PENNSYLVANIA UNIV PHILADELPHIA SCHOOL OF METALLURGICAL ENGINEERING
The experimental evidence on mechanical behavior of fcc, bcc and hcp metals is briefly reviewed. Extended linear hardening, largely independent of temperature, strain rate and other testing conditions, is found not only in all fcc metals stage II and in Ge but also in polycrystalline Fe and simple steels. The average value of the shear modulus by work hardening coefficient in the linear range is about 300 in fcc metals and 500 in steels. The corresponding value for hcp metals is by far larger, and it is concluded that the linear hardening in them cannot be compared to that in fcc and bcc metals. A qualitative theory of easy glide is presented. Linear hardening in stage II is explained on the basis of 3 simple assumptions. The resultant theory is applicable to a great variety of materials, testing conditions and dislocation arrangements, and in particular also to the tangled dislocation structures which are believed to be due to interactions between point defects and dislocations.