力學性能的影響
( 1. 清華大學 材料科學與工程系，北京 100084;
2. 北京廣靈精華科技有限公司，北京 100072)
摘 要: 研究了Al3Ti3B中間合金對AZ91D鎂合金顯微組織及力學性能的影響。通過光學顯微鏡和掃描電子顯微鏡觀察發(fā)現(xiàn)，Al3Ti3B中間合金能顯著減小AZ91D合金的二次枝晶臂間距與晶粒尺寸，在加入0.3％Al3Ti3B時晶粒尺寸就由原來的約260 μm減小至約100 μm。伴隨著合金晶粒尺寸的減小，合金的抗拉強度、屈服強度和延伸率都明顯提高，這主要是由于晶粒細化后能阻礙裂紋擴展的有效晶界增多，晶界強化作用顯著；同時，Al3Ti3B中間合金的加入促使溶質(zhì)均勻分布，使共晶體(α＋Mg17Al12)形貌發(fā)生改變，共晶體尺寸減小，這有利于裂紋切過脆性的共晶體傳播，提高合金的變形協(xié)調(diào)能力。
關(guān)鍵字: 鎂合金；Al3Ti3B；晶粒細化；二次枝晶臂間距；共晶體；力學性能
TONG Zhong-sheng2, TAO Zhan-dong2
（ 1. Department of Materials Science and Engineering,
Tsinghua University, Beijing 100084, China;
2. Guangling Magnesium Science and Technology Co. Ltd，
Beijing 100072, China）
Abstract: The influence of Al3Ti3B master alloy on the microstructure and mechanical properties of AZ91D magnesium alloy was investigated. Apparent grain refinement and decrement of the secondary dendrite arm space were found in the castings treated with Al3Ti3B by optical microscope and scanning electron microscope, and the grain size decreased from 260 μm to 100 μm merely with 0.3% addition. With the decreasing of secondary dendrite arm space or grain size, the ultimate tensile strength, yield strength and elongation are increased in the as-cast alloys. It can be explained that the density of grain boundaries becomes higher, which act as obstacles to the crack propagation with a smaller grain size; the addition of Al3Ti3B alloy leads to the homogeneous distribution of solute, and refines the eutectic Mg17Al12 phase, improves the deformability.
Key words: magnesium alloy; Al3Ti3B; grain refinement; secondary dendrite arm space; eutectic; mechanical property
