半固态ZA27合金挤压成形的试验研究

分别对常规ZA27合金和经机械搅拌得到的半固态ZA27合金在不同的温度下进行二次重熔挤压成形试验；并对ZA27合金在二次重熔后的金相组织与挤压成形得到的金相组织进行了分析。结果表明，半固态ZA27合金在390－415℃下二次重熔，组织中蔷薇状α-Al分离球化，晶粒更加细化，近球形的α相长大，边缘更加光谱，此时进行挤压成形挤压应力较小，挤压件的金相组织与外部品质都较好。     

挤压铸造工艺参数对柱塞式大高径比ZA27合金铸件力学性能的影响

研究了大高径比(M=H/D=7)ZA27合金铸件的柱塞式挤压铸造.主要分析了挤压铸造工艺参数对大高径比ZA27合金的通体力学性能和显微组织影响规律,初步确定了适合大高径比ZA27合金铸件柱塞式挤压铸造的工艺参数.试验结果表明,挤压铸造能够改善大高径比ZA27合金铸件的通体力学性能,为扩大锌铝合金的应用范围提供了有力的技术保证.     

挤压铸造大高径比杯形铸件组织

研究大高径比铸件的挤压铸造将拓宽挤压铸造技术的应用范围。研究了挤压铸造ZA27合金大高径比杯形铸件的凝固组织。结果表明,铸件中压力分布极不均匀,铸件的上部边缘和底部压力较大,中下部压力较小;增大压力导致晶粒细化并发生塑性变形;ZA27合金大高径比杯形铸件的下部组织中出现分界面,界面两侧组织明显不同,后凝固一侧晶粒较细,含有较多共晶体。     

电磁搅拌和等温挤压对ZA27合金半固态组织的影响

采用电磁搅拌和等温挤压的方法,研究了ZA27合金半固态成形的合理工艺参数,分析了电磁搅拌过程中输入电压、搅拌温度、冷却方式以及挤压过程中挤压温度对ZA27合金的半固态显微组织的影响。结果表明,输入电压为180～200V、搅拌温度为465～475℃和急冷的方式可得到近似球形和球形的细小显微组织;挤压温度为390～410℃时,挤压过程中发生动态再结晶,挤压后晶粒变得更加细小、均匀。     

自孕育法制备ZA27合金半固态浆料水淬组织

采用自孕育法制备了ZA27合金半固态浆料,研究了不同熔体处理温度、等温保温温度和等温保温时间对ZA27合金半固态浆料水淬组织的影响。结果表明,自孕育法制备半固态浆料,其形核包括两个阶段,能够有效细化ZA27合金的晶粒,获得细小的蔷薇状等轴晶。在等温保温球化过程中,随等温保温时间的延长,平均晶粒尺寸不断增加,形状因子先减小后增大。适合ZA27合金半固态浆料的等温保温温度为470℃,等温保温时间为3min,平均晶粒尺寸为60.02μm。     

ZA27合金蜗轮毛坯的成形性与力学性能

对ZA27蜗轮毛坯进行了金属型铸造、挤压铸造和半固态挤压成形试验,研究了在不同工艺条件下,制件的宏观成形性、微观组织形貌和力学性能。结果发现,金属型铸造蜗轮毛坯组织从齿顶到分度圆,均为细密发达的树枝晶;挤压铸件齿顶无树枝状枝晶,齿根的树枝晶晶臂有碎断现象,分度圆枝晶组织破碎圆整痕迹较为明显;半固态挤压件齿顶晶粒组织细化,分布较为均匀,齿根部呈典型的玫瑰状半固态组织形貌,分度圆为细小的等轴晶粒组织。金属型铸造蜗轮齿型成形困难;挤压铸造制备的蜗轮,外观轮廓清晰,齿形饱满;半固态挤压件成形性更加优良。半固态成形件力学性能高于挤压铸造和金属型铸件。     

挤压铸造ZA27合金的凝固特性及组织分析

研究了ZA27合金挤压铸造的凝固特性和组织.差热分析表明挤压铸造可以使锌铝合金的凝固过程发生变化,压力在750MPa以上可抑制共晶反应的发生.压力下凝固,可大大减少ZA27合金的缩孔、缩松、气孔等缺陷,提高合金致密度,细化和改善组织,减轻枝晶偏析,使铸件整体的成分均匀.     

