Abstract
Latent hardening in aluminum single crystals has been studied by measuring the flow stress on the secondary slip systems. Parent crystals were prestressed to various stress levels at room temperature. Secondary crystals oriented for the coplanar and intersecting slips were cut from a parent crystal and pulled at room temperature and 77°K.
Results obtained are as follows:
1) The shear stress-shear strain curve, the critical resolved shear stress (CRSS) and the work hardening rate in secondary crystals oriented for the coplanar slip are similar to those for the primary slip. While, in secondary crystals oriented for the intersecting slip, CRSS increases and the work hardening rate decreases compared with those in the parent crystal.
2) Slip lines in secondary crystals oriented for the primary and coplanar slips are fine and distributed uniformly, while those in the intersecting slip are coarse and concentrated.
3) In the coplanar slip, latent hardening is not recognized. In the intersecting slip, the following relations exist between the prestress τp and CRSS τl, τl(RT)=1.25τp(RT)+60 (g/mm2) τl(77)=1.5τp(RT)+100 (g/mm2) For the intersecting slip the dependence of CRSS on the slip system is not observed.
4) The latent hardening ratio in the intersecting slip is high when τp is relatively small and decreases to 1.2-1.4 at room temperature and 1.5-1.7 at 77°K with increasing τp.
