To investigate the influence of primary texture and thermomechanical parameters on hot working behavior of AZ63 magnesium alloy, the flow behavior and deformation texture of hot compression test was compared for both cast and extruded samples. The extruded samples were machined in two extruded and normal directions. Compression tests were carried out at 250oC and the strain rate of 1 s-1 and 0.01 s-1 and various strains. Microstructural observations and texture investigation in various conditions reveal that the presence of extensive twins and contraction twins in extruded samples and extensive TWINNING in cast samples at primary deformation strains and recrystallization at final strains of extruded samples have a significant influence on texture evolutions.

In this paper، the correlation between the surface rumpling and cracking phenomena with TWINNING mechanism during plastic deformation of Hadfield steel has been investigated. The effect of stacking fault energy and the amount of strain are evaluated. The experimental samples with specific amounts of carbon، manganese and aluminum resulting in different stacking fault energies، were produced using investment casting process. The tensile tests were conducted at ambient temperature. The microscopic and macroscopic investigations were done using optical and scanning electron microscopes. The observations have shown that surface crinkling of austenitic manganese steels is related to twining mechanism during plastic deformation. This plastic deformation mechanism causes rotation and inhomogeneous deformation of the grains and therefore، surface grains with free surfaces were becoming more crinkled and cracked. It was observed that crinkling and cracking phenomena takes place more and coarser with an increase in the strain.

An AM30 magnesium alloy was processed through ECAP method at 200 ° C. Optical and transmission electron microscopy as well as electron back scattered diffraction (EBSD) technique were employed to characterize the deformed microstructure. A partially recrystallized microstructure including ultrafine/nano structures was obtained. The area fraction of 49% was measured for the recrystallized regions, where grains of 95 nm to 1 micron were detected. X-ray diffraction pole figure measurements were conducted to assess the final texture. The processed material exhibited moderate randomized texture including three basal pole peaks denoting the effect of dynamic recrystallization on deformation texture. TEM analysis confirmed the contribution of nano TWINNING during deformation of AM30 alloy. EBSD characterization implied that extension twin may contribute to the nucleation of new grains and thereby to be related to texture evolution. The apparent crossing pattern of intersected extension twins provided fine domains with high angle grain boundaries, which act as DRX nuclei. The formation of intersection boundaries also plays a critical role in pileup of dislocations and provide a local high stored-energy for dynamic recrystallization nucleation site. The aforementioned recrystallization mechanisms generally adopt orientations which are different from those produced by conventional recrystallization mechanisms, and thus it offers a route to manipulate the texture.

Introduction: Cattle are a monotocous species meaning that, under most circumstances, a successful pregnancy results in the birth of one calf. TWINNING rate has been reported in dairy cows from 3 to 5 percent, which can be influenced by maternal age. The birth of twins is detrimental to the majority of beef and dairy cattle producer. Financial loss arising from any of TWINNING has been reported in Europe between 109 to 201 dollars in recent years. Because it is associated with undesirable consequences such as reduced survival, calf, cow increased removal rate and poor performance. This also reduces pregnancy rates and profitability herds. One of the effects of TWINNING severe is reduction of the number of calves for replacement fertility in dairy cows. This is a loss arising from an increase in infant mortality and a gender bias in bull calves homo zygote. TWINNING rate increases significantly the incidence of reproductive abnormalities, including the retained placenta, dystocia, stillbirth and abortion. Many studies have been done on the effect of multiple pregnancies in cattle production and reproduction. Higher milk production for cows twin issue is controversial as some studies have shown that there is a positive correlation between the rate of TWINNING in dairy cattle and milk production. But in the next lactation, production for cows that have been the twin of the infected cow metabolic disease in the previous period was lower. In a study reported that cows spend fewer days in the twin peak production. The results of the study on the effect of TWINNING on reproductive traits of Holstein cows-Farzin showed that only half of the twin cows are prone to reproduce in the next period. It is also reported a greater number of insemination per conception in twin compared to single cows. In addition, it has been reported that the twin was more than 15 days from calving to first services. Average twin cows experiencing 1.7 times more death and removal in lifetime production than cows single. The aim of this study was to estimate the rate of TWINNING in Iranian Holstein dairy cows and the estimated effect on production traits and reproductive TWINNING....