Recently a new martensitic filler material has been designed and made, which has good mechanical properties as well as corrosion resistance. This alloy also exhibits a low austenite to martensite phase transformation temperature (Ms), which means the volume change associated with this martensitic phase transformation completely apposes material shrinkage caused by thermal contraction. Because of variant selection, the volume change becomes nonuniform under stressed conditions. Therefore ENGIN-X is required to analyses the effect of variant selection on the residual stress mitigation properties of this alloy. This is to be achieved by comparing the stresses forming in 8-pass, fusion welds. One constrained during welding (high stress condition) and one left unconstrained (lower stress condition).