Hello Tom, I realize that your material may be proprietary in nature and thus you may not be able to share completely the make-up of this alloy. Fuse welding a material or even using strips of the same material as a filler can still pose some problems with making sounds welds on a given material. When welding takes place, rearrangement of the structure of the material will occur on some level and can certainly lead to some of the issues you have described. Are you aware if there are any fillers available for welding this alloy that would still allow for the specifications and requirements of your finished product to be met? I bring this up based on the idea that fillers sometimes contain additional alloys to allow for prevention of cracking and other physical issues when welding particular materials or alloys. Also, are you aware if there are any specific welding procedures laid out by the manufacturer of this alloy for joining and working with it? Sometimes if you inquire with the manufacturer they will have the necessary information that can be made available to you to deal with your specific issues. I am mainly referring to things such as starting with the material in an annealed state possibly as you begin working with it, or providing for pre-weld treatments, in-process welding requirements, and post-weld treatments.
     I am not familiar with the alloy that you have questions about in your post, yet I do believe there are many avenues that individuals need to address whenever they are facing problems. Many times these issues are common across the board regardless of the specific material. I did notice that your material is high in nickel, I also seem to recall in some of the posts on the forum here that the Europeans and some of the folks in the states here have made mention of using Argon/Hydrogen gas mixes to deal with some Nickel related issues, this may be a possibility in your case?
     You may want to use the private message function of the forum and pose your question directly to Lawrence, Stephan, or js55. There are also a couple of other individuals who are possibly knowledgeable of or could lead you to the information that you requested here, I just can't remember their screen names right now. Good luck and best regards, aevald

Hi Tom
I've welded MU Alloy 4.  I used sheared Mu for filler always.  I never had a problem.  I never fused unless just for
tacking.  Since a lot of our shields were small we also used a glove box purged with argon sometimes.  We never had a problem there either.  The old saying is when welding use filler as close to the base as possible.  I've never checked with the manufacturer about filler.  That's a good idea.  I guess, I can't really help much.
Dan Pendell