新工艺制备半固态A356铝合金浆料

提出了在电磁搅拌制备半固态A356铝合金浆料时插拔Cu棒的一个新工艺.由于在半固态铸锭轴向区域引入低温,可进一步提高电磁搅拌效果,铸锭各部位均由细小α-Al晶粒组成.该工艺还可适当提高低过热度浇注的温度而有利于实际生产.     

Effect of pouring temperature on semi-solid slurry of A356 Al alloy prepared by weak electromagnetic stirring

The semi-solid slurry of A356 Al alloy was manufactured by low superheat pouring and weak electromagnetic stirring. The effects of pouring temperature on the slurry manufactured by weak electromagnetic stirring were researched. The results indicate that it is feasible to manufacture the slurry with particle-like primary phases by low superheat pouring and weak electromagnetic stirring, and there is an important effect of the pouring temperature （superheat temperature） on the morphology and the size of primary α -Al in A356 Al alloy. By the action of suitable weak electromagnetic stirring, increasing pouring temperature to put low superheat pouring in practice is capable of obtaining semi-solid slurry of A356 Al alloy with particle-like primary phase. Compared with the samples made only by low superheat pouring without stirring, raising pouting temperature by 15-35℃ above the liquidus temperature under condition of weak electromagnetic stirring can ensure the same grain size and morphology of the primary phase.     

近液相线半连续铸造A356铝合金显微组织

采用近液相线半连续铸造法制备铸造A356铝合金，获得金属半固态加工要求的细小，等轴的“非枝晶”组织，研究了铸造温度、保温时间及冷却速度对该组织的影响规律。结果表明，在液相线附近，降低铸造温度，有利于减小晶粒尺寸；晶粒平均等积圆直径最小可达42．6μm，初始固相体积分数最多可达98．4％，同一温度下，晶粒尺寸随保温时间的延长而粗化；冷却速度快，晶粒尺寸细小；同一铸锭，其中心部位的组织比边缘部位的组织粗大，且分布均匀、等轴特征明显。     

Rheo-squeeze casting of semi-solid A356 aluminum alloy slurry

The effect of pouring temperature, electromagnetic stirring power and holding process on semi-solid A356 aluminum alloy slurry was investigated, then the slurry was squeeze-cast. The results show that when the pouring temperatures are properly above the liquidus line, for example 630-650 °C, the slurry with spherical primary α(Al) grains can be prepared under the stirring power of 1.27 kW. The slurry is then homogeneously held for a short time, and the primary α(Al) grains are further ripened and distributed evenly in the slurry. The results of the rheo-squeezed casting experiments show that the injection specific pressure has a great effect on the filling ability of the semi-solid A356 aluminum alloy slurry, and the higher the injection specific pressure is, the better the ability for the slurry to fill the mould cavity is. When the injection specific pressure is equal to or above 34 MPa, the whole and compact rheo-squeezed castings can be obtained. The microstructure of the castings indicates that the shape, size and numbers of the primary α(Al) grains in different parts of the castings are highly consistent. After being held at 535 °C for 5 h and then aged at 155 °C for 12 h, the ultimate strength of the rheo-squeezed castings can reach 300-320 MPa, the yield strength 230-255 MPa, and the elongation 11%-15%.     

硅线石／2024液态挤压成形件的摩擦学特性

以２０２４铝合金为基体，使之与硅线石颗粒搅融混合成均匀浆料，经半固态挤压成形，获得一种新型的复合材料制件。对它进行摩擦磨损性能测定后发现，虽然增强体硅线石颗粒是直接从矿石开采获得的，但由于采用搅融混合半固态挤压新技术，其耐磨性明显高于ＺＱＳｎ６－６－３铜合金。为此，对其摩擦学特性进行了研究，以便为硅线石颗粒作为一种廉价的增强剂应用提供依据。     

近液相线法铸造非枝晶A356合金组织与成形性能

用近液相线半连续铸造法制备出具有等轴晶粒的半固态A356合金坯料,合适的铸造工艺为铸造温度615℃,保温20min,铸造温度120mm/min,冷却水流量0.086m^3/min,在电阻炉加热的条件下,半固态A356合金坯料的重熔加热温度场均匀,合适的加热温度为580-590℃,在模具温度400-600℃的条件下,触变成形汽车发动机用轴瓦盖热处理后的σ值达到290.2MPa,δ5达到12.9%。     

A356合金化学镀Ni-P工艺及其性能研究

用直接化学镀Ni-P和先电镀Ni后化学镀Ni-P两种方法在A356合金表面施加镀层.利用恒电位仪、盐雾实验、扫描电镜和显微硬度计等分析测试手段研究了两种工艺处理后镀层的性能.结果表明：两种不同工艺得到的镀Ni-P样品均具有优异的耐蚀性和较高的硬度,对Al合金基体均有很好的保护作用;其中带镀Ni中间层的化学镀Ni-P层更致密,具有更好的耐蚀性和硬度.     

