【作者】 范科；

【导师】 高家诚；

【作者基本信息】 重庆大学 ， 材料科学与工程， 2010， 硕士

【摘要】 镁合金的优异性能和产业化、市场化前景使其成为公认的21世纪绿色工程材料,对建立资源节约型环境友好型的低碳社会将具有重要作用。Mg-Mn系合金由于具有优异的挤压特性,良好的焊接性和耐蚀性得以广泛应用,其中Mn作为Mg-Mn系合金的基本元素,一般以中间合金的形式加入,但实际生产中Mg和Mn的熔点差别较大固溶度极小,故Mg-Mn中间合金的制备十分困难,目前商用Mg-Mn中间合金的Mn含量不超过3wt%,严重影响了其使用效率。因此,发展高含Mn量Mg-Mn中间合金已成为镁合金发展的瓶颈之一。本文首先采用电磁搅拌铸造法制备Mn含量10wt%和12wt%的高含Mn量Mg-Mn中间合金,通过正交试验,研究了Mn粉粒度,冷却方式,搅拌时间和搅拌功率对Mn含量及Mn均匀度的影响,确定了最佳制备工艺;然后采用粉末冶金技术方法制备了Mg-15wt%Mn中间合金,通过正交试验,研究了Mn粉粒度,压制温度,压制压力和粘结剂对压坯强度和塑性的影响,确定了最佳制备工艺;第三,通过自制固液扩散偶,从理论上研究了在963K,983K,1003K下固态Mn在液态镁及镁合金的溶解扩散行为;第四,将自制的中间合金用来熔炼M1A,AZ91和ZM21镁合金,并从化学成分,显微组织和力学性能三个方面与相应牌号的国家标准对比,进而评价自制中间合金的应用性。研究发现:①电磁搅拌铸造法制备Mg-10wt%Mn中间合金的最佳熔炼工艺:Mn粉粒度150~68μm,冷却方式铜模空冷,搅拌时间4min,搅拌功率12.5kW;Mg-12wt%中间合金最佳熔炼工艺:Mn粉粒度150~68μm,冷却方式铜模空冷,搅拌时间4min,搅拌功率10kW。②粉末冶金法制备Mg-15wt%中间合金最佳工艺:Mn粉粒度150~68μm,压制温度是室温,压制压力125MPa,不用添加粘结剂。③利用菲克第二定律和Boltzmann-Matano法计算了963K,983K,1003K下固态Mn在液态镁中的平均扩散系数分别为1.72×10-14m2/s,4.07×10-14m2/s,6.91×10-14m2/s,平均溶解速率分别为9.393×10-10m/s,2.219×10-9 m/s,3.771×10-9 m/s;固态Mn在液态AZ91中平均扩散系数分别为8.10×10-15m2/s,8.29×10-15m2/s,2.27×10-14m2/s,平均溶解速率分别为4.419×10-10m/s,4.522×10-10 m/s,1.473×10-9 m/s;固态Mn在液态ZM21中的平均扩散系数分别为1.24×10-14m2/s,2.92×10-14m2/s,4.17×10-14m2/s,平均溶解速率分别为6.747×10-10m/s,1.593×10-9m/s,2.273×10-9m/s。再根据Arrhenius方程,计算出了固态Mn在液态镁,液态AZ91及液态ZM21的溶解扩散激活能分别为:266.1 kJ/mol,202.8kJ/mol,232.33kJ/mol。为了节约能源和提高中间合金的收得率,根据激活能及溶解扩散速率结果,得出熔炼M1A,AZ91和ZM21的加热功率可以按照PAZ91<PZM21<PM1A ,保温时间可以按照tM1A<tZM21<tAZ91的规律确定中间合金应用的熔炼工艺。④自制Mg-Mn中间合金可以制备出M1A,AZ91和ZM21,铸态下的化学成分和显微组织与相应合金的标准相比没有太大差别,而在力学性能方面,电磁搅拌铸造法制备的中间合金熔炼出的M1A,AZ91和ZM21力学性能达到标准,而粉末冶金法制备的中间合金熔炼出的ZM21可以达到标准,而熔炼出的M1A和AZ91没有达到国家标准。更多还原

