基于Murty准则的ZnAl10Cu2合金热变形机制及工艺优化

在Gleeble-1500D热模拟机上研究了ZnAl10Cu2合金在变形温度为180～330℃、应变速率为0.01～10 s-1、最大变形量为0.7条件下的热变形行为,采用动态材料模型的Murty失稳准则绘制了ZnAl10Cu2合金的热加工图,结合微观组织观察研究了该合金在实验条件下的微观变形机制及流动失稳现象,并优化了热变形的工艺参数。结果表明:ZnAl10Cu2合金在高应变速率区域容易发生流变失稳现象,45°剪切开裂、绝热剪切带和局部塑性流动是流动失稳区的主要变形机理,在变形安全区片状α1和α2相均发生了不同程度的球化和扭折,且基体β相发生了动态再结晶,在变形温度为240℃、应变速率为0.1 s-1时,能量耗散率达到峰值,约为53%。

ZnAl10Cu2合金在热压缩条件下绝热剪切带的形成及其特征

采用Gleeble-1500D热模拟试验机研究了ZnAl10Cu2合金热变形行为,使用光学显微镜(OM)、扫描电镜(SEM)分析了压缩后合金试样的显微组织。结果表明,绝热剪切带的宽带随应变速率的增加而减小,位于剪切带中心区域的初生枝晶沿其扩展方向被剧烈拉长成纤维状,且表现出塑性流动局域失稳的特征。基体β相发生动态再结晶,形成细小的等轴晶粒。

ZnAl10Cu2合金在热变形过程中的球化及动态再结晶

采用Gleeble-1500D热模拟实验机研究ZnAl10Cu2合金在变形温度180～330℃、应变速率0．01～30s-1、真应变0．3～1．2时的热变形组织演化行为。结果表明：在不同变形条件下，共晶中的片状az相发生了不同程度的球化和弯折，其球化程度随着应变速率的降低、变形温度的升高、真应变的增大而增加；同时，基体β相发生了动态再结晶。当变形温度小于270℃时，随着变形温度的升高，再结晶晶粒更为细小均匀。变形温度进一步升高，晶粒出现局部长大；当应变速率小于1s^-1时，动态再结晶晶粒随应变速率的增大而减小；应变速率约为ls^-1时，晶粒细小均匀；应变速率继续增加时，动态再结晶晶粒出现不均匀现象。

Influence of AlTi3C0.15 modification treatment on damping properties of ZnAl10 alloy

Zn-Al alloys constitute an interesting group of foundry alloys. Due to a relatively low melting temperature, they allow a decrease in energy-consumption of the melting process and alloy preparation. The vibration damping ability is one of the most interesting properties of the Zn-Al alloys. Zn-Al alloys are divided into two groups: the low-aluminium and high-aluminium alloys. The investigated Zn-10 wt.% Al(ZnAl10) alloy is representative of the high-aluminium alloys, which, on account of its tendency of forming coarse-grained structures, has rather low plastic properties, including elongation. In order to improve the plastic properties, a modification treatment is usually applied. The dependence of the damping coefficient of the ultrasound wave on the amount of the introduced inoculant was studied. Investigations were performed using the AlT i3C0.15 inoculant as the modifier of the ZnAl10 alloy. It was found that titanium additions, in a range from 25 to 100 ppm in relation to the melted charge mass, can reduce the damping coefficient value. An increase of the inoculant addition causes a rise of the damping coefficient, which is probably related to the scattering of the ultrasound wave on Al_3Ti and TiC particles introduced with the inoculant.

铸态ZnAl10Cu2合金热变形本构方程

在Gleeble-3500热模拟机上采用等温压缩实验研究了ZnAl10Cu2合金在温度为210～300℃、应变速率为10-2～10 s-1条件下的热变形行为,获得了该合金热变形过程中的真应力-应变曲线。结果表明:ZnAl10Cu2合金的峰值流变应力随温度升高而降低,随应变速率的提高而增大。通过双曲正弦模型确定了该合金的高温材料常数,Q=144.161 kJ/mol,n=4.443,A=4.7×1012s-1,α=0.01037 MPa-1,并采用修正的Kumar模型建立了考虑应变对流变应力影响的高温本构关系,其拟合度为9.14%。