【作者】 何淼；

【导师】 白彦华； 于宝义；

【作者基本信息】 沈阳工业大学 ， 材料加工工程， 2008， 硕士

【摘要】 本文设计了一种可加热控温的封闭的镁合金拉拔装置和拉拔模具,采用挤压和拉拔两种工艺成形了φ4.0mm×0.25mm的WE43镁合金细薄管;探讨了拉拔管材的壁厚变化特点;完成了对不同工艺参数条件下拉拔力的实测,分析了拉拔工艺参数对拉拔力的影响;并探讨了热处理对挤压WE43镁合金性能和组织的影响,以及变形量对WE43镁合金拉拔棒材的性能和组织的影响,分析了拉拔镁合金的变形机制。实验结果表明,本课题设计的拉拔装置和拉拔模具能够实现镁合金棒材和管材的拉拔。采用挤压、拉拔、机械加工以及热处理等一系列工艺成形出的φ4.0mm×0.25mm细薄镁合金管材壁厚均匀,组织性能良好,表面光洁度好。此细薄镁合金管的力学性能可达到:σ_b＞200MPa,δ＞15%。多道次拉拔和减小道次加工率能够减小管材在拉拔过程中所受的环向压应力,有效地阻止细薄管材在拉拔过程中增壁的倾向,也可以促进管材壁厚均匀化;T₄处理也可以减小管材壁厚的增长。拉拔管材的延伸系数越大,所需的拉拔力越大;管材拉拔力随着拉拔速度的增加呈现先降低后增长的趋势,当v=0.25mm/s时拉拔力达到最小值,实现了拉拔速度的优化。本课题所设计的管材拉拔工艺切实可行,各道次的安全系数K均大于1,保证了棒材和管材拉拔过程中没有试样断裂现象。固溶处理能够明显改善挤压WE43镁合金的组织和性能,极大地减小了管材拉拔过程中发生折叠的几率。经过525℃×8h的固溶处理,合金具备良好的室温综合力学性能,组织中的稀土相呈细小颗粒状均匀分布于α-基体中。多道次拉拔使得WE43镁合金棒材的抗拉强度逐渐变大,伸长率逐渐减小。孪晶形核是拉拔镁合金的形核方式之一,有利于再结晶过程的进行和镁合金晶粒的细化。当变形程度达到84.2%时,晶粒由23μm减小到8μm以下。更多还原

【Abstract】 In this paper,a kind of closed drawing device,with capacity of heating and temperature-controlling,and drawing die are designed.Extruding and drawing are used to form thin-walled WE43 magnesium alloy tubes ofΦ4.0mm×0.25mm and alternation rules of wall thickness of the tubes are discussed;drawing forces under different processing parameters are measured and effect of drawing processing parameter on drawing force is analyzed;effect of heat treatment on properties and structure of extruded WE43 magnesium is discussed,and impact of deformation degree on properties and structure of drawed WE43 magnesium alloy,as well as its deformation mechanics,is researched.The results show that drawing processing of magnesium alloy bars and tubes can be realized in the presence of drawing device and dies designed.Thin-walled magnesium alloy tubes ofΦ4.0mm×0.25mm formed through a series of crafts of extruding,drawing, machining and heat treatment have homogeneous wall thickness,good performance and structure and surface quality.Mechanical properties of the tubes can reach:σ_b＞200MPa,δ＞15%.Multi-pass drawing and decreasing elongation coefficient can reduce circumferential compressive stresses which tubes bears during drawing,prevent effectively increasing tendency of wall thickness,and are also favorable to homogeneous wall-thickness;T4 heat treatment can also prevent the increasing tendency of wall thickness.The bigger the Elongation coefficient,the bigger the drawing force needed;drawing force first decline and then increase with the increasing of drawing velocity.When v equals to 0.25mm/s,drawing force is lowest,making that optimization of drawing velocity is realized.Drawing processing of tubes designed is feasible,and assurance coefficient K of all passes is much greater than 1,making sure that no breaking occurs during drawing.Solution treatment can improve structure and properties of extruded WE43 magnesium alloy,and reduce probability of tubes overlapping during drawing.Through solution treatment of 525℃×8h,this alloy have excellent comprehensive properties in room temperature,rare-earth phases chang into fine particles and distribute homogeneously inα-matrix.Multi-pass drawing makes tensile strength of WE43 magnesium alloy increase and elongation decrease.Twin nucleation is main nucleation way of drawed magnesium alloy, and is favorable to recrystallization and refinement of magnesium alloy grains.When deformation degree is up to 84.2%,grain size reduces from 23μm to below 8μm.更多还原