The Effects of Temperature and Strain-Rate on the Strength of Pure Aluminium and on that of Aluminium-Magnesium Alloy

Abstract

The effects of temperature and strain-rate on the strength of polycrystalline pure aluminium and on that of aluminium-magnesium alloy have been investigated within the range of temperature from -195 to 450°C and strain-rate from 10-4 to 3×102/s.The test results have been studied from the standpoint of the thermally activated deformation theory. The parameter Z=εexp(Ht/R.T.) (ε is the strain-rate, Ht the apparent activation energy, R gas constant and T the absolute temperature) is effective in prescribing the flow stress in two limited temperature ranges (The intermediate temperature range and the high temperature range) up to ε=10∼50/s.In the case of pure aluminium, the value of the apparent activation energy Ht increases with the increase of strain (Ht=6600∼19000cal/mol for ε=5∼20%) in the intermediate temperature range (-20∼80°C) and is nearly constant (Ht=34000∼32000cal/mol) in the high temperature range (250∼450°C), while in the case of aluminium-magnesium alloy, Ht is nearly constant in the intermediate temperature range (-20∼80°C) and also in the high temperature range (350∼450°C) (Ht=9000∼12000cal/mol and 42000∼39000cal/mol respectively).