“Anomaly” of work-hardening coefficient in zinc single crystals

Work‐hardening characteristics of Zn‐Ti alloy single crystals

“…Once agglomeration starts their hardening contribution increases (regime T min < T < T max ) due to a decrease of L and ρ m . Indeed, such agglomerates in the form of prismatic dislocation loops on the basal plane with non-basal Burgers vectors have been observed by Mikulowski and Wielke [10]. At higher temperatures (regime T > T max ) dissolution of the vacancy agglomerates and annihilation of vacancies as well as annihilation of dislocations start leading to a decrease of the work-hardening coefficient due to an increase of L and ρ m .…”

“…This leads to a strong concentration of vacancy-dislocation interaction in these planes giving rise to an up to ten times larger hardening effect than in isotropic lattices. Based on these ideas already partly formulated by Mikulowski and Wielke [10] and Zehetbauer and Mikulowski [21] the work-hardening of the pure Zn single crystals oriented for easy glide may be interpreted in the following way. In addition to dislocations yielding Θ/G of about 10 -4 there is a small contribution of single vacancies decreasing with temperature due to thermal overcoming, thus increasing L and ρ m (regime 4.2 K < T < T min ).…”

“…decreasing L. On the other hand, the solute atoms may lower the formation energy for vacancy formation yielding a higher vacancy production during deformation and may be a faster agglomeration. Therefore, it would be interesting to see, if similar to Ag and Ga alloyed Zn single crystals [9,10] the work-hardening in Zn-Ti alloys goes over a maximum at temperatures below 77 K.…”

“…To understand the mechanical behaviour of Zn alloys, previously, based on a detailed microstructural characterization, solid solution and precipitation hardening was studied on Zn single crystals of controlled orientation and Ti concentration [7]. Compared with other closepacked metals, work-hardening in hexagonal crystals, like Zn, Cd and Be, is characterized by an anomalous temperature dependence, which is not well understood so far [8][9][10][11][12]. Therefore, it is the aim of the present work to study the effect of Ti alloying on the work-hardening behaviour of Zn single crystals oriented for basal slip.…”

“…Normalized work-hardening coefficient as a function of temperature for basal slip in Zn single crystals with different constituents and purities but comparable shear strain rate: Zn 1, 7×10 -4 s -1[8]; Zn 2, Zn-0.2Ag, Zn-0.2Ga, 1.4×10 -4 s -1[9,10]; Zn-0.14Ti, 2×10 -4 s -1 .…”