Split-age hardening and temperature dependence of yield stress of chill cast Al-Li-Zr alloys.

本文对激冷铸造Al-Li-Zr合金的劈裂时效硬化和屈服应力的温度依赖性进行了实验研究，结果如下：1.激冷铸造条件：在3 mm间隙的水冷铜模中激冷铸造，可以使Zr在Al中固溶1 mass %。2.最佳热处理条件：在673 K时效1.08 × 10^6s的第一阶段和在473 K时效1.08 × 10^4s的第二阶段，使激冷铸造Al的屈服应力有较大的提高。3.屈服应力的温度依赖性：时效至峰值强度的二元Al-Li合金的屈服应力与温度呈正相关。另一方面，二元Al-Zr合金的屈服应力随温度的升高而单调下降。随着合金中Zr含量的增加，合金的屈服应力与温度的负相关性变得明显。4.应变诱导位错的透射电镜观察：在Al_3-Li二元合金屈服强度与温度正相关的温度范围内，位错成对穿过δ ′-Al_3Li颗粒运动，在Al-Zr二元合金中位错绕过δ ′-Al_3Li颗粒，Al-Li-Zr合金中β '相的错移或攀移，促进了位错的错移或攀移，使合金在高温下更容易变形。

Experimental studies were made on split-age hardening and temperature dependence of yield stress in the chill cast Al-Li-Zr alloys.Results are as follows.1.Chill cast condition:It is possible to dissolve lmass% Zr in Al by chill casting in a water colled copper mold of 3mm gap.2.Optimum heat treatment condition : The first stage aging at 673K for 1.08x10^6s and the successively second stage aging at 473K for 1.08x10^4s provides a rather increase in the yield stress of chill cast Al-Li-Zr alloys than that by aging only at 473K.3.Temperature dependence of yield stress : The binary Al-Li alloys aged to its peak strength show positive temperature dependence of yield stress. On the other hand,the yield stress of binary Al-Zr alloys decreases monotonically with increasing temperature. With increasing the Zr content of Al-Li-Zr alloy,the negative temperature dependence of the yield stress becomes apparent.4.Observation of strain-induced dislocations by transmission electron microscopy: Dislocations move in pairs cutting through the delta'-Al_3Li particles during deformation at the temperature range showing positive temperature dependence of yield strength in the binary Al_3-Li alloys.Dislocations in the binary Al-Zr alloys by-pass,cross slip or climb over the beta'precipitates in the Al-Li-Zr alloys promote the cross slipping or climing over of dislocations and then make the alloy to deform more easily at elevated temperature.