SIMA法制备AZ91D镁合金非枝晶组织锭料

研究了利用应变诱发熔体激活法SIMA(Strain InducedMeltActivation)制备AZ91D镁合金半固态非枝晶时的组织转变过程.实验结果表明:具有树枝晶形态的AZ91D合金经20%及30%的预变形后,在半固态升温(540～580℃)或保温(570℃)过程中,其组织形貌由粗化的等轴晶及短树枝晶依次转变为小块状细晶粒→团块状→球状大晶粒.另外,在等温热处理过程中,试样内部体系寻求能量最低状态也是组织转变的一个不可忽略的因素.与未预变形的合金制备的非枝晶组织相比较,经预变形处理的试样是较好的半固态成型材料.

SIMA法工艺参数对7075铝合金半固态组织的影响

利用应变诱发熔化激活法(SIMA)制备了7075铝合金半固态坯料。分别研究了变形程度、半固态加热温度与保温时间对7075铝合金半固态坯料显微组织的影响。结果表明:变形程度越大,再结晶形核率越高,获得的半固态固相颗粒越均匀、细小;半固态加热温度越高,则半固态组织的固相颗粒越细小,液相率越高;当保温时间为30 min时,固相颗粒球化最好、最均匀。

SIMA处理工艺参数对AZ61镁合金组织和性能的影响

采用应变诱发熔体激活法(SIMA)制备出AZ61镁合金半固态坯料,同时对其组织演变过程进行观察,并研究预形变量和等温处理对组织及其机械性能的影响。试验样品经过0%、22%、40%的预形变量和各种加热温度处理。结果表明:在相同的等温温度条件下,预形变量越大,维氏硬度也越高。具有树枝晶形态的AZ61镁合金经22%预形变量后,在加热温度为595℃、保温时间40 min条件下,可以制备出理想的AZ61镁合金半固态非枝晶组织,而未经预变形的AZ61镁合金不宜进行半固态制坯。

SIMA法制备半固态AM60-2Nd镁合金组织的演变

主要研究了等温温度和等温时间对应变诱导熔化激活法制备的半固态AM60-2Nd合金组织演变的影响。结果表明,在230℃以45%的压缩比压缩变形后,组织呈明显的纤维流线状,针状Al11）Nd3相被拉长、碎断成颗粒状不连续分布在晶界上。随着等温温度的升高或等温时间的延长,固相颗粒圆整度增加,固相率减少。固相颗粒尺寸随等温温度的升高先减小后增大,随时间的延长一直增大。综合考虑,在590℃保温17～20 min或600℃保温15 min可获得最佳的半固态球状组织。在等温处理期间,呈颗粒状弥散分布的Al11Nd3相在高温下对晶界有明显的钉扎作用,通过阻碍再结晶过程以及减慢Ostwald熟化速度,获得细小的半固态球状组织。

压缩变形量对SIMA法制备Mg−10%Al−1%Zn−1%Si合金显微组织演变的影响

采用应变诱发熔化激活法(SIMA)制备具有非枝晶显微组织的Mg-10%Al-1%Zn-1%Si合金,并且研究压缩变形量对Mg-10%Al-1%Zn-1%Si合金半固态显微组织演变的影响。研究结果表明:随着压缩变形量从0提高到40%,α-Mg晶粒的平均尺寸减小并且其球化趋势变得更为明显。此外,在SIMA法制备的Mg-10%Al-1%Zn-1%Si合金中的共晶Mg2Si相从初始鱼骨状完全转变成为近球状;随着压缩变形量的增大,共晶Mg2Si相的整体形貌和平均尺寸没有发生明显变化。并且,研究SIMA法制备的Mg-10%Al-1%Zn-1%Si合金中共晶Mg2Si相的形貌转变机制。

Microstructure of AZ91D magnesium alloy semi-solid billets prepared by SIMA method from chips

AZ91D magnesium alloy chips were adopted to prepare semi-solid billets.The chips were subjected to a series ofisothermal treatments for various holding times at 783?843 K after being compressed into billet at 523 K.The semi-solid microstructure of AZ91D magnesium alloy containing spherical solid particles was studied.The effects of reheating temperature and holding time on microstructures were investigated.And the semi-solid forming mechanism was discussed.The result shows that semi-solid billets with highly spheroidal and homogeneous grains can be prepared from chips by strain induced melt activation(SIMA) method.Meanwhile,it is found that increasing the heating temperature can accelerate the spheroidizing process and reduce the solid volume fraction.With the increase of the holding time,the solid particles become more globular,the grains grow slowly and the solid volume fraction slightly changes.At the same time,owing to the decrease ofinterfacial energy,the intragranular liquid phases form by the diffusion of solute atoms,the grain boundaries melt and grains separate from each other during the isothermal treatment.The grains gradually spheroidize and begin to merge with a further increase of the holding time.It is considered that the semi-solid forming process includes three stages:the recrystallization and the growth of grain stage,the semi-solid microstructure forming stage controlled by the diffusion of solute,and the spheroidization of solid particle stage controlled by the liquid-solid interface tension.

