A method of establishing filler metal composition for joining components includes determining an initial desired filler metal chemistry, adjoining a first filler rod having a first portion of the desired filler metal chemistry with a second filler rod having a second portion of the desired filler metal chemistry to form a test filler rod, joining a first component formed from a first material to a second component formed from a second material at a weld joint with the test filler rod providing a filler metal portion of the weld joint, and testing the weld joint for desired mechanical, chemical, and weldability properties to establish a desired filler metal composition.