ZA84镁合金在半固态等温热处理过程中的组织演变

研究了ZA84镁合金在半固态等温热处理过程中的组织演变.研究结果表明,通过半固态等温热处理制备非枝晶组织ZA84合金是可能的.当ZA84合金经570℃×120 min半固态等温热处理后,可获得液相率为22%和未熔初生相颗粒尺寸为57um的非枝晶组织.ZA84合金在半固态等温热处理过程中的组织演变主要包括最初的粗化、组织分离和球化3个阶段.没有发现球状晶粒最后的粗化.     

固液混合铸造ZA60合金微观组织的研究

采用固液混合铸造技术制备了ZA60舍金,并与传统金属型铸造、半固态铸造对比,研究ZA60合金的组织变化规律及粉末加入量对固液混合铸造工艺ZA60合金组织的影响。结果表明,在合金熔体过热度为40℃,加入粉末粒度为200～400目时,加入40％的粉末量对ZA60合金有明显的组织细化作用;相对于金属型铸造和半固态铸造,固液混合铸造ZA60合金组织明显细化、球化,且组织比较均匀。固液混合铸造时组织改变的原因主要与搅拌作用和加入合金粉末时的激冷作用、形核作用有关;固液混合铸造时试样中β相和η相数量较少,主要与冷却速度相对较快有关。     

挤压铸造方式对ZA43合金力学性能的影响

从合金液的流动和压力损失的角度,研究了两种挤压铸造方式对ZA43合金力学性能的影响。结果表明:冲头式挤压铸造使合金液反向充型流动,改善了ZA43合金的凝固条件,有利于补缩,且压力损失小。柱塞式挤压铸造虽然也加强合金液流动,但没有宏观的充型运动,且压力损失大。为获得高塑性ZA43合金铸件,柱塞式挤压铸造所需的比压比冲头式挤压铸造的大得多。     

SiCp／ZA27复合材料在半固态等温热处理中的组织演变

研究了Zr变质处理的SiCp／ZA27复合材料在半固态温度保温过程中的组织演变情况,并与基体合金作了对比。结果表明：经0．6％Zr处理SiCp/ZA27复合材料在460℃保温30－40min可获得良好的半固态成形所需的组织;复合材料的组织演变速率比基体合金的快,且在长时间保温（＞40min）时,其组织的粗化现象不如基体合金明显。     

Effects of holding temperature and time on semi-solid isothermal heat-treated microstructure of ZA84 magnesium alloy

The feasibility of fabricating ZA84 magnesium alloy with non-dendritic microstructure by a semi-solid isothermal heat treatment process and the effects of holding temperature and time on the semi-solid isothermal heat-treated microstructure of the alloy were investigated. The results indicate that it is possible to produce ZA84 alloy with non-dendritic microstructure by suitable semi-solid isothermal heat treatment. After being treated at 560-575℃ for 120min, ZA84 magnesium alloy can obtain a non-dendritic microstructure with 14.2%-25.6% liquid fraction and an average size of 56-65μm of the unmelted primary solid particles. With the increasing holding time from 30 to 120min or holding temperature from 560 to 575℃, the average size of unmelted primary solid particles decreases and globular tendency becomes more obvious. Under the experimental condition, the microstructural evolution of ZA84 alloy during semi-solid isothermal treatment is mainly composed of three stages of initial coarsening. structulseparation and spheroidization. The subsequent coarsening of spheroidal grains is not observed.     

半固态等温热处理对ZA12合金组织和性能的影响

将初生相为枝晶形态的常规ＺＡ１２合金铸锭重新加热到半固态进行等温热处理，可获得具有良好触变性的非枝晶组织合金。文中对半固态热处理工艺参数与显微组织之间的关系进行了研究，并对铸态和经过半固态热处理的两种材料的半固态形性能以及成形制品的力学行为进行了试验对比。结果表明，经适当工艺热处理后，ＺＡ１２合金可以实现半固态成形，不仅成形抗力低，液相偏析少，且提高了制品的力学性能。     