EFFECT OF PREDEFORMATION MANNER ON SEMI-SOLID STRUCTURE OF AZ61 MAGNESIUM ALLOY IN SIMA PROCESS

The effect of predeformation manner, predeformation ratio and isothermal heat-treat parameter on the non-dendrite structure of AZ61 magnesium alloy in SIMA process was studied. Under coequal heat-treat condition, the impact of the hot upsetting pre- deformation on semi-solid microstructure in SIMA process was compared with that of the cold compressive predeformation. The results indicate that non-dendrite microstructure in AZ61 magnesium alloy billets can be obtained by hot or cold upsetting predeformation in SIMA process, although their mechanisms of evolution are different. Increasing hot or cold upsetting predeformation ratio can enhance the effect and quality of the non-dendrite microstructure formed before storage energy up to saturation, but the proper isothermal temperature and holding time should be selected.

Compound fabrication technology of semi-solid billet of Al-Si alloy based on SIMA method

Based on SIMA, the Al-Si alloy semi-solid billets were successfully fabricated by means of strain inducement and isothermal treatment for AlSi9Mg poured in the range of near-liquidus. Through orthogonal test, the effects of combination action of near-liquidus casting, strain inducement and isothermal treatment on the morphology of primaryα-Al phase of AlSi9Mg close to eutectic point were investigated, and the optimal match relation between the processing parameters of solidification, deformation parameters of strain inducement, processing parameters of isothermal treatment and microstructure parameters of semi-solid alloy was established. The results indicate that compared with the single near-liquidus casting or SIMA, the microstructure of primaryα-Al phase in AlSi9Mg alloy prepared by compound fabrication process is more homogeneous, with more globular and finer particles, which has average grain size of 40-50 urn and shape factor of greater than 0.75. After holding at 605℃for 30-40 min under a certain cooling rate, increased deformation volume in SIMA benefits the refinement of the grain and the improvement of the morphology for primary phase.

异步轧制SIMA法制备半固态AM60镁合金的组织研究

采用异步轧制SIMA法制备了AM60半固态坯料,分析了轧前预热保温时间和半固态保温时间对半固态成形的影响,研究了异步轧制SIMA法制备半固态AM60镁合金的组织演化。结果表明:当轧制温度480℃和轧前预热时间12 min,半固态处理温度580℃和保温时间40 min时,半固态液相率高,固相颗粒均匀、圆整。异步轧制细化了铸态组织晶粒,为后续半固态形成提供了更多的形变储存能。

Structure evolution of AZ61 magnesium alloy in SIMA process

The effect of prior compressive deformation, isothermal temperature and holding time on the structure of AZ61 magnesium alloy fabricated by strain-induced melt activation(SIMA) processing was investigated. The specimens were subjected under deformation ratios of 0%, 22% and 40% and various heat treatment time and temperature regions. The results indicate that the ideal technological parameters of semi-solid AZ61 alloy produced with non-dendrites are recommended as 22% (prior compressive deformation), 595 ℃ (heat treatment temperature) and 40 min(time). The as-cast AZ61 magnesium alloy isn't fit for semi-solid forming.

AZ61合金半固态二次加热工艺及组织演变

研究了应力诱发熔体激活法(SIMA)制备的AZ61镁合金半固态坯料在二次加热时加热温度和保温时间对其组织的影响,研究表明,二次加热初期半固态组织首先熔合合并,随着保温时间延长,晶粒逐渐长大和球化,液相份数增加;保温温度越高,晶粒长大和球化速度加快。在592℃加热、保温20min^40min,可以获得均匀、圆整的半固态组织,晶粒大小为80μm^90μm,液相率为40%~42%。高于597℃时,试样重熔过程中易发生严重变形。

重熔工艺对应变诱导熔化激活法制备ZCuSn10铜合金半固态组织的影响

采用包括锻造与重熔的应变诱导熔化激活(SIMA)法制备ZCuSn10铜合金半固态坯料,分析重熔过程中重熔温度和保温时间对ZCuSn10半固态坯料微观组织的影响。结果表明:在900℃保温时,随着保温时间的延长,合金的平均晶粒直径增大,保温时间由5 min延长至50 min时,平均晶粒直径由45.9μm增大至74.7μm;晶粒形状因子随保温时间的延长先减小后增大。保温30 min时,随着保温温度的升高,平均晶粒直径减小,当保温温度由850℃升高至925℃时,平均晶粒直径由72.6μm减小至64.1μm;晶粒形状因子随保温温度的升高而增大。900℃保温30 min获得的半固态组织均匀、球化效果好,平均晶粒尺寸为64.7μm,形状因子为1.65。

