(中南大學(xué) 材料科學(xué)與工程學(xué)院， 長(zhǎng)沙 410083)
摘 要: 通過(guò)在Mg-Gd二元合金中添加少量的Zr后制備一種新型的Mg-15Gd-0.6Zr合金， 并對(duì)合金的微觀組織、 時(shí)效特性和不同溫度下的力學(xué)性能及拉伸斷裂方式進(jìn)行研究。 合金在非平衡凝固過(guò)程中容易形成MgxGd(x=2， 3， 5)相， 但用熱處理的方法幾乎不可能消除。 在合金的Cast-T5、 Cast-T6、 Ext-T5和Ext-T6的4種時(shí)效狀態(tài)中， Ext-T5態(tài)達(dá)到峰值硬度的時(shí)間最短， 峰值硬度值最高； 而Cast-T5態(tài)的則相反。 合金具有較高的耐熱強(qiáng)度和延伸率， 其在不同溫度下的抗拉強(qiáng)度與WE54的相當(dāng)， 而延伸率明顯優(yōu)于WE54及其它耐熱鎂合金的。 合金在25 ℃時(shí)的斷裂方式以準(zhǔn)解理斷裂為主， 而250 ℃時(shí)的斷裂方式以微孔聚集型斷裂為主， 300 ℃和350 ℃時(shí)的斷裂方式以典型的微孔聚集型斷裂為主。
關(guān)鍵字: Mg-Gd-Zr合金； 耐熱鎂合金； 微觀組織； 力學(xué)性能； 時(shí)效特性； 斷裂方式
（School of Materials Science and Engineering, Central South University,
Changsha 410083, China）
Abstract: A new Mg-15Gd-0.6Zr alloy was developed by adding minor Zr to Mg-Gd binary alloy. The microstructures, aging characteristics, mechanical properties and fracture modes at 25, 250, 300 and 350 ℃ were investigated. A large number of MgxGd (x=2, 3, 5) phases form due to non-equilbrium solidification which can be hardly eliminated by subsequent heat treatments. Among Cast-T5, Cast-T6, Ext-T5 and Ext-T6, the highest hardness in the shortest time is in the Ext-T5 temper, while the lowest hardness in the longest time is in the Cast-T5. The tensile strengths of the alloy at the studied temperatures are as high as that of WE54 alloy, but the elongations are higher than those of WE54 alloy and some other conventional heat resistant magnesium alloys. The fracture modes of quasi-cleavage and microviod coalescence are dominant at 25 and 250 ℃, respectively, while at 300 and 350 ℃, the typical microviod coalescence are observed.
Key words: Mg-Gd-Zr alloy; heat-resistant magnesium alloy; microstructures; mechanical
properties; aging characteristics; fracture mode
