摘要
金属间化合物Mg_2Si具有高熔点、高硬度和高的弹性模量等特点，适宜做中高温结构材料。就使其应用领域从可发电、制冷、加热和恒温控制的通讯、半导体制造、激光、医学、计算机等领域拓展到了军事、航空航天、汽车工业和石油化工等领域。但是由于其本征脆性，很难进行加工和应用。所以对金属间化合物Mg_2Si的增韧研究，不论从理论还是从其实际应用都有很现实的意义。
本文以金属间化合物Mg_2Si为基体，用价格低廉，资源丰富的Mg作为增韧相，通过自蔓延模式燃烧合成和热爆模式燃烧合成两种方法制备了Mg／Mg_2Si复合材料，并对其进行了研究。
通过对理想状态下反应绝热温度的计算，明确了体系的预热温度与反应绝热温度及稀释剂添加量与绝热温度的关系。随着预热温度的升高Mg-Si体系的绝热温度也升高，最后达到一平台；随着稀释剂添加量的增加，Mg-Si体系的绝热温度逐渐减小，绝热平台也逐渐减小。
研究了自蔓延模式燃烧合成制备Mg／Mg_2Si复合材料中的影响因素如：预热温度，压坯压力，Mg粉粒度，Mg的质量百分含量以及热爆模式燃烧合成制备Mg／Mg_2Si复合材料中的影响因素如：升温速率，压坯压力，Mg粉粒度，Mg的质量百分含量对反应产物相及致密性的影响。研究发现各单因素对反应产物致密性影响不同，总体来讲具有以下规律：Mg粉粒度的影响＞预热温度(升温速率)的影响＞压坯压力的影响。
通过价电子结构分析，发现Mg_2Si晶胞的最强键上分布的电子对数介于镁和硅的最强键之间。Mg_2Si的密度、熔点也介于镁和硅之间，与所计算得到的最强健上分布的电子对数的情况相对应。
Intermetallic compound Mg_2Si is fit for moderate and high temperature structural material and hopeful to be used in aeronautics, astronautics and automotive industry for its virtues such as low density, high melting point and high specific strength and so on. But it is very difficult to process because of its intrinsic embrittlement. So the research of improving the brittleness of Mg_2Si has a far importance at not only theoretical side but also practical application side.
In this paper, Mg/Mg_2Si composite material which was based on intermetallic compound Mg_2Si and added with tenacious phase-Mg was synthesized by self-propagating combustion mode and explosion mode respectively and researched. In ideal state the relationships of preheat temperature, adiabatic temperature and quantity of diluents, adiabatic temperature were calculated. The results show that with the increasing of preheat temperature the adiabatic temperature of Mg-Si system increases and reaches a flat roof; with the increasing of quantity of diluents the adiabatic temperature decreases, so does the flat roof .
The influences to compactness of samples of the influential factors such as preheating temperature, pressure of green compact, powder size of Mg, Mg(wt)% in the progress of Mg/Mg2Si composite synthesized by self-propagating combustion mode and the influential factors such as preheating velocity pressure of green compact, powder size of Mg, Mg(wt)% in the progress of Mg/Mg_2Si composite synthesized by explosion mode were discussed. The investigation indicats that the influences of every factors are different on samples' compactness. But there is a regulation that is influence of powder size of Mg>influence of preheating velocity(preheating temperature)>influence of pressure of green compact.
By analysis of valence electronic structure, it is found that the amount of the valence electron pairs on the strongest bond of Mg2Si unit cell is intervenient between Mg and Si. The density and the melting point of Mg2Si is also intervenient between Mg and Si, which is relative with the calculate result.
引文
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