【作者】 熊爱华；

【导师】 袁森； 王武孝；

【作者基本信息】 西安理工大学 ， 材料加工工程， 2005， 硕士

【摘要】 本文在自行研制的镁合金半固态成形原理试验样机上,采用正交试验设计,研究了SIUA法压缩变形制备半固态AZ91D镁合金的挤压成形性能,分析了工艺参数对镁合金半固态挤压成形性能的影响及半固态浆料的流动方式,对成形制品的力学性能进行了初步测试,采用日本JSM公司JSM-6700F扫描电子显微镜(SEM)对断口进行了分析,采用PHILIPS公司XL20扫描电子显微镜和EDAX公司DX4能谱分析仪,观测、分析了半固态挤压制品凝固组织的特点及凝固方式。试验结果表明:① 半固态等温温度对挤压充型性能的影响作用最明显,其次是保温时间,形变率的影响作用最小;随着半固态等温温度的升高或保温时间的延长,合金浆料的充型性能一直升高,但形变率对合金浆料的充型性能的影响比较复杂,随着形变率的增人合金的充型性能先升高,后急剧降低,再升高。② 在本文的试验条件下,优选的工艺参数分别为:半固态等温温度580℃,保温时间20min,形变率20%。③ 在半固态条件下,当原始固相晶粒较多时,初晶α相的生长方式表现为依附生长为主:当浆料中液相率较高时,初晶α相主要以树枝晶方式生长。④ 半固态液相发生共晶转变,既存在离异生长方式,也存在共生生长方式,主要取决于初晶α的生长方式。如果初晶α相以依附方式生长,则形成离异共晶:如果初晶α相以树枝晶方式生长,则形成共生共晶。西安理工大学硕士学位论文 ⑤铸态镁合金试棒的断裂方式是解理断裂或者准解理断裂,解理台阶十分明显;而经过SI\IA法半固态处理挤压成形后的试棒以沿晶断裂为土,同时也有韧窝出现。说明具有非枝品组织的半固态合金力学性能有所提高。关键词:SI狱法镁合金半固态挤压成形性能凝固组织更多还原

【Abstract】 In this paper, with the prototype machine made by ourselves for magnesium alloys formation in semi-solid, according to the orthogonal experiment design, the capability of filling cavity of AZ91D magnesium alloys that were compressed in semisolid with SIMA process was studied. Effects of process parameters on forming capability and the flowing modes of slurry in semisolid state were analyzed. Mechanical properties of products were tested; the fracture morphology of tensile tested specimens was examined by scanning electron microscopy (JSM-6700F). The solidified microstructures were observed by means of SEM (PHILIPS XL20) and EDS (EDAX DX4), characteristic and modes of Solidification were analyzed. The results showed as follows:①The effect of reheating temperature in semisolid on capability of filling cavity was the greatest, the influence of holding time was greater. With the rise of temperature or holding time, the capability improved. However, the effect of deformation rate was complex, as deformation rate increased, forming capability changed from increasing to decreasing rapidly, and to increasing again.②The optimum parameters were that the reheating temperature, holding time and deformation rate was 580℃,20min,20%,respectively.③Under the condition of semisolid state, when there are many original crystal grains,α -Mg grew mainly by means of cling to crystal grains. But when the fraction of liquid phase was high, α -Mg grew in the form of dendrite crystal.④With eutectic reaction occurring in liquid phase, the eutectic grew not only in the form of divorced eutectic but intergrown eutectic, which depended on the growing form of α -Mg. If a -Mg grew in the form of cling, eutectic microstructures formed divorced eutectic. When α -Mg grew by means of dendrite, eutectic formed intergrown eutectic.⑤The fracture morphology of tensile tested specimens that were cast was cleavage or/and quasi-cleavage and cleavage steps were obvious. But the tensile tested specimens that were treated by SIMA fractured along grain boundaries mainly. At the same time, the fracture morphology at some crystal boundaries was featured as ductile fracture, evidenced by the existence of dimples, which indicated that the mechanical properties of alloys in semisolid that formed non-dendritic microstructures improved更多还原