It has been repeatedly demonstrated that reward contingencies and other extrinsic constraints on behavior can lead to reduced levels of interest in and/or decreased engagement in a target activity in a subsequent noncontingent situation. It has been hypothesized that this effect is caused by a change in the self-perceived locus of motivation from intrinsic to extrinsic. It follows from this hypothesis that effective rewards are more likely to produce the overjustification effect than are ineffective rewards. However, a review of empirical studies suggests the opposite conclusion. This experiment was designed to assess the reinforcement-overjustincation effect relationship. Four levels of the behavior constraint -reinforcement variable were manipulated: attractive reward, unattractive reward, request to perform, and a no-reward, no-request control. Only the unattractive reward and request groups showed the performance decrements that suggest the Overjustification effect. The attractive reward group was significantly different from these two groups on this measure. It is concluded that reinforcement does not cause the Overjustification effect. It is suggested that the behavior constraining aspect of a contingency produces the effect, whereas the reinforcement, or "reward value," aspect leads to the opposite effect-an increase in interest and postcontingency performance.Since 1971 more than 25 studies have attempted to investigate the effects of extrinsic reward on intrinsic motivation. The well replicated but not universal finding that rewards lead to decreases in intrinsic motivation is called the Overjustification effect. In many studies of the Overjustification effect, a standard experimental paradigm is used. There is a baseline period, in which the degree of initial interest in the target behavior is assessed; a contingency (or manipulation) period, in which the target behavior is rewarded; and a postcontingency, free-choice period, in which the amount of interest in the target behavior is again assessed and is predicted to be less than the initial degree of interest. Many studies have employed control groups that engage in the target behavior Portions of this study were presented at the 59th annual meeting of the Western Psychological Association, San Diego, California, April 1979.Requests for reprints should be sent to Bruce W. Williams, who is now at Forest Haven, Department of Human Services, Laurel, Maryland 20810. during the manipulation period but without expectation of getting a reward for their performance. Some of these studies have omitted the baseline phase and have relied strictly on between-groups comparisons of postmanipulation performance.The term Overjustification effect will be used to refer to a below-baseline decrease in rate of performance of initially "intrinsically motivated" behavior that follows a period during which the behavior is extrinsically rewarded. Although this term unfortunately implies a theoretical interpretation of .the effect, it will be used because of its continued usag...

Uniaxial tension and compression tests were conducted to investigate the quasi-static performance of ZK60 Mg alloy in cast, followed by forging at optimum temperature of 450 ºC and a ram speed of 39 mm min -1 condition. Microstructure and texture analysis showed that the as-cast alloy exhibited a dendritic structure with casting porosity and random texture. In contrast, the forged alloy exhibited a refined grain structure with a significant reduction in casting porosity, while the texture changed to sharp basal texture. Measured mechanical properties of the forged alloy showed that the strength did not change, however, the ductility improved by 75%.The analysis of the fracture surface of the forged alloy under tension revealed a ductile fractureThe final publication is available at Elsevier via http://dx.

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The effect of forging on the low cycle fatigue (LCF) behavior of cast AZ31B was investigated.The forging process was conducted at a temperature of 450°C and speed of 390mm/min. Fully reversed (R ε =-1) strain controlled cyclic tests were performed on as-cast and forged materials under total strain amplitudes of 0.1%-1.2%. Forging eliminated the dendritic morphology and reduced β-phase intermetallics observed in the cast alloy. Additionally sharp basal texture and bimodal grain structure were developed. Generally, the forged material was found to exhibit longer fatigue life, especially at lower strain amplitudes. This was attributed to the grain refinement and the developed basal texture that changed the alloy's deformation behavior. Also, the forged material achieved significantly higher stresses at the same total strain amplitudes compared to cast AZ31B, and substantial cyclic hardening occurred during cyclic loading. At the same time, considerable tension-compression asymmetry was observed in the forged AZ31B during LCF testing. The Smith-Watson-Topper model and Jahed-Varvani energy model were employed and both models were found to accurately predict the experimentally obtained fatigue life of both alloy conditions. The Jahed-Varvani model accurately predicted fatigue life within a factor of 1.5 especially for the asymmetric behavior of forged AZ31B.

Tensile and strain-controlled fatigue tests were performed to investigate the influence of forging on the performance of cast AZ80 magnesium alloy. The obtained microstructural analysis showed that the as-cast AZ80 magnesium alloy has dendritic α-Mg phase with eutectic Mg 17 Al 12 morphology and a random texture. In contrast, the forged samples showed refined grains and a strong basal texture. During tensile testing, a maximum yield and ultimate tensile strength of 182 MPa and 312 MPa were obtained for the forged samples, representing increases of 121% and 33%, respectively, from the as-cast condition. At the same time, a significant improvement (73%) in ductility was obtained in forged samples. It was also observed that the forged samples achieved comparatively longer fatigue life under strain-controlled cyclic loading. Analysis of the fracture surfaces showed that a cleavage-type morphology was typical for the ascast samples, while the occurrence of dimples and other evidence of plastic deformation were identified in the fracture surfaces of the forged specimens, indicating a more ductile response. Forging caused grain refinement and texture modification, both of which enhance alloy performance by improving strength and ductility, and leading to longer fatigue life. Strain and energy-based models were investigated for their suitability to predict the life of the forged material. Both the Smith-Watson Topper and the Jahed-Varvani energy-based models gave reliable life prediction.