The Influence of Temperature on Slip Behaviour of Molybdenum Single Crystals Deformed in Tension in the Range from 293 to 573 °K .II. Slip Geometry and Structure of Slip Bands

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Abstract
The slip line pattern of molybdenum single crystals deformed in tension at temperatures between 293 and 573 °K (T/Tm = 0.1 to 0.2) was systematically investigated using optical and electron microscopy. The transition from parabolic stress‐strain behaviour to three‐stage hardening which occurs in a transition range Tt ≈ 340 to 400 °K [1] is associated with a basic change in the slip line pattern. At temperatures T < Tt multiple slip occurs whereas for T > Tt single slip in stage I is characteristical. For T > Tt the slip lines are pronounced wavy or zigzag‐like indicating that at elevated temperatures cross‐slip is an important slip process. Furthermore, composite slip on non‐parallel {110} planes was found at temperatures T > Tt. The observations suggest that the influence of temperature on slip line pattern results from the strong increase of mobility of screw dislocations with increasing temperature.