scispace - formally typeset
Search or ask a question

Showing papers by "Bhagwati Prasad Kashyap published in 1983"


Journal ArticleDOI
TL;DR: In this paper, a microduplex stainless steel was investigated to examine grain growth during static annealing and superplastic deformation at 1000° C. The grain size at a constant strain rate of 1×10−4 sec−1 increases according to d∼8t 0.19e0.49 where d is the grain size and t is the time involved in deformation.
Abstract: A microduplex stainless steel (25.7 wt% Cr-6.6 wt% Ni) was investigated to examine grain growth during static annealing and superplastic deformation at 1000° C. The grain size at a constant strain rate of 1×10−4 sec−1 increases according to d∼8t 0.49 where d is the grain size and t is the time (in min) involved in deformation. Under the present test condition, the contribution of both static (time, t S) and dynamic (strain, e) annealing appear to be significant and can be expressed by d∞ 0.19e0.29. While the exponent of the first term is constant, the exponent of the second term may depend on the strain rate. Strain rate sensitivities were evaluated from differential strain rate tests for different initial grain sizes. Both strain rate sensitivity and grain size were noticed to increase with deformation.

22 citations


Journal ArticleDOI
TL;DR: In this article, the superplastic behavior of a microduplex stainless steel (IN744) was studied by deforming specimens with initially elongated grains, and microstructural instabilities resulted in strain hardening or strain softening, respectively.
Abstract: Superplastic behavior of a microduplex stainless steel (IN744) was studied by deforming specimens with initially elongated grains. As a result of deformation, grain growth and breaking up of elongated grains were noticed to occur concurrently. These microstructural instabilities result in strain hardening or strain softening, respectively. This then leads to nonuniqueness in the flow behavior. Some examples of nonuniqueness in stress-strain rate relation include the presence of: strength anisotropy, increase in strain rate sensitivity, constant stress level for varying grain size, and two distinct stress-strain rate curves over comparable test condition for the same initial microstructure. These have been explained by the concomitant microstructural changes and the influence of such changes on instantaneous flow stress. Emphasis is made on the need to eliminate microstructural instability in order to characterize the deformation phenomena under steady state.

7 citations