中Mg-5Gd-3Y-0.6Ca-0.5Zr合金的腐蝕速率最小,耐蝕性能最好。
[Abstract]:Due to its good mechanical properties at room temperature and high temperature, rare earth magnesium alloys have attracted wide attention and become the focus of research in recent years. However, the price of rare earth metals is generally more expensive. As a result, it can not be widely used. Ca is one of alkali soil elements, its melting point is low, its density is close to magnesium, and the price is low. Therefore, Ca is added to rare earth magnesium alloy. Using Ca to substitute or partially replace the rare earth elements in magnesium alloys, on the basis of ensuring its mechanical properties, reducing its economic cost, and then developing new magnesium alloys containing Ca. In this paper, based on Mg-5Gd-3Y-0.5Zr alloy, the content of Ca is 0.3wtand 0.6wt and 0.9wt%. 1.2wt% of the alloy was added to the alloy to study the microstructure of the alloy. Mechanical properties and corrosion resistance. The results show that the as-cast and solid solution aging microstructures of Mg-Gd-Y-Ca-Zr alloys with different content of W Ca are all formed by 偽 -Mg matrix Mg2CA. The phase composition of Mg5Gd and Mg24Y5. With the increase of Ca content, the grain size of the alloy was refined, but the increase of Ca content also resulted in the increase of the second phase of the alloy. In the as-cast alloy with Ca content of 1.2 wt%, the second phase has been distributed continuously on the grain boundary and partially covered the grain boundary, which makes the boundary contour not clear. After the heat treatment process of solution aging, the grain boundary is not clear. At the same temperature, with the increase of Ca content, the tensile strength of the four experimental alloys increased first and then decreased. The tensile strength of Mg-5Gd-3Y-0.6Ca-0.5Zr alloy is the highest. The tensile strength of the four experimental alloys decreased with the increase of temperature, and the elongation of the alloys decreased with the increase of Ca content. Compared with the Mg-5Gd-3Y-0.5Zr alloy, the tensile strength of the alloy increased obviously after adding Ca at room temperature or at high temperature. The tensile strength of Mg-5Gd-3Y-0.6Ca-0.5Zr alloy is 230 MPA at room temperature. 20% higher than Mg-5Gd-3Y-0.5Zr alloy. The creep resistance of Mg-5Gd-3Y-0.6Ca-0.5Zr alloy above MPa is good at high temperature. The stress range is in the range of 200-300 鈩，

本文編號(hào)：1425673