【作者】 孙立涛；

【导师】 于海朋；

【作者基本信息】 沈阳工业大学 ， 材料加工工程， 2002， 硕士

【摘要】 液态挤压具有压力下凝固和塑性变形双重作用，是在挤压铸造和固态热挤压的基础上建立起来的一种全新的金属成形工艺。本文以ZA43合金为研究对象，通过正交试验分析了液态挤压工艺参数对ZA43合金力学性能影响的显著性水平，确定了锌铝合金液态挤压的合理工艺参数范围；通过对液态挤压ZA43合金宏观及微观组织的观察分析，研究了其不同部位组织特征的成因及影响因素，探讨了液态挤压件的成形特点，并提出改善和减少过渡区组织的措施；利用上限原理的方法求出了液态挤压中的单位挤压力和半锥角，确定了临界比压值，对挤压过程中变形区内金属的流动速度和等效应变做了分析；并研究了热处理和合金化对液态挤压ZA43合金组织和性能的影响。 结果表明：工艺参数对液态挤压ZA43合金力学性能影响的主次顺序为：加压前停留时间、浇注温度、模具温度，其中加压前停留时间的影响最显著。本试验条件下，液态挤压的适宜工艺参数为：模具温度160℃左右，浇注温度630-670℃，加压前停留时间15-22s。液态挤压后ZA43合金的强度和塑性均大幅度提高，特别是塑性提高更显著。液态挤压ZA43合金宏观变形特征明显，金属固相率的较大差别是其产生明显侧壁流线的原因。液态挤压ZA43合金的显微组织细小、均匀，并有明显的变形组织特征。宏观及微观组织观察均表明液态挤压制件的外侧部分存在明显的过渡区。断面减缩比，所需制件高径比，摩擦因子，半锥角和金属的高温屈服极限都是影响临界比压的重要因素。变形区内金属的流动速度沿径向分布为由中心向两边逐渐减小，等效应变为由中心向两边逐渐增大。沿轴向分布为越靠近盛料筒出口处，金属的流速和变形程度越大。其中，金属的固相率差是影响金属流动和变形的重要因素。Mg的加入使合金的塑性有很大的提高；Cu和Mn的强化作用比较明显；合理选择热处理工艺也是获得所需性能制件的一种有效的方法。更多还原

【Abstract】 The liquid extrusion process is a new forming technology which is developed on the basis of the squeeze casting and the hot extrusion. It not only retains the character of liquid metal crystallized under pressure, but also imparts to the alloy significant plastic deformation. The notable level of the effect of the processing parameters in liquid extrusion on the mechanical properties of ZA43 alloy was studied with the help of the orthogonal experiments. A reasonable extent of parameters was determined. The forming reasons and influencing factors to the structure in different sections were analyzed through observing macrostructure.and microstructure of ZA43 alloy by liquid extrusion process. The forming features of the process were discussed and the measures of improving and reducing transition structure were raised. The expressions of unit pressure and half cone angle were established by applying upper limit principle. The value of critical specific pressure was determined. The flow velocity and equivalent strain of the metal in the process of liquid extrusion were analyzed. Furthermore, the effect of alloying and heat treatment on the microstructure and mechanical properties of ZA43 alloy were studied.The experimental results show that the order of influential factor is deferring period before applying pressure, pouring temperature and die temperature. The influence of the deferring period before applying pressure on mechanical properties of ZA43 Alloy is the most remarkable. The befitting processing parameters obtained in the experiment are that the mold temperature is about 160 , the pouring temperature is 630-670 and the deferring period before applying pressure is 15-22s. The mechanical properties of ZA43 alloy are highly improved. Especially, the elongation of the alloy is greatly improved. The characteristics of macro structure of ZA43 alloy are distinct. The marked streamlines in side wall of workpiece are50405caused by the difference of solid phase ratio. The microstructure of ZA43 alloy is tiny and uniform. The characteristics of deformation of the alloy are remarkable. A transitionary section exist in the side wall of the liquid extrusion workpiece by observing macrostructure and microstructure of ZA43 alloy. The influencing factor on the value of critical specific pressure include ratio of section reduced, height to thickness ratio, friction factor, half cone angle and the high temperature yield limit of metal. The flow velocity of metal reduces gradually from center to side along radius in deformation region. The equivalent strain of metal increases from center to side along radius in deformation region. The shorter the distance away from the exit of’ the cavity of mould, the greater the flow velocity and equivalent strain of the metal along axes in deformation region. The difference of solid phase ratio is an important influencing factor on flow and deformation of the metal. The element Mg joined to the alloy make plasticity increase markedly. Strengthening function of Cu and Mn is quite bright. Choosing heat treatment process reasonably is a effective method to obtain the workpiece required.更多还原