EVOLUTION OF AS—CAST MICROSTRUCTURES OF 356 ALUMINIUM ALLOY CAST BY LIQUIDUS CASTING

A new method (liquidus casting) was used for 356 Al alloy semi-solid slurry making. The structures of 356 Al alloy cast by a Fe mould and semi-continuous casting machine at different temperatures were investigated. How the globular grains form was also discussed. The results show that either being cast by single Fe mould or semi-continuous machine, the micro structures are not conventional dendrites but fine and net-globular grains. The average gram size is smaller than 30?m and suitable enough for thixoforming, meanwhile it can improve the mechanical properties of following products. Under the suitable casting velocity and cooling intensity, most of global grains prolong their global growth and collide with each other before dendritic growth because of the large amount of the nucleation sites.     

A356合金流变压铸成型试验研究

采用自行设计的台阶板流变性能试件和半固态合金压铸模具,对A356合金的制浆-成形分离式流变压铸技术进行了试验研究。结果表明,选用适当的坩埚结构和涂料配方,采用搅拌坩埚直接输送半固态合金浆料,可简便快速地实现合金浆料从制备系统到成形系统的转移,从而实现二者的分离;在优化后的流变压铸工艺(增压压力180MPa,模具温度200～220℃)下,试件的抗拉强度和断后伸长率(Rm=280～310MPa,A=12%～15%)分别比液态压铸提高11.6%～18.2%和42.5%～50%;在适当的压铸工艺下,流变压铸充型过程平稳,不易发生紊流,试样的内部组织致密,且具有一定的热处理强化潜力。     

中间合金及其状态对A356合金半固态浆料组织的影响

通过实验分析了采用A356合金粉末、纯铝粉末、Al-5Ti-B合金粉末和Al-5Ti—B变形合金进行细化处理对A356合金半固态浆料组织的影响。结果表明，在“熔体处理＋双向电磁搅拌”复合制备技术中，加入约0．15％、平均粒度为100μm的Al-5Ti-B合金粉末进行晶粒细化，可在1min左右制备出形状因子大于0．8、晶粒半径为80μm（空冷）A356合金半固态浆料；加入10％-15％的微米级纯铝粉末可取得与Al-5Ti-B变形合金相当的细化效果；而采用平均粒度为100μm的A356合金粉末进行固液混合铸造，不适合于A356合金半固态浆料的快速制备。     

Continuous cleaning of A356 alloy melt using high frequency electromagnetic field

A set of device for electromagnetic separation (EMS) was designed and applied to process the continuous flowing melt. Tensile test was employed to compare effect of electromagnetic separation with that of the traditional processes. Compared with filtration by ceramic foam filter and process without filtration, multiple process combined with filtration and electromagnetic separation can effectively remove most of inclusions with diameter finer than 10μm in A356 alloy casting, hence improve its tensile properties. After being processed by electromagnetic filtration,the tensile strength of A356 scrap is enhanced by 8.27%, approaching the level of fresh A356 alloy.     

Annulus electromagnetic stirring for preparing semisolid A357 aluminum alloy slurry

The effects of pouring temperature and annulus gap width on the microstructure of the semi-solid A357 aluminum alloy slurry prepared by annulus electromagnetic stirring(AEMS) technology were investigated. The results show that low pouring temperature and narrow annulus gap are advantageous to obtaining the small spherical primary α(Al) phase. The lower the pouring temperature is and the smaller the annulus gap width is, the more uniform, the smaller and the more spherical the microstructure is. The microstructures obtained by the ordinary electromagnetic stirring and AEMS were compared. The results indicate that the primary α(Al) particles are globular, small and distribute homogeneously in the slurry obtained by AEMS. But in the slurry obtained by the ordinary electromagnetic stirring, the primary α(Al) particles are small dendrites in the edge of the slurry and they are large and rosette-like or dendritic in the inner of the slurry.     