AZ61镁合金在形变诱导法中的组织演变

研究了AZ61镁合金在应力诱发熔体激活法(SIMA)制备半固态坯料过程中预变形量、等温温度和保温时间对其组织的影响。试验样品经过0、22%、40%的预变形和不同等温热处理条件处理,结果表明,制备AZ61 镁合金半固态非枝晶组织的理想工艺参数为形变量22%、等温温度595℃、保温时间40min。未预变形AZ61镁合金不宜进行半固态制坯。

铝含量对应变诱发法半固态镁合金的影响

结合半固态合金成分设计原则,通过热力学计算,研究了3种成分的半固态镁合金。通过组织观察和流变学参数分析表明,半固态组织的形成速度随铝含量增加而加快,固相粒子变得细小、圆整。分析得出铝元素主要通过两个方面影响半固态组织,一个是液相形核,另一个是再结晶晶粒尺寸。随着铝含量增加,液相形核数量增多,再结晶晶粒尺寸减小,这些都促进了半固态组织的形成和演变,有利于镁合金半固态加工。

半固态加热工艺对7075合金组织与性能的影响

利用应变诱发熔化激活法(SIMA)制备了7075铝合金半固态坯料。研究了半固态加热温度与保温时间对7075铝合金半固态坯料显微组织及压缩性能的影响。结果表明:半固态等温温度越高,球形率越好,液相率越高,初生α-Al固相颗粒的尺寸呈先降后升的趋势,而坯料的抗压强度则呈与之相反的趋势,等温温度595~610℃时达到理想状态;随着保温时间的延长,初生α-Al固相颗粒的球形率越好,颗粒尺寸逐渐增大,液相率无明显变化,而坯料的抗压强度呈先升高后略微下降的趋势,保温时间15~30 min时达到理想状态;在595℃保温30 min时,获得的7075铝合金半固态坯料的初生固相颗粒均匀、细小、圆整,抗压强度可达426.82 MPa。

冷变形对LC9铝合金等温转变半固态组织的影响

对冷变形金属进行等温加热转变制备半固态LC9铝合金坯料,并对其工艺过程及组织演变进行了研究,讨论了变形量、加热温度和保温时间等工艺参数对LC9铝合金组织的影响。结果表明,对冷变形金属采用等温处理,可获得均匀、细小的半固态坯料,很好地满足半固态制坯的要求;增加变形量使组织中的液相比例明显增加,晶粒尺寸变小;提高加热温度或延长保温时间有利于晶粒粒化,但是过高的温度和保温时间,会加快晶粒长大,促使晶粒粗化。

形变AZ91D镁合金重熔过程中共晶激活能研究

采用DSC技术研究了SIMA法制备半固态AZ91D镁合金坯料过程中形变率与共晶熔化激活能的关系。结果表明:形变AZ91D镁合金内部存在位错、孪晶缺陷,合金的共晶熔化激活能随变形率的增大而变小,当形变率达到40%时,共晶熔化激活能下降很少;共晶熔化开始温度随变形率的增大略有下降。

冷轧-重熔SIMA法制备半固态ZCuSn10铜合金的组织研究

采用冷轧-重熔的应变诱导熔化激活(SIMA)法制备半固态ZCu Sn10铜合金坯料,分析不同重熔工艺对半固态组织的影响。结果表明:采用冷轧-重熔的SIMA法能制备出理想的半固态坯料。重熔过程中ZCu Sn10合金组织中低熔点的(α+δ)共析组织及枝晶α相与(α+δ)共析组织连接处的过渡区域会逐渐熔化,形成液相,并使得α固相枝晶逐渐熔断,成为α固相颗粒。在850/875℃重熔时,半固态组织中的液相量较少,晶粒黏连较严重,晶粒的球化效果较差。半固态坯料的液相量随保温时间的延长而增加,保温时间从10 min延长至20 min,在850℃重熔时,液相量从6.7%增加到8.5%;875℃重熔时,液相量从17.1%增加到19.6%。900℃保温获得的半固态组织均匀,球化效果好。随着保温时间的增加,半固态坯料的液相先由24.3%增加至30.9%后减小至25.1%,液相的减少是由金相试样取样位置或金相组织分析测量的误差造成的;在相同的重熔保温时间下,重熔温度越高液相的析出速度越快,液相量越大。