Metal sheet article and process for making

Claim 1

A PROCESS OF FABRICATING A SHEET METAL PANEL HAVING A SMOOTH HARD COMPONENT LAYER AND DISTENSIONS RAISED FROM THE OPPOSITE SOFTER COMPONENT LAYER TO FORM HOLLOW PORTIONS IN SAID PANEL, SAID PANEL COMPRISING, AS THE HARD COMPONENT, A SHEET OF ALUMINUM CONTAINING FROM 0.1% TO 0.3% ZIRCONIUM UNIFORMLY DISPERSED THEREIN IN A FINELY DIVIDED FORM, AND A SHEET OF ESSENTIALLY SAID ALUMINUM AS THE SOFTER COMPONENT, COMPRISING THE STEPS OF (A) FORMING A BLANK BY POSITIONONG SAID SHEETS ADJACENT ONE ANOTHER, ONE OF SAID SHEETS HAVING APPLIED TO A CONFRONTING SURFACE THEREOF A PATTERN OF WELD INHIBITING MATERIAL, (B) HEATING SAID BLANK TO A TEMPERATURE WITHIN THE RANGE OF 700* TO 975*F., (C) PRESSURE WELDING SAID SHEETS TOGETHER IN THE AREAS NOT COVERED BY SAID WELD INHIBITING MATERIAL, (D) COOLING AND COLD WORKING SAID BLANK TO DEVELOP A HIGH STRENGTH LEVEL IN SAID SHEETS, (E) PARTIALLY ANNEALING SAID BLANK IN A CRITICAL TEMPERATURE RANGE IN WHICH SIAD SOFTER ALUMINUM COMPONENT UNDERGOES CONSIDERABLE JLOSS OF STRENGTH BY RECOVERY AND RECRYSTALLIZATION BUT IN WHICH SAID ALUMINUM WITH ZIRCONIUM COMPONENT UNDERGOES ONLY SLIGHT LOSS OF STRENGTH BY RECOVERY RELATIVE TO SAID SOFTER ALUMINUM COMPONENT THEREBY DEVELOPING A DIFFERENTIAL IN YIELD STRENGTH BETWEEN THE COMPONENT LAYERS THEROF WHILE PRESERVING THE FINELY DIVIDED ZIRCONIUM DISPERSION, (F) AND INFLATING THE BLANK IN THE UNWELDED AREAS BY THE APPLICATION OF FLUID PRESSURE THEREIN.