TEM in-situ deformation of magnesium-ytrium alloys

Yttrium (Y) addition is known to be effective in enhancing the formability of magnesium (Mg) alloys by reducing the plasticity anisotropy of the hexagonal crystal, viz. improving the ease of dislocation slip in relation to the dislocation slip. In this work, in-situ TEM compression test has been carried out to observe the nucleation and movement of dislocations in two Mg-Y binary alloys with different Y contents (0.4 wt.%Y versus 4 wt.%Y). The results have shown (Figure 1) that in the Mg-0.4Y alloy, the edge segments of dislocations are sessile. The increased Y content in the Mg-4Y alloy has shown (Figure 2) to increase the dislocation mobility and the cross-slip propensity. The results will be discussed with computer simulation results published. Please click Additional Files below to see the full abstract

Incorporating machine reliability issue and backlogging into the EMQ model - Part I: Random breakdown occurring in backorder filling time

This study is concerned with determination of the optimal replenishment policy for economic manufacturing quantity (EMQ) model with backlogging and machine reliability issue. Classic EMQ model does not consider nonconforming items generated during a production cycle, nor does it deal with the machine breakdown situation. It is noted that in manufacturing system when back-ordering is permitted, a random machine failure can take place in either backorder filling time or in on-hand inventory piling period. The first phase of this study examines the aforementioned practical issues by incorporating rework process of defective items, scrap and random machine failure taking place specifically in backorder satisfying time into the EMQ model. The objective is to determine the optimal replenishment lot-size that minimizes the overall production-inventory costs. Mathematical modelling and analysis is used and the renewal reward theorem is employed to cope with the variable cycle length. Theorem on conditional convexity of total cost function is proposed and proved. The optimal lot size for such a real-life imperfect manufacturing system is derived. A numerical example is given to demonstrate its practical usage