电磁调质A356合金的组织研究

采用低频电磁场对水平连续铸造方法制备A356合金锭坯，通过金相显微镜观察，比较了磁场频率和电流大小对亚共晶区内初生廿灿形貌、晶粒大小的影响，通过扫描电镜分析，确定电磁场对Si在铝中晶内含量的影响。结果表明：与普通电磁铸造比较，低频电磁铸造可以细化晶粒，获得细小的α-Al组织和共晶组织。随着磁场频率降低，晶粒细化更加明显。而电流的增加也可以使晶粒细化，从而获得α-Al非枝晶组织和细小均匀的共晶组织。施加低频电磁场，可以提高Si在铝中的晶内含量，使共晶区域和晶界变窄，且Si的分布更加均匀。     

热处理对半固态A356铝合金挤压铸件组织与性能的影响

将低温浇注制备的半固态A356铝合金坯料加热至半固态浇注、挤压成形。采用正交试验法研究了固溶、时效对半固态A356铝合金挤压铸件组织与力学性能的影响。结果表明,时效时间对抗拉强度、屈服强度、伸长率影响最大,且都是随着时效时间增长先上升后下降;试验6获得较好的综合力学性能,其抗拉强度、屈服强度、伸长率分别为340 MPa、325 MPa、9.56%。     

液-固温区A356合金剪切速率阶梯变化的瞬态流变行为

采用自制的流变装置进行瞬态流变实验,研究了A356合金剪切速率阶梯变化对液-固温区不同初生α相形态瞬态流变行为的影响,初始剪切速率为367.3s^-1,剪切速率阶梯变化值分别为：50.2,83.7,118.6,141.8和195.3s^-1,结果表明,剪切速率由较低值向初始值阶梯变化时,剪切应力首先出现瞬时峰值。并且随着剪切过程的进行剪切应力逐渐降低至稳定态,对实验结果进行曲线拟合,得出剪切应力与时间的瞬态流变经验方程式：T-Ts=T△p^e^-kt,以及方程参数与半固态合金初生α相形态和剪切速率的关系。     

挤压铸造半固态A356铝合金的组织与力学性能

采用低温铸造方法制备A356铝合金半固态坯料.在200 t立式油压机上用挤压铸造方法将A356铝合金半固态浆料挤压成件.研究挤压铸造件的微观组织、力学性能,并与液态挤压铸造件进行比较.结果表明,A356铝合金半固态挤压铸造件组织由球形及椭圆形α-Al晶粒和α+Si共晶成分组成,且制件充型完整、无宏观缩孔、组织致密.在比压48.7 MPa,浇注温度575℃,保压时间3s条件下成形的半固态挤压铸造件的抗拉强度、屈服强度、伸长率分别达到278 MPa、225 MPa、13.2％,相比于在比压48.7 MPa,保压时间3s,710℃液态挤压铸造件性能分别提高了8.6％、8.2％、24.5％.A356铝合金半固态挤压铸造成形件具有较高的综合力学性能.     

Taper barrel rheomoulding process for semi-solid slurry preparation and microstructure evolution of A356 aluminum alloy

The self-developed taper barrel rheomoulding (TBR) machine for light alloy semi-solid slurry preparation was introduced. The semi-solid slurry was obtained from the intense shearing turbulence of the alloy melt in the cause of solidification, which was further caused by the relative rotation of the internal and external taper barrel whose surface contained wale and groove. The heat transmission model of TBR process, the flow rules and the shearing model of the alloy melt were deduced. Taking A365 as experimental material, the microstructure evolution rules under different slurry preparation processes were analyzed. The results show that decreasing the pouring temperature of A365 alloy melt properly or increasing the shearing rate helps to obtain ideal semi-solid microstructure with the primary particle size of about 70 μm and the shape factor of above 0.8.     

液相线铸造A356铝合金结晶过程初探

采用液相线铸造法即在液相线温度附近铸造A356铝合金获得了金属半固态加工要求的细小、等轴的“非枝晶”组织,考查了铸造温度、保温时间对组织形成过程的影响。结果表明,由于过冷和扩散的共同影响,A356铝合金液相线铸造最佳保温温度605℃,在60min时间内,晶核数目随保温时间的延长而增加,且分布愈加均匀。     

熔体处理和双向电磁搅拌复合快速制浆技术

分析了中间合金微细粉末熔体处理工艺和双向电磁搅拌工艺中,Al-5Ti-B合金粉末粒度、粉末加入量、加入温度、静置时间、中间合金加入顺序、单向旋转时间、电源频率、浇注温度和搅拌时间等工艺参数对A356合金半固态浆料的组织和制备效率的影响规律及其原因,开发出适合于铝合金的熔体处理 双向电磁搅拌半固态浆料复合制备技术。结果表明:该技术可在20~25 s内制备出α(Al)的形状因子约为0.85、晶粒尺寸为70~80μm(空冷尺寸)的A356合金半固态浆料。     

Sr变质对A356合金细化效果的影响

Sr变质处理后,A356合金初晶形核温度略有提高,共晶温度明显降低,从而通过影响初晶凝固过程提高晶粒细化效果;不添加细化剂,Sr本身对晶粒细化的影响并不明显;添加细化剂后,变质处理不仅可以激活更多的形核核心,而且由于明显增加了枝晶凝聚后二次枝晶的生长过冷度,从而减小了二次枝晶臂间距.