ZA27合金半固态模锻成形性能的研究

采用模具对ZA27合金进行半固态模锻成形,对比分析了成形工艺参数对成形零件表面质量以及内部组织的影响,探讨了半固态金属的变形机理。结果表明,成形温度在475℃左右时的制件表面平整光滑,内部组织较致密;高的变形速率更有利于组织均化;随变形温度的不同,半固态ZA27合金呈现不同的变形机理。     

MICROSTRUCTURE ANALYSIS AND MECHANICAL PROPERTIES OF Zn—Al ALLOY ROD PRODUCED BY HEATED MOLD CONTINUOUS CASTING

The new technology of continuous casting by heated mold was used to produce directional solidification ZA alloy lines to eliminate the inter defects of these lines and increase their mechanical properties. The results are as follows: (1) The microstruc-ture of the ZA alloy lines is the parallel directional dendritic columnar crystal. Every dendritic crystal of eutectic alloy ZA5 was composed of many layer eutectic β and η phases. The micro structure of hypereutectic ZA alloys is primary dendritic crystal and interdendritic eutectic structure. The primary phase of ZA8 and ZA12 is β, among them, but the primary phase of ZA22 and ZA27 is a. (2) Through the test to the as-cast ZA alloy lines made in continuous casting by heated mold, it is found that the tensile strength and hardness increase greatly, but the elongation decreases. With the increase of aluminum amount from ZA 5 to ZA 12, ZA22 and ZA27, the tensile strength increases gradually. ZA27 has the best comprehensive mechanical properties in these     

Effect of specific pressure on microstructure and mechanical properties of squeeze casting ZA27 alloy

The effect of specific pressure on the microstructure and mechanical properties of ZA27 squeezed castings with high height-to-thickness ratio was studied. The results of DTA and SEM show that at high specific pressure the eutectic reaction of squeeze casting ZA27 alloy is restrained, and the final solidified structure is (η+ε) phases instead of eutectic phase (β+η+ε). At the same time, the primary reaction is promoted in squeeze casting ZA27 alloy solidified at high pressure, and the fine microstructure is obtained with the increase of pressure. Al and Cu elements are homogeneously distributed in matrix of squeeze casting ZA27 alloy. The homogenously distributed high-density fine ε phase can effectively hinder dislocation motion, and then the strength and plasticity of squeeze casting ZA27 alloy are increased.     

热型连铸锌铝合金定向凝固线材的组织分析

对热型连铸锌铝合金定向凝固线材的铸态及热处理组织进行了观察、分析和讨论。结果表明：热型连铸锌铝合金线材的显微组织为定向生长的平行柱状枝晶组织;共晶合金ZA5的枝状芥是的每个枝晶都由多层片状共晶β和η两相构成,过共晶合金的组织为初生树枝晶和枝晶间共晶组织,其中ZA8,ZA12初生相为β相,ZA22和ZA27的初生相是α相。     

细化剂对ZA27合金触变组织的影响

采用半固态等温处理法研究了细化剂Zr加入量对ZA27合金在半固态等温热处理中组织的影响。 结果表明,只要达到0．04％Zr时,就能获得触变成形组织,随Zr量的增加,初生相由发达的树枝晶逐渐演变为细化的短轴晶和等轴晶,但Zr含量不宜超过0．2％;在半固态等温处理后发现初生相细化得愈好,所得到的组织粒度愈小,圆整度愈好。     

Preparation of semi-solid billet of magnesium alloy and its thixoforming

Preparation of semi-solid billet of magnesium alloy and thixoforming was investigated by applying equal channel angularextrusion to magnesium alloy.The results show that mechanical properties of AZ91D alloy at room temperature,such as yieldstrength(YS),ultimate tensile strength(UTS)and elongation,are enhanced greatly by four-pass equal channel angularextrusion(ECAE)at 573 K and microstructure of AZ91D alloy is refined to the average grain size of 20μm.Through using ECAE asstrain induced step in SIMA and completing melt activated step by semi-solid isothermal treatment,semi-solid billet with finespheroidal grains of 25μm can be prepared successfully.Compared with common SIMA,thixoformed satellite angle framecomponents using semi-solid billet prepared by new SIMA have higher mechanical properties at room temperature and hightemperature of 373 K.     

ZA27合金离心铸件的组织与缺陷

介绍了ＺＡ２７ 合金离心铸件的组织特点及其特有的铸造缺陷,对其形成原因进行了简要分析和阐述。