【Abstract】 Magnesium alloys with outstanding performance,industrialization and market prospect are widely recognized as green engineering materials in the 21st century. It also takes an important role in establishing resource-saving and environment-friendly low-carbon society. Mg-Mn alloy is widely used with excellent extrusion property,good weldability and corrosion resistance. Mn is the basic element in Mg-Mn alloy and is joined in the form of master alloy. However Mn-content of the current commercial Mg-Mn master alloy is not more than 3wt%,affecting its efficiency. Therefore,the development of high Mn-content Mg-Mn alloy has become a bottleneck in the development of magnesium alloys.In this paper,firstly Mg-10wt%Mn and Mg-12wt%Mn master alloy were prepared by electromagnetic stirring method.The key processing parameters such as the particle size of Mn powder,the power of electromagnetic stirring,the stirring time and the way of cooling have been developed for the higher Mn-content and the better distribution of Mn by orthogonal experiment and obtained the best process.Secondly Mg-15wt%Mn master alloy was prepared by powder metallurgy process.The key processing parameters such as the particle size of Mn powder,pressing temperature,zinc stearate and pressing temperature were developed for the higher compressive stress and better plasticity and the best technology parameters have been determined. Thirdly,Mn/Mg,Mn/AZ91 and Mn/ZM21 solid-liquid diffusion couple were made to study solid manganese diffuse behavior in liquid magnesium,AZ91 and ZM21.At last,slef-made master alloys were applied to manufacture M1A,AZ91 and ZM21.The research results show that:①In the experiment conditions,Mg-10wt%Mn master alloy with excellent performance can be manufactured by adding Mn powder with the particle size ranged between 150~68μm in stirring at 12.5kW for 4min,cooling in the mold made from Cu. Mg-12wt%Mn master alloy with excellent performance can be manufactured by adding Mn powder with the particle size ranged between 150~68μm in stirring at 10kW for 4min,cooling in the mold made from Cu.②In this experiment conditions,the best technology parameters of Mg-15wt%Mn master alloy are manganese powder size 150~68μm,room temperature,zinc stearate free,compressive stress of 125MPa. ③Based on Fick’s second law and Boltzmann-Matano methold,the average diffusion coefficients of solid Mn in liquid Mg in 963K,983K and 1003K were respectively 1.72×10-14m2/s,4.07×10-14m2/s,6.91×10-14m2/s,the average dissolution rates were 9.393×10-10m/s,2.219×10-9 m/s,3.771×10-9 m/s;the average diffusion coefficients of solid Mn in liquid AZ91 were 8.10×10-15m2/s,8.29×10-15m2/s,2.27×10-14m2/s and the average dissolution rates were 4.419×10-10m/s,4.522×10-10 m/s and 1.473×10-9 m/s;the average diffusion coefficients of solid Mn in liquid ZM21 were 1.24×10-14m2/s,2.92×10-14m2/s and 4.17×10-14m2/s and the average dissolution rates were respectively 6.747×10-10m/s,1.593×10-9m/s and 2.273×10-9m/s.Then, according to Arrhenius equation,the solution diffusion activation energy of solid Mn in liquid Mg,AZ91 and ZM21 were 266.1 kJ/mol,202.8kJ/mol,232.33kJ/mol.In order to save energy and improve the recovery rate of Mn in M1A,AZ91 and ZM21,The heating power of melting M1A,AZ91 and ZM21 can be as follow: PAZ91 <PZM21 <PM1A and the holding time can be as follow: tM1A <tZM21 <tAZ91.④M1A,AZ91 and ZM21 can be prepared with self-made Mg-Mn master alloy.As cast , both chemical compositions and microstructure met related standards . M1A , AZ91 and ZM21 with self-made master alloy prepared by electromagnetic stirring also reached the national standards in mechanical properties.However,M1A and AZ91 can not attained the national standard except for ZM21.更多还原